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6man Working Group                                           S. Krishnan
Internet-Draft                                               A. Kavanagh
Intended status: Standards Track                                Ericsson
Expires: September 9, 2010                                      S. Ooghe
                                                          Alcatel-Lucent
                                                                B. Varga
                                                          Magyar Telekom
                                                           March 8, 2010


        Line identification in IPv6 Router Solicitation messages
                     draft-krishnan-6man-rs-mark-04

Abstract

   In ethernet and PON based aggregation networks, several subscriber
   premises may be 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.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 9, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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 BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Conventions used in this document  . . . . . . . . . . . .  3
   2.  Issues with identifying the subscriber in an n:1 vlan model  .  4
   3.  Basic operation  . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Access Node Behavior . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  On receiving a router solicitation from the subscriber . .  6
     4.2.  On receiving a router advertisement from the edge
           router . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Edge Router Behavior . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  On receiving a router solicitation from the subscriber . .  7
     5.2.  On sending a router advertisement towards the
           subscriber . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Line Identification Option . . . . . . . . . . . . . . . . . .  8
   7.  Interactions with SEND . . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   11. Normative References . . . . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14



















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1.  Introduction

   DSL is a widely deployed access technology for Broadband Access for
   Next Generation Networks.  While traditionally DSL access networks
   were PPP 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].  One of the ethernet and PON aggregation models specified in
   this document bridges sessions from multiple subscribers behind a DSL
   Access Node (AN), also referred to as a DSLAM, into a single VLAN in
   the aggregation network.  This is called the N:1 VLAN allocation
   model.


   +---+   +----+    +----------+
   |CPE|---| RG |----|          |
   +---+   +----+    |          |
                     |    AN    |\
   +---+   +----+    |          | \
   |CPE|---| RG |----|          |  \
   +---+   +----+    +----------+   \                    +----------+
                                     \                   |          |
                                   +-------------+       |          |
                                   | Aggregation |       |  Edge    |
                                   |    Node     |-------|  Router  |
                                   +-------------+       |          |
                                     /                   |          |
                     +----------+   /                    +----------+
                     |          |  /
   +---+   +----+    |          | /
   |CPE|---| RG |----|    AN    |/
   +---+   +----+    |          |
                     |          |
                     +----------+


              Figure 1: Broadband Forum Network Architecture

1.1.  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 fixed Broadband Network, IPv6 hosts are connected to an Access
   Node (AN).  These hosts today will typically send a Route
   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 host will use to
   automatically configure an IPv6 Address.  Upon sending the Route
   Solicitation message the node connecting the host 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 host on the circuit line the host is connected on.  To
   accomplish this, the AN needs to add line identification information
   to the Route Solicitation message and forward this to the 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.































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3.  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 initiated
   by the host 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.









































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4.  Access Node Behavior

4.1.  On receiving a router solicitation from the subscriber

   When a host sends out a router solicitation, it is received by the
   access node.  The AN then tunnels the received Router solicitation in
   a newly created IPv6 datagram with the LIO destination option.  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 it
   MUST use the unspecified address as the Source Address of the outer
   IPv6 datagram.  The destination address of the ouer 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 also insert a LIO destination option
   and set the line identification data of the option to contain the
   subscriber agent circuit identifier corresponding to the logical
   access loop port of the Access Node from which the RS was initiated.

4.2.  On receiving a router advertisement from the edge router

   When the edge router sends out a 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 identifier
   corresponding to the logical access loop port of the Access Node on
   which the RA should be sent.






















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5.  Edge Router Behavior

5.1.  On receiving a router solicitation from the subscriber

   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.  If an LIO option
   is present, the edge router MAY use the contents of the line
   identification field to lookup the addressing information and policy
   that need to be applied to the subscriber.  The edge router MUST then
   process the inner RS message as specified in [RFC4861]

5.2.  On sending a router advertisement towards the subscriber

   When the edge router sends out a router advertisement in response to
   a tunneled RS that included an LIO option, it SHOULD unicast the RA
   back to the sender of the RS.  It MUST tunnel the RA to the AN using
   an outer IPv6 datagram that contains the LIO option.  The Source
   Address of the outer IPv6 datagram MUST be copied from the Source
   Address of the RA.  The Destination Address of the outer IPv6
   datagram MUST be set to the Source Address of the outer datagram of
   the received RS.  The line identification data field of the LIO
   option MUST be set to the same value as was received in the LIO
   option of the received tunneled RS.  Using the LIO option to tunnel
   multicast RAs is NOT RECOMMENDED.


























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6.  Line Identification Option

   The Line Identification Option (LIO) is a destination option that can
   be included in IPv6 datagrams that tunnel Router Solicitation and
   Router Advertisement messages.  Multiple Line Identification 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 2: Line Identification 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  0 is
       considered invalid.

    Line Identification

       In a Router Solicitation:

       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.

       In a Router Advertisement:

       Variable length data inserted by the Edge Router describing the
       subscriber agent circuit identifier corresponding to the logical
       access loop port of the Access Node on which the RA needs to be
       sent out.






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7.  Interactions with SEND

   Since the SEND protected RS/RA packets are not modified in anyway by
   the mechanism described in this document, there are no issues with
   SEND verification.














































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8.  Acknowledgements

   The author would like to thank Margaret Wasserman, Mark Townsley,
   David Miles, John Kaippallimalil, and Eric Levy-Abegnoli for
   reviewing this document and suggesting changes.














































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9.  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
   modifed, 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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10.  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

   <TBA> Line Identification Option [RFCXXXX]

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







































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11.  Normative References

   [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>.

































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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


   Sven Ooghe
   Alcatel-Lucent
   Copernicuslaan 50
   2018 Antwerp,
   Belgium

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


   Balazs Varga
   Magyar Telekom

   Email: varga.balazs@telekom.hu

















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