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   Individual Submission                                       B. Haberman
   Internet Draft                                                J. Martin
   draft-haberman-ipngwg-auto-prefix-01.txt                Nortel Networks
   July 2001



                Automatic Prefix Delegation Protocol for
                   Internet Protocol Version 6 (IPv6)

               <draft-haberman-ipngwg-auto-prefix-01.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
   Drafts. 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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


Abstract

   The expansion of the IP address space provided by IPv6 makes it both
   possible and reasonable to allocate entire subnets to environments
   that had been previously limited to a few individual IP addresses.
   Other protocols such as Neighbor Discovery and Stateless Address
   Autoconfiguration allow hosts within those subnets to be
   automatically configured. The router between this subnet and the
   upstream world requires just one more piece to make this process
   automatic, a network prefix.

   This document describes a mechanism for the automated delegation of
   an IPv6 network prefix. It allows routers to request a specific size
   prefix and inform the upstream router of the routing protocols of
   which it is capable. Upon authorizing the request the delegating
   router then returns a prefix, the desired routing protocol, and a
   lifetime for the use of the prefix.



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1. Introduction

   This specification defines the Prefix Delegation (PD) protocol for
   Internet Protocol Version 6 (IPv6). Routers use Prefix Delegation to
   request a network prefix for use on directly attached networks.
   Prefix Delegation also allows the requesting router to specify the
   routing protocols in which it is capable of participating. Upon
   receipt of the request, the delegating router may authenticate the
   request, and will establish if the requested prefix size is
   acceptable. The delegating router then specifies the prefix for use,
   the length of time for which that prefix is delegated, and the
   routing protocol to be used.

   Unless specified otherwise (in a document that covers operating IP
   over a particular link type) this document applies to all link
   types. However, because PD uses link-layer multicast, it is possible
   that on some link types (e.g., NBMA links) alternative mechanisms to
   implement PD must be specified (in the appropriate document covering
   the operation of IP over a particular link type).


2. Terminology

  2.1 General

   This document uses the terminology defined in [RFC 2460] and [RFC
   2461] and in addition:

        - Requesting Router - The router that is requesting that a
           prefix be assigned

        - Delegating Router - The router that is responding to the
           prefix request

  2.2 Addresses

   Prefix Delegation makes use of a number of different addresses
   defined in [ADDR-ARCH], including:

        - Global address - A unicast address having global scope

  2.3 Requirements

   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 [RFC 2119].


3. Scope of Work



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   This proposal is meant to give a singly homed leaf router the
   ability to obtain an IPv6 prefix that can be used within its leaf
   network.  Future revisions of this document may support a more
   generic approach to dynamic prefix delegation.

   It is also assumed that the delegating server/router shares a
   network connection with the requesting router.  Future revisions may
   remove this restriction and allow for either multi-hop messages or a
   relay function.


4. Protocol Overview

   The Prefix Delegation protocol defines two new ICMP message types,
   the Prefix Request and the Prefix Delegation. The Prefix Request is
   used by the Requesting Router to communicate requests to the
   Delegating Router. Conversely, the Prefix Delegation is used by the
   Delegating Router to communicate prefix and error information with
   the Requesting Router.

  4.1 Delegator Query

   The Requesting Router begins the Prefix Delegation process by
   sending a Prefix Request message of type [DELEGATOR QUERY] to the
   ALL-DELEGATORS link-local multicast address (XXXX::XX).

   Upon receipt of the Delegator query, a Delegating Router determines
   if it is configured to provide prefixes of the specified scope. If
   so, it unicasts a Prefix Delegation of type Prefix Delegator to the
   Requestor. If not, the message is silently discarded.

   After sending the query, the Requestor waits for Query Interval
   (Default: 5) seconds for one or more Delegating Routers to respond.
   If there is no response, the Delegator Query is sent again up to Max
   Query times (Default: 3). If no response is received, there are no
   Prefix Delegation services available, and Prefix Delegation has
   failed.

