path: root/doc/rfc/rfc4779.txt

Network Working Group                                       S. Asadullah
Request for Comments: 4779                                      A. Ahmed
Category: Informational                                     C. Popoviciu
                                                           Cisco Systems
                                                               P. Savola
                                                               CSC/FUNET
                                                                J. Palet
                                                             Consulintel
                                                            January 2007


       ISP IPv6 Deployment Scenarios in Broadband Access Networks

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document provides a detailed description of IPv6 deployment and
   integration methods and scenarios in today's Service Provider (SP)
   Broadband (BB) networks in coexistence with deployed IPv4 services.
   Cable/HFC, BB Ethernet, xDSL, and WLAN are the main BB technologies
   that are currently deployed, and discussed in this document.  The
   emerging Broadband Power Line Communications (PLC/BPL) access
   technology is also discussed for completeness.  In this document we
   will discuss main components of IPv6 BB networks, their differences
   from IPv4 BB networks, and how IPv6 is deployed and integrated in
   each of these networks using tunneling mechanisms and native IPv6.
















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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Common Terminology . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Core/Backbone Network  . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Layer 2 Access Provider Network  . . . . . . . . . . . . .  5
     3.2.  Layer 3 Access Provider Network  . . . . . . . . . . . . .  6
   4.  Tunneling Overview . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Access over Tunnels - Customers with Public IPv4
           Addresses  . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.2.  Access over Tunnels - Customers with Private IPv4
           Addresses  . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.3.  Transition a Portion of the IPv4 Infrastructure  . . . . .  8
   5.  Broadband Cable Networks . . . . . . . . . . . . . . . . . . .  9
     5.1.  Broadband Cable Network Elements . . . . . . . . . . . . .  9
     5.2.  Deploying IPv6 in Cable Networks . . . . . . . . . . . . . 10
       5.2.1.  Deploying IPv6 in a Bridged CMTS Network . . . . . . . 12
       5.2.2.  Deploying IPv6 in a Routed CMTS Network  . . . . . . . 14
       5.2.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . 23
       5.2.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . 24
       5.2.5.  IPv6 Security Considerations . . . . . . . . . . . . . 24
       5.2.6.  IPv6 Network Management  . . . . . . . . . . . . . . . 25
   6.  Broadband DSL Networks . . . . . . . . . . . . . . . . . . . . 26
     6.1.  DSL Network Elements . . . . . . . . . . . . . . . . . . . 26
     6.2.  Deploying IPv6 in IPv4 DSL Networks  . . . . . . . . . . . 28
       6.2.1.  Point-to-Point Model . . . . . . . . . . . . . . . . . 29
       6.2.2.  PPP Terminated Aggregation (PTA) Model . . . . . . . . 30
       6.2.3.  L2TPv2 Access Aggregation (LAA) Model  . . . . . . . . 33
       6.2.4.  Hybrid Model for IPv4 and IPv6 Service . . . . . . . . 36
     6.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 38
       6.3.1.  ASM-Based Deployments  . . . . . . . . . . . . . . . . 39
       6.3.2.  SSM-Based Deployments  . . . . . . . . . . . . . . . . 39
     6.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 40
     6.5.  IPv6 Security Considerations . . . . . . . . . . . . . . . 41
     6.6.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 42
   7.  Broadband Ethernet Networks  . . . . . . . . . . . . . . . . . 42
     7.1.  Ethernet Access Network Elements . . . . . . . . . . . . . 42
     7.2.  Deploying IPv6 in IPv4 Broadband Ethernet Networks . . . . 43
       7.2.1.  Point-to-Point Model . . . . . . . . . . . . . . . . . 44
       7.2.2.  PPP Terminated Aggregation (PTA) Model . . . . . . . . 46
       7.2.3.  L2TPv2 Access Aggregation (LAA) Model  . . . . . . . . 48
       7.2.4.  Hybrid Model for IPv4 and IPv6 Service . . . . . . . . 50
     7.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 52
     7.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 53
     7.5.  IPv6 Security Considerations . . . . . . . . . . . . . . . 54
     7.6.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 55





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   8.  Wireless LAN . . . . . . . . . . . . . . . . . . . . . . . . . 55
     8.1.  WLAN Deployment Scenarios  . . . . . . . . . . . . . . . . 55
       8.1.1.  Layer 2 NAP with Layer 3 termination at NSP Edge
               Router . . . . . . . . . . . . . . . . . . . . . . . . 56
       8.1.2.  Layer 3 Aware NAP with Layer 3 Termination at
               Access Router  . . . . . . . . . . . . . . . . . . . . 59
       8.1.3.  PPP-Based Model  . . . . . . . . . . . . . . . . . . . 61
     8.2.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 63
     8.3.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 65
     8.4.  IPv6 Security Considerations . . . . . . . . . . . . . . . 65
     8.5.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 67
   9.  Broadband Power Line Communications (PLC)  . . . . . . . . . . 67
     9.1.  PLC/BPL Access Network Elements  . . . . . . . . . . . . . 68
     9.2.  Deploying IPv6 in IPv4 PLC/BPL . . . . . . . . . . . . . . 69
       9.2.1.  IPv6 Related Infrastructure Changes  . . . . . . . . . 69
       9.2.2.  Addressing . . . . . . . . . . . . . . . . . . . . . . 69
       9.2.3.  Routing  . . . . . . . . . . . . . . . . . . . . . . . 70
     9.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 71
     9.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 71
     9.5.  IPv6 Security Considerations . . . . . . . . . . . . . . . 71
     9.6.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 71
   10. Gap Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 71
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 74
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 74
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 74
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 74
     13.2. Informative References . . . . . . . . . . . . . . . . . . 76
























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1.  Introduction

   This document presents the options available in deploying IPv6
   services in the access portion of a BB Service Provider (SP) network
   - namely Cable/HFC, BB Ethernet, xDSL, WLAN, and PLC/BPL.

   This document briefly discusses the other elements of a provider
   network as well.  It provides different viable IPv6 deployment and
   integration techniques, and models for each of the above-mentioned BB
   technologies individually.  The example list is not exhaustive, but
   it tries to be representative.

   This document analyzes how all the important components of current
   IPv4-based Cable/HFC, BB Ethernet, xDSL, WLAN, and PLC/BPL networks
   will behave when IPv6 is integrated and deployed.

   The following important pieces are discussed:

   A. Available tunneling options

   B. Devices that would have to be upgraded to support IPv6

   C. Available IPv6 address assignment techniques and their use

   D. Possible IPv6 Routing options and their use

   E. IPv6 unicast and multicast packet transmission

   F. Required IPv6 Quality of Service (QoS) parameters

   G. Required IPv6 Security parameters

   H. Required IPv6 Network Management parameters

   It is important to note that the addressing rules provided throughout
   this document represent an example that follows the current
   assignment policies and recommendations of the registries.  However,
   they can be adapted to the network and business model needs of the
   ISPs.

   The scope of the document is to advise on the ways of upgrading an
   existing infrastructure to support IPv6 services.  The recommendation
   to upgrade a device to dual stack does not stop an SP from adding a
   new device to its network to perform the necessary IPv6 functions
   discussed.  The costs involved with such an approach could be offset
   by lower impact on the existing IPv4 services.





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2.  Common Terminology

   BB: Broadband

   CPE: Customer Premise Equipment

   GWR: Gateway Router

   ISP: Internet Service Provider

   NAP: Network Access Provider

   NSP: Network Service Provider

   QoS: Quality of Service

   SP: Service Provider

3.  Core/Backbone Network

   This section intends to briefly discuss some important elements of a
   provider network tied to the deployment of IPv6.  A more detailed
   description of the core network is provided in other documents
   [RFC4029].

   There are two types of networks identified in the Broadband
   deployments:

   A.  Access Provider Network: This network provides the broadband
       access and aggregates the subscribers.  The subscriber traffic is
       handed over to the Service Provider at Layer 2 or 3.

   B.  Service Provider Network: This network provides Intranet and
       Internet IP connectivity for the subscribers.

   The Service Provider network structure beyond the Edge Routers that
   interface with the Access provider is beyond the scope of this
   document.

3.1.  Layer 2 Access Provider Network

   The Access Provider can deploy a Layer 2 network and perform no
   routing of the subscriber traffic to the SP.  The devices that
   support each specific access technology are aggregated into a highly
   redundant, resilient, and scalable Layer 2 core.  The network core
   can involve various technologies such as Ethernet, Asynchronous
   Transfer Mode (ATM), etc.  The Service Provider Edge Router connects
   to the Access Provider core.



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   This type of network may be transparent to the Layer 3 protocol.
   Some possible changes may come with the intent of supporting IPv6
   provisioning mechanisms, as well as filtering and monitoring IPv6
   traffic based on Layer 2 information such as IPv6 Ether Type Protocol
   ID (0x86DD) or IPv6 multicast specific Media Access Control (MAC)
   addresses (33:33:xx:xx:xx:xx).

3.2.  Layer 3 Access Provider Network

   The Access Provider can choose to terminate the Layer 2 domain and
   route the IP traffic to the Service Provider network.  Access Routers
   are used to aggregate the subscriber traffic and route it over a
   Layer 3 core to the SP Edge Routers.  In this case, the impact of the
   IPv6 deployment is significant.

   The case studies in this document discuss only the relevant network
   elements of such a network: Customer Premise Equipment, Access
   Router, and Edge Router.  In real networks, the link between the
   Access Router and the Edge Router involves other routers that are
   part of the aggregation and the core layer of the Access Provider
   network.

   The Access Provider can forward the IPv6 traffic through its Layer 3
   core in three possible ways:

   A.  IPv6 Tunneling: As a temporary solution, the Access Provider can
       choose to use a tunneling mechanism to forward the subscriber
       IPv6 traffic to the Service Provider Edge Router.  This approach
       has the least impact on the Access Provider network; however, as
       the number of users increase and the amount of IPv6 traffic
       grows, the ISP will have to evolve to one of the scenarios listed
       below.

   B.  Native IPv6 Deployment: The Access Provider routers are upgraded
       to support IPv6 and can become dual stack.  In a dual-stack
       network, an IPv6 Interior Gateway Protocol (IGP), such as OSPFv3
       [RFC2740] or IS-IS [ISISv6], is enabled.  RFC 4029 [RFC4029]
       discusses the IGP selection options with their benefits and
       drawbacks.

   C.  MPLS 6PE Deployment [6PE]: If the Access Provider is running MPLS
       in its IPv4 core, it could use 6PE to forward IPv6 traffic over
       it.  In this case, only a subset of routers close to the edge of
       the network need to be IPv6 aware.  With this approach, BGP
       becomes important in order to support 6PE.

   The 6PE approach has the advantage of having minimal impact on the
   Access Provider network.  Fewer devices need to be upgraded and



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   configured while the MPLS core continues to switch the traffic,
   unaware that it transports both IPv4 and IPv6. 6PE should be
   leveraged only if MPLS is already deployed in the network.  At the
   time of writing this document, a major disadvantage of the 6PE
   solution is that it does not support multicast IPv6 traffic.

   The native approach has the advantage of supporting IPv6 multicast
   traffic, but it may imply a significant impact on the IPv4
   operational network in terms of software configuration and possibly
   hardware upgrade.

   More detailed Core Network deployment recommendations are discussed
   in other documents [RFC4029].  The handling of IPv6 traffic in the
   Core of the Access Provider Network will not be discussed for the
   remainder of this document.

4.  Tunneling Overview

   If SPs are not able to deploy native IPv6, they might use tunneling-
   based transition mechanisms to start an IPv6 service offering, and
   move to native IPv6 deployment at a later time.

   Several tunneling mechanisms were developed specifically to transport
   IPv6 over existing IPv4 infrastructures.  Several of them have been
   standardized and their use depends on the existing SP IPv4 network
   and the structure of the IPv6 service.  The requirements for the most
   appropriate mechanisms are described in [v6tc] with more updates to
   follow.  Deploying IPv6 using tunneling techniques can imply as
   little changes to the network as upgrading software on tunnel end
   points.  A Service Provider could use tunneling to deploy IPv6 in the
   following scenarios:

4.1.  Access over Tunnels - Customers with Public IPv4 Addresses

   If the customer is a residential user, it can initiate the tunnel
   directly from the IPv6 capable host to a tunnel termination router
   located in the NAP or ISP network.  The tunnel type used should be
   decided by the SP, but it should take into consideration its
   availability on commonly used software running on the host machine.
   Of the many tunneling mechanisms developed, such as IPv6 Tunnel
   Broker [RFC3053], Connection of IPv6 Domains via IPv4 Clouds
   [RFC3056], Generic Packet Tunneling in IPv6 [RFC2473], ISATAP
   [RFC4214], Basic Transition Mechanisms for IPv6 Hosts and Routers
   [RFC4213], and Transmission of IPv6 over IPv4 Domains without
   Explicit Tunnels [RFC2529], some are more popular than the others.
   At the time of writing this document, the IETF Softwire Working Group
   was tasked with standardizing a single tunneling protocol [Softwire]
   for this application.



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   If the end customer has a GWR installed, then it could be used to
   originate the tunnel, thus offering native IPv6 access to multiple
   hosts on the customer network.  In this case, the GWR would need to
   be upgraded to dual stack in order to support IPv6.  The GWR can be
   owned by the customer or by the SP.

4.2.  Access over Tunnels - Customers with Private IPv4 Addresses

   If the end customer receives a private IPv4 address and needs to
   initiate a tunnel through Network Address Translation (NAT),
   techniques like 6to4 may not work since they rely on public IPv4
   address.  In this case, unless the existing GWRs support protocol-41-
   forwarding [Protocol41], the end user might have to use tunnels that
   can operate through NATs (such as Teredo [RFC4380]).  Most GWRs
   support protocol-41-forwarding, which means that hosts can initiate
   the tunnels - in which case the GWR is not affected by the IPv6
   service.

   The customer has the option to initiate the tunnel from the device
   (GWR) that performs the NAT functionality, similar to the GWR
   scenario discussed in Section 4.1.  This will imply hardware
   replacement or software upgrade and a native IPv6 environment behind
   the GWR.

   It is also worth observing that initiating an IPv6 tunnel over IPv4
   through already established IPv4 IPsec sessions would provide a
   certain level of security to the IPv6 traffic.

4.3.  Transition a Portion of the IPv4 Infrastructure

   Tunnels can be used to transport the IPv6 traffic across a defined
   segment of the network.  As an example, the customer might connect
   natively to the Network Access Provider, where a tunnel is used to
   transit the traffic over IPv4 to the ISP.  In this case, the tunnel
   choice depends on its capabilities (for example, whether or not it
   supports multicast), routing protocols used (there are several types
   that can transport Layer 2 messages, such as GRE [RFC2784], L2TPv3
   [RFC3931], or pseudowire), manageability, and scalability (dynamic
   versus static tunnels).

   This scenario implies that the access portion of the network has been
   upgraded to support dual stack, so the savings provided by tunneling
   in this scenario are very small compared with the previous two
   scenarios.  Depending on the number of sites requiring the service,
   and considering the expenses required to manage the tunnels (some
   tunnels are static while others are dynamic [DynamicTunnel]) in this
   case, the SPs might find the native approach worth the additional
   investments.



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   In all the scenarios listed above, the tunnel selection process
   should consider the IPv6 multicast forwarding capabilities if such
   service is planned.  As an example, 6to4 tunnels do not support IPv6
   multicast traffic.

   The operation, capabilities, and deployment of various tunnel types
   have been discussed extensively in the documents referenced earlier
   as well as in [RFC4213] and [RFC3904].  Details of a tunnel-based
   deployment are offered in the next section of this document, which
   discusses the case of Cable Access, where the current Data Over Cable
   Service Interface Specification (DOCSIS 2.0) [RF-Interface] and prior
   specifications do not provide support for native IPv6 access.
   Although Sections 6, 7, 8, and 9 focus on a native IPv6 deployments
   over DSL, Fiber to the Home (FTTH), wireless, and PLC/BPL and because
   this approach is fully supported today, tunnel-based solutions are
   also possible in these cases based on the guidelines of this section
   and some of the recommendations provided in Section 5.

5.  Broadband Cable Networks

   This section describes the infrastructure that exists today in cable
   networks providing BB services to the home.  It also describes IPv6
   deployment options in these cable networks.

   DOCSIS standardizes and documents the operation of data over cable
   networks.  DOCSIS 2.0 and prior specifications have limitations that
   do not allow for a smooth implementation of native IPv6 transport.
   Some of these limitations are discussed in this section.  For this
   reason, the IPv6 deployment scenarios discussed in this section for
   the existing cable networks are tunnel based.  The tunneling examples
   presented here could also be applied to the other BB technologies
   described in Sections 6, 7, 8, and 9.

5.1.  Broadband Cable Network Elements

   Broadband cable networks are capable of transporting IP traffic to/
   from users to provide high speed Internet access and Voice over IP
   (VoIP) services.  The mechanism for transporting IP traffic over
   cable networks is outlined in the DOCSIS specification
   [RF-Interface].

   Here are some of the key elements of a cable network:

   Cable (HFC) Plant: Hybrid Fiber Coaxial plant, used as the underlying
   transport

   CMTS: Cable Modem Termination System (can be a Layer 2 bridging or
   Layer 3 routing CMTS)



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   GWR: Residential Gateway Router (provides Layer 3 services to hosts)

   Host: PC, notebook, etc., which is connected to the CM or GWR

   CM: Cable Modem

   ER: Edge Router

   MSO: Multiple Service Operator

   Data Over Cable Service Interface Specification (DOCSIS): Standards
   defining how data should be carried over cable networks

   Figure 5.1 illustrates the key elements of a Cable Network.



   |--- ACCESS  ---||------ HFC ------||----- Aggregation / Core -----|

   +-----+  +------+
   |Host |--| GWR  |
   +-----+  +--+---+
               |        _ _ _ _ _ _
            +------+   |           |
            |  CM  |---|           |
            +------+   |           |
                       |    HFC    |   +------+   +--------+
                       |           |   |      |   | Edge   |
   +-----+  +------+   |  Network  |---| CMTS |---|        |=>ISP
   |Host |--|  CM  |---|           |   |      |   | Router | Network
   +-----+  +--+---+   |           |   +------+   +--------+
                       |_ _ _ _ _ _|
            +------+         |
   +-----+  | GWR/ |         |
   |Host |--| CM   |---------+
   +-----+  |      |
            +------+

                              Figure 5.1

5.2.  Deploying IPv6 in Cable Networks

   One of the motivators for an MSO to deploy IPv6 over its cable
   network is to ease management burdens.  IPv6 can be enabled on the
   CM, CMTS, and ER for management purposes.  Currently portions of the
   cable infrastructure use IPv4 address space [RFC1918]; however, there
   is a finite number of those.  Thus, IPv6 could have utility in the
   cable space implemented on the management plane initially and focused



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   on the data plane for end-user services later.  For more details on
   using IPv6 for management in cable networks, please refer to Section
   5.6.1.

