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+Internet Engineering Task Force (IETF)                          H. Singh
+Request for Comments: 7084                                     W. Beebee
+Obsoletes: 6204                                      Cisco Systems, Inc.
+Category: Informational                                        C. Donley
+ISSN: 2070-1721                                                CableLabs
+                                                                B. Stark
+                                                                    AT&T
+                                                           November 2013
+
+
+           Basic Requirements for IPv6 Customer Edge Routers
+
+Abstract
+
+   This document specifies requirements for an IPv6 Customer Edge (CE)
+   router.  Specifically, the current version of this document focuses
+   on the basic provisioning of an IPv6 CE router and the provisioning
+   of IPv6 hosts attached to it.  The document also covers IP transition
+   technologies.  Two transition technologies in RFC 5969's IPv6 Rapid
+   Deployment on IPv4 Infrastructures (6rd) and RFC 6333's Dual-Stack
+   Lite (DS-Lite) are covered in the document.  The document obsoletes
+   RFC 6204.
+
+Status of This Memo
+
+   This document is not an Internet Standards Track specification; it is
+   published for informational purposes.
+
+   This document is a product of the Internet Engineering Task Force
+   (IETF).  It represents the consensus of the IETF community.  It has
+   received public review and has been approved for publication by the
+   Internet Engineering Steering Group (IESG).  Not all documents
+   approved by the IESG are a candidate for any level of Internet
+   Standard; see Section 2 of RFC 5741.
+
+   Information about the current status of this document, any errata,
+   and how to provide feedback on it may be obtained at
+   http://www.rfc-editor.org/info/rfc7084.
+
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+Singh, et al.                 Informational                     [Page 1]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+Copyright Notice
+
+   Copyright (c) 2013 IETF Trust and the persons identified as the
+   document authors.  All rights reserved.
+
+   This document is subject to BCP 78 and the IETF Trust's Legal
+   Provisions Relating to IETF Documents
+   (http://trustee.ietf.org/license-info) in effect on the date of
+   publication of this document.  Please review these documents
+   carefully, as they describe your rights and restrictions with respect
+   to this document.  Code Components extracted from this document must
+   include Simplified BSD License text as described in Section 4.e of
+   the Trust Legal Provisions and are provided without warranty as
+   described in the Simplified BSD License.
+
+Table of Contents
+
+   1. Introduction ....................................................3
+      1.1. Requirements Language ......................................3
+   2. Terminology .....................................................4
+   3. Architecture ....................................................5
+      3.1. Current IPv4 End-User Network Architecture .................5
+      3.2. IPv6 End-User Network Architecture .........................5
+           3.2.1. Local Communication .................................7
+   4. Requirements ....................................................7
+      4.1. General Requirements .......................................7
+      4.2. WAN-Side Configuration .....................................8
+      4.3. LAN-Side Configuration ....................................12
+      4.4. Transition Technologies Support ...........................14
+           4.4.1. 6rd ................................................14
+           4.4.2. Dual-Stack Lite (DS-Lite) ..........................15
+      4.5. Security Considerations ...................................16
+   5. Acknowledgements ...............................................17
+   6. Contributors ...................................................17
+   7. References .....................................................18
+      7.1. Normative References ......................................18
+      7.2. Informative References ....................................20
+
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+Singh, et al.                 Informational                     [Page 2]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+1.  Introduction
+
+   This document defines basic IPv6 features for a residential or small-
+   office router, referred to as an "IPv6 CE router", in order to
+   establish an industry baseline for features to be implemented on such
+   a router.
+
+   These routers typically also support IPv4.
+
+   Mixed environments of dual-stack hosts and IPv6-only hosts (behind
+   the CE router) can be more complex if the IPv6-only devices are using
+   a translator to access IPv4 servers [RFC6144].  Support for such
+   mixed environments is not in scope of this document.
+
+   This document specifies how an IPv6 CE router automatically
+   provisions its WAN interface, acquires address space for provisioning
+   of its LAN interfaces, and fetches other configuration information
+   from the service provider network.  Automatic provisioning of more
+   complex topology than a single router with multiple LAN interfaces is
+   out of scope for this document.
+
+   See [RFC4779] for a discussion of options available for deploying
+   IPv6 in service provider access networks.
+
+   The document also covers the IP transition technologies that were
+   available at the time this document was written.  Two transition
+   technologies in 6rd [RFC5969] and DS-Lite [RFC6333] are covered in
+   the document.
+
+1.1.  Requirements Language
+
+   Take careful note: Unlike other IETF documents, the key words "MUST",
+   "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
+   "RECOMMENDED", "MAY", and "OPTIONAL" in this document are not used as
+   described in RFC 2119 [RFC2119].  This document uses these keywords
+   not strictly for the purpose of interoperability, but rather for the
+   purpose of establishing industry-common baseline functionality.  As
+   such, the document points to several other specifications (preferable
+   in RFC or stable form) to provide additional guidance to implementers
+   regarding any protocol implementation required to produce a
+   successful CE router that interoperates successfully with a
+   particular subset of currently deploying and planned common IPv6
+   access networks.