   If more than one response is received to the query, the response
   with the numerically highest source IP address is used.

  4.2 Initial Request

   Once a Delegating Router is chosen, the Requestor sends a Prefix
   Request message of type Initial Request to the unicast IP address of
   the Delegating Router.

   The Requestor may or may not have a Security Association with the
   Delegating Router, however if Authentication is required and no SA
   is present, the Delegator will reject the request with an error
   response indicating that Authentication is required. The Requestor

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   then builds a Security Association with the Delegator and sends
   another Initial Request including the SA information.

   If no response is heard within Request Timeout seconds (Default: 5),
   the Initial Request should be sent again, up to Max Initial Request
   (Default: 3) tries. If no response is heard, a Delegator Query is
   sent and the process restarted. If this cycle is repeated Max
   Delegation Attempts times (Default: 3), Prefix Delegation has
   failed.

  4.3 Authentication and Authorization

   Upon receipt of the Prefix Request of any type, the Delegating
   Router establishes if there is a need for Authentication, based upon
   local policy. If Authentication is required and none is provided,
   the Delegator will return a Prefix Delegation message, with a code
   of Authentication Required.

   Once the authentication credentials of the requestor, if present,
   are established, any request that requires the allocation of a
   prefix must be checked for Authorization. Authorization is
   established by verifying that the requested prefix length for the
   specific Requestor is acceptable by locally configured policy.  If
   the prefix length requested falls outside of policy, a Prefix
   Delegation error message of type Not Authorized is returned.

  4.4 Prefix Delegation

   After the request is verified to be acceptable, the Delegating
   Router allocates the requested prefix size from its pool of
   available addresses. The creation and management of that pool is
   beyond the scope of this document, but it can be supposed that
   minimalistically a Delegating Router will be statically configured
   with a fixed pool. If no acceptable prefix is available, a Prefix
   Delegation message with a code of Prefix Unavailable is returned.

   The Delegating Router then compares the list of available routing
   protocols in the Request against its own capabilities and the local
   policies regarding routing. For the purposes of this comparison,
   static routes are considered a routing protocol. If no acceptable
   match is found, static routes are used.

   The Delegating Router then sends a Prefix Delegation message to the
   Requesting Router containing a code of Prefix Delegation and all of
   the prefix and routing information.  The Delegating router then
   activates the negotiated protocol on the interface to which the
   Requestor is attached.

  4.5 Prefix Refresh



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   All Prefix Delegations have a finite lifetime. Upon receiving a
   Prefix Delegation, the requesting router initiates a timer such that
   before the lifetime is expired, the Requesting Router sends a Prefix
   Request with code=REFRESH directly to the Delegating router.

   If the Requestor receives no response within [RENEWAL TIMEOUT]
   seconds (Default: 5), the Renewal Request should be sent again, up
   to [MAX RENEWAL REQUEST] (Default: 3) tries.  If no response is
   heard the previously allocated prefix is not renewed.

   A Requesting Router receiving the Prefix Unavailable code, or no
   response at all, has not had the prefix renewed.  It will expire at
   the end of the initial lifetime.  To acquire a new prefix, the
   Requesting Router must begin anew as described in Section 4.1.

  4.6 Prefix Return

   If the Requesting Router no longer requires the use of a prefix, it
   can return that prefix to the control of the Delegating Router
   through the use of the Prefix Return code in a Prefix Request. The
   requesting router sends a Prefix Request directly to the Delegating
   Router.

   Upon receipt and verification (if needed) of this message, the
   Delegating Router returns the prefix to the pool and issues a Prefix
   Delegation with a code of Prefix Returned.

5. Messages

   All messages have the following general format:

      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      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                          Message Body                         +
     |                                                               |

  5.1 Prefix Request Message

   The Prefix Request Message is sent to request, renew, or release a
   prefix.








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      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      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |S|Prefix Length|    Reserved   |      Routing Capabilities     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                          IPv6 Prefix                          +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   IP Fields

      Source Address
          An IP address assigned to the sending interface.

