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Versions: (draft-boucadair-dhc-triggered-reconfigure) 00 01 02 03 04 05 06 07 RFC 6977

DHC Working Group                                           M. Boucadair
Internet-Draft                                               X. Pougnard
Updates: 3315, 6422 (if approved)                         France Telecom
Intended status: Standards Track                       December 17, 2012
Expires: June 20, 2013


              RECONFIGURE Triggered by DHCPv6 Relay Agents
                draft-ietf-dhc-triggered-reconfigure-02

Abstract

   This document defines a new DHCPv6 message type: RECONFIGURE-REQUEST.
   This message is sent by a DHCPv6 relay agent to notify a DHCPv6
   server about a configuration information change, so that the DHCPv6
   server can send a RECONFIGURE message accordingly.

   This document updates RFC3315 and RFC6422.

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
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   This Internet-Draft will expire on June 20, 2013.

Copyright Notice

   Copyright (c) 2012 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
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Problem . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . . . 4
   2.  Proposed Solution . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Link Address Option . . . . . . . . . . . . . . . . . . . . . . 5
   4.  RECONFIGURE-REQUEST . . . . . . . . . . . . . . . . . . . . . . 6
     4.1.  Message Format  . . . . . . . . . . . . . . . . . . . . . . 6
     4.2.  Message Validation  . . . . . . . . . . . . . . . . . . . . 6
     4.3.  Creation and Transmission of RECONFIGURE-REQUEST  . . . . . 7
     4.4.  Server Behaviour  . . . . . . . . . . . . . . . . . . . . . 8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 9
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9




























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1.  Introduction

1.1.  Problem

   [RFC6422] updates the DHCPv6 specification [RFC3315] with a new
   feature to let a DHCPv6 relay agent communicate information towards a
   DHCPv6 Client, and which is not available at the DHCPv6 server.  This
   is achieved owing to the use of RSOO (Relay-Supplied Options option)
   which carries configuration data to the DHCPv6 server.  The data
   conveyed in an RSOO is then sent back by the DHCPv6 server to the
   requesting DHCPv6 client.

   An example of a RSOO context is shown in Figure 1; only a subset of
   exchanged DHCPv6 and RADIUS messages is represented.

      +-------+                   +-------+                    +-------+
      |DHCPv6 |                   |  NAS  |                    |Radius |
      |Client |                   |(DHCPv6|                    |Server |
      |       |                   | Relay)|                    |       |
      +-------+                   +-------+                    +-------+
          |                           |                            |
          |---Solicit---------------->|                            |
          |                           |---Access-Request---------->|
                                      |<--Access-Accept------------|
                                      |  (e.g. DS-Lite-Tunnel-Name)|
                                    ....

                                      |                        +-------+
                                      |                        |DHCPv6 |
                                      |                        |Server |
                                      |                        |       |
                                      |                        +-------+
                                      |                            |
                                      |---Relay-Forward----------->|
                                      | (RSOO(DS-Lite-Tunnel-Name))|
                                      |                            |
          |                           |<--Relay-Reply--------------|
          |<--Advertise---------------|
          |  (e.g., OPTION_AFTR_NAME) |
                                     ....


               Figure 1: An Example of the RSOO Option Usage

   The change of the configuration may result in RADIUS exchanges
   ([RFC5176]) between the NAS/DHCPv6 relay agent and Dynamic
   Authorization Client (DAC) server as shown in Figure 2.  Note the
   change of the configuration in the DHCPv6 relay agent can be



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   triggered by any other out-of-band mechanism.



      +-------+                   +-------+                    +-------+
      |DHCPv6 |                   |  NAS  |                    |Radius |
      |Client |                   |(DHCPv6|                    |Server/|
      |       |                   | Relay)|                    |  DAC  |
      +-------+                   +-------+                    +-------+
          |                           |                            |
                                      |<-----CoA-Request-----------|
                                      | (e.g. DS-Lite-Tunnel-Name) |
                                      |------CoA-Response--------->|
                                    ....

      CoA (Change-of-Authorization, [RFC5176])

                     Figure 2: Change of configuration

   Whenever the configuration information sent by the DHCPv6 relay agent
   to the DHCPv6 server change, the DHCPv6 server has no means to detect
   it so that it can send a Reconfigure message with the updated
   configuration data accordingly.  A solution is sketched in Section 2.

