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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: Standards Track                                R. Droms
Updates: 3315                                        Cisco Systems, Inc.
Expires: October 18, 2012                                       S. Jiang
                                            Huawei Technologies Co., Ltd
                                                          April 16, 2012


            Rebind Capability in DHCPv6 Reconfigure Messages
            draft-ietf-dhc-dhcpv6-reconfigure-rebind-10.txt

Abstract

   This document updates RFC 3315 (DHCPv6) to allow the Rebind message
   type to appear in the Reconfigure Message option of a Reconfigure
   message.  It 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.

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 October 18, 2012.

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
   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



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   to this document.  Code Components extracted from this document must
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   This document may contain material from IETF Documents or IETF
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   it for publication as an RFC or to translate it into languages other
   than English.



































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The Reconfigure Message option of the DHCPv6 Reconfigure
       Message  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Server Behavior  . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Client Behavior  . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Clarification of section 19.4.2, RFC 3315  . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   10. Change log [RFC Editor please remove]  . . . . . . . . . . . . 10
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     11.1.  Normative References  . . . . . . . . . . . . . . . . . . 10
     11.2.  Informative References  . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11


































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1.  Introduction

   DHCPv6 [RFC3315] allows a server to send an unsolicited Reconfigure
   message to a client.  The client's response to a Reconfigure message,
   according to section 19 of RFC 3315 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.  The RFC 3315 specification is
   only suitable for the scenarios that client would communicate with
   the same DHCPv6 servers.

   There are also scenarios that the client must communicate with a
   different server: for example, a network administrator may choose to
   shut down a DHCPv6 server and move these clients who most recently
   communicated with it to another different server.  Hence, this
   document expands the allowed values of the message type field with in
   reconfiguration message to allow the server to indicate the client 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 the timer 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
   [RFC3315].


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.




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   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.

   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, and 19.2 of RFC
   3315.

   Section 19.1.1:

   OLD:

   The server MUST include a Reconfigure Message option (defined in
   section 22.19) to select whether the client responds with a Renew
   message or an Information-Request message.

   The server MUST NOT include any other options in the Reconfigure
   except as specifically allowed in the definition of individual
   options.

   A server sends each Reconfigure message to a single DHCP client,
   using an IPv6 unicast address of sufficient scope belonging to the
   DHCP client.  If the server does not have an address to which it can
   send the Reconfigure message directly to the client, the server uses
   a Relay-reply message (as described in section 20.3) to send the
   Reconfigure message to a relay agent that will relay the message to
   the client.  The server may obtain the address of the client (and the
   appropriate relay agent, if required) through the information the
   server has about clients that have been in contact with the server,
   or through some external agent.




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   To reconfigure more than one client, the server unicasts a separate
   message to each client.  The server may initiate the reconfiguration
   of multiple clients concurrently; for example, a server may send a
   Reconfigure message to additional clients while previous
   reconfiguration message exchanges are still in progress.

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

   NEW:

   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 server MUST NOT include any other options in the Reconfigure
   except as specifically allowed in the definition of individual
   options.

   A server sends each Reconfigure message to a single DHCP client,
   using an IPv6 unicast address of sufficient scope belonging to the
   DHCP client.  If the server does not have an address to which it can
   send the Reconfigure message directly to the client, the server uses
   a Relay-reply message (as described in section 20.3) to send the
   Reconfigure message to a relay agent that will relay the message to
   the client.  The server may obtain the address of the client (and the
   appropriate relay agent, if required) through the information the
   server has about clients that have been in contact with the server,
   or through some external agent.

   To reconfigure more than one client, the server unicasts a separate
   message to each client.  The server may initiate the reconfiguration
   of multiple clients concurrently; for example, a server may send a
   Reconfigure message to additional clients while previous
   reconfiguration message exchanges are still in progress.

   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.