      Destination Address
          The ALL-DELEGATORS link-local multicast address (XXXX::XX)for
          Delegator Query messages. All other Prefix Request messages
          should be sent to a unicast address of the Delegating Router.

      Authentication Header
          If a Security Association for the IP Authentication Header
          exists between the sender and the destination address, then
          the sender SHOULD include this header. No such header is
          required for the initial prefix request that is multicast,
          but may be required for further progress.

    ICMP Fields

      Type
          XXX (Where XXX is assigned by IANA)

      Code
          They Type of Request Code:

          Delegator Query (0)
                The Delegator Query is used by the Requestor to
                identify potential Delegating Routers. It is sent to
                the all-delegators link-local multicast address with no
                Authentication Header. For this Query, the Scope field
                is required. Unused fields MUST be set to zero.

          Initial Request (1)
                The Initial Request is used to initiate the request
                process. It is sent to the unicast IP address of the

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Internet Draft      <Automatic Prefix Delegation>           July 2001

                Delegating Router, and may carry an Authentication
                Header. For this initial request, the Scope, Prefix
                Length, and Routing Capabilities fields are required.
                Unused fields MUST be set to zero.


          Renewal Request (2)
                The Renewal Request is used to renew a prefix that has
                been previously allocated.  It is sent to a unicast IP
                address of the Delegating Router and may carry an
                Authentication Header. For the renewal, the Scope,
                Prefix Length, Routing Capabilities, and Prefix fields
                are required.

          Prefix Return (3)
                The Prefix Return is used to return an unused prefix,
                or portion of a prefix to the control of the Delegating
                Router. It is sent to a unicast IP address of the
                Delegating Router and may carry an Authentication
                Header. For the Return, the Scope, Prefix Length, and
                Prefix fields are required. Unused fields MUST be set
                to zero.

      Checksum
          The ICMP checksum as defined in [RFC 2463].

    Prefix Request Fields

      S
          A one bit Scope Flag.  A value of zero (0) indicates that the
          request is for a prefix of Global Scope, a one (1) indicates
          site-local.

      Prefix Length
          The length of the prefix being requested, renewed, or
          released.

      Routing Capabilities
          This bit-field allows the requestor to specify the routing
          protocols in which it is capable of participating. For the
          purposes of this field, a static route is considered a
          routing protocol.

          At this time, the only defined value is zero (0), indicating
          that the requestor is capable of static routes. This is an
          area for further work.

      Reserved
          This field is unused. It MUST be initialized to zero by the
          sender and MUST be ignored by the receiver.

      IPv6 Prefix

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Internet Draft      <Automatic Prefix Delegation>           July 2001

          The Prefix field is used to carry a previously assigned
          prefix. The host portion of the IP address MUST be padded
          with zeros.


  5.2 Prefix Delegation Message

   The Prefix Delegation Messages are sent to provide the addresses of
   available Prefix Delegators, to provide prefix and routing data, and
   for error returns.

      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      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |S|Prefix Length|   Rt Proto    |          Lifetime             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                          IPv6 Prefix                          +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Rt Info Length        | Rt Info . . . .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |

   IP Fields

      Source Address
          An IP address assigned to the sending interface.

      Destination Address
          The IP address of the Requestor as specified by the Source
          Address of the Prefix Request message.

      Authentication Header
          If a Security Association for the IP Authentication Header
          exists between the sender and the destination address, then
          the sender SHOULD include this header.

    ICMP Fields

      Type
          XXX+1 (Where XXX+1 is assigned by IANA)

      Code
          The Type of Response Code:


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Internet Draft      <Automatic Prefix Delegation>           July 2001


          Prefix Delegator (0)
                The Prefix Delegator is used by the Delegator to inform
                the Requestor that it is available to provide prefixes
                of the desired type. It is sent to the unicast IP
                address in the Source Address portion of the Prefix
                Request packet. For this Response, the Scope field is
                required. Unused fields MUST be set to zero.