   There are two different deployment modes in current cable networks: a
   bridged CMTS environment and a routed CMTS environment.  IPv6 can be
   deployed in both of these environments.

   1.  Bridged CMTS Network

   In this scenario, both the CM and CMTS bridge all data traffic.
   Traffic to/from host devices is forwarded through the cable network
   to the ER.  The ER then routes traffic through the ISP network to the
   Internet.  The CM and CMTS support a certain degree of Layer 3
   functionality for management purposes.

   2.  Routed CMTS Network

   In a routed network, the CMTS forwards IP traffic to/from hosts based
   on Layer 3 information using the IP source/destination address.  The
   CM acts as a Layer 2 bridge for forwarding data traffic and supports
   some Layer 3 functionality for management purposes.

   Some of the factors that hinder deployment of native IPv6 in current
   routed and bridged cable networks include:

   A.  Changes need to be made to the DOCSIS specification
       [RF-Interface] to include support for IPv6 on the CM and CMTS.
       This is imperative for deploying native IPv6 over cable networks.

   B.  Problems with IPv6 Neighbor Discovery (ND) on CM and CMTS.  In
       IPv4, these devices rely on Internet Group Multicast Protocol
       (IGMP) join messages to track membership of hosts that are part
       of a particular IP multicast group.  In order to support ND, a
       multicast-based process, the CM and CMTS will need to support
       IGMPv3/Multicast Listener Discovery Version 2 (MLDv2) or v1
       snooping.

   C.  Classification of IPv6 traffic in the upstream and downstream
       direction.  The CM and CMTS will need to support classification
       of IPv6 packets in order to give them the appropriate priority
       and QoS.  Service providers that wish to deploy QoS mechanisms
       also have to support classification of IPv6 traffic.

   Due to the above mentioned limitations in deployed cable networks, at
   the time of writing this document, the only option available for
   cable operators is to use tunneling techniques in order to transport
   IPv6 traffic over their current IPv4 infrastructure.  The following



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   sections will cover tunneling and native IPv6 deployment scenarios in
   more detail.

5.2.1.  Deploying IPv6 in a Bridged CMTS Network

   In IPv4, the CM and CMTS act as Layer 2 bridges and forward all data
   traffic to/from the hosts and the ER.  The hosts use the ER as their
   Layer 3 next hop.  If there is a GWR behind the CM it can act as a
   next hop for all hosts and forward data traffic to/from the ER.

   When deploying IPv6 in this environment, the CM and CMTS will
   continue to act as bridging devices in order to keep the transition
   smooth and reduce operational complexity.  The CM and CMTS will need
   to bridge IPv6 unicast and multicast packets to/from the ER and the
   hosts.  If there is a GWR connected to the CM, it will need to
   forward IPv6 unicast and multicast traffic to/from the ER.

   IPv6 can be deployed in a bridged CMTS network either natively or via
   tunneling.  This section discusses the native deployment model.  The
   tunneling model is similar to ones described in Sections 5.2.2.1 and
   5.2.2.2.

   Figure 5.2.1 illustrates the IPv6 deployment scenario.


   +-----+  +-----+
   |Host |--| GWR |
   +-----+  +--+--+
               |              _ _ _ _ _ _
               |  +------+   |           |
               +--|  CM  |---|           |
                  +------+   |           |
                             |   HFC     |   +------+  +--------+
                             |           |   |      |  | Edge   |
         +-----+  +------+   |  Network  |---| CMTS |--|        |=>ISP
         |Host |--|  CM  |---|           |   |      |  | Router |Network
         +-----+  +------+   |           |   +------+  +--------+
                             |_ _ _ _ _ _|
   |-------------||---------------------------------||---------------|
       L3 Routed              L2 Bridged                 L3 Routed

                             Figure 5.2.1









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5.2.1.1.  IPv6 Related Infrastructure Changes

   In this scenario, the CM and the CMTS bridge all data traffic so they
   will need to support bridging of native IPv6 unicast and multicast
   traffic.  The following devices have to be upgraded to dual stack:
   Host, GWR, and ER.

5.2.1.2.  Addressing

   The proposed architecture for IPv6 deployment includes two components
   that must be provisioned: the CM and the host.  Additionally if there
   is a GWR connected to the CM, it will also need to be provisioned.
   The host or the GWR use the ER as their Layer 3 next hop.

5.2.1.2.1.  IP Addressing for CM

   The CM will be provisioned in the same way as in currently deployed
   cable networks, using an IPv4 address on the cable interface
   connected to the MSO network for management functions.  During the
   initialization phase, it will obtain its IPv4 address using Dynamic
   Host Configuration Protocol (DHCPv4), and download a DOCSIS
   configuration file identified by the DHCPv4 server.

5.2.1.2.2.  IP Addressing for Hosts

   If there is no GWR connected to the CM, the host behind the CM will
   get a /64 prefix via stateless auto-configuration or DHCPv6.

   If using stateless auto-configuration, the host listens for routing
   advertisements (RAs) from the ER.  The RAs contain the /64 prefix
   assigned to the segment.  Upon receipt of an RA, the host constructs
   its IPv6 address by combining the prefix in the RA (/64) and a unique
   identifier (e.g., its modified EUI-64 (64-bit Extended Unique
   Identifier) format interface ID).

   If DHCPv6 is used to obtain an IPv6 address, it will work in much the
   same way as DHCPv4 works today.  The DHCPv6 messages exchanged
   between the host and the DHCPv6 server are bridged by the CM and the
   CMTS.

5.2.1.2.3.  IP Addressing for GWR

   The GWR can use stateless auto-configuration (RA) to obtain an
   address for its upstream interface, the link between itself and the
   ER.  This step is followed by a request via DHCP-PD (Prefix
   Delegation) for a prefix shorter than /64, typically /48 [RFC3177],
   which in turn is divided into /64s and assigned to its downstream
   interfaces connecting to the hosts.



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5.2.1.3.  Data Forwarding

   The CM and CMTS must be able to bridge native IPv6 unicast and
   multicast traffic.  The CMTS must provide IP connectivity between
   hosts attached to CMs, and must do so in a way that meets the
   expectation of Ethernet-attached customer equipment.  In order to do
   that, the CM and CMTS must forward Neighbor Discovery (ND) packets
   between ER and the hosts attached to the CM.

   Communication between hosts behind different CMs is always forwarded
   through the CMTS.  IPv6 communication between the different sites
   relies on multicast IPv6 ND [RFC2461] frames being forwarded
   correctly by the CM and the CMTS.

   In order to support IPv6 multicast applications across DOCSIS cable
   networks, the CM and bridging CMTS need to support IGMPv3/MLDv2 or v1
   snooping.  MLD is almost identical to IGMP in IPv4, only the name and
   numbers are changed.  MLDv2 is identical to IGMPv3 and also supports
   ASM (Any-Source Multicast) and SSM (Source-Specific Multicast)
   service models.  Implementation work on CM/CMTS should be minimal
   because the only significant difference between IPv4 IGMPv3 and IPv6
   MLDv2 is the longer addresses in the protocol.

5.2.1.4.  Routing

   The hosts install a default route that points to the ER or the GWR.
   No routing protocols are needed on these devices, which generally
   have limited resources.  If there is a GWR present, it will also use
   static default route to the ER.

   The ER runs an IGP such as OSPFv3 or IS-IS.  The connected prefixes
   have to be redistributed.  If DHCP-PD is used, with every delegated
   prefix a static route is installed by the ER.  For this reason, the
   static routes must also be redistributed.  Prefix summarization
   should be done at the ER.

5.2.2.  Deploying IPv6 in a Routed CMTS Network

   In an IPv4/IPv6 routed CMTS network, the CM still acts as a Layer 2
   device and bridges all data traffic between its Ethernet interface
   and cable interface connected to the cable operator network.  The
   CMTS acts as a Layer 3 router and may also include the ER
   functionality.  The hosts and the GWR use the CMTS as their Layer 3
   next hop.

   When deploying IPv6, the CMTS/ER will need to either tunnel IPv6
   traffic or natively support IPv6.




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   There are five possible deployment scenarios for IPv6 in a routed
   CMTS network:

   1.  IPv4 Cable (HFC) Network

   In this scenario, the cable network, including the CM and CMTS,
   remain IPv4 devices.  The host and ER are upgraded to dual stack.
   This is the easiest way for a cable operator to provide IPv6 service,
   as no changes are made to the cable network.

   2.  IPv4 Cable (HFC) Network, GWR at Customer Site

   In this case, the cable network, including the CM and CMTS, remain
   IPv4 devices.  The host, GWR, and ER are upgraded to dual stack.
   This scenario is also easy to deploy since the cable operator just
   needs to add GWR at the customer site.

   3.  Dual-stacked Cable (HFC) Network, CM, and CMTS Support IPv6

   In this scenario, the CMTS is upgraded to dual stack to support IPv4
   and IPv6.  Since the CMTS supports IPv6, it can act as an ER as well.
   The CM will act as a Layer 2 bridge, but will need to bridge IPv6
   unicast and multicast traffic.  This scenario is not easy to deploy
   since it requires changes to the DOCSIS specification.  The CM and
   CMTS may require hardware and software upgrades to support IPv6.

   4.  Dual-stacked Cable (HFC) Network, Standalone GWR, and CMTS
   Support IPv6

   In this scenario there is a stand-alone GWR connected to the CM.
   Since the IPv6 functionality exists on the GWR, the CM does not need
   to be dual stack.  The CMTS is upgraded to dual stack and it can
   incorporate the ER functionality.  This scenario may also require
   hardware and software changes on the GWR and CMTS.

   5.  Dual-stacked Cable (HFC) Network, Embedded GWR/CM, and CMTS
   Support IPv6

   In this scenario, the CM and GWR functionality exists on a single
   device, which needs to be upgraded to dual stack.  The CMTS will also
   need to be upgraded to a dual-stack device.  This scenario is also
   difficult to deploy in existing cable network since it requires
   changes on the Embedded GWR/CM and the CMTS.

   The DOCSIS specification will also need to be modified to allow
   native IPv6 support on the Embedded GWR/CM.





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5.2.2.1.  IPv4 Cable Network, Host, and ER Upgraded to Dual Stack

   This is one of the most cost-effective ways for a cable operator to
   offer IPv6 services to its customers.  Since the cable network
   remains IPv4, there is relatively minimal cost involved in turning up
   IPv6 service.  All IPv6 traffic is exchanged between the hosts and
   the ER.

   Figure 5.2.2.1 illustrates this deployment scenario.


                           +-----------+   +------+   +--------+
     +-----+  +-------+    |   Cable   |   |      |   |  Edge  |
     |Host |--|  CM   |----|  (HFC)    |---| CMTS |---|        |=>ISP
     +-----+  +-------+    |  Network  |   |      |   | Router |Network
                           +-----------+   +------+   +--------+
             _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
           ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                          IPv6-in-IPv4 tunnel

     |---------||---------------------------------------||------------|
     IPv4/v6                 IPv4 only                    IPv4/v6

                              Figure 5.2.2.1

5.2.2.1.1.  IPv6 Related Infrastructure Changes

   In this scenario, the CM and the CMTS will only need to support IPv4,
   so no changes need to be made to them or the cable network.  The
   following devices have to be upgraded to dual stack: Host and ER.

5.2.2.1.2.  Addressing

   The only device that needs to be assigned an IPv6 address at the
   customer site is the host.  Host address assignment can be done in
   multiple ways.  Depending on the tunneling mechanism used, it could
   be automatic or might require manual configuration.

   The host still receives an IPv4 address using DHCPv4, which works the
   same way in currently deployed cable networks.  In order to get IPv6
   connectivity, host devices will also need an IPv6 address and a means
   to communicate with the ER.









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5.2.2.1.3.  Data Forwarding

   All IPv6 traffic will be sent to/from the ER and the host device.  In
   order to transport IPv6 packets over the cable operator IPv4 network,
   the host and the ER will need to use one of the available IPv6 in
   IPv4 tunneling mechanisms.

   The host will use its IPv4 address to source the tunnel to the ER.
   All IPv6 traffic will be forwarded to the ER, encapsulated in IPv4
   packets.  The intermediate IPv4 nodes will forward this traffic as
   regular IPv4 packets.  The ER will need to terminate the tunnel
   and/or provide other IPv6 services.

5.2.2.1.4.  Routing

   Routing configuration on the host will vary depending on the
   tunneling technique used.  In some cases, a default or static route
   might be needed to forward traffic to the next hop.

   The ER runs an IGP such as OSPFv3 or ISIS.

5.2.2.2.  IPv4 Cable Network, Host, GWR and ER Upgraded to Dual Stack

   The cable operator can provide IPv6 services to its customers, in
   this scenario, by adding a GWR behind the CM.  Since the GWR will
   facilitate all IPv6 traffic between the host and the ER, the cable
   network, including the CM and CMTS, does not need to support IPv6,
   and can remain as IPv4 devices.

   Figure 5.2.2.2 illustrates this deployment scenario.

    +-----+
    |Host |
    +--+--+
       |                   +-----------+   +------+   +--------+
   +---+---+  +-------+    |   Cable   |   |      |   |  Edge  |
   |  GWR  |--|  CM   |----|  (HFC)    |---| CMTS |---|        |=>ISP
   +-------+  +-------+    |  Network  |   |      |   | Router |Network
                           +-----------+   +------+   +--------+
             _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
           ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                          IPv6-in-IPv4 tunnel

   |---------||--------------------------------------||-------------|
     IPv4/v6                 IPv4 only                    IPv4/v6

                              Figure 5.2.2.2




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5.2.2.2.1.  IPv6 Related Infrastructure Changes

   In this scenario, the CM and the CMTS will only need to support IPv4,
   so no changes need to be made to them or the cable network.  The
   following devices have to be upgraded to dual stack: Host, GWR, and
   ER.

5.2.2.2.2.  Addressing

   The only devices that need to be assigned an IPv6 address at customer
   site are the host and GWR.  IPv6 address assignment can be done
   statically at the GWR downstream interface.  The GWR will send out RA
   messages on its downstream interface, which will be used by the hosts
   to auto-configure themselves with an IPv6 address.  The GWR can also
   configure its upstream interface using RA messages from the ER and
   use DHCP-PD for requesting a /48 [RFC3177] prefix from the ER.  This
   /48 prefix will be used to configure /64s on hosts connected to the
   GWR downstream interfaces.  The uplink to the ISP network is
   configured with a /64 prefix as well.

   The GWR still receives a global IPv4 address on its upstream
   interface using DHCPv4, which works the same way in currently
   deployed cable networks.  In order to get IPv6 connectivity to the
   Internet, the GWR will need to communicate with the ER.

5.2.2.2.3.  Data Forwarding

   All IPv6 traffic will be sent to/from the ER and the GWR, which will
   forward IPv6 traffic to/from the host.  In order to transport IPv6
   packets over the cable operator IPv4 network, the GWR and the ER will
   need to use one of the available IPv6 in IPv4 tunneling mechanisms.
   All IPv6 traffic will need to go through the tunnel, once it comes
   up.

   The GWR will use its IPv4 address to source the tunnel to the ER.
   The tunnel endpoint will be the IPv4 address of the ER.  All IPv6
   traffic will be forwarded to the ER, encapsulated in IPv4 packets.
   The intermediate IPv4 nodes will forward this traffic as regular IPv4
   packets.  In case of 6to4 tunneling, the ER will need to support 6to4
   relay functionality in order to provide IPv6 Internet connectivity to
   the GWR, and hence, the hosts connected to the GWR.

5.2.2.2.4.  Routing

   Depending on the tunneling technique used, additional configuration
   might be needed on the GWR and the ER.  If the ER is also providing a
   6to4 relay service then a default route will need to be added to the
   GWR pointing to the ER, for all non-6to4 traffic.



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   If using manual tunneling, the GWR and ER can use static routing or
   an IGP such as RIPng [RFC2080].  The RIPng updates can be transported
   over a manual tunnel, which does not work when using 6to4 tunneling
   since it does not support multicast.

   Customer routes can be carried to the ER using RIPng updates.  The ER
   can advertise these routes in its IGP.  Prefix summarization should
   be done at the ER.

   If DHCP-PD is used for address assignment, a static route is
   automatically installed on the ER for each delegated /48 prefix.  The
   static routes need to be redistributed into the IGP at the ER, so
   there is no need for a routing protocol between the ER and the GWR.

   The ER runs an IGP such as OSPFv3 or ISIS.

5.2.2.3.  Dual-Stacked Cable (HFC) Network, CM, and CMTS Support IPv6

   In this scenario the cable operator can offer native IPv6 services to
   its customers since the cable network, including the CMTS, supports
   IPv6.  The ER functionality can be included in the CMTS or it can
   exist on a separate router connected to the CMTS upstream interface.
   The CM will need to bridge IPv6 unicast and multicast traffic.

   Figure 5.2.2.3 illustrates this deployment scenario.


                           +-----------+   +-------------+
     +-----+  +-------+    |   Cable   |   | CMTS / Edge |
     |Host |--|  CM   |----|  (HFC)    |---|             |=>ISP
     +-----+  +-------+    |  Network  |   |   Router    | Network
                           +-----------+   +-------------+

     |-------||---------------------------||---------------|
      IPv4/v6              IPv4/v6              IPv4/v6

                             Figure 5.2.2.3

5.2.2.3.1.  IPv6 Related Infrastructure Changes

   Since the CM still acts as a Layer 2 bridge, it does not need to be
   dual stack.  The CM will need to support bridging of IPv6 unicast and
   multicast traffic and IGMPv3/MLDv2 or v1 snooping, which requires
   changes in the DOCSIS specification.  In this scenario, the following
   devices have to be upgraded to dual stack: Host and CMTS/ER.






