path: root/doc/rfc/rfc6788.txt

Internet Engineering Task Force (IETF)                       S. Krishnan
Request for Comments: 6788                                   A. Kavanagh
Category: Standards Track                                       B. Varga
ISSN: 2070-1721                                                 Ericsson
                                                                S. Ooghe
                                                          Alcatel-Lucent
                                                             E. Nordmark
                                                                   Cisco
                                                           November 2012


                     The Line-Identification Option

Abstract

   In Ethernet-based aggregation networks, several subscriber premises
   may be logically connected to the same interface of an Edge Router.
   This document proposes a method for the Edge Router to identify the
   subscriber premises using the contents of the received Router
   Solicitation messages.  The applicability is limited to broadband
   network deployment scenarios in which multiple user ports are mapped
   to the same virtual interface on the Edge Router.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in 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/rfc6788.















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Copyright Notice

   Copyright (c) 2012 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. Terminology ................................................4
      1.2. Conventions Used in This Document ..........................6
   2. Applicability Statement .........................................6
   3. Issues with Identifying the Subscriber Premises in an
      N:1 VLAN Model ..................................................7
   4. Basic Operation .................................................7
   5. AN Behavior .....................................................8
      5.1. On Initialization ..........................................8
      5.2. On Receiving a Router Solicitation from the End-Device .....8
      5.3. On Receiving a Router Advertisement from the Edge Router ...9
           5.3.1. Identifying Tunneled Router Advertisements ..........9
      5.4. On Detecting a Subscriber Circuit Coming Up ................9
      5.5. On Detecting Edge Router Failure ..........................10
      5.6. RS Retransmission Algorithm ...............................10
   6. Edge Router Behavior ...........................................10
      6.1. On Receiving a Tunneled Router Solicitation from the AN ...10
      6.2. On Sending a Router Advertisement Towards the End-Device ..10
      6.3. Sending Periodic Unsolicited Router Advertisements
           Towards the End-Device ....................................11
   7. Line-Identification Option (LIO) ...............................12
      7.1. Encoding of Line ID .......................................13
   8. Garbage Collection of Unused Prefixes ..........................14
   9. Interactions with Secure Neighbor Discovery ....................14
   10. Acknowledgements ..............................................14
   11. Security Considerations .......................................14
   12. IANA Considerations ...........................................14
   13. References ....................................................15
      13.1. Normative References .....................................15
      13.2. Informative References ...................................16




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1.  Introduction

   Digital Subscriber Line (DSL) is a widely deployed access technology
   for Broadband Access for Next Generation Networks.  While traditional
   DSL access networks were Point-to-Point Protocol (PPP) [RFC1661]
   based, some networks are migrating from the traditional PPP access
   model into a pure IP-based Ethernet aggregated access environment.
   Architectural and topological models of an Ethernet aggregation
   network in the context of DSL aggregation are described in [TR101].

   +----+   +----+    +----------+
   |Host|---| RG |----|          |
   +----+   +----+    |          |
                      |    AN    |\
   +----+   +----+    |          | \
   |Host|---| RG |----|          |  \
   +----+   +----+    +----------+   \                    +----------+
                                      \                   |          |
                                    +-------------+       |          |
                                    | Aggregation |       |  Edge    |
                                    |   Network   |-------|  Router  |
                                    +-------------+       |          |
                                      /                   |          |
                      +----------+   /                    +----------+
                      |          |  /
   +----+   +----+    |          | /
   |Host|---| RG |----|    AN    |/
   +----+   +----+    |          |
                      |          |
                      +----------+

              Figure 1: Broadband Forum Network Architecture



















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   One of the Ethernet and Gigabit-capable Passive Optical Network
   (GPON) aggregation models specified in this document bridges sessions
   from multiple user ports behind a DSL Access Node (AN), also referred
   to as a Digital Subscriber Line Access Multiplexer (DSLAM), into a
   single VLAN in the aggregation network.  This is called the N:1 VLAN
   allocation model.