+
+
+
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+Singh, et al.                 Informational                     [Page 3]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+2.  Terminology
+
+   End-User Network          one or more links attached to the IPv6 CE
+                             router that connect IPv6 hosts.
+
+   IPv6 Customer Edge Router a node intended for home or small-office
+                             use that forwards IPv6 packets not
+                             explicitly addressed to itself.  The IPv6
+                             CE router connects the end-user network to
+                             a service provider network.
+
+   IPv6 Host                 any device implementing an IPv6 stack
+                             receiving IPv6 connectivity through the
+                             IPv6 CE router.
+
+   LAN Interface             an IPv6 CE router's attachment to a link in
+                             the end-user network.  Examples are
+                             Ethernet (simple or bridged), 802.11
+                             wireless, or other LAN technologies.  An
+                             IPv6 CE router may have one or more
+                             network-layer LAN interfaces.
+
+   Service Provider          an entity that provides access to the
+                             Internet.  In this document, a service
+                             provider specifically offers Internet
+                             access using IPv6, and it may also offer
+                             IPv4 Internet access.  The service provider
+                             can provide such access over a variety of
+                             different transport methods such as DSL,
+                             cable, wireless, and others.
+
+   WAN Interface             an IPv6 CE router's attachment to a link
+                             used to provide connectivity to the service
+                             provider network; example link technologies
+                             include Ethernet (simple or bridged), PPP
+                             links, Frame Relay, or ATM networks, as
+                             well as Internet-layer (or higher-layer)
+                             "tunnels", such as tunnels over IPv4 or
+                             IPv6 itself.
+
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+Singh, et al.                 Informational                     [Page 4]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+3.  Architecture
+
+3.1.  Current IPv4 End-User Network Architecture
+
+   An end-user network will likely support both IPv4 and IPv6.  It is
+   not expected that an end user will change their existing network
+   topology with the introduction of IPv6.  There are some differences
+   in how IPv6 works and is provisioned; these differences have
+   implications for the network architecture.  A typical IPv4 end-user
+   network consists of a "plug and play" router with NAT functionality
+   and a single link behind it, connected to the service provider
+   network.
+
+   A typical IPv4 NAT deployment by default blocks all incoming
+   connections.  Opening of ports is typically allowed using a Universal
+   Plug and Play Internet Gateway Device (UPnP IGD) [UPnP-IGD] or some
+   other firewall control protocol.
+
+   Another consequence of using private address space in the end-user
+   network is that it provides stable addressing; that is, it never
+   changes even when you change service providers, and the addresses are
+   always there even when the WAN interface is down or the customer edge
+   router has not yet been provisioned.
+
+   Many existing routers support dynamic routing (which learns routes
+   from other routers), and advanced end-users can build arbitrary,
+   complex networks using manual configuration of address prefixes
+   combined with a dynamic routing protocol.
+
+3.2.  IPv6 End-User Network Architecture
+
+   The end-user network architecture for IPv6 should provide equivalent
+   or better capabilities and functionality than the current IPv4
+   architecture.
+
+
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+Singh, et al.                 Informational                     [Page 5]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   The end-user network is a stub network.  Figure 1 illustrates the
+   model topology for the end-user network.
+
+                   +-------+-------+                      \
+                   |   Service     |                       \
+                   |   Provider    |                        | Service
+                   |    Router     |                        | Provider
+                   +-------+-------+                        | Network
+                           |                               /
+                           | Customer                     /
+                           | Internet Connection         /
+                           |
+                    +------+--------+                    \
+                    |     IPv6      |                     \
+                    | Customer Edge |                      \
+                    |    Router     |                      /
+                    +---+-------+-+-+                     /
+        Network A       |       |   Network B            | End-User
+  ---+-------------+----+-    --+--+-------------+---    | Network(s)
+     |             |               |             |        \
+ +----+-----+ +-----+----+     +----+-----+ +-----+----+   \
+ |IPv6 Host | |IPv6 Host |     | IPv6 Host| |IPv6 Host |   /
+ |          | |          |     |          | |          |  /
+ +----------+ +-----+----+     +----------+ +----------+ /
+
+            Figure 1: An Example of a Typical End-User Network
+
+   This architecture describes the:
+
+   o  Basic capabilities of an IPv6 CE router
+
+   o  Provisioning of the WAN interface connecting to the service
+      provider
+
+   o  Provisioning of the LAN interfaces
+
+   For IPv6 multicast traffic, the IPv6 CE router may act as a Multicast
+   Listener Discovery (MLD) proxy [RFC4605] and may support a dynamic
+   multicast routing protocol.
+
+   The IPv6 CE router may be manually configured in an arbitrary
+   topology with a dynamic routing protocol.  Automatic provisioning and
+   configuration are described for a single IPv6 CE router only.
+
+
+
+
+
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+
+Singh, et al.                 Informational                     [Page 6]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+3.2.1.  Local Communication
+
+   Link-local IPv6 addresses are used by hosts communicating on a single
+   link.  Unique Local IPv6 Unicast Addresses (ULAs) [RFC4193] are used
+   by hosts communicating within the end-user network across multiple
+   links, but without requiring the application to use a globally
+   routable address.  The IPv6 CE router defaults to acting as the
+   demarcation point between two networks by providing a ULA boundary, a
+   multicast zone boundary, and ingress and egress traffic filters.
