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Versions: 00 01 02 03 04 05 06 07 08 RFC 6788

6man Working Group                                           S. Krishnan
Internet-Draft                                               A. Kavanagh
Intended status: Standards Track                                B. Varga
Expires: February 16, 2013                                      Ericsson
                                                                S. Ooghe
                                                          Alcatel-Lucent
                                                             E. Nordmark
                                                                   Cisco
                                                         August 15, 2012


               The Line Identification Destination Option
                       draft-ietf-6man-lineid-07

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 where multiple user ports are mapped to
   the same virtual interface on the edge router.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 16, 2013.

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



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   (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  . . . . . . . . . . . .  5
   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 . . . . . . . . . . . . .  9
     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 Destination Option (LIO) . . . . . . . . . 11
     7.1.  Encoding of Line ID  . . . . . . . . . . . . . . . . . . . 12
   8.  Garbage collection of unused prefixes  . . . . . . . . . . . . 13
   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
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 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

   One of the Ethernet and Gigabit 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.










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

                         Figure 2: n:1 VLAN model

1.1.  Terminology

   1:1 VLAN                  It is a broadband network deployment
                             scenario where 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                  It is a broadband network deployment
                             scenario where 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]
   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



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                             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 Broadband Network.  It is comprised of
                             ethernet switches that provide very limited
                             IP functionality (e.g.  IGMP snooping, 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 the cases
                             where the Residential Gateway (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.
   End-device                A node that sends Router Solicitations and
                             processes received Router Advertisements.
                             When a Layer 3 RG is used it is considered
                             an end-device in the context of this
                             document.  When a Layer 2 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].



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2.  Applicability Statement

   The line identification destination option 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 the document is useful for allowing 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 including
   reliability initiated by the end-device (the end-device retransmits
   DHCP messages until it receives a response), as well as a way to
   detect when the end-device is not active for an extended period of
   time (the end-device would not renew 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 the robustness over solely relying on the
   end-device's few initial retransmissions of RSes.

   But 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. e.g.  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 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 can not 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



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   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.  These end-devices today 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, would forward the RS to the Edge
   Router upstream over a switched network.  However, 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 that are located on the same subscriber premises.


4.  Basic operation

   This document uses a mechanism that tunnels Neighbor discovery
   packets inside another IPv6 packet that uses a destination option to
   convey line identification information as depicted in Figure 3.  The
   Neighbor discovery packets are left unmodified inside the
   encapsulating IPv6 packet.  In particular, the Hop Limit field of the
   Neighbor Discovery (ND) message is not decremented when the packet is
   being tunneled.  This is because ND messages 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].












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   +----+     +----+       +-----------+
   |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
   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 a LIO destination option and set the
   line identification 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.



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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
   option present, the AN MUST use the line identification data of the
   LIO option 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 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.

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.
   BFD).  When such edge router failure is detected, the AN needs to
   start transmitting RSes for each of its subscriber circuits that are
   up as described in Section 5.4.






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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:

     IRT  1 Second
     MRT  30 Seconds
     MRC  0
     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 identification 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 option, it MUST tunnel the Router
   Advertisement in a newly created IPv6 datagram with the Line
   Identification Option (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 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 a LIO destination option
   and set the line identification field of the option to contain the
   same value as that of the Line ID option in the received RS.  The



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   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 tunneled RA MUST be resolved using regular
   Neighbour 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 [to be allocated].  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 which 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. i.e.  The outer IPv6 datagram would require
   fragmentation.  This is required 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 ANCP.  Please consult Section 8
   for more details.


7.  Line Identification Destination Option (LIO)

   The Line Identification Destination 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 Identification destination options MUST NOT
   be present in the same IPv6 datagram.  The LIO has no alignment



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   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 Identification...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 4: Line Identification Destination Option Layout


    Option Type

       8-bit identifier of the type of option. The option identifier
       for the line identification option will be 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 Identification
       field in number of octets.

    Line Identification

       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 idenfication should be encoded as specified in
       Section 7.1.


7.1.  Encoding of Line ID

   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].  Both of those derive from
   and cite the basic DHCP options specification [RFC2132].  Those
   widely deployed DHCP options use the NVT character set



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   [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 which 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 option's
   data 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 maximise 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.


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.





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9.  Interactions with Secure Neighbor Discovery

   Since the SEND [RFC3971] protected RS/RA packets are not modified in
   anyway 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 identification 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 is requested to assign a new destination option
   type in the Destination Options registry maintained at

   http://www.iana.org/assignments/ipv6-parameters

   <TBA1> Line Identification Option [RFCXXXX]

   The act bits for this option need to be 10 and the chg bit needs to
   be 0.

   This document also requires the allocation of a well-known link-local
   scope multicast address from the IPv6 Multicast Address Space
   Registry located at

   http://www.iana.org/assignments/ipv6-multicast-addresses/
   ipv6-multicast-addresses.xml

   <TBA2> All-BBF-Access-Nodes [RFCXXXX]



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13.  References

13.1.  Normative References

   [RFC1661]  Simpson, W., "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., 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., 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>.

   [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.





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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", draft-dec-6man-rs-access-harmful-00
              (work in progress), June 2011.


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




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   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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