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6man Working Group                                           S. Krishnan
Internet-Draft                                               A. Kavanagh
Intended status: Standards Track                                Ericsson
Expires: February 5, 2011                                       S. Ooghe
                                                          Alcatel-Lucent
                                                                B. Varga
                                                          Magyar Telekom
                                                             E. Nordmark
                                                                  Oracle
                                                          August 4, 2010


        Line identification in IPv6 Router Solicitation messages
                     draft-krishnan-6man-rs-mark-06

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.  The applicability is limited to the
   N:1 VLAN allocation model.

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 5, 2011.

Copyright Notice

   Copyright (c) 2010 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.  Conventions used in this document . . . . . . . . . . . . . 3
   2.  Issues with identifying the subscriber in an N:1 VLAN model . . 4
   3.  Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Basic operation . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Access Node Behavior  . . . . . . . . . . . . . . . . . . . . . 4
     5.1.  On receiving a Router Solicitation from the subscriber  . . 5
     5.2.  On receiving a Router Advertisement from the subscriber . . 5
   6.  Edge Router Behavior  . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  On receiving a Router Solicitation from the subscriber  . . 5
     6.2.  On sending a Router Advertisement towards the
           subscriber  . . . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Line Identification Option  . . . . . . . . . . . . . . . . . . 6
   8.  Interactions with Secure Neighbor Discovery . . . . . . . . . . 7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   10. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   12. Normative References  . . . . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8





















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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 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 Router
   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 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 option is intended to be used only for the
   N:1 VLAN deployment model.  For the other VLAN deployment models
   there is no need to carry line identification.


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 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.


5.  Access Node Behavior







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5.1.  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 Link 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 subscriber agent circuit identifier
   corresponding to the logical access loop port of the Access Node from
   which the RS was initiated.  It MUST also insert the hardware address
   of the client (from the source hardware address of the RS) into the
   client hardware address field of the option.

5.2.  On receiving a Router Advertisement from the subscriber

   Since the Router Advertisements are unicasted by the edge router
   towards the subscriber the access node does not need to intercept the
   downstream Router Advertisements.


6.  Edge Router Behavior

6.1.  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 MUST verify that the Option Length field
   of this option is set to ClientHWALen+LineIDLen+2.  If not the edge
   router MUST discard the tunneled Router Solicitation.  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]

6.2.  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 MUST unicast the RA at



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   layer 2 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, other wise the
   IPv6 destination address is copied from the inner IPv6 source address
   of the Router Soliciation.  In both cases the link-layer destination
   address MUST be set to the unicast link-layer address which is in
   Client Hardware Address field in the LIO.


7.  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 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   LineIDLen   |     Line Identification...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ClientHWALen  |     Client Hardware Address...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                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.

    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.

    ClientHWALen

       Length of the Client Hardware Address in number of octets.

    Client Hardware Address

       Variable length client hardware address as detected by the
       access node.



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 and Wojciech Dec for reviewing this
   document and suggesting changes.





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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.


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

   <TBA> Line Identification Option [RFCXXXX]

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


12.  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


   Erik Nordmark
   Oracle
   17 Network Circle
   Menlo Park, CA 94025
   USA

   Email: erik.nordmark@oracle.com








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