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6man Working Group                                           S. Krishnan
Internet-Draft                                               A. Kavanagh
Intended status: Standards Track                                Ericsson
Expires: November 24, 2010                                      S. Ooghe
                                                          Alcatel-Lucent
                                                                B. Varga
                                                          Magyar Telekom
                                                            May 23, 2010


        Line identification in IPv6 Router Solicitation messages
                     draft-krishnan-6man-rs-mark-05

Abstract

   In Ethernet and PON 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.

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
   Task Force (IETF), its areas, and its working groups.  Note that
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   This Internet-Draft will expire on November 24, 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 . . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   11. Normative References . . . . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15



















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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 or PON aggregation models specified in
   this document bridges sessions from multiple subscribers behind a DSL
   Access Node (AN), also referred to as a DSLAM or OLT, 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 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 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).  Therefore, 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
   (LIO) to the Router Solicitation message and forward this to the Edge
   Router.  This document proposes a method for transporting access loop
   related information from AN towards 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 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 also insert a LIO
   destination option and set (i) the line identification data of the
   option to contain the subscriber agent circuit identifier and (ii)
   the agent remote identifier containing the link-layer address of the
   sender.  LIO related data values MUST correspond 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

   The Edge Router SHOULD send Router Advertisement messages per
   endpoint without Tunnel Encapsulation.  Therefore AN MUST forward RA
   message towards the appropriate endpoint based on the destination
   link-layer address of the RA.






















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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 can 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.  If the source address of the RS was
   the unspecified address, then the IPv6 destination address of the RA
   MUST be set to the all-nodes multicast address, but the link-layer
   destination address MUST be set to the unicast link-layer address of
   the sender of the RS.  Edge Router MUST send periodic RA messages as
   defined above in order to update e.g. default-router table in IPv6
   hosts.




























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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


































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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.

    Line Identification

       In a Router Solicitation:

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

       Note:
       Considering the scenario, where multiple customers' IPv6 hosts
       are located behind a bridged modem, there may be multiple
       tunneled RS messages containing the same agent circuit identifier
       but different agent remote identifier.


















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7.  Interactions with SEND

   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.














































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8.  Acknowledgements

   The authors would like to thank Margaret Wasserman, Mark Townsley,
   David Miles, John Kaippallimalil, Eric Levy-Abegnoli, Thomas Narten,
   Erik Nordmark and Jonne Soininen 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
   Magyar Tudosok krt. 9
   1117 Budapest,
   Hungary

   Email: varga.balazs@telekom.hu














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