      +----------+
      |          |
      |          |
      |    AN    |\
      |          | \
      |          |  \ VLANx
      +----------+   \                    +----------+
                      \                   |          |
                    +-------------+       |          |
                    | Aggregation | VLANx |  Edge    |
                    |   Network   |-------|  Router  |
                    +-------------+       |          |
                      /                   |          |
      +----------+   /                    +----------+
      |          |  / VLANx
      |          | /
      |    AN    |/
      |          |
      |          |
      +----------+

                         Figure 2: n:1 VLAN model

1.1.  Terminology

   1:1 VLAN               A broadband network deployment scenario in
                          which each user port is mapped to a different
                          VLAN on the Edge Router.  The uniqueness of
                          the mapping is maintained in the Access Node
                          and across the aggregation network.

   N:1 VLAN               A broadband network deployment scenario in
                          which multiple user ports are mapped to the
                          same VLAN on the Edge Router.  The user ports
                          may be located in the same or different Access
                          Nodes.

   GPON                   Gigabit-capable Passive Optical Network is an
                          optical access network that has been
                          introduced into the Broadband Forum
                          architecture in [TR156].



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   AN                     A DSL or a GPON Access Node.  The Access Node
                          terminates the physical layer (e.g., DSL
                          termination function or GPON termination
                          function), may physically aggregate other
                          nodes implementing such functionality, or may
                          perform both functions at the same time.  This
                          node contains at least one standard Ethernet
                          interface that serves as its "northbound"
                          interface into which it aggregates traffic
                          from several user ports or Ethernet-based
                          "southbound" interfaces.  It does not
                          implement an IPv6 stack but performs some
                          limited inspection/modification of IPv6
                          packets.  The IPv6 functions required on the
                          Access Node are described in Section 5 of
                          [TR177].

   Aggregation Network    The part of the network stretching from the
                          Access Nodes to the Edge Router.  In the
                          context of this document, the aggregation
                          network is considered to be Ethernet based,
                          providing standard Ethernet interfaces at the
                          edges, for connecting the Access Nodes and the
                          broadband network.  It is comprised of
                          Ethernet switches that provide very limited IP
                          functionality (e.g., IGMP snooping, Multicast
                          Listener Discovery (MLD) snooping, etc.).

   RG                     A residential gateway device.  It can be a
                          Layer-3 (routed) device or a Layer-2 (bridged)
                          device.  The residential gateway for Broadband
                          Forum networks is defined in [TR124].

   Edge Router            The Edge Router, also known as the Broadband
                          Network Gateway (BNG), is the first IPv6 hop
                          for the user.  In cases where the RG is
                          bridged, the BNG acts as the default router
                          for the hosts behind the RG.  In cases where
                          the RG is routed, the BNG acts as the default
                          router for the RG itself.  This node
                          implements IPv6 router functionality.

   Host                   A node that implements IPv6 host
                          functionality.







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   End-Device             A node that sends Router Solicitations and
                          processes received Router Advertisements.
                          When a Layer-3 (L3) RG is used, it is
                          considered an end-device in the context of
                          this document.  When a Layer-2 (L2) RG is
                          used, the host behind the RG is considered to
                          be an end-device in the context of this
                          document.

1.2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Applicability Statement

   The Line-Identification Option (LIO) is intended to be used only for
   the N:1 VLAN deployment model.  For the other VLAN deployment models,
   line identification can be achieved differently.  The mechanism
   described in this document allows the connection of hosts that only
   support IPv6 stateless address auto-configuration to attach to
   networks that use the N:1 VLAN deployment model.

   When the Dynamic Host Configuration Protocol (DHCP) [RFC3315] is used
   for IPv6 address assignment, it has the side-effect of providing end-
   device-initiated reliability as well as inactivity detection.  The
   reliability is provided by the end-device continuing to retransmit
   DHCP messages until it receives a response), and inactivity is
   detected by the end-device not renewing its DHCP lease.  The "IPv6
   Stateless Address Autoconfiguration" protocol [RFC4862] was not
   designed to satisfy such requirements [RSDA].  While this option
   improves the reliability of operation in deployments that use Router
   Solicitations rather than DHCP, there are some limitations as
   specified below.