+
+   At the time of this writing, several host implementations do not
+   handle the case where they have an IPv6 address configured and no
+   IPv6 connectivity, either because the address itself has a limited
+   topological reachability (e.g., ULA) or because the IPv6 CE router is
+   not connected to the IPv6 network on its WAN interface.  To support
+   host implementations that do not handle multihoming in a multi-prefix
+   environment [MULTIHOMING-WITHOUT-NAT], the IPv6 CE router should not,
+   as detailed in the requirements below, advertise itself as a default
+   router on the LAN interface(s) when it does not have IPv6
+   connectivity on the WAN interface or when it is not provisioned with
+   IPv6 addresses.  For local IPv6 communication, the mechanisms
+   specified in [RFC4191] are used.
+
+   ULA addressing is useful where the IPv6 CE router has multiple LAN
+   interfaces with hosts that need to communicate with each other.  If
+   the IPv6 CE router has only a single LAN interface (IPv6 link), then
+   link-local addressing can be used instead.
+
+   Coexistence with IPv4 requires any IPv6 CE router(s) on the LAN to
+   conform to these recommendations, especially requirements ULA-5 and
+   L-4 below.
+
+4.  Requirements
+
+4.1.  General Requirements
+
+   The IPv6 CE router is responsible for implementing IPv6 routing; that
+   is, the IPv6 CE router must look up the IPv6 destination address in
+   its routing table to decide to which interface it should send the
+   packet.
+
+   In this role, the IPv6 CE router is responsible for ensuring that
+   traffic using its ULA addressing does not go out the WAN interface
+   and does not originate from the WAN interface.
+
+
+
+
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+Singh, et al.                 Informational                     [Page 7]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   G-1:  An IPv6 CE router is an IPv6 node according to the IPv6 Node
+         Requirements specification [RFC6434].
+
+   G-2:  The IPv6 CE router MUST implement ICMPv6 according to
+         [RFC4443].  In particular, point-to-point links MUST be handled
+         as described in Section 3.1 of [RFC4443].
+
+   G-3:  The IPv6 CE router MUST NOT forward any IPv6 traffic between
+         its LAN interface(s) and its WAN interface until the router has
+         successfully completed the IPv6 address and the delegated
+         prefix acquisition process.
+
+   G-4:  By default, an IPv6 CE router that has no default router(s) on
+         its WAN interface MUST NOT advertise itself as an IPv6 default
+         router on its LAN interfaces.  That is, the "Router Lifetime"
+         field is set to zero in all Router Advertisement messages it
+         originates [RFC4861].
+
+   G-5:  By default, if the IPv6 CE router is an advertising router and
+         loses its IPv6 default router(s) and/or detects loss of
+         connectivity on the WAN interface, it MUST explicitly
+         invalidate itself as an IPv6 default router on each of its
+         advertising interfaces by immediately transmitting one or more
+         Router Advertisement messages with the "Router Lifetime" field
+         set to zero [RFC4861].
+
+4.2.  WAN-Side Configuration
+
+   The IPv6 CE router will need to support connectivity to one or more
+   access network architectures.  This document describes an IPv6 CE
+   router that is not specific to any particular architecture or service
+   provider and that supports all commonly used architectures.
+
+   IPv6 Neighbor Discovery and DHCPv6 protocols operate over any type of
+   IPv6-supported link layer, and there is no need for a link-layer-
+   specific configuration protocol for IPv6 network-layer configuration
+   options as in, e.g., PPP IP Control Protocol (IPCP) for IPv4.  This
+   section makes the assumption that the same mechanism will work for
+   any link layer, be it Ethernet, the Data Over Cable Service Interface
+   Specification (DOCSIS), PPP, or others.
+
+
+
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+Singh, et al.                 Informational                     [Page 8]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   WAN-side requirements:
+
+   W-1:  When the router is attached to the WAN interface link, it MUST
+         act as an IPv6 host for the purposes of stateless [RFC4862] or
+         stateful [RFC3315] interface address assignment.
+
+   W-2:  The IPv6 CE router MUST generate a link-local address and
+         finish Duplicate Address Detection according to [RFC4862] prior
+         to sending any Router Solicitations on the interface.  The
+         source address used in the subsequent Router Solicitation MUST
+         be the link-local address on the WAN interface.
+
+   W-3:  Absent other routing information, the IPv6 CE router MUST use
+         Router Discovery as specified in [RFC4861] to discover a
+         default router(s) and install a default route(s) in its routing
+         table with the discovered router's address as the next hop.
+
+   W-4:  The router MUST act as a requesting router for the purposes of
+         DHCPv6 prefix delegation ([RFC3633]).
+
+   W-5:  The IPv6 CE router MUST use a persistent DHCP Unique Identifier
+         (DUID) for DHCPv6 messages.  The DUID MUST NOT change between
+         network-interface resets or IPv6 CE router reboots.