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5.2.2.3.2.  Addressing

   In cable networks today, the CM receives a private IPv4 address using
   DHCPv4 for management purposes.  In an IPv6 environment, the CM will
   continue to use an IPv4 address for management purposes.  The cable
   operator can also choose to assign an IPv6 address to the CM for
   management, but the CM will have to be upgraded to support this
   functionality.

   IPv6 address assignment for the CM and host can be done via DHCP or
   stateless auto-configuration.  If the CM uses an IPv4 address for
   management, it will use DHCPv4 for its address assignment and the
   CMTS will need to act as a DHCPv4 relay agent.  If the CM uses an
   IPv6 address for management, it can use DHCPv6, with the CMTS acting
   as a DHCPv6 relay agent, or the CMTS can be statically configured
   with a /64 prefix and it can send out RA messages out the cable
   interface.  The CMs connected to the cable interface can use the RA
   messages to auto-configure themselves with an IPv6 address.  All CMs
   connected to the cable interface will be in the same subnet.

   The hosts can receive their IPv6 address via DHCPv6 or stateless
   auto-configuration.  With DHCPv6, the CMTS may need to act as a
   DHCPv6 relay agent and forward DHCP messages between the hosts and
   the DHCP server.  With stateless auto-configuration, the CMTS will be
   configured with multiple /64 prefixes and send out RA messages to the
   hosts.  If the CMTS is not also acting as an ER, the RA messages will
   come from the ER connected to the CMTS upstream interface.  The CMTS
   will need to forward the RA messages downstream or act as an ND
   proxy.

5.2.2.3.3.  Data Forwarding

   All IPv6 traffic will be sent to/from the CMTS and hosts.  Data
   forwarding will work the same way it works in currently deployed
   cable networks.  The CMTS will forward IPv6 traffic to/from hosts
   based on the IP source/destination address.

5.2.2.3.4.  Routing

   No routing protocols are needed between the CMTS and the host since
   the CM and host are directly connected to the CMTS cable interface.
   Since the CMTS supports IPv6, hosts will use the CMTS as their Layer
   3 next hop.

   If the CMTS is also acting as an ER, it runs an IGP such as OSPFv3 or
   IS-IS.





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5.2.2.4.  Dual-Stacked Cable (HFC) Network, Stand-Alone GWR, and CMTS
          Support IPv6

   In this case, the cable operator can offer IPv6 services to its
   customers by adding a GWR between the CM and the host.  The GWR will
   facilitate IPv6 communication between the host and the CMTS/ER.  The
   CMTS will be upgraded to dual stack to support IPv6 and can act as an
   ER as well.  The CM will act as a bridge for forwarding data traffic
   and does not need to support IPv6.

   This scenario is similar to the case described in Section 5.2.2.2.
   The only difference in this case is that the ER functionality exists
   on the CMTS instead of on a separate router in the cable operator
   network.

   Figure 5.2.2.4 illustrates this deployment scenario.


                                    +-----------+   +-----------+
   +------+  +-------+  +-------+   |   Cable   |   |CMTS / Edge|
   | Host |--| GWR   |--|  CM   |---|  (HFC)    |---|           |=>ISP
   +------+  +-------+  +-------+   |  Network  |   |   Router  |Network
                                    +-----------+   +-----------+
                      _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
                    ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                             IPv6-in-IPv4 tunnel
   |-----------------||-----------------------------||--------------|
         IPv4/v6                      IPv4                  IPv4/v6

                               Figure 5.2.2.4

5.2.2.4.1.  IPv6 Related Infrastructure Changes

   Since the CM still acts as a Layer 2 bridge, it does not need to be
   dual stack, nor does it need to support IPv6.  In this scenario, the
   following devices have to be upgraded to dual stack: Host, GWR, and
   CMTS/ER.

5.2.2.4.2.  Addressing

   The CM will still receive a private IPv4 address using DHCPv4, which
   works the same way in existing cable networks.  The CMTS will act as
   a DHCPv4 relay agent.

   The address assignment for the host and GWR happens in a similar
   manner as described in Section 5.2.2.2.2.





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5.2.2.4.3.  Data Forwarding

   Data forwarding between the host and CMTS/ER is facilitated by the
   GWR and happens in a similar manner as described in Section
   5.2.2.2.3.

5.2.2.4.4.  Routing

   In this case, routing is very similar to the case described in
   Section 5.2.2.2.4.  Since the CMTS now incorporates the ER
   functionality, it will need to run an IGP such as OSPFv3 or IS-IS.

5.2.2.5.  Dual-Stacked Cable (HFC) Network, Embedded GWR/CM, and CMTS
          Support IPv6

   In this scenario, the cable operator can offer native IPv6 services
   to its customers since the cable network, including the CM/Embedded
   GWR and CMTS, supports IPv6.  The ER functionality can be included in
   the CMTS or it can exist on a separate router connected to the CMTS
   upstream interface.  The CM/Embedded GWR acts as a Layer 3 device.

   Figure 5.2.2.5 illustrates this deployment scenario.


                              +-----------+   +-------------+
    +-----+   +-----------+   |   Cable   |   | CMTS / Edge |
    |Host |---| CM / GWR  |---|  (HFC)    |---|             |=>ISP
    +-----+   +-----------+   |  Network  |   |   Router    |Network
                              +-----------+   +-------------+

    |---------------------------------------------------------|
                              IPv4/v6

                          Figure 5.2.2.5

5.2.2.5.1.  IPv6 Related Infrastructure Changes

   Since the CM/GWR acts as a Layer 3 device, IPv6 can be deployed end-
   to-end.  In this scenario, the following devices have to be upgraded
   to dual stack: Host, CM/GWR, and CMTS/ER.

5.2.2.5.2.  Addressing

   Since the CM/GWR is dual stack, it can receive an IPv4 or IPv6
   address using DHCP for management purposes.  As the GWR functionality
   is embedded in the CM, it will need an IPv6 address for forwarding
   data traffic.  IPv6 address assignment for the CM/GWR and host can be
   done via DHCPv6 or DHCP-PD.



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   If using DHCPv6, the CMTS will need to act as a DHCPv6 relay agent.
   The host and CM/GWR will receive IPv6 addresses from pools of /64
   prefixes configured on the DHCPv6 server.  The CMTS will need to
   glean pertinent information from the DHCP Offer messages, sent from
   the DHCP server to the DHCP clients (host and CM/GWR), much like it
   does today in DHCPv4.  All CM/GWR connected to the same cable
   interface on the CMTS belong to the same management /64 prefix.  The
   hosts connected to the same cable interface on the CMTS may belong to
   different /64 customer prefixes, as the CMTS may have multiple /64
   prefixes configured under its cable interfaces.

   It is also possible to use DHCP-PD for an IPv6 address assignment.
   In this case, the CM/GWR will use stateless auto-configuration to
   assign an IPv6 address to its upstream interface using the /64 prefix
   sent by the CMTS/ER in an RA message.  Once the CM/GWR assigns an
   IPv6 address to its upstream interface, it will request a /48
   [RFC3177] prefix from the CMTS/ER and chop this /48 prefix into /64s
   for assigning IPv6 addresses to hosts.  The uplink to the ISP network
   is configured with a /64 prefix as well.

5.2.2.5.3.  Data Forwarding

   The host will use the CM/GWR as the Layer 3 next hop.  The CM/GWR
   will forward all IPv6 traffic to/from the CMTS/ER and hosts.  The
   CMTS/ER will forward IPv6 traffic to/from hosts based on the IP
   source/destination address.

5.2.2.5.4.  Routing

   The CM/GWR can use a static default route pointing to the CMTS/ER or
   it can run a routing protocol such as RIPng or OSPFv3 between itself
   and the CMTS.  Customer routes from behind the CM/GWR can be carried
   to the CMTS using routing updates.

   If DHCP-PD is used for address assignment, a static route is
   automatically installed on the CMTS/ER for each delegated /48 prefix.
   The static routes need to be redistributed into the IGP at the
   CMTS/ER so there is no need for a routing protocol between the
   CMTS/ER and the GWR.

   If the CMTS is also acting as an ER, it runs an IGP such as OSPFv3 or
   IS-IS.

5.2.3.  IPv6 Multicast

   In order to support IPv6 multicast applications across DOCSIS cable
   networks, the CM and bridging CMTS will need to support IGMPv3/MLDv2
   or v1 snooping.  MLD is almost identical to IGMP in IPv4, only the



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   name and numbers are changed.  MLDv2 is almost identical to IGMPv3
   and also supports ASM (Any-Source Multicast) and SSM (Source-Specific
   Multicast) service models.

   SSM is more suited for deployments where the SP intends to provide
   paid content to the users (video or audio).  These types of services
   are expected to be of primary interest.  Moreover, the simplicity of
   the SSM model often overrides the scalability issues that would be
   resolved in an ASM model.  ASM is, however, an option that is
   discussed in Section 6.3.1.  The Layer 3 CM, GWR, and Layer 3 routed
   CMTS/ER will need to be enabled with PIM-SSM, which requires the
   definition and support for IGMPv3/MLDv1 or v2 snooping, in order to
   track join/leave messages from the hosts.  Another option would be
   for the Layer 3 CM or GWR to support MLD proxy routing.  The Layer 3
   next hop for the hosts needs to support MLD.

   Refer to Section 6.3 for more IPv6 multicast details.

5.2.4.  IPv6 QoS

   IPv6 will not change or add any queuing/scheduling functionality
   already existing in DOCSIS specifications.  But the QoS mechanisms on
   the CMTS and CM would need to be IPv6 capable.  This includes support
   for IPv6 classifiers, so that data traffic to/from host devices can
   be classified appropriately into different service flows and be
   assigned appropriate priority.  Appropriate classification criteria
   would need to be implemented for unicast and multicast traffic.

   Traffic classification and marking should be done at the CM for
   upstream traffic and the CMTS/ER for downstream traffic, in order to
   support the various types of services: data, voice, and video.  The
   same IPv4 QoS concepts and methodologies should be applied for IPv6
   as well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases,
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

5.2.5.  IPv6 Security Considerations

   Security in a DOCSIS cable network is provided using Baseline Privacy
   Plus (BPI+).  The only part that is dependent on IP addresses is
   encrypted multicast.  Semantically, multicast encryption would work
   the same way in an IPv6 environment as in the IPv4 network.  However,




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   appropriate enhancements will be needed in the DOCSIS specification
   to support encrypted IPv6 multicast.

   There are limited changes that have to be done for hosts in order to
   enhance security.  The privacy extensions [RFC3041] for auto-
   configuration should be used by the hosts.  IPv6 firewall functions
   could be enabled, if available on the host or GWR.

   The ISP provides security against attacks that come from its own
   subscribers, but it could also implement security services that
   protect its subscribers from attacks sourced from the outside of its
   network.  Such services do not apply at the access level of the
   network discussed here.

   The CMTS/ER should protect the ISP network and the other subscribers
   against attacks by one of its own customers.  For this reason Unicast
   Reverse Path Forwarding (uRPF) [RFC3704] and Access Control Lists
   (ACLs) should be used on all interfaces facing subscribers.
   Filtering should be implemented with regard for the operational
   requirements of IPv6 [IPv6-Security].

   The CMTS/ER should protect its processing resources against floods of
   valid customer control traffic such as: Router and Neighbor
   Solicitations, and MLD Requests.

   All other security features used with the IPv4 service should be
   similarly applied to IPv6 as well.

5.2.6.  IPv6 Network Management

   IPv6 can have many applications in cable networks.  MSOs can
   initially implement IPv6 on the control plane and use it to manage
   the thousands of devices connected to the CMTS.  This would be a good
   way to introduce IPv6 in a cable network.  Later, the MSO can extend
   IPv6 to the data plane and use it to carry customer traffic as well
   as management traffic.

5.2.6.1.  Using IPv6 for Management in Cable Networks

   IPv6 can be enabled in a cable network for management of devices like
   CM, CMTS, and ER.  With the rollout of advanced services like VoIP
   and Video-over-IP, MSOs are looking for ways to manage the large
   number of devices connected to the CMTS.  In IPv4, an RFC1918 address
   is assigned to these devices for management purposes.  Since there is
   a finite number of RFC1918 addresses available, it is becoming
   difficult for MSOs to manage these devices.





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   By using IPv6 for management purposes, MSOs can scale their network
   management systems to meet their needs.  The CMTS/ER can be
   configured with a /64 management prefix that is shared among all CMs
   connected to the CMTS cable interface.  Addressing for the CMs can be
   done via stateless auto-configuration or DHCPv6.  Once the CMs
   receive a /64 prefix, they can configure themselves with an IPv6
   address.

   If there are devices behind the CM that need to be managed by the
   MSO, another /64 prefix can be defined on the CMTS/ER.  These devices
   can also use stateless auto-configuration to assign themselves an
   IPv6 address.

   Traffic sourced from or destined to the management prefix should not
   cross the MSO's network boundaries.

   In this scenario, IPv6 will only be used for managing devices on the
   cable network.  The CM will no longer require an IPv4 address for
   management as described in DOCSIS 3.0 [DOCSIS3.0-Reqs].

5.2.6.2.  Updates to MIB Modules/Standards to Support IPv6

   The current DOCSIS, PacketCable, and CableHome MIB modules are
   already designed to support IPv6 objects.  In this case, IPv6 will
   neither add nor change any of the functionality of these MIB modules.
   The Textual Convention used to represent Structure of Management
   Information Version 2 (SMIv2) objects representing IP addresses was
   updated [RFC4001] and a new Textual Convention InetAddressType was
   added to identify the type of the IP address used for IP address
   objects in MIB modules.

   There are some exceptions; the MIB modules that might need to add
   IPv6 support are defined in the DOCSIS 3.0 OSSI specification
   [DOCSIS3.0-OSSI].

6.  Broadband DSL Networks

   This section describes the IPv6 deployment options in today's high-
   speed DSL networks.

6.1.  DSL Network Elements

   Digital Subscriber Line (DSL) broadband services provide users with
   IP connectivity over the existing twisted-pair telephone lines called
   the local-loop.  A wide range of bandwidth offerings are available
   depending on the quality of the line and the distance between the
   Customer Premise Equipment and the DSL Access Multiplexer (DSLAM).




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   The following network elements are typical of a DSL network:

   DSL Modem: It can be a stand-alone device, be incorporated in the
   host, incorporate router functionalities, and also have the
   capability to act as a CPE router.

   Customer Premise Router (CPR): It is used to provide Layer 3 services
   for customer premise networks.  It is usually used to provide
   firewalling functions and segment broadcast domains for a small
   business.

   DSL Access Multiplexer (DSLAM): It terminates multiple twisted-pair
   telephone lines and provides aggregation to BRAS.

   Broadband Remote Access Server (BRAS): It aggregates or terminates
   multiple Permanent Virtual Circuits (PVCs) corresponding to the
   subscriber DSL circuits.

   Edge Router (ER): It provides the Layer 3 interface to the ISP
   network.

   Figure 6.1 depicts all the network elements mentioned.



   Customer Premise | Network Access Provider | Network Service Provider
          CP                     NAP                        NSP
   +-----+  +------+                +------+   +--------+
   |Hosts|--|Router|             +--+ BRAS +---+ Edge   |      ISP
   +-----+  +--+---+             |  |      |   | Router +==> Network
               |                 |  +------+   +--------+
            +--+---+             |
            | DSL  +-+           |
            |Modem | |           |
            +------+ |  +-----+  |
                     +--+     |  |
            +------+    |DSLAM+--+
   +-----+  | DSL  | +--+     |
   |Hosts|--+Modem +-+  +-----+
   +-----+  +--+---+

                                   Figure 6.1









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6.2.  Deploying IPv6 in IPv4 DSL Networks

   There are three main design approaches to providing IPv4 connectivity
   over a DSL infrastructure:

   1.  Point-to-Point Model: Each subscriber connects to the DSLAM over
       a twisted pair and is provided with a unique PVC that links it to
       the service provider.  The PVCs can be terminated at the BRAS or
       at the Edge Router.  This type of design is not very scalable if
       the PVCs are not terminated as close as possible to the DSLAM (at
       the BRAS).  In this case, a large number of Layer 2 circuits has
       to be maintained over a significant portion of the network.  The
       Layer 2 domains can be terminated at the ER in three ways:

       A.  In a common bridge group with a virtual interface that routes
           traffic out.

       B.  By enabling a Routed Bridged Encapsulation feature, all users
           could be part of the same subnet.  This is the most common
           deployment approach of IPv4 over DSL but it might not be the
           best choice in IPv6 where address availability is not an
           issue.

       C.  By terminating the PVC at Layer 3, each PVC has its own
           prefix.  This is the approach that seems more suitable for
           IPv6 and is presented in Section 6.2.1.

           None of these ways requires that the CPE (DSL modem) be
           upgraded.

   2.  PPP Terminated Aggregation (PTA) Model: PPP sessions are opened
       between each subscriber and the BRAS.  The BRAS terminates the
       PPP sessions and provides Layer 3 connectivity between the
       subscriber and the ISP.  This model is presented in Section
       6.2.2.

   3.  Layer 2 Tunneling Protocol (L2TP) Access Aggregation (LAA) Model:
       PPP sessions are opened between each subscriber and the ISP Edge
       Router.  The BRAS tunnels the subscriber PPP sessions to the ISP
       by encapsulating them into L2TPv2 [RFC2661] tunnels.  This model
       is presented in Section 6.2.3.

   In aggregation models, the BRAS terminates the subscriber PVCs and
   aggregates their connections before providing access to the ISP.

   In order to maintain the deployment concepts and business models
   proven and used with existing revenue generating IPv4 services, the
   IPv6 deployment will match the IPv4 one.  This approach is presented



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   in Sections 6.2.1 - 6.2.3 that describe current IPv4 over DSL
   broadband access deployments.  Under certain circumstances where new
   service types or service needs justify it, IPv4 and IPv6 network
   logical architectures could be different as described in Section
   6.2.4.