1.2.  Requirements Language

   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].


2.  Proposed Solution

   To solve the problem described in Section 1.1, this document proposes
   a new DHCP message called Reconfigure-Request.  In the example
   depicted in Figure 3 a Reconfigure-Request message is sent by the
   DHCPv6 relay agent to a DHCPv6 server as soon as the configuration
   data conveyed in an RSOO option have changed.  Upon receipt of this
   message, and if it is configured to support such mode, the DHCPv6
   server must build a Reconfigure message.  This message is then sent
   to the DHCPv6 relay, which in turn will forward the message to the
   appropriate DHCPv6 client.

   This setup assumes the relay has a record of the client, so that it
   has enough information to send the Reconfigure-Request message to the
   server.  Means to recover state in failure events must be supported,
   but are not discussed in this document.




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      +-------+                   +-------+                    +-------+
      |DHCPv6 |                   |  NAS  |                    |Radius |
      |Client |                   |(DHCPv6|                    |Server/|
      |       |                   | Relay)|                    | DAC   |
      +-------+                   +-------+                    +-------+
          |                           |                            |
                                      |<-----CoA-Request-----------|
                                      | (e.g. DS-Lite-Tunnel-Name) |
                                      |                            |
                                      |------CoA-Response--------->|
                                    ....
                                      |                        +-------+
                                      |                        |DHCPv6 |
                                      |                        |Server |
                                      |                        |       |
                                      |                        +-------+
                                      |                            |
                                      |---Reconfigure-Request----->|
                                      |                            |
                                      |                            |
          |                           |<--Relay-Reply -------------|
          |<--Reconfigure-------------|   (Reconfigure)            |
          |                           |                            |
                                    ....

                Figure 3: RECONFIGURE-REQUEST Flow Example

   The Reconfigure-Request message can also be used in other scenarios
   than those that assume the use of RSOO.  It is out of scope of this
   document to describe all these scenarios.


3.  Link Address Option

   Figure 4 shows the format of the Link Address Option.

      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_LINK_ADDRESS     |         option-len            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                  link-address (IPv6 address)                  |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 4: Message Format of Link Address Option



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   The description of the fields are as follows:

      option-code: OPTION_LINK_ADDRESS (To be assigned by IANA, see
      Section 5).

      option-len: 16 (octets).

      link-address: An IPv6 address used by the server to identify the
      link on which the client is located.

   The Link Address Option is used by the relay agent to indicate to the
   server the link on which the client is located.  The relay agent MUST
   use a link-address value that is equivalent to the value used when
   relaying messages from the client to the server.  Two link-address
   values are said to be equivalent if both values are IPv6 addresses
   that are on-link for the network link to which the client is
   connected.  The relay agent SHOULD use the same value that was sent
   to the DHCP server when relaying messages from the client to the
   server, as in Section 20.1.1 of [RFC3315].

   The relay agent MUST NOT use the IPv6 unspecified address (0::0) in
   this option.  The server MUST discard any Reconfigure Request message
   containing a Link Address Option that carries the unspecified
   address.


4.  RECONFIGURE-REQUEST

4.1.  Message Format

   A new message type code is defined:

      RECONFIGURE-REQUEST (To be assigned by IANA, see Section 5).

   RECONFIGURE-REQUEST uses the same format as defined in Section 6 of
   [RFC3315].

4.2.  Message Validation

   Clients MUST silently discard any received RECONFIGURE-REQUEST
   messages.

   Servers MUST silently discard any received RECONFIGURE-REQUEST
   messages that meet any of the following conditions:

   o  the message does not include a Client Identifier Option [RFC3315].





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   o  the message does not include a Link Address Option (Section 3).

   o  the message includes a Server Identifier Option [RFC3315] but the
      contents of the Server Identifier Option does not match the
      server's identifier.

   The server MUST be configurable to accept or reject RECONFIGURE-
   REQUEST messages.  If the server is configured to reject RECONFIGURE-
   REQUEST, the server MUST silently discard any RECONFIGURE-REQUEST it
   receives.