+
+   W-6:  The WAN interface of the CE router SHOULD support a Port
+         Control Protocol (PCP) client as specified in [RFC6887] for use
+         by applications on the CE router.  The PCP client SHOULD follow
+         the procedure specified in Section 8.1 of [RFC6887] to discover
+         its PCP server.  This document takes no position on whether
+         such functionality is enabled by default or mechanisms by which
+         users would configure the functionality.  Handling PCP requests
+         from PCP clients in the LAN side of the CE router is out of
+         scope.
+
+   Link-layer requirements:
+
+   WLL-1:  If the WAN interface supports Ethernet encapsulation, then
+           the IPv6 CE router MUST support IPv6 over Ethernet [RFC2464].
+
+   WLL-2:  If the WAN interface supports PPP encapsulation, the IPv6 CE
+           router MUST support IPv6 over PPP [RFC5072].
+
+   WLL-3:  If the WAN interface supports PPP encapsulation, in a dual-
+           stack environment with IPCP and IPV6CP running over one PPP
+           logical channel, the Network Control Protocols (NCPs) MUST be
+           treated as independent of each other and start and terminate
+           independently.
+
+
+
+
+Singh, et al.                 Informational                     [Page 9]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   Address assignment requirements:
+
+   WAA-1:   The IPv6 CE router MUST support Stateless Address
+            Autoconfiguration (SLAAC) [RFC4862].
+
+   WAA-2:   The IPv6 CE router MUST follow the recommendations in
+            Section 4 of [RFC5942], and in particular the handling of
+            the L flag in the Router Advertisement Prefix Information
+            option.
+
+   WAA-3:   The IPv6 CE router MUST support DHCPv6 [RFC3315] client
+            behavior.
+
+   WAA-4:   The IPv6 CE router MUST be able to support the following
+            DHCPv6 options: Identity Association for Non-temporary
+            Address (IA_NA), Reconfigure Accept [RFC3315], and
+            DNS_SERVERS [RFC3646].  The IPv6 CE router SHOULD be able to
+            support the DNS Search List (DNSSL) option as specified in
+            [RFC3646].
+
+   WAA-5:   The IPv6 CE router SHOULD implement the Network Time
+            Protocol (NTP) as specified in [RFC5905] to provide a time
+            reference common to the service provider for other
+            protocols, such as DHCPv6, to use.  If the CE router
+            implements NTP, it requests the NTP Server DHCPv6 option
+            [RFC5908] and uses the received list of servers as primary
+            time reference, unless explicitly configured otherwise.  LAN
+            side support of NTP is out of scope for this document.
+
+   WAA-6:   If the IPv6 CE router receives a Router Advertisement
+            message (described in [RFC4861]) with the M flag set to 1,
+            the IPv6 CE router MUST do DHCPv6 address assignment
+            (request an IA_NA option).
+
+   WAA-7:   If the IPv6 CE router does not acquire a global IPv6
+            address(es) from either SLAAC or DHCPv6, then it MUST create
+            a global IPv6 address(es) from its delegated prefix(es) and
+            configure those on one of its internal virtual network
+            interfaces, unless configured to require a global IPv6
+            address on the WAN interface.
+
+   WAA-8:   The CE router MUST support the SOL_MAX_RT option [RFC7083]
+            and request the SOL_MAX_RT option in an Option Request
+            Option (ORO).
+
+
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 10]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   WAA-9:   As a router, the IPv6 CE router MUST follow the weak host
+            (Weak End System) model [RFC1122].  When originating packets
+            from an interface, it will use a source address from another
+            one of its interfaces if the outgoing interface does not
+            have an address of suitable scope.
+
+   WAA-10:  The IPv6 CE router SHOULD implement the Information Refresh
+            Time option and associated client behavior as specified in
+            [RFC4242].
+
+   Prefix delegation requirements:
+
+   WPD-1:  The IPv6 CE router MUST support DHCPv6 prefix delegation
+           requesting router behavior as specified in [RFC3633]
+           (Identity Association for Prefix Delegation (IA_PD) option).
+
+   WPD-2:  The IPv6 CE router MAY indicate as a hint to the delegating
+           router the size of the prefix it requires.  If so, it MUST
+           ask for a prefix large enough to assign one /64 for each of
+           its interfaces, rounded up to the nearest nibble, and SHOULD
+           be configurable to ask for more.
+
+   WPD-3:  The IPv6 CE router MUST be prepared to accept a delegated
+           prefix size different from what is given in the hint.  If the
+           delegated prefix is too small to address all of its
+           interfaces, the IPv6 CE router SHOULD log a system management
+           error.  [RFC6177] covers the recommendations for service
+           providers for prefix allocation sizes.
+
+   WPD-4:  By default, the IPv6 CE router MUST initiate DHCPv6 prefix
+           delegation when either the M or O flags are set to 1 in a
+           received Router Advertisement (RA) message.  Behavior of the
+           CE router to use DHCPv6 prefix delegation when the CE router
+           has not received any RA or received an RA with the M and the
+           O bits set to zero is out of scope for this document.
+
+   WPD-5:  Any packet received by the CE router with a destination
+           address in the prefix(es) delegated to the CE router but not
+           in the set of prefixes assigned by the CE router to the LAN
+           must be dropped.  In other words, the next hop for the
+           prefix(es) delegated to the CE router should be the null
+           destination.  This is necessary to prevent forwarding loops
+           when some addresses covered by the aggregate are not
+           reachable [RFC4632].