6.2.1.  Point-to-Point Model

   In this scenario, the Ethernet frames from the Host or the Customer
   Premise Router are bridged over the PVC assigned to the subscriber.

   Figure 6.2.1 describes the protocol architecture of this model.


        Customer Premise               NAP                 NSP
   |-------------------------|  |---------------| |------------------|
   +-----+  +-------+  +-----+  +--------+        +----------+
   |Hosts|--+Router +--+ DSL +--+ DSLAM  +--------+   Edge   |     ISP
   +-----+  +-------+  |Modem|  +--------+        |  Router  +=>Network
                       +-----+                    +----------+
                           |----------------------------|
                                      ATM

                                  Figure 6.2.1

6.2.1.1.  IPv6 Related Infrastructure Changes

   In this scenario, the DSL modem and the entire NAP is Layer 3
   unaware, so no changes are needed to support IPv6.  The following
   devices have to be upgraded to dual stack: Host, Customer Router (if
   present), and Edge Router.

6.2.1.2.  Addressing

   The Hosts or the Customer Routers have the Edge Router as their Layer
   3 next hop.

   If there is no Customer Router, all the hosts on the subscriber site
   belong to the same /64 subnet that is statically configured on the
   Edge Router for that subscriber PVC.  The hosts can use stateless
   auto-configuration or stateful DHCPv6-based configuration to acquire
   an address via the Edge Router.

   However, as manual configuration for each customer is a provisioning
   challenge, implementers are encouraged to develop mechanism(s) that
   automatically map the PVC (or some other customer-specific
   information) to an IPv6 subnet prefix, and advertise the customer-
   specific prefix to all the customers with minimal configuration.



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   If a Customer Router is present:

   A.  It is statically configured with an address on the /64 subnet
       between itself and the Edge Router, and with /64 prefixes on the
       interfaces connecting the hosts on the customer site.  This is
       not a desired provisioning method being expensive and difficult
       to manage.

   B.  It can use its link-local address to communicate with the ER.  It
       can also dynamically acquire, through stateless auto-
       configuration, the prefix for the link between itself and the ER.
       The later option allows it to contact a remote DHCPv6 server, if
       needed.  This step is followed by a request via DHCP-PD for a
       prefix shorter than /64 that, in turn, is divided in /64s and
       assigned to its downstream interfaces.

   The Edge Router has a /64 prefix configured for each subscriber PVC.
   Each PVC should be enabled to relay DHCPv6 requests from the
   subscribers to DHCPv6 servers in the ISP network.  The PVCs providing
   access for subscribers that use DHCP-PD as well, have to be enabled
   to support the feature.  The uplink to the ISP network is configured
   with a /64 prefix as well.

   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows as much
   summarization as possible at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful DHCPv6 [RFC3315] and stateless DHCPv6 [RFC3736].

6.2.1.3.  Routing

   The CPE devices are configured with a default route that points to
   the Edge Router.  No routing protocols are needed on these devices,
   which generally have limited resources.

   The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
   The connected prefixes have to be redistributed.  If DHCP-PD is used,
   with every delegated prefix a static route is installed by the Edge
   Router.  For this reason, the static routes must also be
   redistributed.  Prefix summarization should be done at the Edge
   Router.

6.2.2.  PPP Terminated Aggregation (PTA) Model

   The PTA architecture relies on PPP-based protocols (PPPoA [RFC2364]
   and PPPoE [RFC2516]).  The PPP sessions are initiated by Customer
   Premise Equipment and are terminated at the BRAS.  The BRAS



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   authorizes the session, authenticates the subscriber, and provides an
   IP address on behalf of the ISP.  The BRAS then does Layer 3 routing
   of the subscriber traffic to the NSP Edge Router.

   When the NSP is also the NAP, the BRAS and NSP Edge Router could be
   the same piece of equipment and provide the above mentioned
   functionality.

   There are two types of PPP encapsulations that can be leveraged with
   this model:

   A. Connection using PPPoA

     Customer Premise               NAP                   NSP
   |--------------------| |----------------------| |----------------|
                                                   +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----------+
   +-----+  +-------+      +--------+ +----+-----+ +-----------+
   |Hosts|--+Router +------+ DSLAM  +-+   BRAS   +-+    Edge   |
   +-----+  +-------+      +--------+ +----------+ |   Router  +=>Core
                |--------------------------|       +-----------+
                             PPP

                              Figure 6.2.2.1

   The PPP sessions are initiated by the Customer Premise Equipment.
   The BRAS authenticates the subscriber against a local or a remote
   database.  Once the session is established, the BRAS provides an
   address and maybe a DNS server to the user; this information is
   acquired from the subscriber profile or from a DHCP server.

   This solution scales better then the Point-to-Point, but since there
   is only one PPP session per ATM PVC, the subscriber can choose a
   single ISP service at a time.














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   B. Connection using PPPoE

          Customer Premise               NAP                 NSP
   |--------------------------| |-------------------| |---------------|
                                                         +-----------+
                                                         |    AAA    |
                                                 +-------+   Radius  |
                                                 |       |   TACACS  |
                                                 |       +-----------+
                                                 |
   +-----+  +-------+           +--------+ +-----+----+ +-----------+
   |Hosts|--+Router +-----------+ DSLAM  +-+   BRAS   +-+    Edge   |  C
   +-----+  +-------+           +--------+ +----------+ |   Router  +=>O
                                                        |           |  R
               |--------------------------------|       +-----------+  E
                              PPP

                                Figure 6.2.2.2

   The operation of PPPoE is similar to PPPoA with the exception that
   with PPPoE multiple sessions can be supported over the same PVC, thus
   allowing the subscriber to connect to multiple services at the same
   time.  The hosts can initiate the PPPoE sessions as well.  It is
   important to remember that the PPPoE encapsulation reduces the IP MTU
   available for the customer traffic due to additional headers.

   The network design and operation of the PTA model is the same,
   regardless of the PPP encapsulation type used.

6.2.2.1.  IPv6 Related Infrastructure Changes

   In this scenario the BRAS is Layer 3 aware and it has to be upgraded
   to support IPv6.  Since the BRAS terminates the PPP sessions it has
   to support the implementation of these PPP protocols with IPv6.  The
   following devices have to be upgraded to dual stack: Host, Customer
   Router (if present), BRAS, and Edge Router.

6.2.2.2.  Addressing

   The BRAS terminates the PPP sessions and provides the subscriber with
   an IPv6 address from the defined pool for that profile.  The
   subscriber profile for authorization and authentication can be
   located on the BRAS or on an Authentication, Authorization, and
   Accounting (AAA) server.  The Hosts or the Customer Routers have the
   BRAS as their Layer 3 next hop.






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   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the BRAS and
   an address is negotiated for the uplink to the BRAS, DHCP-PD can be
   used to acquire prefixes for the Customer Router other interfaces.

   The BRAS has to be enabled to support DHCP-PD and to relay the DHCPv6
   requests of the hosts on the subscriber sites.

   The BRAS has /64 prefixes configured on the link to the Edge router.
   The Edge Router links are also configured with /64 prefixes to
   provide connectivity to the rest of the ISP network.

   The prefixes used for subscribers and the ones delegated via DHCP-PD
   should be planned in a manner that allows maximum summarization at
   the BRAS.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

6.2.2.3.  Routing

   The CPE devices are configured with a default route that points to
   the BRAS router.  No routing protocols are needed on these devices,
   which generally have limited resources.

   The BRAS runs an IGP to the Edge Router: OSPFv3 or IS-IS.  Since the
   addresses assigned to the PPP sessions are represented as connected
   host routes, connected prefixes have to be redistributed.  If DHCP-PD
   is used, with every delegated prefix a static route is installed by
   the Edge Router.  For this reason, the static routes must also be
   redistributed.  Prefix summarization should be done at the BRAS.

   The Edge Router is running the IGP used in the ISP network: OSPFv3 or
   IS-IS.

   A separation between the routing domains of the ISP and the Access
   Provider is recommended if they are managed independently.
   Controlled redistribution will be needed between the Access Provider
   IGP and the ISP IGP.

6.2.3.  L2TPv2 Access Aggregation (LAA) Model

   In the LAA model, the BRAS forwards the CPE initiated session to the
   ISP over an L2TPv2 tunnel established between the BRAS and the Edge
   Router.  In this case, the authentication, authorization, and
   subscriber configuration are performed by the ISP itself.  There are
   two types of PPP encapsulations that can be leveraged with this
   model:



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   A. Connection via PPPoA

     Customer Premise              NAP                    NSP
   |--------------------| |----------------------| |----------------|
                                                   +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
                |----------------------------------------|
                                   PPP
                                            |------------|
                                                 L2TPv2

                           Figure 6.2.3.1

   B. Connection via PPPoE

         Customer Premise                NAP                   NSP
   |--------------------------| |--------------------| |---------------|
                                                        +-----------+
                                                        |    AAA    |
                                                 +------+   Radius  |
                                                 |      |   TACACS  |
                                                 |      +-----+-----+
                                                 |            |
   +-----+  +-------+           +--------+ +----+-----+ +----+------+
   |Hosts|--+Router +-----------+ DSLAM  +-+  BRAS    +-+    Edge   |  C
   +-----+  +-------+           +--------+ +----------+ |   Router  +=>O
                                                        |           |  R
                                                        +-----------+  E
               |-----------------------------------------------|
                                       PPP
                                                |--------------|
                                                      L2TPv2

                             Figure 6.2.3.2

   The network design and operation of the PTA model is the same,
   regardless of the PPP encapsulation type used.






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6.2.3.1.  IPv6 Related Infrastructure Changes

   In this scenario, the BRAS is forwarding the PPP sessions initiated
   by the subscriber over the L2TPv2 tunnel established to the L2TP
   Network Server (LNS), the aggregation point in the ISP network.  The
   L2TPv2 tunnel between the L2TP Access Concentrator (LAC) and LNS can
   run over IPv6 or IPv4.  These capabilities have to be supported on
   the BRAS.  The following devices have to be upgraded to dual stack:
   Host, Customer Router, and Edge Router.  If the tunnel is set up over
   IPv6, then the BRAS must be upgraded to dual stack.

6.2.3.2.  Addressing

   The Edge Router terminates the PPP sessions and provides the
   subscriber with an IPv6 address from the defined pool for that
   profile.  The subscriber profile for authorization and authentication
   can be located on the Edge Router or on an AAA server.  The Hosts or
   the Customer Routers have the Edge Router as their Layer 3 next hop.

   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the Edge
   Router, DHCP-PD can be used to acquire prefixes for the Customer
   Router interfaces.  The Edge Router has to be enabled to support
   DHCP-PD and to relay the DHCPv6 requests generated by the hosts on
   the subscriber sites.

   The BRAS has a /64 prefix configured on the link to the Edge Router.
   The Edge Router links are also configured with /64 prefixes to
   provide connectivity to the rest of the ISP network.  Other
   information of interest to the host, such as DNS, is provided through
   stateful [RFC3315] and stateless [RFC3736] DHCPv6.

   It is important to note here a significant difference between this
   deployment for IPv6 versus IPv4.  In the case of IPv4, the customer
   router or CPE can end up on any Edge Router (acting as LNS), where
   the assumption is that there are at least two of them for redundancy
   purposes.  Once authenticated, the customer will be given an address
   from the IP pool of the ER (LNS) it connected to.  This allows the
   ERs (LNSs) to aggregate the addresses handed out to the customers.
   In the case of IPv6, an important constraint that likely will be
   enforced is that the customer should keep its own address, regardless
   of the ER (LNS) it connects to.  This could significantly reduce the
   prefix aggregation capabilities of the ER (LNS).  This is different
   than the current IPv4 deployment where addressing is dynamic in
   nature, and the same user can get different addresses depending on
   the LNS it ends up connecting to.





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   One possible solution is to ensure that a given BRAS will always
   connect to the same ER (LNS) unless that LNS is down.  This means
   that customers from a given prefix range will always be connected to
   the same ER (primary, if up, or secondary, if not).  Each ER (LNS)
   can carry summary statements in their routing protocol configuration
   for the prefixes for which they are the primary ER (LNS), as well as
   for the ones for which they are the secondary.  This way the prefixes
   will be summarized any time they become "active" on the ER (LNS).

6.2.3.3.  Routing

   The CPE devices are configured with a default route that points to
   the Edge Router that terminates the PPP sessions.  No routing
   protocols are needed on these devices, which generally have limited
   resources.

   The BRAS runs an IPv6 IGP to the Edge Router: OSPFv3 or IS-IS.
   Different processes should be used if the NAP and the NSP are managed
   by different organizations.  In this case, controlled redistribution
   should be enabled between the two domains.

   The Edge Router is running the IPv6 IGP used in the ISP network:
   OSPFv3 or IS-IS.

6.2.4.  Hybrid Model for IPv4 and IPv6 Service

   It was recommended throughout this section that the IPv6 service
   implementation should map the existing IPv4 one.  This approach
   simplifies manageability and minimizes training needed for personnel
   operating the network.  In certain circumstances such mapping is not
   feasible.  This typically becomes the case when a Service Provider
   plans to expand its service offering with the new IPv6 deployed
   infrastructure.  If this new service is not well supported in a
   network design such as the one used for IPv4, then a different design
   might be used for IPv6.

   An example of such circumstances is that of a provider using an LAA
   design for its IPv4 services.  In this case all the PPP sessions are
   bundled and tunneled across the entire NAP infrastructure which is
   made of multiple BRAS routers, aggregation routers etc.  The end
   point of these tunnels is the ISP Edge Router.  If the provider
   decides to offer multicast services over such a design, it will face
   the problem of NAP resources being over utilized.  The multicast
   traffic can be replicated only at the end of the tunnels by the Edge
   Router and the copies for all the subscribers are carried over the
   entire NAP.





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   A Modified Point-to-Point (as described in Section 6.2.4.2) or PTA
   model is more suitable to support multicast services because the
   packet replication can be done closer to the destination at the BRAS.
   Such topology saves NAP resources.

   In this sense, IPv6 deployment can be viewed as an opportunity to
   build an infrastructure that might better support the expansion of
   services.  In this case, an SP using the LAA design for its IPv4
   services might choose a modified Point-to-Point or PTA design for
   IPv6.

6.2.4.1.  IPv4 in LAA Model and IPv6 in PTA Model

   The coexistence of the two PPP-based models, PTA and LAA, is
   relatively straightforward.  The PPP sessions are terminated on
   different network devices for the IPv4 and IPv6 services.  The PPP
   sessions for the existing IPv4 service deployed in an LAA model are
   terminated on the Edge Router.  The PPP sessions for the new IPv6
   service deployed in a PTA model are terminated on the BRAS.

   The logical design for IPv6 and IPv4 in this hybrid model is
   presented in Figure 6.2.4.1.

   IPv6          |--------------------------|
                            PPP                    +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
   IPv4          |----------------------------------------|
                                   PPP
                                            |------------|
                                                 L2TPv2

                             Figure 6.2.4.1

6.2.4.2.  IPv4 in LAA Model and IPv6 in Modified Point-to-Point Model

   In this particular scenario the Point-to-Point model used for the
   IPv6 service is a modified version of the model described in section
   6.2.1.





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   For the IPv4 service in the LAA model, the PVCs are terminated on the
   BRAS and PPP sessions are terminated on the Edge Router (LNS).  For
   IPv6 service in the Point-to-Point model, the PVCs are terminated at
   the Edge Router as described in Section 6.2.1.  In this hybrid model,
   the Point-to-Point link could be terminated on the BRAS, a NAP-owned
   device.  The IPv6 traffic is then routed through the NAP network to
   the NSP.  In order to have this hybrid model, the BRAS has to be
   upgraded to a dual-stack router.  The functionalities of the Edge
   Router, as described in Section 6.2.1, are now implemented on the
   BRAS.

   The other aspect of this deployment model is the fact that the BRAS
   has to be capable of distinguishing between the IPv4 PPP traffic that
   has to be bridged across the L2TPv2 tunnel and the IPv6 packets that
   have to be routed to the NSP.  The IPv6 Routing and Bridging
   Encapsulation (RBE) has to be enabled on all interfaces with PVCs
   supporting both IPv4 and IPv6 services in this hybrid design.

   The logical design for IPv6 and IPv4 in this hybrid model is
   presented in Figure 6.2.4.2.

   IPv6              |----------------|
                            ATM                    +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
   IPv4          |----------------------------------------|
                                   PPP
                                            |------------|
                                                 L2TPv2

                             Figure 6.2.4.2

6.3.  IPv6 Multicast

   The deployment of IPv6 multicast services relies on MLD, identical to
   IGMP in IPv4 and on PIM for routing.  ASM (Any Source Multicast) and
   SSM (Single Source Multicast) service models operate almost the same
   as in IPv4.  Both have the same benefits and disadvantages as in
   IPv4.  Nevertheless, the larger address space and the scoped address
   architecture provide major benefits for multicast IPv6.  Through RFC
   3306, the large address space provides the means to assign global



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   multicast group addresses to organizations or users that were
   assigned unicast prefixes.  It is a significant improvement with
   respect to the IPv4 GLOP mechanism [RFC3180].

   This facilitates the deployment of multicast services.  The
   discussion of this section applies to all the multicast sections in
   the document.

6.3.1.  ASM-Based Deployments

   Any Source Multicast (ASM) is useful for Service Providers that
   intend to support the forwarding of multicast traffic of their
   customers.  It is based on the Protocol Independent Multicast -
   Sparse Mode (PIM-SM) protocol and it is more complex to manage
   because of the use of Rendezvous Points (RPs).  With IPv6, static RP
   and Bootstrap Router [BSR] can be used for RP-to-group mapping
   similar to IPv4.  Additionally, the larger IPv6 address space allows
   for building up of group addresses that incorporate the address of
   the RP.  This RP-to-group mapping mechanism is called Embedded RP and
   is specific to IPv6.

