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Versions: 00 01 02 03 04 05 RFC 6788

6man Working Group                                           S. Krishnan
Internet-Draft                                               A. Kavanagh
Intended status: Standards Track                                B. Varga
Expires: September 15, 2011                                     Ericsson
                                                                S. Ooghe
                                                          Alcatel-Lucent
                                                             E. Nordmark
                                                                   Cisco
                                                          March 14, 2011


               The Line Identification Destination Option
                       draft-ietf-6man-lineid-01

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 September 15, 2011.

Copyright Notice

   Copyright (c) 2011 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.  Issues with identifying the subscriber in an N:1 VLAN model  .  6
   3.  Applicability  . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Basic operation  . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Access Node Behavior . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  On receiving a Router Solicitation from the end-device . .  6
     5.2.  On receiving a Router Advertisement from the Edge
           Router . . . . . . . . . . . . . . . . . . . . . . . . . .  7
       5.2.1.  Identifying tunneled Router Advertisements . . . . . .  7
     5.3.  On detecting a subscriber circuit coming up  . . . . . . .  7
   6.  Edge Router Behavior . . . . . . . . . . . . . . . . . . . . .  8
     6.1.  On receiving a Tunneled Router Solicitation from the
           Access Node  . . . . . . . . . . . . . . . . . . . . . . .  8
     6.2.  On sending a Router Advertisement towards the
           end-device . . . . . . . . . . . . . . . . . . . . . . . .  8
     6.3.  Sending periodic unsolicited Router Advertisements
           towards the end-device . . . . . . . . . . . . . . . . . .  9
   7.  Line Identification Destination Option (LIO) . . . . . . . . .  9
   8.  Interactions with Secure Neighbor Discovery  . . . . . . . . . 10
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   12. Normative References . . . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12














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1.  Introduction

   Digital Subscriber Line (DSL) is a widely deployed access technology
   for Broadband Access for Next Generation Networks.  While
   traditionally 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 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 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.
   AN                        A DSL or a Gigabit Passive Optical Network
                             (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.



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                             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.).
   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 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.
   GPON                      Gigabit-capable Passive Optical Network is
                             an optical access network that has been
                             introduced into the Broadband Forum
                             architecture in [TR156]
   Host                      A node that implements IPv6 host
                             functionality.
   RG                        A residential gateway device.  It can be a
                             Layer 3 (routed) device similar to one
                             specified in or a Layer 2 (bridged) device.
                             The residential gateway for Broadband Forum
                             networks is defined in [TR124]
   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.  Issues with identifying the subscriber in an N:1 VLAN model

   In a DSL or GPON based fixed Broadband Network, IPv6 end-devices are
   connected to an Access Node (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 Access Node (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 the end-
   device is connected on.  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.  This document proposes a method for
   the edge router to identify the subscriber premises using the
   contents of the received Router Solicitation messages.


3.  Applicability

   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.


4.  Basic operation

   This document recommends tunneling Neighbor discovery packets inside
   another IPv6 packet that uses a destination option to convey line
   identification information.  The Neighbor discovery 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 ND messages whose Hop Limit is
   not 255 will be discarded by the receiver of such messages.


5.  Access Node Behavior

5.1.  On receiving a Router Solicitation from the end-device

   When an end-device sends out a Router Solicitation, it is received by
   the access node.  The AN identifies these messages by looking for



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   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 SHOULD use this
   address in the Source Address field of the outer IPv6 datagram.
   Otherwise it MUST use the unspecified address as the Source Address
   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 insert 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 Access Node from which the RS was initiated.

5.2.  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 access node.  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
   Access Node 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.

5.2.1.  Identifying tunneled Router Advertisements

   The Access Node can identify tunneled RAs by installing filters based
   on the destination address (All BBF Access Nodes) of the outer
   packets, and the presence of a destination option header with an LIO
   destination option.

5.3.  On detecting a subscriber circuit coming up

   RSs initiated by end-devices as described in Section 5.1 may be lost
   due to lack of connectivity between the access node 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.  When the access node 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 5.1.

   In case there are connectivity issues between the AN and the edge



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   router, the RSes initiated by the AN can be lost.  The AN MAY
   continue retransmitting the Router Solicitations for a given LIO
   until it receives an RA for that specific LIO.

   Alternately, the AN can send this notification about the subscriber
   circuit coming up using a out-of-band mechanism with acknowledgements
   like ANCP, if such mechanism is available.


6.  Edge Router Behavior

6.1.  On receiving a Tunneled Router Solicitation from the Access Node

   When the edge router receives a tunneled Router Solicitation
   forwarded by the access node, 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).  The edge router creates the Router
   Advertisement message as described in Section 6.2.3 of [RFC4861].
   The edge router may use the contents of the LIO in the received
   router solicitation to determine the contents of this router
   advertisement(es.  The Edge Router then forms a 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 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 edge
   router MUST insert 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 Access Node to which the RA MUST be sent.  The IPv6 destination
   address of the inner RA MUST be set to the all-nodes multicast
   address.  The link-layer destination address of the tunneled RA MUST
   be set to the unicast link-layer address of the Access Node that sent
   the tunneled Router Solicitation which is being responded to.




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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.


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.  Multiple Line
   Identification destination options MUST NOT be present in the same
   IPv6 datagram.  The LIO has an alignment requirement of (none).

    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 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Line Identification...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 3: Line Identification Destination Option Layout



















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    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  0 is
       considered invalid.

    LineIDLen

       Length of the Line Identification field in number of octets.

    Line Identification

       Variable length data inserted by the Access Node describing the
       subscriber agent circuit identifier corresponding to the logical
       access loop port of the Access Node from which the RS was
       initiated.



8.  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.


9.  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 and Joel Halpern for reviewing this document
   and suggesting changes.


10.  Security Considerations

   The line identification information inserted by the access node 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 access node and the edge router needs to be
   trusted.



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11.  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]


12.  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.

   [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.

   [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/



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              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>.


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

   Email: balazs.a.varga@ericsson.com


   Sven Ooghe
   Alcatel-Lucent
   Copernicuslaan 50
   2018 Antwerp,
   Belgium

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







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   Erik Nordmark
   Cisco

   Email: nordmark@acm.org















































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