+
+
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 11]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+      (a)  The IPv6 CE router SHOULD send an ICMPv6 Destination
+           Unreachable message in accordance with Section 3.1 of
+           [RFC4443] back to the source of the packet, if the packet is
+           to be dropped due to this rule.
+
+   WPD-6:  If the IPv6 CE router requests both an IA_NA and an IA_PD
+           option in DHCPv6, it MUST accept an IA_PD option in DHCPv6
+           Advertise/Reply messages, even if the message does not
+           contain any addresses, unless configured to only obtain its
+           WAN IPv6 address via DHCPv6; see [DHCPv6-STATEFUL-ISSUES].
+
+   WPD-7:  By default, an IPv6 CE router MUST NOT initiate any dynamic
+           routing protocol on its WAN interface.
+
+   WPD-8:  The IPv6 CE router SHOULD support the [RFC6603] Prefix
+           Exclude option.
+
+4.3.  LAN-Side Configuration
+
+   The IPv6 CE router distributes configuration information obtained
+   during WAN interface provisioning to IPv6 hosts and assists IPv6
+   hosts in obtaining IPv6 addresses.  It also supports connectivity of
+   these devices in the absence of any working WAN interface.
+
+   An IPv6 CE router is expected to support an IPv6 end-user network and
+   IPv6 hosts that exhibit the following characteristics:
+
+   1.  Link-local addresses may be insufficient for allowing IPv6
+       applications to communicate with each other in the end-user
+       network.  The IPv6 CE router will need to enable this
+       communication by providing globally scoped unicast addresses or
+       ULAs [RFC4193], whether or not WAN connectivity exists.
+
+   2.  IPv6 hosts should be capable of using SLAAC and may be capable of
+       using DHCPv6 for acquiring their addresses.
+
+   3.  IPv6 hosts may use DHCPv6 for other configuration information,
+       such as the DNS_SERVERS option for acquiring DNS information.
+
+   Unless otherwise specified, the following requirements apply to the
+   IPv6 CE router's LAN interfaces only.
+
+   ULA requirements:
+
+   ULA-1:  The IPv6 CE router SHOULD be capable of generating a ULA
+           prefix [RFC4193].
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 12]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   ULA-2:  An IPv6 CE router with a ULA prefix MUST maintain this prefix
+           consistently across reboots.
+
+   ULA-3:  The value of the ULA prefix SHOULD be configurable.
+
+   ULA-4:  By default, the IPv6 CE router MUST act as a site border
+           router according to Section 4.3 of [RFC4193] and filter
+           packets with local IPv6 source or destination addresses
+           accordingly.
+
+   ULA-5:  An IPv6 CE router MUST NOT advertise itself as a default
+           router with a Router Lifetime greater than zero whenever all
+           of its configured and delegated prefixes are ULA prefixes.
+
+   LAN requirements:
+
+   L-1:   The IPv6 CE router MUST support router behavior according to
+          Neighbor Discovery for IPv6 [RFC4861].
+
+   L-2:   The IPv6 CE router MUST assign a separate /64 from its
+          delegated prefix(es) (and ULA prefix if configured to provide
+          ULA addressing) for each of its LAN interfaces.
+
+   L-3:   An IPv6 CE router MUST advertise itself as a router for the
+          delegated prefix(es) (and ULA prefix if configured to provide
+          ULA addressing) using the "Route Information Option" specified
+          in Section 2.3 of [RFC4191].  This advertisement is
+          independent of having or not having IPv6 connectivity on the
+          WAN interface.
+
+   L-4:   An IPv6 CE router MUST NOT advertise itself as a default
+          router with a Router Lifetime [RFC4861] greater than zero if
+          it has no prefixes configured or delegated to it.
+
+   L-5:   The IPv6 CE router MUST make each LAN interface an advertising
+          interface according to [RFC4861].
+
+   L-6:   In Router Advertisement messages ([RFC4861]), the Prefix
+          Information option's A and L flags MUST be set to 1 by
+          default.
+
+   L-7:   The A and L flags' ([RFC4861]) settings SHOULD be user
+          configurable.
+
+   L-8:   The IPv6 CE router MUST support a DHCPv6 server capable of
+          IPv6 address assignment according to [RFC3315] OR a stateless
+          DHCPv6 server according to [RFC3736] on its LAN interfaces.
+
+
+
+
+Singh, et al.                 Informational                    [Page 13]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   L-9:   Unless the IPv6 CE router is configured to support the DHCPv6
+          IA_NA option, it SHOULD set the M flag to zero and the O flag
+          to 1 in its Router Advertisement messages [RFC4861].
+
+   L-10:  The IPv6 CE router MUST support providing DNS information in
+          the DHCPv6 DNS_SERVERS and DOMAIN_LIST options [RFC3646].
+
+   L-11:  The IPv6 CE router MUST support providing DNS information in
+          the Router Advertisement Recursive DNS Server (RDNSS) and DNS
+          Search List options.  Both options are specified in [RFC6106].