   The mechanism described in this document deals with the loss of
   subscriber-originated Router Solicitations (RSes) by initiating RSes
   at the AN, which improves robustness over solely relying on the
   end-device's few initial retransmissions of RSes.

   However, the AN retransmissions imply that some information (e.g.,
   the subscriber's MAC address) that was obtained by the Edge Router
   from subscriber-originated RSes may no longer be available.  For
   example, since there is no L2 frame received from the subscriber in
   case of an RS sent by an AN, the L2-address information of the
   end-device cannot be determined.  One piece of L2-address information
   currently used in some broadband networks is the MAC address.  For



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   this reason, the solution described in this document is NOT
   RECOMMENDED for networks that require the MAC address of the endpoint
   for identification.

   There is no indication when a subscriber is no longer active.  Thus,
   this protocol cannot be used to automatically reclaim resources, such
   as prefixes, that are associated with an active subscriber.  See
   Section 8.  Thus, this protocol is NOT RECOMMENDED for networks that
   require automatic notification when a subscriber is no longer active.

   This mechanism by itself provides no protection against the loss of
   RS-induced state in access routers that would lead to loss of IPv6
   connectivity for end-devices.  Given that regular IPv6 hosts do not
   have RS retransmission behavior that would allow automatic recovery
   from such a failure, this mechanism SHOULD only be used in
   deployments employing N:1 VLANs.

3.  Issues with Identifying the Subscriber Premises in an N:1 VLAN Model

   In a DSL- or GPON-based fixed broadband network, IPv6 end-devices are
   connected to an AN.  Today, these end-devices will typically send a
   Router Solicitation message to the Edge Router, to which the Edge
   Router responds with a Router Advertisement message.  The Router
   Advertisement typically contains a prefix that the end-devices will
   use to automatically configure an IPv6 address.  Upon sending the
   Router Solicitation message, the node connecting the end-device on
   the access circuit, typically an AN, forwards the RS to the Edge
   Router upstream over a switched network.  In such Ethernet-based
   aggregation networks, several subscriber premises may be connected to
   the same interface of an Edge Router (e.g., on the same VLAN).
   However, the Edge Router requires some information to identify the
   end-device on the circuit.  To accomplish this, the AN needs to add
   line-identification information to the Router Solicitation message
   and forward this to the Edge Router.  This is analogous to the case
   where DHCP is being used, and the line-identification information is
   inserted by a DHCP relay agent [RFC3315].  This document proposes a
   method for the Edge Router to identify the subscriber premises using
   the contents of the received Router Solicitation messages.  Note that
   there might be several end-devices located on the same subscriber
   premises.

4.  Basic Operation

   This document uses a mechanism that tunnels Neighbor Discovery (ND)
   packets inside another IPv6 packet that uses a destination option
   (Line-ID option) to convey line-identification information as
   depicted in Figure 3.  The use of the Line-ID option in any other
   IPv6 datagrams, including untunneled RS and RA messages, is not



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   defined by this document.  The ND packets are left unmodified inside
   the encapsulating IPv6 packet.  In particular, the Hop Limit field of
   the ND message is not decremented when the packet is being tunneled.
   This is because an ND message whose Hop Limit is not 255 will be
   discarded by the receiver of such messages, as described in Sections
   6.1.1 and 6.1.2 of [RFC4861].

      +----+     +----+       +-----------+
      |Host|     | AN |       |Edge Router|
      +----+     +----+       +-----------+
        |    RS     |                |
        |---------->|                |
        |           |                |
        |           |Tunneled RS(LIO)|
        |           |--------------->|
        |           |                |
        |           |Tunneled RA(LIO)|
        |           |<---------------|
        |    RA     |                |
        |<----------|                |
        |           |                |


                       Figure 3: Basic Message Flow

5.  AN Behavior

5.1.  On Initialization

   On initialization, the AN MUST join the All-BBF-Access-Nodes
   multicast group on all its upstream interfaces towards the Edge
   Router.