   In inter-domain deployments, Multicast Source Discovery Protocol
   (MSDP) [RFC3618] is an important element of IPv4 PIM-SM deployments.
   MSDP is meant to be a solution for the exchange of source
   registration information between RPs in different domains.  This
   solution was intended to be temporary.  This is one of the reasons
   why it was decided not to implement MSDP in IPv6 [IPv6-Multicast].

   For multicast reachability across domains, Embedded RP can be used.
   As Embedded RP provides roughly the same capabilities as MSDP, but in
   a slightly different way, the best management practices for ASM
   multicast with embedded RP still remain to be developed.

6.3.2.  SSM-Based Deployments

   Based on PIM-SSM, the Source-Specific Multicast deployments do not
   need an RP or related protocols (such as BSR or MSDP), but rely on
   the listeners to know the source of the multicast traffic they plan
   to receive.  The lack of RP makes SSM not only simpler to operate,
   but also robust; it is not impacted by RP failures or inter-domain
   constraints.  It also has a higher level of security (no RP to be
   targeted by attacks).  For more discussions on the topic of IPv6
   multicast, see [IPv6-Multicast].

   The typical multicast service offered for residential and very small
   businesses is video/audio streaming, where the subscriber joins a
   multicast group and receives the content.  This type of service model
   is well supported through PIM-SSM which is very simple and easy to



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   manage.  PIM-SSM has to be enabled throughout the SP network.  MLDv2
   is required for PIM-SSM support.  Vendors can choose to implement
   features that allow routers to map MLDv1 group joins to predefined
   sources.

   Subscribers might use a set-top box that is responsible for the
   control piece of the multicast service (does group joins/leaves).
   The subscriber hosts can also join desired multicast groups as long
   as they are enabled to support MLDv1 or MLDv2.  If a customer premise
   router is used, then it has to be enabled to support MLDv1 and MLDv2
   in order to process the requests of the hosts.  It has to be enabled
   to support PIM-SSM in order to send PIM joins/leaves up to its Layer
   3 next hop whether it is the BRAS or the Edge Router.  When enabling
   this functionality on a CPR, its limited resources should be taken
   into consideration.  Another option would be for the CPR to support
   MLD proxy routing.

   The router that is the Layer 3 next hop for the subscriber (BRAS in
   the PTA model or the Edge Router in the LAA and Point-to-Point model)
   has to be enabled to support MLDv1 and MLDv2 in order to process the
   requests coming from subscribers without CPRs.  It has to be enabled
   for PIM-SSM in order to receive joins/leaves from customer routers
   and send joins/leaves to the next hop towards the multicast source
   (Edge Router or the NSP core).

   MLD authentication, authorization and accounting are usually
   configured on the Edge Router in order to enable the ISP to control
   the subscriber access of the service and do billing for the content
   provided.  Alternative mechanisms that would support these functions
   should be investigated further.

6.4.  IPv6 QoS

   The QoS configuration is particularly relevant on the router that
   represents the Layer 3 next hop for the subscriber (BRAS in the PTA
   model or the Edge Router in the LAA and Point-to-Point model) in
   order to manage resources shared amongst multiple subscribers,
   possibly with various service level agreements.

   In the DSL infrastructure, it is expected that there is already a
   level of traffic policing and shaping implemented for IPv4
   connectivity.  This is implemented throughout the NAP and is beyond
   the scope of this document.

   On the BRAS or the Edge Router, the subscriber-facing interfaces have
   to be configured to police the inbound customer traffic and shape the
   traffic outbound to the customer based on the service level
   agreements (SLAs).  Traffic classification and marking should also be



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   done on the router closest (at Layer 3) to the subscriber in order to
   support the various types of customer traffic (data, voice, and
   video) and to optimally use the infrastructure resources.  Each
   provider (NAP, NSP) could implement their own QoS policies and
   services so that reclassification and marking might be performed at
   the boundary between the NAP and the NSP, in order to make sure the
   traffic is properly handled by the ISP.  The same IPv4 QoS concepts
   and methodologies should be applied with IPv6 as well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases,
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

6.5.  IPv6 Security Considerations

   There are limited changes that have to be done for CPEs in order to
   enhance security.  The privacy extensions for auto-configuration
   [RFC3041] should be used by the hosts.  ISPs can track the prefixes
   it assigns to subscribers relatively easily.  If, however, the ISPs
   are required by regulations to track their users at a /128 address
   level, the privacy extensions may be implemented in parallel with
   network management tools that could provide traceability of the
   hosts.  IPv6 firewall functions should be enabled on the hosts or
   CPR, if present.

   The ISP provides security against attacks that come from its own
   subscribers but it could also implement security services that
   protect its subscribers from attacks sourced from the outside of its
   network.  Such services do not apply at the access level of the
   network discussed here.

   The device that is the Layer 3 next hop for the subscribers (BRAS or
   Edge Router) should protect the network and the other subscribers
   against attacks by one of the provider customers.  For this reason,
   uRPF and ACLs should be used on all interfaces facing subscribers.
   Filtering should be implemented with regard for the operational
   requirements of IPv6 [IPv6-Security].

   The BRAS and the Edge Router should protect their processing
   resources against floods of valid customer control traffic such as:
   Router and Neighbor Solicitations, and MLD Requests.  Rate limiting
   should be implemented on all subscriber-facing interfaces.  The
   emphasis should be placed on multicast-type traffic, as it is most
   often used by the IPv6 control plane.




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   All other security features used with the IPv4 service should be
   similarly applied to IPv6 as well.

6.6.  IPv6 Network Management

   The necessary instrumentation (such as MIB modules, NetFlow Records,
   etc.) should be available for IPv6.

   Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
   can be done over IPv4 if all managed devices have connectivity over
   both IPv4 and IPv6.  This would imply the smallest changes to the
   existing network management practices and processes.  Transport over
   IPv6 could also be implemented, and it might become necessary if IPv6
   only islands are present in the network.  The management applications
   may be running on hosts belonging to the NSP core network domain.
   Network Management Applications should handle IPv6 in a similar
   fashion to IPv4; however, they should also support features specific
   to IPv6 (such as neighbor monitoring).

   In some cases, service providers manage equipment located on
   customers' LANs.  The management of equipment at customers' LANs is
   out of scope of this memo.

7.  Broadband Ethernet Networks

   This section describes the IPv6 deployment options in currently
   deployed Broadband Ethernet Access Networks.

7.1.  Ethernet Access Network Elements

   In environments that support the infrastructure deploying RJ-45 or
   fiber (Fiber to the Home (FTTH) service) to subscribers, 10/100 Mbps
   Ethernet broadband services can be provided.  Such services are
   generally available in metropolitan areas in multi-tenant buildings
   where an Ethernet infrastructure can be deployed in a cost-effective
   manner.  In such environments, Metro-Ethernet services can be used to
   provide aggregation and uplink to a Service Provider.

   The following network elements are typical of an Ethernet network:

   Access Switch: It is used as a Layer 2 access device for subscribers.

   Customer Premise Router: It is used to provide Layer 3 services for
   customer premise networks.

   Aggregation Ethernet Switches: Aggregates multiple subscribers.

   Broadband Remote Access Server (BRAS)



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   Edge Router (ER)

   Figure 7.1 depicts all the network elements mentioned.

   Customer Premise | Network Access Provider | Network Service Provider
          CP                     NAP                        NSP


   +-----+  +------+                +------+  +--------+
   |Hosts|--|Router|              +-+ BRAS +--+ Edge   |       ISP
   +-----+  +--+---+              | |      |  | Router +===> Network
               |                  | +------+  +--------+
            +--+----+             |
            |Access +-+           |
            |Switch | |           |
            +-------+ |  +------+ |
                      +--+Agg E | |
            +-------+    |Switch+-+
   +-----+  |Access | +--+      |
   |Hosts|--+Switch +-+  +------+
   +-----+  +-------+

                                  Figure 7.1

   The logical topology and design of Broadband Ethernet Networks are
   very similar to DSL Broadband Networks discussed in Section 6.

   It is worth noting that the general operation, concepts and
   recommendations described in this section apply similarly to a
   HomePNA-based network environment.  In such an environment, some of
   the network elements might be differently named.

7.2.  Deploying IPv6 in IPv4 Broadband Ethernet Networks

   There are three main design approaches to providing IPv4 connectivity
   over an Ethernet infrastructure:

   A.  Point-to-Point Model: Each subscriber connects to the network
       Access switch over RJ-45 or fiber links.  Each subscriber is
       assigned a unique VLAN on the access switch.  The VLAN can be
       terminated at the BRAS or at the Edge Router.  The VLANs are
       802.1Q trunked to the Layer 3 device (BRAS or Edge Router).

       This model is presented in Section 7.2.1.







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   B.  PPP Terminated Aggregation (PTA) Model: PPP sessions are opened
       between each subscriber and the BRAS.  The BRAS terminates the
       PPP sessions and provides Layer 3 connectivity between the
       subscriber and the ISP.

       This model is presented in Section 7.2.2.

   C.  L2TPv2 Access Aggregation (LAA) Model: PPP sessions are opened
       between each subscriber and the ISP termination devices.  The
       BRAS tunnels the subscriber PPP sessions to the ISP by
       encapsulating them into L2TPv2 tunnels.

       This model is presented in Section 7.2.3.

   In aggregation models the BRAS terminates the subscriber VLANs and
   aggregates their connections before providing access to the ISP.

   In order to maintain the deployment concepts and business models
   proven and used with existing revenue generating IPv4 services, the
   IPv6 deployment will match the IPv4 one.  This approach is presented
   in Sections 7.2.1 - 7.2.3 that describe currently deployed IPv4 over
   Ethernet broadband access deployments.  Under certain circumstances
   where new service types or service needs justify it, IPv4 and IPv6
   network architectures could be different as described in Section
   7.2.4.

7.2.1.  Point-to-Point Model

   In this scenario, the Ethernet frames from the Host or the Customer
   Premise Router are bridged over the VLAN assigned to the subscriber.

   Figure 7.2.1 describes the protocol architecture of this model.

   |   Customer Premise     |  |       NAP       |        NSP         |

   +-----+  +------+  +------+  +--------+        +----------+
   |Hosts|--+Router+--+Access+--+ Switch +--------+   Edge   |    ISP
   +-----+  +------+  |Switch|  +--------+ 802.1Q |  Router  +=>Network
                      +------+                    +----------+

                          |----------------------------|
                                  Ethernet/VLANs

                                 Figure 7.2.1







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7.2.1.1.  IPv6 Related Infrastructure Changes

   In this scenario, the Access Switch is on the customer site and the
   entire NAP is Layer 3 unaware, so no changes are needed to support
   IPv6.  The following devices have to be upgraded to dual stack: Host,
   Customer Router, and Edge Router.

   The Access switches might need upgrades to support certain IPv6-
   related features such as MLD Snooping.

7.2.1.2.  Addressing

   The Hosts or the Customer Routers have the Edge Router as their Layer
   3 next hop.  If there is no Customer Router all the hosts on the
   subscriber site belong to the same /64 subnet that is statically
   configured on the Edge Router for that subscriber VLAN.  The hosts
   can use stateless auto-configuration or stateful DHCPv6-based
   configuration to acquire an address via the Edge Router.

   However, as manual configuration for each customer is a provisioning
   challenge, implementations are encouraged to develop mechanism(s)
   that automatically map the VLAN (or some other customer-specific
   information) to an IPv6 subnet prefix, and advertise the customer-
   specific prefix to all the customers with minimal configuration.

   If a Customer Router is present:

   A.  It is statically configured with an address on the /64 subnet
       between itself and the Edge Router, and with /64 prefixes on the
       interfaces connecting the hosts on the customer site.  This is
       not a desired provisioning method, being expensive and difficult
       to manage.

   B.  It can use its link-local address to communicate with the ER.  It
       can also dynamically acquire, through stateless auto-
       configuration, the address for the link between itself and the
       ER.  This step is followed by a request via DHCP-PD for a prefix
       shorter than /64 that in turn is divided in /64s and assigned to
       its interfaces connecting the hosts on the customer site.

   The Edge Router has a /64 prefix configured for each subscriber VLAN.
   Each VLAN should be enabled to relay DHCPv6 requests from the
   subscribers to DHCPv6 servers in the ISP network.  The VLANs
   providing access for subscribers that use DHCP-PD have to be enabled
   to support the feature.  The uplink to the ISP network is configured
   with a /64 prefix as well.





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   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows as much
   summarization as possible at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

7.2.1.3.  Routing

   The CPE devices are configured with a default route that points to
   the Edge Router.  No routing protocols are needed on these devices,
   which generally have limited resources.

   The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
   The connected prefixes have to be redistributed.  If DHCP-PD is used,
   with every delegated prefix a static route is installed by the Edge
   Router.  For this reason, the static routes must also be
   redistributed.  Prefix summarization should be done at the Edge
   Router.

7.2.2.  PPP Terminated Aggregation (PTA) Model

   The PTA architecture relies on PPP-based protocols (PPPoE).  The PPP
   sessions are initiated by Customer Premise Equipment and are
   terminated at the BRAS.  The BRAS authorizes the session,
   authenticates the subscriber, and provides an IP address on behalf of
   the ISP.  The BRAS then does Layer 3 routing of the subscriber
   traffic to the NSP Edge Router.

   When the NSP is also the NAP, the BRAS and NSP Edge Router could be
   the same piece of equipment and provide the above mentioned
   functionality.

   The PPPoE logical diagram in an Ethernet Broadband Network is shown
   in Fig 7.2.2.1.
















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   |     Customer Premise      | |       NAP       | |      NSP       |

                                                        +-----------+
                                                        |    AAA    |
                                                +-------+   Radius  |
                                                |       |   TACACS  |
                                                |       +-----------+
   +-----+ +-------+ +--------+ +--------+ +----+-----+ +-----------+
   |Hosts|-+Router +-+A Switch+-+ Switch +-+   BRAS   +-+    Edge   |  C
   +-----+ +-------+ +--------+ +--------+ +----------+ |   Router  +=>O
        |----------------  PPP ----------------|        |           |  R
                                                        +-----------+  E

                               Figure 7.2.2.1

   The PPP sessions are initiated by the Customer Premise Equipment
   (Host or Router).  The BRAS authenticates the subscriber against a
   local or remote database.  Once the session is established, the BRAS
   provides an address and maybe a DNS server to the user; this
   information is acquired from the subscriber profile or a DHCP server.

   This model allows for multiple PPPoE sessions to be supported over
   the same VLAN, thus allowing the subscriber to connect to multiple
   services at the same time.  The hosts can initiate the PPPoE sessions
   as well.  It is important to remember that the PPPoE encapsulation
   reduces the IP MTU available for the customer traffic.

7.2.2.1.  IPv6 Related Infrastructure Changes

   In this scenario, the BRAS is Layer 3 aware and has to be upgraded to
   support IPv6.  Since the BRAS terminates the PPP sessions, it has to
   support PPPoE with IPv6.  The following devices have to be upgraded
   to dual stack: Host, Customer Router (if present), BRAS and Edge
   Router.

7.2.2.2.  Addressing

   The BRAS terminates the PPP sessions and provides the subscriber with
   an IPv6 address from the defined pool for that profile.  The
   subscriber profile for authorization and authentication can be
   located on the BRAS, or on an AAA server.  The Hosts or the Customer
   Routers have the BRAS as their Layer 3 next hop.

   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the BRAS,
   DHCP-PD can be used to acquire prefixes for the Customer Router
   interfaces.  The BRAS has to be enabled to support DHCP-PD and to
   relay the DHCPv6 requests of the hosts on the subscriber sites.



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   The BRAS has a /64 prefix configured on the link facing the Edge
   router.  The Edge Router links are also configured with /64 prefixes
   to provide connectivity to the rest of the ISP network.

   The prefixes used for subscribers and the ones delegated via DHCP-PD
   should be planned in a manner that allows maximum summarization at
   the BRAS.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

7.2.2.3.  Routing

   The CPE devices are configured with a default route that points to
   the BRAS router.  No routing protocols are needed on these devices,
   which generally have limited resources.

   The BRAS runs an IGP to the Edge Router: OSPFv3 or IS-IS.  Since the
   addresses assigned to the PPP sessions are represented as connected
   host routes, connected prefixes have to be redistributed.  If DHCP-PD
   is used, with every delegated prefix a static route is installed by
   the BRAS.  For this reason, the static routes must also be
   redistributed.  Prefix summarization should be done at the BRAS.

   The Edge Router is running the IGP used in the ISP network: OSPFv3 or
   IS-IS.  A separation between the routing domains of the ISP and the
   Access Provider is recommended if they are managed independently.
   Controlled redistribution will be needed between the Access Provider
   IGP and the ISP IGP.

7.2.3.  L2TPv2 Access Aggregation (LAA) Model

   In the LAA model, the BRAS forwards the CPE initiated session to the
   ISP over an L2TPv2 tunnel established between the BRAS and the Edge
   Router.  In this case, the authentication, authorization, and
   subscriber configuration are performed by the ISP itself.















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   | Customer Premise   | |         NAP          | |       NSP       |

                                                       +-----------+
                                                       |    AAA    |
                                                +------+   Radius  |
                                                |      |   TACACS  |
                                                |      +-----+-----+
                                                |            |
   +-----+ +-------+ +--------+ +--------+ +----+-----+ +-----------+
   |Hosts|-+Router +-+A Switch+-+ Switch +-+   BRAS   +-+    Edge   |  C
   +-----+ +-------+ +--------+ +--------+ +----------+ |   Router  +=>O
                                                        |           |  R
                                                        +-----------+  E
               |-----------------------------------------------|
                                       PPP
                                                |--------------|
                                                     L2TPv2
                                Figure 7.2.3.1

7.2.3.1.  IPv6 Related Infrastructure Changes

   In this scenario, the BRAS is Layer 3 aware and has to be upgraded to
   support IPv6.  The PPP sessions initiated by the subscriber are
   forwarded over the L2TPv2 tunnel to the aggregation point in the ISP
   network.  The BRAS (LAC) can aggregate IPv6 PPP sessions and tunnel
   them to the LNS using L2TPv2.  The L2TPv2 tunnel between the LAC and
   LNS could run over IPv6 or IPv4.  These capabilities have to be
   supported on the BRAS.  The following devices have to be upgraded to
   dual stack: Host, Customer Router (if present), BRAS and Edge Router.