+
+   L-12:  The IPv6 CE router SHOULD make available a subset of DHCPv6
+          options (as listed in Section 5.3 of [RFC3736]) received from
+          the DHCPv6 client on its WAN interface to its LAN-side DHCPv6
+          server.
+
+   L-13:  If the delegated prefix changes, i.e., the current prefix is
+          replaced with a new prefix without any overlapping time
+          period, then the IPv6 CE router MUST immediately advertise the
+          old prefix with a Preferred Lifetime of zero and a Valid
+          Lifetime of either a) zero or b) the lower of the current
+          Valid Lifetime and two hours (which must be decremented in
+          real time) in a Router Advertisement message as described in
+          Section 5.5.3, (e) of [RFC4862].
+
+   L-14:  The IPv6 CE router MUST send an ICMPv6 Destination Unreachable
+          message, code 5 (Source address failed ingress/egress policy)
+          for packets forwarded to it that use an address from a prefix
+          that has been invalidated.
+
+4.4.  Transition Technologies Support
+
+4.4.1.  6rd
+
+   6rd [RFC5969] specifies an automatic tunneling mechanism tailored to
+   advance deployment of IPv6 to end users via a service provider's IPv4
+   network infrastructure.  Key aspects include automatic IPv6 prefix
+   delegation to sites, stateless operation, simple provisioning, and
+   service that is equivalent to native IPv6 at the sites that are
+   served by the mechanism.  It is expected that such traffic is
+   forwarded over the CE router's native IPv4 WAN interface and not
+   encapsulated in another tunnel.
+
+   The CE router SHOULD support 6rd functionality.  If 6rd is supported,
+   it MUST be implemented according to [RFC5969].  The following CE
+   Requirements also apply:
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 14]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   6rd requirements:
+
+   6RD-1:  The IPv6 CE router MUST support 6rd configuration via the 6rd
+           DHCPv4 Option 212.  If the CE router has obtained an IPv4
+           network address through some other means such as PPP, it
+           SHOULD use the DHCPINFORM request message [RFC2131] to
+           request the 6rd DHCPv4 Option.  The IPv6 CE router MAY use
+           other mechanisms to configure 6rd parameters.  Such
+           mechanisms are outside the scope of this document.
+
+   6RD-2:  If the IPv6 CE router is capable of automated configuration
+           of IPv4 through IPCP (i.e., over a PPP connection), it MUST
+           support user-entered configuration of 6rd.
+
+   6RD-3:  If the CE router supports configuration mechanisms other than
+           the 6rd DHCPv4 Option 212 (user-entered, TR-069 [TR-069],
+           etc.), the CE router MUST support 6rd in "hub and spoke"
+           mode. 6rd in "hub and spoke" requires all IPv6 traffic to go
+           to the 6rd Border Relay.  In effect, this requirement removes
+           the "direct connect to 6rd" route defined in Section 7.1.1 of
+           [RFC5969].
+
+   6RD-4:  A CE router MUST allow 6rd and native IPv6 WAN interfaces to
+           be active alone as well as simultaneously in order to support
+           coexistence of the two technologies during an incremental
+           migration period such as a migration from 6rd to native IPv6.
+
+   6RD-5:  Each packet sent on a 6rd or native WAN interface MUST be
+           directed such that its source IP address is derived from the
+           delegated prefix associated with the particular interface
+           from which the packet is being sent (Section 4.3 of
+           [RFC3704]).
+
+   6RD-6:  The CE router MUST allow different as well as identical
+           delegated prefixes to be configured via each (6rd or native)
+           WAN interface.
+
+   6RD-7:  In the event that forwarding rules produce a tie between 6rd
+           and native IPv6, by default, the IPv6 CE router MUST prefer
+           native IPv6.
+
+4.4.2.  Dual-Stack Lite (DS-Lite)
+
+   Dual-Stack Lite [RFC6333] enables both continued support for IPv4
+   services and incentives for the deployment of IPv6.  It also
+   de-couples IPv6 deployment in the service provider network from the
+   rest of the Internet, making incremental deployment easier.  Dual-
+   Stack Lite enables a broadband service provider to share IPv4
+
+
+
+Singh, et al.                 Informational                    [Page 15]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   addresses among customers by combining two well-known technologies:
+   IP in IP (IPv4-in-IPv6) and Network Address Translation (NAT).  It is
+   expected that DS-Lite traffic is forwarded over the CE router's
+   native IPv6 WAN interface, and not encapsulated in another tunnel.
+
+   The IPv6 CE router SHOULD implement DS-Lite functionality.  If
+   DS-Lite is supported, it MUST be implemented according to [RFC6333].
+   This document takes no position on simultaneous operation of Dual-
+   Stack Lite and native IPv4.  The following CE router requirements
+   also apply:
+
+   WAN requirements:
+
+   DLW-1:  The CE router MUST support configuration of DS-Lite via the
+           DS-Lite DHCPv6 option [RFC6334].  The IPv6 CE router MAY use
+           other mechanisms to configure DS-Lite parameters.  Such
+           mechanisms are outside the scope of this document.
