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Versions: (draft-evans-dhc-dhcpv6-reconfigure-rebind) 00 01 02 03 04 05 06 07 08 09 10 RFC 6644

Network Working Group                                           D. Evans
Internet-Draft                                 ARRIS International, Inc.
Intended status: Informational                                  R. Droms
Expires: May 7, 2009                                 Cisco Systems, Inc.
                                                        November 3, 2008


            Rebind Capability in DHCPv6 Reconfigure Messages
            draft-ietf-dhc-dhcpv6-reconfigure-rebind-05.txt

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   This Internet-Draft will expire on May 7, 2009.

Abstract

   This document updates RFC 3315 to allow the Rebind message type to
   appear in the Reconfigure Message option of a Reconfigure message,
   which extends the Reconfigure message to allow a DHCPv6 server to
   cause a DHCPv6 client to send a Rebind message.  The document also
   clarifies how a DHCPv6 client responds to a received Reconfigure
   message.


1.  Introduction

   DHCPv6 [RFC3315] allows a server to send an unsolicited Reconfigure



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   message to a client.  The client's response to a Reconfigure message,
   according to section 19 of RFC3315 is either a Renew or an
   Information-Request message, depending on the contents of the msg-
   type field in the Reconfigure Message option of the Reconfigure
   message.

   If the client sends a Renew message, it includes a Server Identifier
   option in the Renew message to specify the server that should respond
   to the Renew message.  Under some circumstances, it may be desirable
   for the client to communicate with a different server; for example,
   if the server that the client most recently communicated with is no
   longer available, the network administrator may want the client to
   communicate with a different server.  This document expands the
   allowed values of the msg-type field to allow the server to indicate
   that the client is to send a Rebind message, which does not include a
   Server Identifier option and allows any server to respond to the
   client.

   RFC 3315 does not specify that a Reconfigure message must be sent
   from the server with which the client most recently communicated, and
   it does not specify which server the client should identify with a
   Server Identifier option when the client responds to the Reconfigure
   message.  This document clarifies that the client should send a Renew
   message in response to a Reconfigure message with a Server Identifier
   option identifying the same server that the client would have
   identified if the client had sent the Renew message after expiration
   of T1.


2.  Terminology

   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].

   This document uses IPv6 and DHCPv6 terms as defined in section 4 of
   RFC 3315.


3.  The Reconfigure Message option of the DHCPv6 Reconfigure Message

   This section modifies section 22.19 of RFC 3315 to allow the
   specification of the Rebind message in a Reconfigure message.

   A server includes a Reconfigure Message option in a Reconfigure
   message to indicate to the client whether the client responds with a
   Renew, an Information-request, or a Rebind message.




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   The format of this option is:

        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_RECONF_MSG        |         option-len            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    msg-type   |
       +-+-+-+-+-+-+-+-+

   option-code         OPTION_RECONF_MSG (19).
   option-len          1.
   msg-type            5 for Renew message, 6 for Rebind, 11 for
                       Information-request message.


4.  Server Behavior

   This section updates specific text in sections 19.1, 19.2 and 19.3 of
   RFC 3315.

   The server MUST include a Reconfigure Message option (as defined in
   Section 3) to select whether the client responds with a Renew
   message, a Rebind message or an Information-Request message.

   The Reconfigure message causes the client to initiate a Renew/Reply,
   a Rebind/Reply message exchange or an Information-request/Reply
   message exchange.  The server interprets the receipt of a Renew, a
   Rebind or an Information-request message (whichever was specified in
   the original Reconfigure message) from the client as satisfying the
   Reconfigure message request.

   The server retransmits a Reconfigure message specifying a Rebind
   message in the same way as described in section 19.1.2 of RFC 3315.

   In response to a Rebind message, the server generates and sends a
   Reply message to the client as described in sections 18.2.4 and
   18.2.8, including options for configuration parameters.

   The server MAY include options containing the IAs and new values for
   other configuration parameters in the Reply message, even if those
   IAs and parameters were not requested in the Renew message from the
   client.

4.1.  Client Behavior

   This section updates specific text in section 19.4 of RFC 3315.




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   Upon receipt of a valid Reconfigure message, the client responds with
   a Renew message, a Rebind message or an Information-request message
   as indicated by the Reconfigure Message option (as defined in
   Section 3).  The client ignores the transaction-id field in the
   received Reconfigure message.  While the transaction is in progress,
   the client silently discards any Reconfigure messages it receives.

   When responding to a Reconfigure, the client creates and sends the
   Rebind message in exactly the same manner as outlined in section
   18.1.4 of RFC 3315, with the exception that the client copies the
   Option Request option and any IA options from the Reconfigure message
   into the Rebind message.

   If a client is currently sending Rebind messages, as described in
   section 18.1.4 of RFC 3315, the client ignores any received
   Reconfigure messages.

   The client uses the same variables and retransmission algorithm as it
   does with Renew, Rebind or Information-request messages generated as
   part of a client-initiated configuration exchange.  See sections
   18.1.3, 18.1.4 and 18.1.5 of RFC 3315 for details.  If the client
   does not receive a response from the server by the end of the
   retransmission process, the client ignores and discards the
   Reconfigure message.


5.  Clarification of section 19.4.2, RFC 3315

   When sending a Renew message in response to the receipt of a
   Reconfigure message, the client MUST include a Server Identifier
   option identifying the server the client most recently communicated
   with.


6.  Security Considerations

   This document adds no new security considerations beyond those
   present in RFC 3315.


7.  IANA Considerations

   There are no actions for IANA associated with this document.


8.  Change log

   This section MUST be removed before publication.



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8.1.  Revision -05

   Clarified description of this feature in introduction.

   Clarified action of client if it receives a Reconfigure while sending
   Rebind messages.


9.  Normative References

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

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.


Authors' Addresses

   D. R. Evans
   ARRIS International, Inc.
   7912 Fairview Road
   Boulder, CO  80303
   USA

   Phone: +1 303.494.0394
   Email: N7DR@arrisi.com


   Ralph Droms
   Cisco Systems, Inc.
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   USA

   Phone: +1 978.936.1674
   Email: rdroms@cisco.com













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