5.2.  On Receiving a Router Solicitation from the End-Device

   When an end-device sends out a Router Solicitation, it is received by
   the AN.  The AN identifies these messages by looking for ICMPv6
   messages (IPv6 Next Header value of 58) with ICMPv6 type 133.  The AN
   intercepts and then tunnels the received Router Solicitation in a
   newly created IPv6 datagram with the Line-Identification Option
   (LIO).  The AN forms a new IPv6 datagram whose payload is the
   received Router Solicitation message as described in [RFC2473],
   except that the Hop Limit field of the Router Solicitation message
   MUST NOT be decremented.  If the AN has an IPv6 address, it MUST use
   this address in the Source Address field of the outer IPv6 datagram.
   Otherwise, the AN MUST copy the source address from the received
   Router Solicitation into the Source Address field of the outer IPv6
   datagram.  The destination address of the outer IPv6 datagram MUST be



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   copied from the destination address of the tunneled RS.  The AN MUST
   include a destination options header between the outer IPv6 header
   and the payload.  It MUST insert an LIO destination option and set
   the Line ID field of the option to contain the circuit identifier
   corresponding to the logical access loop port of the AN from which
   the RS was initiated.

5.3.  On Receiving a Router Advertisement from the Edge Router

   When the Edge Router sends out a tunneled Router Advertisement in
   response to the RS, it is received by the AN.  If there is an LIO
   present, the AN MUST use the line-identification data of the LIO to
   identify the subscriber agent circuit of the AN on which the RA
   should be sent.  The AN MUST then remove the outer IPv6 header of
   this tunneled RA and multicast the inner packet (the original RA) on
   this specific subscriber circuit.

5.3.1.  Identifying Tunneled Router Advertisements

   The AN can identify tunneled RAs by installing filters based on the
   destination address (All-BBF-Access-Nodes, which is a reserved
   link-local scoped multicast address) of the outer packets and the
   presence of a destination option header with an LIO destination
   option.

5.4.  On Detecting a Subscriber Circuit Coming Up

   RSes initiated by end-devices as described in Section 5.2 may be lost
   due to lack of connectivity between the AN and the end-device.  To
   ensure that the end-device will receive an RA, the AN needs to
   trigger the sending of periodic RAs on the Edge Router.  For this
   purpose, the AN needs to inform the Edge Router that a subscriber
   circuit has come up.  Each time the AN detects that a subscriber
   circuit has come up, it MUST create a Router Solicitation message as
   described in Section 6.3.7 of [RFC4861].  It MUST use the unspecified
   address as the source address of this RS.  It MUST then tunnel this
   RS towards the Edge Router as described in Section 5.2.

   In case there are connectivity issues between the AN and the Edge
   Router, the RSes initiated by the AN can be lost.  The AN SHOULD
   continue retransmitting the Router Solicitations following the
   algorithm described in Section 5.6 for a given LIO until it receives
   an RA for that specific LIO.








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5.5.  On Detecting Edge Router Failure

   When the Edge Router reboots and loses state or is replaced by a new
   Edge Router, the AN will detect it using connectivity check
   mechanisms that are already in place in broadband networks (e.g.,
   Bidirectional Forwarding Detection).  When such Edge Router failure
   is detected, the AN needs to start transmitting RSes for each of its
   subscriber circuits that have come up, as described in Section 5.4.

5.6.  RS Retransmission Algorithm

   The AN SHOULD use the exponential backoff algorithm for retransmits
   that is described in Section 14 of [RFC3315] in order to continuously
   retransmit the Router Solicitations for a given LIO until a response
   is received for that specific LIO.  The AN SHOULD use the following
   variables as input to the retransmission algorithm:

     Initial retransmission time (IRT)      1 Second
     Maximum retransmission time (MRT)     30 Seconds
     Maximum retransmission count (MRC)     0
     Maximum retransmission duration (MRD)  0

6.  Edge Router Behavior

6.1.  On Receiving a Tunneled Router Solicitation from the AN

   When the Edge Router receives a tunneled Router Solicitation
   forwarded by the AN, it needs to check if there is an LIO destination
   option present in the outer datagram.  The Edge Router can use the
   contents of the Line ID field to lookup the addressing information
   and policy that need to be applied to the line from which the Router
   Solicitation was received.  The Edge Router MUST then process the
   inner RS message as specified in [RFC4861].