7.2.3.2.  Addressing

   The Edge Router terminates the PPP sessions and provides the
   subscriber with an IPv6 address from the defined pool for that
   profile.  The subscriber profile for authorization and authentication
   can be located on the Edge Router or on an AAA server.  The Hosts or
   the Customer Routers have the Edge Router as their Layer 3 next hop.

   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the Edge
   Router and an IPv6 address is assigned to the Customer Router by the
   Edge Router, DHCP-PD can be used to acquire prefixes for the Customer
   Router other interfaces.  The Edge Router has to be enabled to
   support DHCP-PD and to relay the DHCPv6 requests of the hosts on the
   subscriber sites.  The uplink to the ISP network is configured with a
   /64 prefix as well.





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   The BRAS has a /64 prefix configured on the link to the Edge Router.
   The Edge Router links are also configured with /64 prefixes to
   provide connectivity to the rest of the ISP network.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

   The address assignment and prefix summarization issues discussed in
   Section 6.2.3.2 are relevant in the same way for this media access
   type as well.

7.2.3.3.  Routing

   The CPE devices are configured with a default route that points to
   the Edge Router that terminates the PPP sessions.  No routing
   protocols are needed on these devices, which have limited resources.

   The BRAS runs an IPv6 IGP to the Edge Router: OSPFv3 or IS-IS.
   Different processes should be used if the NAP and the NSP are managed
   by different organizations.  In this case, controlled redistribution
   should be enabled between the two domains.

   The Edge Router is running the IPv6 IGP used in the ISP network:
   OSPFv3 or IS-IS.

7.2.4.  Hybrid Model for IPv4 and IPv6 Service

   It was recommended throughout this section that the IPv6 service
   implementation should map the existing IPv4 one.  This approach
   simplifies manageability and minimizes training needed for personnel
   operating the network.  In certain circumstances, such mapping is not
   feasible.  This typically becomes the case when a Service Provider
   plans to expand its service offering with the new IPv6 deployed
   infrastructure.  If this new service is not well supported in a
   network design such as the one used for IPv4, then a different design
   might be used for IPv6.

   An example of such circumstances is that of a provider using an LAA
   design for its IPv4 services.  In this case, all the PPP sessions are
   bundled and tunneled across the entire NAP infrastructure, which is
   made of multiple BRAS routers, aggregation routers, etc.  The end
   point of these tunnels is the ISP Edge Router.  If the SP decides to
   offer multicast services over such a design, it will face the problem
   of NAP resources being over-utilized.  The multicast traffic can be
   replicated only at the end of the tunnels by the Edge Router, and the
   copies for all the subscribers are carried over the entire NAP.





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   A Modified Point-to-Point (see Section 7.2.4.2) or a PTA model is
   more suitable to support multicast services because the packet
   replication can be done closer to the destination at the BRAS.  Such
   a topology saves NAP resources.

   In this sense, IPv6 deployments can be viewed as an opportunity to
   build an infrastructure that can better support the expansion of
   services.  In this case, an SP using the LAA design for its IPv4
   services might choose a modified Point-to-Point or PTA design for
   IPv6.

7.2.4.1.  IPv4 in LAA Model and IPv6 in PTA Model

   The coexistence of the two PPP-based models, PTA and LAA, is
   relatively straightforward.  It is a straightforward overlap of the
   two deployment models.  The PPP sessions are terminated on different
   network devices for the IPv4 and IPv6 services.  The PPP sessions for
   the existing IPv4 service deployed in an LAA model are terminated on
   the Edge Router.  The PPP sessions for the new IPv6 service deployed
   in a PTA model are terminated on the BRAS.

   The logical design for IPv6 and IPv4 in this hybrid model is
   presented in Figure 7.2.4.1.

   IPv6          |--------------------------|
                            PPP                    +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ Switch +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+


   IPv4          |----------------------------------------|
                                   PPP
                                            |------------|
                                                L2TPv2

                            Figure 7.2.4.1








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7.2.4.2.  IPv4 in LAA Model and IPv6 in Modified Point-to-Point Model

   The coexistence of the modified Point-to-Point and the LAA models
   implies a few specific changes.

   For the IPv4 service in LAA model, the VLANs are terminated on the
   BRAS, and PPP sessions are terminated on the Edge Router (LNS).  For
   the IPv6 service in the Point-to-Point model, the VLANs are
   terminated at the Edge Router as described in Section 6.2.1.  In this
   hybrid model, the Point-to-Point link could be terminated on the
   BRAS, a NAP-owned device.  The IPv6 traffic is then routed through
   the NAP network to the NSP.  In order to have this hybrid model, the
   BRAS has to be upgraded to a dual-stack router.  The functionalities
   of the Edge Router, as described in Section 6.2.1, are now
   implemented on the BRAS.

   The logical design for IPv6 and IPv4 in this hybrid model is in
   Figure 7.2.4.2.

   IPv6              |----------------|
                           Ethernet
                                                   +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ Switch +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
   IPv4          |----------------------------------------|
                                   PPP
                                             |------------|
                                                 L2TPv2

                                 Figure 7.2.4.2

7.3.  IPv6 Multicast

   The typical multicast services offered for residential and very small
   businesses are video/audio streaming where the subscriber joins a
   multicast group and receives the content.  This type of service model
   is well supported through PIM-SSM, which is very simple and easy to
   manage.  PIM-SSM has to be enabled throughout the ISP network.  MLDv2
   is required for PIM-SSM support.  Vendors can choose to implement
   features that allow routers to map MLDv1 group joins to predefined
   sources.



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   Subscribers might use a set-top box that is responsible for the
   control piece of the multicast service (does group joins/leaves).
   The subscriber hosts can also join desired multicast groups as long
   as they are enabled to support MLDv1 or MLDv2.  If a CPR is used,
   then it has to be enabled to support MLDv1 and MLDv2 in order to
   process the requests of the hosts.  It has to be enabled to support
   PIM-SSM in order to send PIM joins/leaves up to its Layer 3 next hop
   whether it is the BRAS or the Edge Router.  When enabling this
   functionality on a CPR, its limited resources should be taken into
   consideration.  Another option would be for the CPR to support MLD
   proxy routing.  MLD snooping or similar Layer 2 multicast-related
   protocols could be enabled on the NAP switches.

   The router that is the Layer 3 next hop for the subscriber (BRAS in
   the PTA model or the Edge Router in the LAA and Point-to-Point model)
   has to be enabled to support MLDv1 and MLDv2 in order to process the
   requests coming from subscribers without CPRs.  It has to be enabled
   for PIM-SSM in order to receive joins/leaves from customer routers
   and send joins/leaves to the next hop towards the multicast source
   (Edge Router or the NSP core).

   MLD authentication, authorization, and accounting are usually
   configured on the edge router in order to enable the ISP to control
   the subscriber access of the service and do billing for the content
   provided.  Alternative mechanisms that would support these functions
   should be investigated further.

   Please refer to section 6.3 for more IPv6 multicast details.

7.4.  IPv6 QoS

   The QoS configuration is particularly relevant on the router that
   represents the Layer 3 next hop for the subscriber (BRAS in the PTA
   model or the Edge Router in the LAA and Point-to-Point model) in
   order to manage resources shared amongst multiple subscribers,
   possibly with various service level agreements.

   On the BRAS or the Edge Router, the subscriber-facing interfaces have
   to be configured to police the inbound customer traffic and shape the
   traffic outbound to the customer based on the SLAs.  Traffic
   classification and marking should also be done on the router closest
   (at Layer 3) to the subscriber in order to support the various types
   of customer traffic: data, voice, video, and to optimally use the
   network resources.  This infrastructure offers a very good
   opportunity to leverage the QoS capabilities of Layer 2 devices.
   Diffserv-based QoS used for IPv4 should be expanded to IPv6.





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   Each provider (NAP, NSP) could implement their own QoS policies and
   services so that reclassification and marking might be performed at
   the boundary between the NAP and the NSP, in order to make sure the
   traffic is properly handled by the ISP.  The same IPv4 QoS concepts
   and methodologies should be applied for the IPv6 as well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases,
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

7.5.  IPv6 Security Considerations

   There are limited changes that have to be done for CPEs in order to
   enhance security.  The privacy extensions [RFC3041] for auto-
   configuration should be used by the hosts with the same
   considerations for host traceability as discussed in Section 6.5.
   IPv6 firewall functions should be enabled on the hosts or Customer
   Premise Router, if present.

   The ISP provides security against attacks that come from its own
   subscribers, but it could also implement security services that
   protect its subscribers from attacks sourced from outside its
   network.  Such services do not apply at the access level of the
   network discussed here.

   If any Layer 2 filters for Ethertypes are in place, the NAP must
   permit the IPv6 Ethertype (0X86DD).

   The device that is the Layer 3 next hop for the subscribers (BRAS
   Edge Router) should protect the network and the other subscribers
   against attacks by one of the provider customers.  For this reason
   uRPF and ACLs should be used on all interfaces facing subscribers.
   Filtering should be implemented with regard for the operational
   requirements of IPv6 [IPv6-Security].

   The BRAS and the Edge Router should protect their processing
   resources against floods of valid customer control traffic such as:
   Router and Neighbor Solicitations, and MLD Requests.  Rate limiting
   should be implemented on all subscriber-facing interfaces.  The
   emphasis should be placed on multicast-type traffic, as it is most
   often used by the IPv6 control plane.

   All other security features used with the IPv4 service should be
   similarly applied to IPv6 as well.




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7.6.  IPv6 Network Management

   The necessary instrumentation (such as MIB modules, NetFlow Records,
   etc.) should be available for IPv6.

   Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
   can be done over IPv4 if all managed devices have connectivity over
   both IPv4 and IPv6.  This would imply the smallest changes to the
   existing network management practices and processes.  Transport over
   IPv6 could also be implemented and it might become necessary if IPv6
   only islands are present in the network.  The management applications
   may be running on hosts belonging to the NSP core network domain.
   Network Management Applications should handle IPv6 in a similar
   fashion to IPv4; however, they should also support features specific
   to IPv6 such as neighbor monitoring.

   In some cases, service providers manage equipment located on
   customers' LANs.

8.  Wireless LAN

   This section provides a detailed description of IPv6 deployment and
   integration methods in currently deployed wireless LAN (WLAN)
   infrastructure.

8.1.  WLAN Deployment Scenarios

   WLAN enables subscribers to connect to the Internet from various
   locations without the restriction of staying indoors.  WLAN is
   standardized by IEEE 802.11a/b/g.

   Figure 8.1 describes the current WLAN architecture.

       Customer |             Access Provider        | Service Provider
       Premise  |                                    |

     +------+         +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----   |  | |Access Router/| | Provider | |Edge  |
     |Host/ |-(WLAN)--|AP|-|Layer 2 Switch|-| Network  |-|Router|=>SP
     |Router|  ----   |  | |              | |          | |      |Network
     +------+         +--+ +--------------+ +----------+ +------+
                                                           |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+

                                 Figure 8.1



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   The host should have a wireless Network Interface Card (NIC) in order
   to connect to a WLAN network.  WLAN is a flat broadcast network and
   works in a similar fashion as Ethernet.  When a host initiates a
   connection, it is authenticated by the AAA server located at the SP
   network.  All the authentication parameters (username, password,
   etc.) are forwarded by the Access Point (AP) to the AAA server.  The
   AAA server authenticates the host; once successfully authenticated,
   the host can send data packets.  The AP is located near the host and
   acts as a bridge.  The AP forwards all the packets coming to/from
   host to the Edge Router.  The underlying connection between the AP
   and Edge Router could be based on any access layer technology such as
   HFC/Cable, FTTH, xDSL, etc.

   WLANs operate within limited areas known as WiFi Hot Spots.  While
   users are present in the area covered by the WLAN range, they can be
   connected to the Internet given they have a wireless NIC and required
   configuration settings in their devices (notebook PCs, PDAs, etc.).
   Once the user initiates the connection, the IP address is assigned by
   the SP using DHCPv4.  In most of the cases, SP assigns a limited
   number of public IP addresses to its customers.  When the user
   disconnects the connection and moves to a new WiFi hot spot, the
   above-mentioned process of authentication, address assignment, and
   accessing the Internet is repeated.

   There are IPv4 deployments where customers can use WLAN routers to
   connect over wireless to their service provider.  These deployment
   types do not fit in the typical Hot Spot concept, but rather they
   serve fixed customers.  For this reason, this section discusses the
   WLAN router options as well.  In this case, the ISP provides a public
   IP address and the WLAN Router assigns private addresses [RFC1918] to
   all WLAN users.  The WLAN Router provides NAT functionality while
   WLAN users access the Internet.

   While deploying IPv6 in the above-mentioned WLAN architecture, there
   are three possible scenarios as discussed below.

   A. Layer 2 NAP with Layer 3 termination at NSP Edge Router

   B. Layer 3 aware NAP with Layer 3 termination at Access Router

   C. PPP-Based Model

8.1.1.  Layer 2 NAP with Layer 3 termination at NSP Edge Router

   When a Layer 2 switch is present between AP and Edge Router, the AP
   and Layer 2 switch continues to work as a bridge, forwarding IPv4 and
   IPv6 packets from WLAN Host/Router to Edge Router and vice versa.




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   When initiating the connection, the WLAN Host is authenticated by the
   AAA server located at the SP network.  All the parameters related to
   authentication (username, password, etc.) are forwarded by the AP to
   the AAA server.  The AAA server authenticates the WLAN Hosts, and
   once the WLAN Host is authenticated and associated successfully with
   the WLAN AP, it acquires an IPv6 address.  Note that the initiation
   and authentication process is the same as used in IPv4.

   Figure 8.1.1 describes the WLAN architecture when a Layer 2 Switch is
   located between AP and Edge Router.

       Customer |             Access Provider        | Service Provider
       Premise  |                                    |

     +------+         +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----   |  | |              | | Provider | |Edge  |
     |Host/ |-(WLAN)--|AP|-|Layer 2 Switch|-| Network  |-|Router|=>SP
     |Router|  ----   |  | |              | |          | |      |Network
     +------+         +--+ +--------------+ +----------+ +------+
                                                           |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+

                                 Figure 8.1.1

8.1.1.1.  IPv6 Related Infrastructure Changes

   IPv6 will be deployed in this scenario by upgrading the following
   devices to dual stack: WLAN Host, WLAN Router (if present), and Edge
   Router.

8.1.1.2.  Addressing

   When a customer WLAN Router is not present, the WLAN Host has two
   possible options to get an IPv6 address via the Edge Router.

   A.  The WLAN Host can get the IPv6 address from an Edge Router using
       stateless auto-configuration [RFC2462].  All hosts on the WLAN
       belong to the same /64 subnet that is statically configured on
       the Edge Router.  The IPv6 WLAN Host may use stateless DHCPv6 for
       obtaining other information of interest such as DNS, etc.

   B.  The IPv6 WLAN Host can use DHCPv6 [RFC3315] to get an IPv6
       address from the DHCPv6 server.  In this case, the DHCPv6 server
       would be located in the SP core network, and the Edge Router
       would simply act as a DHCP Relay Agent.  This option is similar



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       to what is done today in case of DHCPv4.  It is important to note
       that host implementation of stateful auto-configuration is rather
       limited at this time, and this should be considered if choosing
       this address assignment option.

   When a customer WLAN Router is present, the WLAN Host has two
   possible options as well for acquiring IPv6 address.

   A.  The WLAN Router may be assigned a prefix between /48 and /64
       [RFC3177] depending on the SP policy and customer requirements.
       If the WLAN Router has multiple networks connected to its
       interfaces, the network administrator will have to configure the
       /64 prefixes to the WLAN Router interfaces connecting the WLAN
       Hosts on the customer site.  The WLAN Hosts connected to these
       interfaces can automatically configure themselves using stateless
       auto-configuration.

   B.  The WLAN Router can use its link-local address to communicate
       with the ER.  It can also dynamically acquire through stateless
       auto-configuration the address for the link between itself and
       the ER.  This step is followed by a request via DHCP-PD for a
       prefix shorter than /64 that, in turn, is divided in /64s and
       assigned to its interfaces connecting the hosts on the customer
       site.

   In this option, the WLAN Router would act as a requesting router and
   the Edge Router would act as a delegating router.  Once the prefix is
   received by the WLAN Router, it assigns /64 prefixes to each of its
   interfaces connecting the WLAN Hosts on the customer site.  The WLAN
   Hosts connected to these interfaces can automatically configure
   themselves using stateless auto-configuration.  The uplink to the ISP
   network is configured with a /64 prefix as well.

   Usually it is easier for the SPs to stay with the DHCP-PD and
   stateless auto-configuration model and point the clients to a central
   server for DNS/domain information, proxy configurations, etc.  Using
   this model, the SP could change prefixes on the fly, and the WLAN
   Router would simply pull the newest prefix based on the valid/
   preferred lifetime.

   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows maximum
   summarization at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] and stateless [RFC3736] DHCPv6.





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8.1.1.3.  Routing

   The WLAN Host/Router is configured with a default route that points
   to the Edge Router.  No routing protocols are needed on these
   devices, which generally have limited resources.

   The Edge Router runs the IGP used in the SP network such as OSPFv3 or
   IS-IS for IPv6.  The connected prefixes have to be redistributed.
   Prefix summarization should be done at the Edge Router.  When DHCP-PD
   is used, the IGP has to redistribute the static routes installed
   during the process of prefix delegation.

8.1.2.  Layer 3 Aware NAP with Layer 3 Termination at Access Router

   When an Access Router is present between the AP and Edge Router, the
   AP continues to work as a bridge, bridging IPv4 and IPv6 packets from
   WLAN Host/Router to Access Router and vice versa.  The Access Router
   could be part of the SP network or owned by a separate Access
   Provider.

   When the WLAN Host initiates the connection, the AAA authentication
   and association process with WLAN AP will be similar, as explained in
   Section 8.1.1.

   Figure 8.1.2 describes the WLAN architecture when the Access Router
   is located between the AP and Edge Router.