          Authentication Required (1)
                The Authentication Required message indicates to the
                Requestor that a Security Association must be
                established before a prefix can be delegated. It is
                sent to the unicast IP address in the Source Address
                portion of the Prefix Request packet. For this message,
                no additional fields are required. Unused fields MUST
                be set to zero.

          Authorization Failed (2)
                The Authorization Failed message indicates to the
                Requestor that either it is not authorized to request a
                prefix, or that the prefix requested fell outside of
                local policy. It is sent to the unicast IP address in
                the Source Address portion of the Prefix Request
                packet. For this message, no additional fields are
                required. Unused fields MUST be set to zero.

          Prefix Unavailable (3)
                The Prefix Unavailable indicates that the Prefix
                Request was acceptable, but the Delegator does not have
                sufficient available address space to fulfill the
                request.  It is sent to the unicast IP address in the
                Source Address portion of the Prefix Request packet.
                For this message, no additional fields are required.
                Unused fields MUST be set to zero.

          Prefix Delegated (4)
                The Prefix Delegated message actually provides the
                prefix information that the Requestor has requested. It
                is sent to the unicast IP address in the Source Address
                portion of the Prefix Request packet. For this message,
                all fields are required.

          Prefix Returned (5)
                The Prefix Return is used to confirm the return of a
                prefix. It is sent to the unicast IP address in the
                Source Address portion of the Prefix Request packet.
                For this message, the Prefix Length and IPv6 Prefix
                fields are required.


      Checksum

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Internet Draft      <Automatic Prefix Delegation>           July 2001

          The ICMP checksum.

    Prefix Delegation Fields

      S
          A one bit Scope Flag. A value of zero (0) indicates that the
          response is for a prefix of Global Scope, a one (1) indicates
          site-local.

      Prefix Length
          The length of the prefix being provided.


      Rt Proto
          This field specifies the routing protocol in which the
          Requestor should participate.

          At this time, the only defined value is zero, for Static
          Routes. This is an area for further development of this
          document.

      Lifetime
          The time (in seconds) that the Requestor is permitted to use
          the allocated prefix. At the end of this period, the
          Delegator assumes control of the prefix. This lifetime can be
          extended through the renewal process.

      IPv6 Prefix
          The Prefix field is used to carry the assigned prefix. The
          host portion of the IP address MUST be padded with zeros.

      Rt Info Length
          The length, in octets, of the Routing Information field. At
          this time, since Static is the only defined protocol; this
          field should have a value of zero.

      Routing Information
          This field carries protocol specific information to allow the
          Requesting router to configure itself to participate in
          routing.

          This field will be described in later versions of this
          document. At this time, since Static is the only defined
          protocol; this field should be zero length.


6. To Do's

   - Additional security discussion
   - Expand routing protocol negotiation
   - Multiple hops between requestor and delegator


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   - Cascading delegations
   - Removal of leaf network restriction
   - Negotiation between routers
   - Spanning Tree rooted at delegator
   - DNS updates

7. Acknowledgements

   We would like to acknowledge and thank Jun-ichiro itojun Hagino for
   his feedback and suggestions for this document.

8. References


   [RFC 2460] S. Deering and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC 2461] T. Narten, E. Nordmark, and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461, December
              1998.

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

   [RFC 2463] A. Conta and S. Deering, "Internet Control Message
              Protocol (ICMPv6) for the Internet Protocol Version 6
              (IPv6) Specification", RFC 2463, December 1998.


Authors' Addresses

   Brian Haberman
   Nortel Networks
   300 Perimeter Park
   Morrisville, NC  27560

   Phone : 1-919-905-7484
   Email : haberman@nortelnetworks.com


   Jim Martin
   Nortel Networks
   4401 Great America Parkway
   Santa Clara, Ca 95054

   Phone : 1-408-495-3792
   Email : jrm@nortelnetworks.com






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