6.2.  On Sending a Router Advertisement Towards the End-Device

   When the Edge Router sends out a Router Advertisement in response to
   a tunneled RS that included an LIO, it MUST tunnel the Router
   Advertisement in a newly created IPv6 datagram with the LIO as
   described below.  First, the Edge Router creates the Router
   Advertisement message as described in Section 6.2.3 of [RFC4861].
   The Edge Router MUST include a Prefix Information option in this RA
   that contains the prefix that corresponds to the received LIO.  (The
   LIO from the received tunneled RS is usually passed on from the Edge
   Router to some form of provisioning system that returns the prefix to
   be included in the RA.  It could e,g., be based on RADIUS.)  Then,
   the Edge Router forms the new IPv6 datagram whose payload is the
   Router Advertisement message, as described in [RFC2473], except that



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   the Hop Limit field of the Router Advertisement message MUST NOT be
   decremented.  The Edge router MUST use a link-local IPv6 address on
   the outgoing interface in the Source Address field of the outer IPv6
   datagram.  The Edge Router MUST include a destination options header
   between the outer IPv6 header and the payload.  It MUST insert an LIO
   and set the Line ID field of the option to contain the same value as
   that of the Line-ID option in the received RS.  The IPv6 destination
   address of the inner RA MUST be set to the all-nodes multicast
   address.

   If the Source Address field of the received IPv6 datagram was not the
   unspecified address, the Edge Router MUST copy this address into the
   Destination Address field of the outer IPv6 datagram sent back
   towards the AN.  The link-layer destination address of the outer IPv6
   datagram containing the outer IPv6 datagram MUST be resolved using
   regular Neighbor Discovery procedures.

   If the Source Address field of the received IPv6 datagram was the
   unspecified address, the destination address of the outer IPv6
   datagram MUST be set to the well-known link-local scope
   All-BBF-Access-Nodes multicast address (ff02::10).  The link-layer
   destination address of the tunneled RA MUST be set to the unicast
   link-layer address of the AN that sent the tunneled Router
   Solicitation that is being responded to.

   The Edge Router MUST ensure that it does not transmit tunneled RAs
   whose size is larger than the MTU of the link between the Edge Router
   and the AN, which would require that the outer IPv6 datagram undergo
   fragmentation.  This limitation is imposed because the AN may not be
   capable of handling the reassembly of such fragmented datagrams.

6.3.  Sending Periodic Unsolicited Router Advertisements Towards the
      End-Device

   After sending a tunneled Router Advertisement as specified in Section
   6.2 in response to a received RS, the Edge Router MUST store the
   mapping between the LIO and the prefixes contained in the Router
   Advertisement.  It should then initiate periodic sending of
   unsolicited Router Advertisements as described in Section 6.2.3. of
   [RFC4861] .  The Router Advertisements MUST be created and tunneled
   as described in Section 6.2.  The Edge Router MAY stop sending Router
   Advertisements if it receives a notification from the AN that the
   subscriber circuit has gone down.  This notification can be received
   out-of-band using a mechanism such as the Access Node Control
   Protocol (ANCP).  Please consult Section 8 for more details.






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7.  Line-Identification Option (LIO)

   The Line-Identification Option (LIO) is a destination option that can
   be included in IPv6 datagrams that tunnel Router Solicitation and
   Router Advertisement messages.  The use of the Line-ID option in any
   other IPv6 datagrams is not defined by this document.  Multiple Line-
   ID destination options MUST NOT be present in the same IPv6 datagram.
   The LIO has no alignment requirement.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |  Option Type  | Option Length |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | LineIDLen     |     Line ID...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 4: Line-Identification Option Layout

    Option Type

       8-bit identifier of the type of option.  The option identifier
       for the Line-Identification Option (0x8C) has been allocated by
       the IANA.