   Section 19.1.2:




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   OLD:

   If the server does not receive a Renew or Information-request message
   from the client in REC_TIMEOUT milliseconds, the server retransmits
   the Reconfigure message, doubles the REC_TIMEOUT value and waits
   again.  The server continues this process until REC_MAX_RC
   unsuccessful attempts have been made, at which point the server
   SHOULD abort the reconfigure process for that client.

   NEW:

   If the server does not receive a Renew, Rebind or Information-request
   message from the client in REC_TIMEOUT milliseconds, the server
   retransmits the Reconfigure message, doubles the REC_TIMEOUT value
   and waits again.  The server continues this process until REC_MAX_RC
   unsuccessful attempts have been made, at which point the server
   SHOULD abort the reconfigure process for that client.

   Section 19.2:

   OLD:

   19.2.  Receipt of Renew or Rebind Messages

   The server generates and sends a Reply message to the client as
   described in sections 18.2.3 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.

   NEW:

   19.2.  Receipt of Renew Messages

   In response to a Renew message, the server generates and sends a
   Reply message to the client as described in sections 18.2.3 and
   18.2.8, including options for configuration parameters.

   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 or Rebind message



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   from the client.


5.  Client Behavior

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

   Section 19.4.1:

   OLD:

   Upon receipt of a valid Reconfigure message, the client responds with
   either a Renew message or an Information-request message as indicated
   by the Reconfigure Message option (as defined in section 22.19).  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.

   NEW:

   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.

   Section 19.4.2:

   ADD new second and third paragraphs:

   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.

   Section 19.4.4:

   OLD:

   The client uses the same variables and retransmission algorithm as it
   does with Renew or Information-request messages generated as part of
   a client-initiated configuration exchange.  See sections 18.1.3 and



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   18.1.5 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.

   NEW:

   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.


6.  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.


7.  Security Considerations

   This document allows the Rebind message type to appear in the
   Reconfigure Message option of a Reconfigure message so that the
   client rebinds to a different DHCPv6 server.  A malicious attacker
   may use a faked Reconfigure message to force the client to disconnect
   from the current server and relink to a faked server by quickly
   responding to the client's Rebind message.  A similar attack is
   available in DHCPv6 by an attacker spoofing itself as a valid DHCPv6
   server in response to a Solicit or Request message.  These attacks
   can be prevented by using the AUTH option [RFC3315].  DHCPv6 clients
   that support Reconfigure-Rebind MUST implement the Reconfigure Key
   authentication protocol as described in [RFC3315] section 21.5.
   Other authentication mechanisms may optionally be implemented.  For
   example, the Secure DHCPv6 [I-D.ietf-dhc-secure-dhcpv6], based on
   Cryptographically Generated Addresses (CGA) [RFC3972], can provide
   source address ownership validation, message origin authentication
   and message integrity without requesting symmetric key pairs or
   supporting from any key management system.


8.  Acknowledgements

   Valuable comments were made by Jari Arkko, Sean Turner, Ted Lemon and
   Stephen Farrell.



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9.  IANA Considerations

   There are no actions for IANA associated with this document.


10.  Change log [RFC Editor please remove]

   Revision -05

   Clarified description of this feature in introduction.

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

   Revision -08

   Add a new co-author.  Refreshed expired draft.  Refine the motivation
   and suitable scenarios, also add some new security considerations.
   Correct the intended status to standard track.

   Revision-10

   Adopt OLD-NEW style according to IESG comment and address other IESG
   comments.


11.  References

11.1.  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.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005.

11.2.  Informative References

   [I-D.ietf-dhc-secure-dhcpv6]
              Jiang, S. and S. Shen, "Secure DHCPv6 Using CGAs",
              draft-ietf-dhc-secure-dhcpv6-06 (work in progress),
              March 2012.





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Authors' Addresses

   D. R. Evans
   ARRIS International, Inc.
   IPfonix, Inc., 330 WCR 16 1/2
   Longmont, CO  80504-9467
   USA

   Phone: +1 303.682.2412
   Email: N7DR@ipfonix.com


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

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


   Sheng Jiang
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   P.R. China

   Email: jiangsheng@huawei.com






















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