   The relay agent MUST be configurable to accept or reject RECONFIGURE-
   REQUEST messages received from other relay agents.  If the relay is
   configured to reject RECONFIGURE-REQUEST, the relay MUST silently
   discard any RECONFIGURE-REQUEST it receives.  If the relay is
   configured to accept RECONFIGURE-REQUEST messages, these messages are
   relayed as specified in Section 20.1.1 of [RFC3315].

   Because RECONFIGURE-REQUEST message provides a mechanism for
   triggering the DHCP Reconfigure message, and the DHCP Reconfigure
   message can raise security threats (e.g., to control the timing of a
   DHCP renewal), the DHCP server MUST have some mechanism for
   determining that the relay agent is a trusted entity.  RECONFIGURE-
   REQUEST messages originating from unknown relay agents MUST be
   silently dropped.

4.3.  Creation and Transmission of RECONFIGURE-REQUEST

   For any event (e.g., modification of the configuration information)
   that requires the server to issue a Reconfigure message, the relay
   agent determines the client which is affected by the change and then
   builds a Reconfigure-Request message: the relay agent sets the "msg-
   type" field to RECONFIGURE-REQUEST and sets the "transaction-id "
   field to 0.  The relay agent MUST include a Client Identifier Option
   [RFC3315] and a Link Address Option (Section 3) so that the DHCPv6
   server can identify the corresponding client and the link on which
   the client is located.  The relay agent MAY supply the updated
   configuration in the RSOO [RFC6422].  The relay agent MAY supply a
   Reconfigure Message Option to indicate which form of Reconfigure to
   use.

   When several clients on the same link are concerned with a
   configuration change, the relay MUST include several Client
   Identifier Options, each of them identifies a specific client.  If
   including Client Identifier Options of all impacted clients exceeds
   the maximum message size, the relay MUST generate several
   RECONFIGURE-REQUEST messages required to carry all Client Identifier
   Options.



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4.4.  Server Behaviour

   Upon receipt of a valid Reconfigure-Request message from a DHCPv6
   relay agent (see Section 4.2), the server determines the client(s)
   for which a Reconfigure message is to be sent.

   The server MAY use the content of the Reconfigure Message Option
   supplied by the relay agent to determine which form of Reconfigure to
   use.

   If RSOO is supplied, the server MAY use its content to double check
   whether a Reconfigure is required to be sent to the client.  This
   assumes the server store the content of RSOO it used to generate
   configuration data sent to requesting clients.

   Then, the server MUST follow the procedure defined in Section 19.1 of
   [RFC3315] to construct a Reconfigure message.  This message may be
   sent directly to the DHCPv6 client or to a relay agent [RFC3315].


5.  IANA Considerations

   IANA is requested to assign the following new DHCPv6 Message type in
   the registry maintained in
   http://www.iana.org/assignments/dhcpv6-parameters:

      RECONFIGURE-REQUEST

   IANA is requested to assign the following new DHCPv6 Option Codes in
   the registry maintained in
   http://www.iana.org/assignments/dhcpv6-parameters:

      OPTION_LINK_ADDRESS


6.  Security Considerations

   Security considerations elaborated in [RFC3315] and [RFC6422] must be
   taken into account.  In addition, DHCPv6 servers MAY be configured to
   discard relayed RECONFIGURE-REQUEST messages or restrict relay
   chaining (see [RFC5007] for more discussion about the rationale of
   this recommended behavior).  Relay agents SHOULD implement
   appropriate means to prevent using RECONFIGURE-REQUEST messages as a
   denial-of-service attack on the DHCPv6 servers.







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7.  Acknowledgements

   Many thanks to R. Maglione, A. Kostur, G. Halwasia, C. Jacquenet and
   B. Volz for the comments and review.

   Special thanks to T. Lemon who provided a detailed review.


8.  References

8.1.  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.

   [RFC6422]  Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options",
              RFC 6422, December 2011.

8.2.  Informative References

   [RFC5007]  Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
              "DHCPv6 Leasequery", RFC 5007, September 2007.

   [RFC5176]  Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
              Aboba, "Dynamic Authorization Extensions to Remote
              Authentication Dial In User Service (RADIUS)", RFC 5176,
              January 2008.


Authors' Addresses

   Mohamed Boucadair
   France Telecom
   Rennes,   35000
   France

   Email: mohamed.boucadair@orange.com










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   Xavier Pougnard
   France Telecom
   Lannion,
   France

   Phone:
   Email: xavier.pougnard@orange.com












































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