    Option Length

       8-bit unsigned integer.  The length of the option (excluding the
       Option Type and Option Length fields).  The value MUST be greater
       than 0.

    LineIDLen

       8-bit unsigned integer.  The length of the Line ID field in
       number of octets.

    Line ID

       Variable-length data inserted by the AN describing the
       subscriber-agent circuit identifier corresponding to the logical
       access loop port of the AN from which the RS was initiated.  The
       line identification MUST be unique across all the ANs that share
       a link to the Edge Router, e.g., one such line- identification
       scheme is described in Section 3.9 of [TR101].  The line
       identification should be encoded as specified in Section 7.1.






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7.1.  Encoding of the Line ID Field Content

   This IPv6 Destination option is derived from an existing widely
   deployed DHCPv6 option [RFC4649], which is in turn derived from a
   widely deployed DHCPv4 option [RFC3046].  These options derive from
   and cite the basic DHCP options specification [RFC2132].  These
   widely deployed DHCP options use the Network Virtual Terminal (NVT)
   character set [RFC2132] [RFC0020].  Since the data carried in the
   Line-ID option is used in the same manner by the provisioning systems
   as the DHCP options, it is beneficial for it to maintain the same
   encoding as the DHCP options.

   The IPv6 Line ID option contains a description that identifies the
   line using only character positions (decimal 32 to decimal 126,
   inclusive) of the US-ASCII character set [X3.4] [RFC0020].
   Consistent with [RFC2132], [RFC3046], and [RFC4649], the Line ID
   field SHOULD NOT contain the US-ASCII NUL character (decimal 0).
   However, implementations receiving this option MUST NOT fail merely
   because an ASCII NUL character is (erroneously) present in the Line
   ID field.

   Some existing widely deployed implementations of Edge Routers and ANs
   that support the previously mentioned DHCP option only support
   US-ASCII and strip the high-order bit from any 8-bit characters
   entered by the device operator.  The previously mentioned DHCP
   options do not support 8-bit character sets either.  Therefore, for
   compatibility with the installed base and to maximize
   interoperability, the high-order bit of each octet in this field MUST
   be set to zero by any device inserting this option in an IPv6 packet.

   Consistent with [RFC3046] and [RFC4649], this option always uses
   binary comparison.  Therefore, two Line IDs MUST be equal when they
   match when compared byte-by-byte.  Line-ID A and Line-ID B match
   byte-by-byte when (1) A and B have the same number of bytes, and (2)
   for all byte indexes P in A: the value of A at index P has the same
   binary value as the value of B at index P.

   Two Line IDs MUST NOT be equal if they do not match byte-by-byte.
   For example, an IPv6 Line-ID option containing "f123" is not equal to
   a Line-ID option "F123".

   Intermediate systems MUST NOT alter the contents of the Line ID.









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8.  Garbage Collection of Unused Prefixes

   Following the mechanism described in this document, the broadband
   network associates a prefix to a subscriber line based on the LIO.
   Even when the subscriber line goes down temporarily, this prefix
   stays allocated to that specific subscriber line, i.e., the prefix is
   not returned to the unused pool.  When a subscriber line no longer
   needs a prefix, the prefix can be reclaimed by manual action
   dissociating the prefix from the LIO in the backend systems.

9.  Interactions with Secure Neighbor Discovery

   Since the RS/RA packets that are protected by the "SEcure Neighbor
   Discovery (SEND)" [RFC3971] are not modified in any way by the
   mechanism described in this document, there are no issues with SEND
   verification.