+
+   DLW-2:  The IPv6 CE router MUST NOT perform IPv4 Network Address
+           Translation (NAT) on IPv4 traffic encapsulated using DS-Lite.
+
+   DLW-3:  If the IPv6 CE router is configured with an IPv4 address on
+           its WAN interface, then the IPv6 CE router SHOULD disable the
+           DS-Lite Basic Bridging BroadBand (B4) element.
+
+4.5.  Security Considerations
+
+   It is considered a best practice to filter obviously malicious
+   traffic (e.g., spoofed packets, "Martian" addresses, etc.).  Thus,
+   the IPv6 CE router ought to support basic stateless egress and
+   ingress filters.  The CE router is also expected to offer mechanisms
+   to filter traffic entering the customer network; however, the method
+   by which vendors implement configurable packet filtering is beyond
+   the scope of this document.
+
+   Security requirements:
+
+   S-1:  The IPv6 CE router SHOULD support [RFC6092].  In particular,
+         the IPv6 CE router SHOULD support functionality sufficient for
+         implementing the set of recommendations in [RFC6092],
+         Section 4.  This document takes no position on whether such
+         functionality is enabled by default or mechanisms by which
+         users would configure it.
+
+
+
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 16]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   S-2:  The IPv6 CE router SHOULD support ingress filtering in
+         accordance with BCP 38 [RFC2827].  Note that this requirement
+         was downgraded from a MUST from RFC 6204 due to the difficulty
+         of implementation in the CE router and the feature's redundancy
+         with upstream router ingress filtering.
+
+   S-3:  If the IPv6 CE router firewall is configured to filter incoming
+         tunneled data, the firewall SHOULD provide the capability to
+         filter decapsulated packets from a tunnel.
+
+5.  Acknowledgements
+
+   Thanks to the following people (in alphabetical order) for their
+   guidance and feedback:
+
+   Mikael Abrahamsson, Tore Anderson, Merete Asak, Rajiv Asati, Scott
+   Beuker, Mohamed Boucadair, Rex Bullinger, Brian Carpenter, Tassos
+   Chatzithomaoglou, Lorenzo Colitti, Remi Denis-Courmont, Gert Doering,
+   Alain Durand, Katsunori Fukuoka, Brian Haberman, Tony Hain, Thomas
+   Herbst, Ray Hunter, Joel Jaeggli, Kevin Johns, Erik Kline, Stephen
+   Kramer, Victor Kuarsingh, Francois-Xavier Le Bail, Arifumi Matsumoto,
+   David Miles, Shin Miyakawa, Jean-Francois Mule, Michael Newbery,
+   Carlos Pignataro, John Pomeroy, Antonio Querubin, Daniel Roesen,
+   Hiroki Sato, Teemu Savolainen, Matt Schmitt, David Thaler, Mark
+   Townsley, Sean Turner, Bernie Volz, Dan Wing, Timothy Winters, James
+   Woodyatt, Carl Wuyts, and Cor Zwart.
+
+   This document is based in part on CableLabs' eRouter specification.
+   The authors wish to acknowledge the additional contributors from the
+   eRouter team:
+
+   Ben Bekele, Amol Bhagwat, Ralph Brown, Eduardo Cardona, Margo Dolas,
+   Toerless Eckert, Doc Evans, Roger Fish, Michelle Kuska, Diego
+   Mazzola, John McQueen, Harsh Parandekar, Michael Patrick, Saifur
+   Rahman, Lakshmi Raman, Ryan Ross, Ron da Silva, Madhu Sudan, Dan
+   Torbet, and Greg White.
+
+6.  Contributors
+
+   The following people have participated as co-authors or provided
+   substantial contributions to this document: Ralph Droms, Kirk
+   Erichsen, Fred Baker, Jason Weil, Lee Howard, Jean-Francois Tremblay,
+   Yiu Lee, John Jason Brzozowski, and Heather Kirksey.  Thanks to Ole
+   Troan for editorship in the original RFC 6204 document.
+
+
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 17]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+7.  References
+
+7.1.  Normative References
+
+   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
+              Communication Layers", STD 3, RFC 1122, October 1989.
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol", RFC
+              2131, March 1997.
+
+   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
+              Networks", RFC 2464, December 1998.
+
+   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
+              Defeating Denial of Service Attacks which employ IP Source
+              Address Spoofing", BCP 38, RFC 2827, May 2000.
+
+   [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.
+
+   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
+              Host Configuration Protocol (DHCP) version 6", RFC 3633,
+              December 2003.
+
+   [RFC3646]  Droms, R., "DNS Configuration options for Dynamic Host
+              Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
+              December 2003.
+
+   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
+              Networks", BCP 84, RFC 3704, March 2004.
+
+   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
+              (DHCP) Service for IPv6", RFC 3736, April 2004.
+
+   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
+              More-Specific Routes", RFC 4191, November 2005.
+
+   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
+              Addresses", RFC 4193, October 2005.
+
+   [RFC4242]  Venaas, S., Chown, T., and B. Volz, "Information Refresh
+              Time Option for Dynamic Host Configuration Protocol for
+              IPv6 (DHCPv6)", RFC 4242, November 2005.