       Customer |             Access Provider        | Service Provider
       Premise  |                                    |

     +------+         +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----   |  | |              | | Provider | |Edge  |
     |Host/ |-(WLAN)--|AP|-|Access Router |-| Network  |-|Router|=>SP
     |Router|  ----   |  | |              | |          | |      |Network
     +------+         +--+ +--------------+ +----------+ +------+
                                                           |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+

                                  Figure 8.1.2

8.1.2.1.  IPv6 Related Infrastructure Changes

   IPv6 is deployed in this scenario by upgrading the following devices
   to dual stack: WLAN Host, WLAN Router (if present), Access Router,
   and Edge Router.



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8.1.2.2.  Addressing

   There are three possible options in this scenario for IPv6 address
   assignment:

   A.  The Edge Router interface facing towards the Access Router is
       statically configured with a /64 prefix.  The Access Router
       receives/ configures a /64 prefix on its interface facing towards
       the Edge Router through stateless auto-configuration.  The
       network administrator will have to configure the /64 prefixes to
       the Access Router interface facing toward the customer premise.
       The WLAN Host/Router connected to this interface can
       automatically configure itself using stateless auto-
       configuration.

   B.  This option uses DHCPv6 [RFC3315] for IPv6 prefix assignments to
       the WLAN Host/Router.  There is no use of DHCP PD or stateless
       auto-configuration in this option.  The DHCPv6 server can be
       located on the Access Router, the Edge Router, or somewhere in
       the SP network.  In this case, depending on where the DHCPv6
       server is located, the Access Router or the Edge Router would
       relay the DHCPv6 requests.

   C.  It can use its link-local address to communicate with the ER.  It
       can also dynamically acquire through stateless auto-configuration
       the address for the link between itself and the ER.  This step is
       followed by a request via DHCP-PD for a prefix shorter than /64
       that, in turn, is divided in /64s and assigned to its interfaces
       connecting the hosts on the customer site.

       In this option, the Access Router would act as a requesting
       router, and the Edge Router would act as a delegating router.
       Once the prefix is received by the Access Router, it assigns /64
       prefixes to each of its interfaces connecting the WLAN Host/
       Router on the customer site.  The WLAN Host/Router connected to
       these interfaces can automatically configure itself using
       stateless auto-configuration.  The uplink to the ISP network is
       configured with a /64 prefix as well.

   It is easier for the SPs to stay with the DHCP PD and stateless auto-
   configuration model and point the clients to a central server for
   DNS/domain information, proxy configurations, and others.  Using this
   model, the provider could change prefixes on the fly, and the Access
   Router would simply pull the newest prefix based on the valid/
   preferred lifetime.






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   As mentioned before, the prefixes used for subscriber links and the
   ones delegated via DHCP-PD should be planned in a manner that allows
   the maximum summarization possible at the Edge Router.  Other
   information of interest to the host, such as DNS, is provided through
   stateful [RFC3315] and stateless [RFC3736] DHCPv6.

8.1.2.3.  Routing

   The WLAN Host/Router is configured with a default route that points
   to the Access Router.  No routing protocols are needed on these
   devices, which generally have limited resources.

   If the Access Router is owned by an Access Provider, then the Access
   Router can have a default route, pointing towards the SP Edge Router.
   The Edge Router runs the IGP used in the SP network such as OSPFv3 or
   IS-IS for IPv6.  The connected prefixes have to be redistributed.  If
   DHCP-PD is used, with every delegated prefix a static route is
   installed by the Edge Router.  For this reason the static routes must
   be redistributed.  Prefix summarization should be done at the Edge
   Router.

   If the Access Router is owned by the SP, then the Access Router will
   also run IPv6 IGP, and will be part of the SP IPv6 routing domain
   (OSPFv3 or IS-IS).  The connected prefixes have to be redistributed.
   If DHCP-PD is used, with every delegated prefix a static route is
   installed by the Access Router.  For this reason, the static routes
   must be redistributed.  Prefix summarization should be done at the
   Access Router.

8.1.3.  PPP-Based Model

   PPP Terminated Aggregation (PTA) and L2TPv2 Access Aggregation (LAA)
   models, as discussed in Sections 6.2.2 and 6.2.3, respectively, can
   also be deployed in IPv6 WLAN environment.

8.1.3.1.  PTA Model in IPv6 WLAN Environment

   While deploying the PTA model in IPv6 WLAN environment, the Access
   Router is Layer 3 aware and it has to be upgraded to support IPv6.
   Since the Access Router terminates the PPP sessions initiated by the
   WLAN Host/Router, it has to support PPPoE with IPv6.

   Figure 8.1.3.1 describes the PTA Model in IPv6 WLAN environment.








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       Customer |             Access Provider        | Service Provider
       Premise  |                                    |
     +------+         +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----   |  | |              | | Provider | |Edge  |
     |Host/ |-(WLAN)--|AP|-|Access Router |-| Network  |-|Router|=>SP
     |Router|  ----   |  | |              | |          | |      |Network
     +------+         +--+ +--------------+ +----------+ +------+
                                                           |
       |---------------------------|                    +------+
                   PPP                                  |AAA   |
                                                        |Server|
                                                        +------+

                                Figure 8.1.3.1

8.1.3.1.1.  IPv6 Related Infrastructure Changes

   IPv6 is deployed in this scenario by upgrading the following devices
   to dual stack: WLAN Host, WLAN Router (if present), Access Router,
   and Edge Router.

8.1.3.1.2.  Addressing

   The addressing techniques described in Section 6.2.2.2 apply to the
   IPv6 WLAN PTA scenario as well.

8.1.3.1.3.  Routing

   The routing techniques described in Section 6.2.2.3 apply to the IPv6
   WLAN PTA scenario as well.

8.1.3.2.  LAA Model in IPv6 WLAN Environment

   While deploying the LAA model in IPv6 WLAN environment, the Access
   Router is Layer 3 aware and has to be upgraded to support IPv6.  The
   PPP sessions initiated by the WLAN Host/Router are forwarded over the
   L2TPv2 tunnel to the aggregation point in the SP network.  The Access
   Router must have the capability to support L2TPv2 for IPv6.

   Figure 8.1.3.2 describes the LAA Model in IPv6 WLAN environment.











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       Customer |             Access Provider        | Service Provider
       Premise  |                                    |

     +------+         +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----   |  | |              | | Provider | |Edge  |
     |Host/ |-(WLAN)--|AP|-|Access Router |-| Network  |-|Router|=>SP
     |Router|  ----   |  | |              | |          | |      |Network
     +------+         +--+ +--------------+ +----------+ +------+
                                                           |
       |-------------------------------------------------- |
                               PPP                         |
                                    |--------------------- |
                                               L2TPv2      |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+

                                Figure 8.1.3.2

8.1.3.2.1.  IPv6 Related Infrastructure Changes

   IPv6 is deployed in this scenario by upgrading the following devices
   to dual stack: WLAN Host, WLAN Router (if present), Access Router,
   and Edge Router.

8.1.3.2.2.  Addressing

   The addressing techniques described in Section 6.2.3.2 apply to the
   IPv6 WLAN LAA scenario as well.

8.1.3.2.3.  Routing

   The routing techniques described in Section 6.2.3.3 apply to the IPv6
   WLAN LAA scenario as well.

8.2.  IPv6 Multicast

   The typical multicast services offered are video/audio streaming
   where the IPv6 WLAN Host joins a multicast group and receives the
   content.  This type of service model is well supported through PIM-
   SSM, which is enabled throughout the SP network.  MLDv2 is required
   for PIM-SSM support.  Vendors can choose to implement features that
   allow routers to map MLDv1 group joins to predefined sources.







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   It is important to note that in the shared wireless environments,
   multicast can have a significant bandwidth impact.  For this reason,
   the bandwidth allocated to multicast traffic should be limited and
   fixed, based on the overall capacity of the wireless specification
   used in 802.11a, 802.11b, or 802.11g.

   The IPv6 WLAN Hosts can also join desired multicast groups as long as
   they are enabled to support MLDv1 or MLDv2.  If WLAN/Access Routers
   are used, then they have to be enabled to support MLDv1 and MLDv2 in
   order to process the requests of the IPv6 WLAN Hosts.  The WLAN/
   Access Router also needs to be enabled to support PIM-SSM in order to
   send PIM joins up to the Edge Router.  When enabling this
   functionality on a WLAN/Access Router, its limited resources should
   be taken into consideration.  Another option would be for the WLAN/
   Access Router to support MLD proxy routing.

   The Edge Router has to be enabled to support MLDv1 and MLDv2 in order
   to process the requests coming from the IPv6 WLAN Host or WLAN/Access
   Router (if present).  The Edge Router has also needs to be enabled
   for PIM-SSM in order to receive joins from IPv6 WLAN Hosts or WLAN/
   Access Router (if present), and send joins towards the SP core.

   MLD authentication, authorization, and accounting are usually
   configured on the Edge Router in order to enable the SP to do billing
   for the content services provided.  Further investigation should be
   made in finding alternative mechanisms that would support these
   functions.

   Concerns have been raised in the past related to running IPv6
   multicast over WLAN links.  Potentially these are the same kind of
   issues when running any Layer 3 protocol over a WLAN link that has a
   high loss-to-signal ratio, where certain frames that are multicast
   based are dropped when settings are not adjusted properly.  For
   instance, this behavior is similar to an IGMP host membership report,
   when done on a WLAN link with a high loss-to-signal ratio and high
   interference.

   This problem is inherited by WLAN that can impact both IPv4 and IPv6
   multicast packets; it is not specific to IPv6 multicast.

   While deploying WLAN (IPv4 or IPv6), one should adjust their
   broadcast/multicast settings if they are in danger of dropping
   application dependent frames.  These problems are usually caused when
   the AP is placed too far (not following the distance limitations),
   high interference, etc.  These issues may impact a real multicast
   application such as streaming video or basic operation of IPv6 if the
   frames were dropped.  Basic IPv6 communications uses functions such
   as Duplicate Address Detection (DAD), Router and Neighbor



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   Solicitations (RS, NS), Router and Neighbor Advertisement (RA, NA),
   etc., which could be impacted by the above mentioned issues as these
   frames are Layer 2 Ethernet multicast frames.

   Please refer to Section 6.3 for more IPv6 multicast details.

8.3.  IPv6 QoS

   Today, QoS is done outside of the WiFi domain, but it is nevertheless
   important to the overall deployment.

   The QoS configuration is particularly relevant on the Edge Router in
   order to manage resources shared amongst multiple subscribers
   possibly with various service level agreements (SLAs).  However, the
   WLAN Host/Router and Access Router could also be configured for QoS.
   This includes support for appropriate classification criteria, which
   would need to be implemented for IPv6 unicast and multicast traffic.

   On the Edge Router, the subscriber-facing interfaces have to be
   configured to police the inbound customer traffic and shape the
   traffic outbound to the customer, based on the SLA.  Traffic
   classification and marking should also be done on the Edge Router in
   order to support the various types of customer traffic: data, voice,
   and video.  The same IPv4 QoS concepts and methodologies should be
   applied for the IPv6 as well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases,
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

8.4.  IPv6 Security Considerations

   There are limited changes that have to be done for WLAN the Host/
   Router in order to enhance security.  The privacy extensions
   [RFC3041] for auto-configuration should be used by the hosts with the
   same consideration for host traceability as described in Section 6.5.
   IPv6 firewall functions should be enabled on the WLAN Host/Router, if
   present.

   The ISP provides security against attacks that come from its own
   subscribers, but it could also implement security services that
   protect its subscribers from attacks sourced from outside its
   network.  Such services do not apply at the access level of the
   network discussed here.




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   If the host authentication at hotspots is done using a web-based
   authentication system, then the level of security would depend on the
   particular implementation.  User credentials should never be sent as
   clear text via HTTP.  Secure HTTP (HTTPS) should be used between the
   web browser and authentication server.  The authentication server
   could use RADIUS and LDAP services at the back end.

   Authentication is an important aspect of securing WLAN networks prior
   to implementing Layer 3 security policies.  For example, this would
   help avoid threats to the ND or stateless auto-configuration
   processes. 802.1x [IEEE8021X] provides the means to secure the
   network access; however, the many types of EAP (PEAP, EAP-TLS, EAP-
   TTLS, EAP-FAST, and LEAP) and the capabilities of the hosts to
   support some of the features might make it difficult to implement a
   comprehensive and consistent policy.

   The 802.11i [IEEE80211i] amendment has many components, the most
   obvious of which are the two new data-confidentiality protocols,
   Temporal Key Integrity Protocol (TKIP) and Counter-Mode/CBC-MAC
   Protocol (CCMP). 802.11i also uses 802.1X's key-distribution system
   to control access to the network.  Because 802.11 handles unicast and
   broadcast traffic differently, each traffic type has different
   security concerns.  With several data-confidentiality protocols and
   the key distribution, 802.11i includes a negotiation process for
   selecting the correct confidentiality protocol and key system for
   each traffic type.  Other features introduced include key caching and
   pre-authentication.

   The 802.11i amendment is a step forward in wireless security.  The
   amendment adds stronger encryption, authentication, and key
   management strategies that could make wireless data and systems more
   secure.

   If any Layer 2 filters for Ethertypes are in place, the NAP must
   permit the IPv6 Ethertype (0X86DD).

   The device that is the Layer 3 next hop for the subscribers (Access
   or Edge Router) should protect the network and the other subscribers
   against attacks by one of the provider customers.  For this reason
   uRPF and ACLs should be used on all interfaces facing subscribers.
   Filtering should be implemented with regard for the operational
   requirements of IPv6 [IPv6-Security].

   The Access and the Edge Router should protect their processing
   resources against floods of valid customer control traffic such as:
   RS, NS, and MLD Requests.  Rate limiting should be implemented on all





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   subscriber-facing interfaces.  The emphasis should be placed on
   multicast-type traffic, as it is most often used by the IPv6 control
   plane.

8.5.  IPv6 Network Management

   The necessary instrumentation (such as MIB modules, NetFlow Records,
   etc) should be available for IPv6.

   Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
   can be done over IPv4 if all managed devices have connectivity over
   both IPv4 and IPv6.  This would imply the smallest changes to the
   existing network management practices and processes.  Transport over
   IPv6 could also be implemented and it might become necessary if IPv6
   only islands are present in the network.  The management applications
   may be running on hosts belonging to the NSP core network domain.
   Network Management Applications should handle IPv6 in a similar
   fashion to IPv4; however, they should also support features specific
   to IPv6 (such as neighbor monitoring).

   In some cases, service providers manage equipment located on
   customers' LANs.

9.  Broadband Power Line Communications (PLC)

   This section describes the IPv6 deployment in Power Line
   Communications (PLC) Access Networks.  There may be other choices,
   but it seems that this is the best model to follow.  Lessons learnt
   from cable, Ethernet, and even WLAN access networks may be applicable
   also.

   Power Line Communications are also often called Broadband Power Line
   (BPL) and sometimes even Power Line Telecommunications (PLT).

   PLC/BPL can be used for providing, with today's technology, up to
   200Mbps (total, upstream+downstream) by means of the power grid.  The
   coverage is often the last half mile (typical distance from the
   medium-to-low voltage transformer to the customer premise meter) and,
   of course, as an in-home network (which is out of the scope of this
   document).

   The bandwidth in a given PLC/BPL segment is shared among all the
   customers connected to that segment (often the customers connected to
   the same medium-to-low voltage transformer).  The number of customers
   can vary depending on different factors, such as distances and even
   countries (from a few customers, just 5-6, up to 100-150).





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   PLC/BPL could also be used in the medium voltage network (often
   configured as Metropolitan Area Networks), but this is also out of
   the scope of this document, as it will be part of the core network,
   not the access one.

9.1.  PLC/BPL Access Network Elements

   This section describes the different elements commonly used in PLC/
   BPL access networks.

   Head End (HE): Router that connects the PLC/BPL access network (the
   power grid), located at the medium-to-low voltage transformer, to the
   core network.  The HE PLC/BPL interface appears to each customer as a
   single virtual interface, all of them sharing the same physical
   media.

   Repeater (RPT): A device that may be required in some circumstances
   to improve the signal on the PLC/BPL.  This may be the case if there
   are many customers in the same segment or building.  It is often a
   bridge, but it could also be a router if, for example, there is a lot
   of peer-to-peer traffic in a building and due to the master-slave
   nature of the PLC/BPL technology, is required to improve the
   performance within that segment.  For simplicity within this
   document, the RPT will always be considered a transparent Layer 2
   bridge, so it may or may not be present (from the Layer 3 point of
   view).

   Customer Premise Equipment (CPE): Modem (internal to the host),
   modem/bridge (BCPE), router (RCPE), or any combination among those
   (i.e., modem+bridge/router), located at the customer premise.

   Edge Router (ER)

   Figure 9.1 depicts all the network elements indicated above.

   Customer Premise | Network Access Provider | Network Service Provider

    +-----+  +------+  +-----+        +------+   +--------+
    |Hosts|--| RCPE |--| RPT |--------+ Head +---+ Edge   |    ISP
    +-----+  +------+  +-----+        | End  |   | Router +=>Network
                                      +--+---+   +--------+
    +-----+  +------+  +-----+           |
    |Hosts|--| BCPE |--| RPT |-----------+
    +-----+  +------+  +-----+

                                    Figure 9.1





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   The logical topology and design of PLC/BPL is very similar to
   Ethernet Broadband Networks as discussed in Section 7.  IP
   connectivity is typically provided in a Point-to-Point model, as
   described in Section 7.2.1

9.2.  Deploying IPv6 in IPv4 PLC/BPL

   The most simplistic and efficient model, considering the nature of
   the PLC/BPL networks, is to see the network as a point-to-point, one
   to each customer.  Even if several customers share the same physical
   media, the traffic is not visible among them because each one uses
   different channels, which are, in addition, encrypted by means of
   3DES.

   In order to maintain the deployment concepts and business models
   proven and used with existing revenue-generating IPv4 services, the
   IPv6 deployment will match the IPv4 one.  Under certain circumstances
   where new service types or service needs justify it, IPv4 and IPv6
   network architectures could be different.  Both approaches are very
   similar to those already described for the Ethernet case.