10.  Acknowledgements

   The authors would like to thank Margaret Wasserman, Mark Townsley,
   David Miles, John Kaippallimalil, Eric Levy-Abegnoli, Thomas Narten,
   Olaf Bonness, Thomas Haag, Wojciech Dec, Brian Haberman, Ole Troan,
   Hemant Singh, Jari Arkko, Joel Halpern, Bob Hinden, Ran Atkinson,
   Glen Turner, Kathleen Moriarty, David Sinicrope, Dan Harkins, Stephen
   Farrell, Barry Leiba, Sean Turner, Ralph Droms, and Mohammed
   Boucadair for reviewing this document and suggesting changes.

11.  Security Considerations

   The line identification information inserted by the AN or the Edge
   Router is not protected.  This means that this option may be
   modified, inserted, or deleted without being detected.  In order to
   ensure validity of the contents of the Line ID field, the network
   between the AN and the Edge Router needs to be trusted.

12.  IANA Considerations

   This document defines a new IPv6 destination option for carrying line
   identification.  IANA has assigned the following new destination
   option type in the "Destination Options and Hop-by-Hop Options"
   registry maintained at
   <http://www.iana.org/assignments/ipv6-parameters>:

      0x8C  Line-Identification Option  [RFC6788]

   The act bits for this option are 10 and the chg bit is 0.





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   Per this document, IANA has also allocated the following well-known
   link-local scope multicast address from the "IPv6 Multicast Address
   Space Registry" located at
   <http://www.iana.org/assignments/ipv6-multicast-addresses/>:

      FF02:0:0:0:0:0:0:10  All-BBF-Access-Nodes  [RFC6788]

13.  References

13.1.  Normative References

   [RFC1661]  Simpson, W., Ed., "The Point-to-Point Protocol (PPP)", STD
              51, RFC 1661, July 1994.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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

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

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [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.

   [TR101]    Broadband Forum, "Migration to Ethernet-based DSL
              aggregation", <http://www.broadband-forum.org/
              technical/download/TR-101.pdf>.

   [TR124]    Broadband Forum, "Functional Requirements for Broadband
              Residential Gateway Devices",
              <http://www.broadband-forum.org/technical/
              download/TR-124_Issue-2.pdf>.

   [TR156]    Broadband Forum, "Using GPON Access in the context of
              TR-101", <http://www.broadband-forum.org/
              technical/download/TR-156.pdf>.





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   [TR177]    Broadband Forum, "IPv6 in the context of TR-101",
              <www.broadband-forum.org/technical/download/TR-177.pdf>.

   [X3.4]     American National Standards Institute, "American Standard
              Code for Information Interchange (ASCII)", Standard X3.4,
              1968.

13.2.  Informative References

   [RFC0020]  Cerf, V., "ASCII format for network interchange", RFC 20,
              October 1969.

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, March 1997.

   [RFC3046]  Patrick, M., "DHCP Relay Agent Information Option", RFC
              3046, January 2001.

   [RFC4649]  Volz, B., "Dynamic Host Configuration Protocol for IPv6
              (DHCPv6) Relay Agent Remote-ID Option", RFC 4649, August
              2006.

   [RSDA]     Dec, W., "IPv6 Router Solicitation Driven Access
              Considered Harmful", Work in Progress, June 2011.



























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Authors' Addresses

   Suresh Krishnan
   Ericsson
   8400 Blvd Decarie
   Town of Mount Royal, Quebec
   Canada

   EMail: suresh.krishnan@ericsson.com


   Alan Kavanagh
   Ericsson
   8400 Blvd Decarie
   Town of Mount Royal, Quebec
   Canada

   EMail: alan.kavanagh@ericsson.com


   Balazs Varga
   Ericsson
   Konyves Kalman krt. 11. B.
   1097 Budapest
   Hungary

   EMail: balazs.a.varga@ericsson.com


   Sven Ooghe
   Alcatel-Lucent
   Copernicuslaan 50
   2018 Antwerp,
   Belgium

   Phone:
   EMail: sven.ooghe@alcatel-lucent.com


   Erik Nordmark
   Cisco
   510 McCarthy Blvd.
   Milpitas, CA, 95035
   USA

   Phone: +1 408 527 6625
   EMail: nordmark@cisco.com




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