+
+
+
+
+Singh, et al.                 Informational                    [Page 18]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   [RFC4443]  Conta, A., Deering, S., and M. Gupta, "Internet Control
+              Message Protocol (ICMPv6) for the Internet Protocol
+              Version 6 (IPv6) Specification", RFC 4443, March 2006.
+
+   [RFC4605]  Fenner, B., He, H., Haberman, B., and H. Sandick,
+              "Internet Group Management Protocol (IGMP) / Multicast
+              Listener Discovery (MLD)-Based Multicast Forwarding
+              ("IGMP/MLD Proxying")", RFC 4605, August 2006.
+
+   [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
+              (CIDR): The Internet Address Assignment and Aggregation
+              Plan", BCP 122, RFC 4632, August 2006.
+
+   [RFC4779]  Asadullah, S., Ahmed, A., Popoviciu, C., Savola, P., and
+              J. Palet, "ISP IPv6 Deployment Scenarios in Broadband
+              Access Networks", RFC 4779, January 2007.
+
+   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
+              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
+              September 2007.
+
+   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
+              Address Autoconfiguration", RFC 4862, September 2007.
+
+   [RFC5072]  Varada, S., Haskins, D., and E. Allen, "IP Version 6 over
+              PPP", RFC 5072, September 2007.
+
+   [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
+              Time Protocol Version 4: Protocol and Algorithms
+              Specification", RFC 5905, June 2010.
+
+   [RFC5908]  Gayraud, R. and B. Lourdelet, "Network Time Protocol (NTP)
+              Server Option for DHCPv6", RFC 5908, June 2010.
+
+   [RFC5942]  Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
+              Model: The Relationship between Links and Subnet
+              Prefixes", RFC 5942, July 2010.
+
+   [RFC5969]  Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
+              Infrastructures (6rd) -- Protocol Specification", RFC
+              5969, August 2010.
+
+   [RFC6092]  Woodyatt, J., "Recommended Simple Security Capabilities in
+              Customer Premises Equipment (CPE) for Providing
+              Residential IPv6 Internet Service", RFC 6092, January
+              2011.
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 19]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   [RFC6106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
+              "IPv6 Router Advertisement Options for DNS Configuration",
+              RFC 6106, November 2010.
+
+   [RFC6177]  Narten, T., Huston, G., and L. Roberts, "IPv6 Address
+              Assignment to End Sites", BCP 157, RFC 6177, March 2011.
+
+   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
+              Stack Lite Broadband Deployments Following IPv4
+              Exhaustion", RFC 6333, August 2011.
+
+   [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
+              Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
+              RFC 6334, August 2011.
+
+   [RFC6434]  Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
+              Requirements", RFC 6434, December 2011.
+
+   [RFC6603]  Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
+              "Prefix Exclude Option for DHCPv6-based Prefix
+              Delegation", RFC 6603, May 2012.
+
+   [RFC6887]  Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
+              Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
+              2013.
+
+   [RFC7083]  Droms, R., "Modification to Default Values of SOL_MAX_RT
+              and INF_MAX_RT", RFC 7083, November 2013.
+
+7.2.  Informative References
+
+   [DHCPv6-STATEFUL-ISSUES]
+              Troan, O. and B. Volz, "Issues with multiple stateful
+              DHCPv6 options", Work in Progress, May 2013.
+
+   [MULTIHOMING-WITHOUT-NAT]
+              Troan, O., Ed., Miles, D., Matsushima, S., Okimoto, T.,
+              and D. Wing, "IPv6 Multihoming without Network Address
+              Translation", Work in Progress, December 2010.
+
+   [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
+              IPv4/IPv6 Translation", RFC 6144, April 2011.
+
+   [TR-069]   Broadband Forum, "CPE WAN Management Protocol", TR-069
+              Amendment 4, July 2011,
+              <http://www.broadband-forum.org/technical/trlist.php>.
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 20]
+
+RFC 7084               IPv6 CE Router Requirements         November 2013
+
+
+   [UPnP-IGD] UPnP Forum, , "InternetGatewayDevice:2 Device Template
+              Version 1.01", December 2010,
+              <http://upnp.org/specs/gw/igd2/>.
+
+Authors' Addresses
+
+   Hemant Singh
+   Cisco Systems, Inc.
+   1414 Massachusetts Ave.
+   Boxborough, MA  01719
+   USA
+
+   Phone: +1 978 936 1622
+   EMail: shemant@cisco.com
+   URI:   http://www.cisco.com/
+
+
+   Wes Beebee
+   Cisco Systems, Inc.
+   1414 Massachusetts Ave.
+   Boxborough, MA  01719
+   USA
+
+   Phone: +1 978 936 2030
+   EMail: wbeebee@cisco.com
+   URI:   http://www.cisco.com/
+
+
+   Chris Donley
+   CableLabs
+   858 Coal Creek Circle
+   Louisville, CO  80027
+   USA
+
+   EMail: c.donley@cablelabs.com
+
+
+   Barbara Stark
+   AT&T
+   1057 Lenox Park Blvd. NE
+   Atlanta, GA  30319
+   USA
+
+   EMail: barbara.stark@att.com
+
+
+
+
+
+
+
+Singh, et al.                 Informational                    [Page 21]
+