9.2.1.  IPv6 Related Infrastructure Changes

   In this scenario, only the RPT is Layer 3 unaware, but the other
   devices have to be upgraded to dual stack Hosts, RCPE, Head End, and
   Edge Router.

9.2.2.  Addressing

   The Hosts or the RCPEs have the HE as their Layer 3 next hop.

   If there is no RCPE, but instead a BCPE, all the hosts on the
   subscriber site belong to the same /64 subnet that is statically
   configured on the HE.  The hosts can use stateless auto-configuration
   or stateful DHCPv6-based configuration to acquire an address via the
   HE.

   If an RCPE is present:

   A.  It is statically configured with an address on the /64 subnet
       between itself and the HE, and with /64 prefixes on the
       interfaces connecting the hosts on the customer site.  This is
       not a desired provisioning method, being expensive and difficult
       to manage.

   B.  It can use its link-local address to communicate with the HE.  It
       can also dynamically acquire through stateless auto-configuration
       the address for the link between itself and the HE.  This step is



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       followed by a request via DHCP-PD for a prefix shorter than /64
       (typically /48 [RFC3177]) that, in turn, is divided in /64s and
       assigned to its interfaces connecting the hosts on the customer
       site.  This should be the preferred provisioning method, being
       cheaper and easier to manage.

   The Edge Router needs to have a prefix, considering that each
   customer in general will receive a /48 prefix, and that each HE will
   accommodate customers.  Consequently, each HE will require n x /48
   prefixes.

   It could be possible to use a kind of Hierarchical Prefix Delegation
   to automatically provision the required prefixes and fully auto-
   configure the HEs, and consequently reduce the network setup,
   operation, and maintenance cost.

   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows as much
   summarization as possible at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

9.2.3.  Routing

   If no routers are used on the customer premise, the HE can simply be
   configured with a default route that points to the Edge Router.  If a
   router is used on the customer premise (RCPE), then the HE could also
   run an IGP (such as OSPFv3, IS-IS or even RIPng) to the ER.  The
   connected prefixes should be redistributed.  If DHCP-PD is used, with
   every delegated prefix a static route is installed by the HE.  For
   this reason, the static routes must also be redistributed.  Prefix
   summarization should be done at the HE.

   The RCPE requires only a default route pointing to the HE.  No
   routing protocols are needed on these devices, which generally have
   limited resources.

   The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
   The connected prefixes have to be redistributed, as well as any
   routing protocols (other than the ones used on the ER) that might be
   used between the HE and the ER.









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9.3.  IPv6 Multicast

   The considerations regarding IPv6 Multicast for Ethernet are also
   applicable here, in general, assuming the nature of PLC/BPL is a
   shared media.  If a lot of Multicast is expected, it may be worth
   considering using RPT which are Layer 3 aware.  In that case, one
   extra layer of Hierarchical DHCP-PD could be considered, in order to
   facilitate the deployment, operation, and maintenance of the network.

9.4.  IPv6 QoS

   The considerations introduced for QoS in Ethernet are also applicable
   here.  PLC/BPL networks support QoS, which basically is the same
   whether the transport is IPv4 or IPv6.  It is necessary to understand
   that there are specific network characteristics, such as the
   variability that may be introduced by electrical noise, towards which
   the PLC/BPL network will automatically self-adapt.

9.5.  IPv6 Security Considerations

   There are no differences in terms of security considerations if
   compared with the Ethernet case.

9.6.  IPv6 Network Management

   The issues related to IPv6 Network Management in PLC networks should
   be similar to those discussed for Broadband Ethernet Networks in
   Section 7.6.  Note that there may be a need to define MIB modules for
   PLC networks and interfaces, but this is not necessarily related to
   IPv6 management.

10.  Gap Analysis

   Several aspects of deploying IPv6 over SP Broadband networks were
   highlighted in this document, aspects that require additional work in
   order to facilitate native deployments, as summarized below:

   A.  As mentioned in section 5, changes will need to be made to the
       DOCSIS specification in order for SPs to deploy native IPv6 over
       cable networks.  The CM and CMTS will both need to support IPv6
       natively in order to forward IPv6 unicast and multicast traffic.
       This is required for IPv6 Neighbor Discovery to work over DOCSIS
       cable networks.  Additional classifiers need to be added to the
       DOCSIS specification in order to classify IPv6 traffic at the CM
       and CMTS in order to provide QoS.  These issues are addressed in
       a recent proposal made to Cable Labs for DOCSIS 3.0
       [DOCSIS3.0-Reqs].




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   B.  Section 6 stated that current RBE-based IPv4 deployment might not
       be the best approach for IPv6, where the addressing space
       available gives the SP the opportunity to separate the users on
       different subnets.  The differences between IPv4 RBE and IPv6 RBE
       were highlighted in Section 6.  If, however, support and reason
       are found for a deployment similar to IPv4 RBE, then the
       environment becomes NBMA and the new feature should observe
       RFC2491 recommendations.

   C.  Section 6 discussed the constraints imposed on an LAA-based IPv6
       deployment by the fact that it is expected that the subscribers
       keep their assigned prefix, regardless of LNS.  A deployment
       approach was proposed that would maintain the addressing schemes
       contiguous and offers prefix summarization opportunities.  The
       topic could be further investigated for other solutions or
       improvements.

   D.  Sections 6 and 7 pointed out the limitations (previously
       documented in [IPv6-Multicast]) in deploying inter-domain ASM;
       however, SSM-based services seem more likely at this time.  For
       such SSM-based services of content delivery (video or audio),
       mechanisms are needed to facilitate the billing and management of
       listeners.  The currently available feature of MLD AAA is
       suggested; however, other methods or mechanisms might be
       developed and proposed.

   E.  In relation to Section 8, concerns have been raised related to
       running IPv6 multicast over WLAN links.  Potentially, these are
       the same kind of issues when running any Layer 3 protocol over a
       WLAN link that has a high loss-to-signal ratio; certain frames
       that are multicast based are dropped when settings are not
       adjusted properly.  For instance this behavior is similar to an
       IGMP host membership report, when done on a WLAN link with high
       loss-to-signal ratio and high interference.  This problem is
       inherited by WLAN that can impact both IPv4 and IPv6 multicast
       packets; it is not specific to IPv6 multicast.

   F.  The privacy extensions were mentioned as a popular means to
       provide some form of host security.  ISPs can track relatively
       easily the prefixes assigned to subscribers.  If, however, the
       ISPs are required by regulations to track their users at host
       address level, the privacy extensions [RFC3041] can be
       implemented only in parallel with network management tools that
       could provide traceability of the hosts.  Mechanisms should be
       defined to implement this aspect of user management.






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   G.  Tunnels are an effective way to avoid deployment dependencies on
       the IPv6 support on platforms that are out of the SP control
       (GWRs or CPEs) or over technologies that did not standardize the
       IPv6 support yet (cable).  They can be used in the following
       ways:

        i.  Tunnels directly to the CPE or GWR with public or private
            IPv4 addresses.

        ii. Tunnels directly to hosts with public or private IPv4
            addresses.  Recommendations on the exact tunneling
            mechanisms that can/should be used for last-mile access need
            to be investigated further and should be addressed by the
            IETF Softwire Working Group.

   H.  Through its larger address space, IPv6 allows SPs to assign
       fixed, globally routable prefixes to the links connecting each
       subscriber.

       This approach changes the provisioning methodologies that were
       used for IPv4.  Static configuration of the IPv6 addresses for
       all these links on the Edge Routers or Access Routers might not
       be a scalable option.  New provisioning mechanisms or features
       might need to be developed in order to deal with this issue, such
       as automatic mapping of VLAN IDs/PVCs (or other customer-specific
       information) to IPv6 prefixes.

   I.  New deployment models are emerging for the Layer 2 portion of the
       NAP where individual VLANs are not dedicated to each subscriber.
       This approach allows Layer 2 switches to aggregate more then 4096
       users.  MAC Forced Forwarding [RFC4562] is an example of such an
       implementation, where a broadcast domain is turned into an NBMA-
       like environment by forwarding the frames based on both Source
       and Destination MAC addresses.  Since these models are being
       adopted by the field, the implications of deploying IPv6 in such
       environments need to be further investigated.

   J.  The deployment of IPv6 in continuously evolving access service
       models raises some issues that may need further investigation.
       Examples of such topics are [AUTO-CONFIG]:

        i.  Network Service Selection & Authentication (NSSA) mechanisms
            working in association with stateless auto-configuration.
            As an example, NSSA relevant information, such as ISP
            preference, passwords, or profile ID, can be sent by hosts
            with the RS [RFC4191].





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        ii. Providing additional information in Router Advertisements to
            help access nodes with prefix selection in multi-ISP/
            multi-homed environments.

   Solutions to some of these topics range from making a media access
   capable of supporting native IPv6 (cable) to improving operational
   aspects of native IPv6 deployments.

11.  Security Considerations

   Please refer to the individual "IPv6 Security Considerations"
   technology sections for details.

12.  Acknowledgements

   We would like to thank Brian Carpenter, Patrick Grossetete, Toerless
   Eckert, Madhu Sudan, Shannon McFarland, Benoit Lourdelet, and Fred
   Baker for their valuable comments.  The authors would like to
   acknowledge the structure and information guidance provided by the
   work of Mickles, et al., on "Transition Scenarios for ISP Networks"
   [ISP-CASES].

13.  References

13.1.  Normative References

   [RFC1918]         Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot,
                     G., and E. Lear, "Address Allocation for Private
                     Internets", BCP 5, RFC 1918, February 1996.

   [RFC2080]         Malkin, G. and R. Minnear, "RIPng for IPv6",
                     RFC 2080, January 1997.

   [RFC2364]         Gross, G., Kaycee, M., Lin, A., Malis, A., and J.
                     Stephens, "PPP Over AAL5", RFC 2364, July 1998.

   [RFC2461]         Narten, T., Nordmark, E., and W. Simpson, "Neighbor
                     Discovery for IP Version 6 (IPv6)", RFC 2461,
                     December 1998.

   [RFC2462]         Thomson, S. and T. Narten, "IPv6 Stateless Address
                     Autoconfiguration", RFC 2462, December 1998.

   [RFC2473]         Conta, A. and S. Deering, "Generic Packet Tunneling
                     in IPv6 Specification", RFC 2473, December 1998.






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   [RFC2516]         Mamakos, L., Lidl, K., Evarts, J., Carrel, D.,
                     Simone, D., and R. Wheeler, "A Method for
                     Transmitting PPP Over Ethernet (PPPoE)", RFC 2516,
                     February 1999.

   [RFC2529]         Carpenter, B. and C. Jung, "Transmission of IPv6
                     over IPv4 Domains without Explicit Tunnels",
                     RFC 2529, March 1999.

   [RFC2661]         Townsley, W., Valencia, A., Rubens, A., Pall, G.,
                     Zorn, G., and B. Palter, "Layer Two Tunneling
                     Protocol "L2TP"", RFC 2661, August 1999.

   [RFC2740]         Coltun, R., Ferguson, D., and J. Moy, "OSPF for
                     IPv6", RFC 2740, December 1999.

   [RFC2784]         Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
                     Traina, "Generic Routing Encapsulation (GRE)",
                     RFC 2784, March 2000.

   [RFC3041]         Narten, T. and R. Draves, "Privacy Extensions for
                     Stateless Address Autoconfiguration in IPv6",
                     RFC 3041, January 2001.

   [RFC3053]         Durand, A., Fasano, P., Guardini, I., and D. Lento,
                     "IPv6 Tunnel Broker", RFC 3053, January 2001.

   [RFC3056]         Carpenter, B. and K. Moore, "Connection of IPv6
                     Domains via IPv4 Clouds", RFC 3056, February 2001.

   [RFC3177]         IAB and IESG, "IAB/IESG Recommendations on IPv6
                     Address Allocations to Sites", RFC 3177,
                     September 2001.

   [RFC3180]         Meyer, D. and P. Lothberg, "GLOP Addressing in
                     233/8", BCP 53, RFC 3180, September 2001.

   [RFC3315]         Droms, R., Bound, J., Volz, B., Lemon, T., Perkins,
                     C., and M. Carney, "Dynamic Host Configuration
                     Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3618]         Fenner, B. and D. Meyer, "Multicast Source
                     Discovery Protocol (MSDP)", RFC 3618, October 2003.

   [RFC3704]         Baker, F. and P. Savola, "Ingress Filtering for
                     Multihomed Networks", BCP 84, RFC 3704, March 2004.





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   [RFC3736]         Droms, R., "Stateless Dynamic Host Configuration
                     Protocol (DHCP) Service for IPv6", RFC 3736,
                     April 2004.

   [RFC3904]         Huitema, C., Austein, R., Satapati, S., and R. van
                     der Pol, "Evaluation of IPv6 Transition Mechanisms
                     for Unmanaged Networks", RFC 3904, September 2004.

   [RFC3931]         Lau, J., Townsley, M., and I. Goyret, "Layer Two
                     Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931,
                     March 2005.

   [RFC4001]         Daniele, M., Haberman, B., Routhier, S., and J.
                     Schoenwaelder, "Textual Conventions for Internet
                     Network Addresses", RFC 4001, February 2005.

   [RFC4029]         Lind, M., Ksinant, V., Park, S., Baudot, A., and P.
                     Savola, "Scenarios and Analysis for Introducing
                     IPv6 into ISP Networks", RFC 4029, March 2005.

   [RFC4191]         Draves, R. and D. Thaler, "Default Router
                     Preferences and More-Specific Routes", RFC 4191,
                     November 2005.

   [RFC4213]         Nordmark, E. and R. Gilligan, "Basic Transition
                     Mechanisms for IPv6 Hosts and Routers", RFC 4213,
                     October 2005.

   [RFC4214]         Templin, F., Gleeson, T., Talwar, M., and D.
                     Thaler, "Intra-Site Automatic Tunnel Addressing
                     Protocol (ISATAP)", RFC 4214, October 2005.

   [RFC4380]         Huitema, C., "Teredo: Tunneling IPv6 over UDP
                     through Network Address Translations (NATs)",
                     RFC 4380, February 2006.

13.2.  Informative References

   [6PE]             De Clercq, J., Ooms, D., Prevost, S., and F. Le
                     Faucheur, "Connecting IPv6 Islands across IPv4
                     Clouds with BGP", Work in Progress, December 2006.

   [AUTO-CONFIG]     Wen, H., Zhu, X., Jiang, Y., and R. Yan, "The
                     deployment of IPv6 stateless auto-configuration in
                     access network", 8th International Conference on
                     Telecommunications, ConTEL 2005, June 2005.





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   [BSR]             Bhaskar, N., Gall, A., Lingard, J., and S. Venaas,
                     "Bootstrap Router (BSR) Mechanism for PIM", Work
                     in Progress, June 2006.

   [DOCSIS3.0-OSSI]  CableLabs, CL., "DOCSIS 3.0 OSSI Specification(CM-
                     SP-OSSIv3.0-D02-060504)", May 2006.

   [DOCSIS3.0-Reqs]  Droms, R., Durand, A., Kharbanda, D., and J-F.
                     Mule, "DOCSIS 3.0 Requirements for IPv6 Support",
                     Work in Progress, March 2006.

   [DynamicTunnel]   Palet, J., Diaz, M., and P. Savola, "Analysis of
                     IPv6 Tunnel End-point Discovery Mechanisms", Work
                     in Progress, January 2005.

   [IEEE80211i]      IEEE, "IEEE Standards for Information Technology:
                     Part 11: Wireless LAN Medium Access Control (MAC)
                     and Physical Layer (PHY) specifications, Amendment
                     6: Medium Access Control (MAC) Security
                     Enhancements", July 2004.

   [IEEE8021X]       IEEE, "IEEE Standards for Local and Metropolitan
                     Area Networks: Port based Network Access Control,
                     IEEE Std 802.1X-2001", June 2001.

   [IPv6-Multicast]  Savola, P., "IPv6 Multicast Deployment Issues",
                     Work in Progress, April 2004.

   [IPv6-Security]   Convery, S. and D. Miller, "IPv6 and IPv4 Threat
                     Comparison and Best-Practice Evaluation",
                     March 2004.

   [ISISv6]          Hopps, C., "Routing IPv6 with IS-IS", Work
                     in Progress, October 2005.

   [ISP-CASES]       Mickles, C., "Transition Scenarios for ISP
                     Networks", Work in Progress, September 2002.

   [Protocol41]      Palet, J., Olvera, C., and D. Fernandez,
                     "Forwarding Protocol 41 in NAT Boxes", Work
                     in Progress, October 2003.

   [RF-Interface]    CableLabs, CL., "DOCSIS 2.0(CM-SP-RFIv2.0-I10-
                     051209)", December 2005.

   [RFC4562]         Melsen, T. and S. Blake, "MAC-Forced Forwarding: A
                     Method for Subscriber Separation on an Ethernet
                     Access Network", RFC 4562, June 2006.



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   [Softwire]        Dawkins, S., Ed., "Softwire Problem Statement",
                     Work in Progress, May 2006.

   [v6tc]            Palet, J., Nielsent, K., Parent, F., Durand, A.,
                     Suryanarayanan, R., and P. Savola, "Goals for
                     Tunneling Configuration", Work in Progress,
                     August 2005.












































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Authors' Addresses

   Salman Asadullah
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Phone: 408 526 8982
   EMail: sasad@cisco.com


   Adeel Ahmed
   Cisco Systems
   2200 East President George Bush Turnpike
   Richardson, TX  75082
   USA

   Phone: 469 255 4122
   EMail: adahmed@cisco.com


   Ciprian Popoviciu
   Cisco Systems
   7025-6 Kit Creek Road
   Research Triangle Park, NC  27709
   USA

   Phone: 919 392 3723
   EMail: cpopovic@cisco.com


   Pekka Savola
   CSC - Scientific Computing Ltd.
   Espoo
   Finland

   EMail: psavola@funet.fi













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   Jordi Palet Martinez
   Consulintel
   San Jose Artesano, 1
   Alcobendas, Madrid  E-28108
   Spain

   Phone: +34 91 151 81 99
   EMail: jordi.palet@consulintel.es











































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