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6man Working Group                                           S. Krishnan
Internet-Draft                                               A. Kavanagh
Intended status: Standards Track                                Ericsson
Expires: September 9, 2009                                      S. Ooghe
                                                          Alcatel-Lucent
                                                                B. Varga
                                                          Magyar Telekom
                                                           March 8, 2009


        Line identification in IPv6 Router Solicitation messages
                     draft-krishnan-6man-rs-mark-02

Status of this Memo

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   This Internet-Draft will expire on September 9, 2009.

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Abstract

   In ethernet 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.


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.  Access Node Behavior . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  On receiving a router solicitation from the subscriber . .  5
     3.2.  On receiving a router advertisement from the edge
           router . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Edge Router Behavior . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  On receiving a router solicitation from the subscriber . .  6
     4.2.  On sending a router advertisement towards the
           subscriber . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Line Identification Neighbor Discovery Option  . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   8.  Normative References . . . . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
























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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 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.  Access Node Behavior

3.1.  On receiving a router solicitation from the subscriber

   When a host sends out a router solicitation, it is received by the
   access node.  First, the access node needs to verify if there are no
   LIO options present in the router solicitation.  If there are any LIO
   options present, the AN MUST drop the router solicitation.  If there
   are no LIO options present, the AN SHOULD insert a new LIO option
   into the router solicitation message.  The AN MUST set the line
   identification data of the LIO 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.

3.2.  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.  If the LIO option was present in the
   received RA, the AN MUST remove the option before forwarding the RA
   to the subscriber premise.



























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4.  Edge Router Behavior

4.1.  On receiving a router solicitation from the subscriber

   When the edge router receives a router solicitation forwarded by the
   access node, it needs to check if there is an LIO option present in
   the router solicitation.  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.

4.2.  On sending a router advertisement towards the subscriber

   When the edge router sends out a router advertisement in response to
   an RS that contained an LIO option, it MUST unicast the RA back to
   the sender of the RS.Whenever the edge router needs to send out a
   multicast router advertisement message (e.g. because the unicast MAC
   address has aged out in the Neighbor Cache), it SHOULD insert an LIO
   option in the RA.  If the LIO option is included, 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 RS.






























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5.  Line Identification Neighbor Discovery Option

   The Line Identification Option (LIO) can be included in Router
   Solicitation and Router Advertisement messages.  Multiple Line
   Identification options MUST NOT be present in a Neighbor Discovery
   message.  The LIO has an alignment requirement of 4n.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type      |   Length      |           Reserved            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Line Identification...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 2: Line Identification Option Layout


    Type

       8-bit identifier of the type of option. The option identifier
       for the line identification option will be allocated by the IANA.

    Length

       8-bit unsigned integer.  The length of the option (including
       the type and length fields) in units of 8 octets.  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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6.  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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7.  IANA Considerations

   This document defines a new IPv6 neighbor discovery option for
   carrying line identification.  IANA is requested to assign a new
   neighbor discovery option type in the registry maintained at

   http://www.iana.org/assignments/icmpv6-parameters

   <TBA> Line Identification Option [RFCXXXX]










































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8.  Normative References

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

   [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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