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Versions: 01 draft-ietf-dhc-dhcpv4-over-dhcpv6

Network Working Group                                             Q. Sun
Internet-Draft                                                    Y. Cui
Intended status: Standards Track                     Tsinghua University
Expires: October 05, 2013                                   M. Siodelski
                                                                     ISC
                                                             S. Krishnan
                                                                Ericsson
                                                               I. Farrer
                                                     Deutsche Telekom AG
                                                          April 03, 2013


                      DHCPv4 over DHCPv6 Transport
                 draft-scskf-dhc-dhcpv4-over-dhcpv6-01

Abstract

   This document describes a mechanism for obtaining IPv4 parameters in
   IPv6 networks by carrying DHCPv4 messages over DHCPv6 transport.

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 05, 2013.

Copyright Notice

   Copyright (c) 2013 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
   to this document.  Code Components extracted from this document must



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   2
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Architecture Overview . . . . . . . . . . . . . . . . . . . .   3
   5.  BOOTP Message Option Format . . . . . . . . . . . . . . . . .   4
   6.  Client Behavior . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Relay Agent Behavior  . . . . . . . . . . . . . . . . . . . .   5
   8.  Server Behavior . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   11. Contributors List . . . . . . . . . . . . . . . . . . . . . .   6
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     12.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     12.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   As the migration towards IPv6 continues, IPv6 only networks will
   become more prevalent.  However, IPv4 connectivity will continue to
   be provided as a service over these IPv6 only networks.  In addition
   to providing IPv4 addresses for clients of this service, other IPv4
   configuration parameters may also need to be provided, (e.g.
   addresses of IPv4-only services).

   Several approaches for provisioning such information have been
   already been proposed.  This document describes one such approach.

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].

3.  Terminology

   This document makes use of the following terms:

   BOOTREQUESTV6 (TBD):  A new type of DHCPv6 Client/Server message
                         defined in this document.  A client sends a
                         BOOTREQUESTV6 message to a server, which
                         contains a BOOTP Message Option.  Each BOOTP



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                         Message Option contains a BOOTREQUEST message
                         that the client uses to request IPv4
                         configuration parameters from the server.

   BOOTREPLYV6 (TBD):    A new type of DHCPv6 Client/Server message
                         defined in this document.  A server sends a
                         BOOTREPLYV6 message containing a BOOTP Message
                         Option in response to a client's BOOTREQUESTV6
                         message.  Each BOOTP Message Option, wrapped in
                         a BOOTREPLYV6 message, contains a BOOTREPLY
                         message.  This contains the BOOTREQUEST
                         response corresponding to a client's
                         BOOTREQUESTV6 message.

4.  Architecture Overview

   The architecture described in this document addresses a typical use
   case, whereby a DHCP client's uplink supports IPv6 only and the
   Service Provider's network supports IPv6 and limited IPv4 services.
   In this scenario, the client can only use the IPv6 network to access
   IPv4 services and so it must configure IPv4 services using IPv6 as
   the underlying transport protocol.

   Although the purpose of this document is to address the problem of
   communication between DHCPv4 client and DHCPv4 server, the mechanisms
   it describes do not restrict the transported types of messages to
   DHCPv4.  In additional, BOOTP messages can be transported using the
   same mechanism.

   DHCP clients can be running on CPE devices, end hosts or any other
   device which supports the DHCP client function.  At the time of
   writing, DHCP clients on CPE devices are relatively easier to modify
   compared to those implemented on end hosts.  As a result, this
   document uses the CPE as an example for describing the mechanism.
   This doesn't preclude end hosts from implementing the mechanism in
   the future.

   This mechanism works by carrying encapsulated DHCPv4 messages over
   DHCPv6 messages.  Figure 1, below, illustrates one possible
   deployment architecture.

   The DHCP client implements a new DHCPv6 message called BOOTREQUESTV6,
   which contains a new option called the BOOTP Message Option.  The
   format of the option is described in Section 5.  The client sends all
   DHCPv6 packets, including DHCPv4 over DHCPv6 packets, to the well-
   known All_DHCP_Relay_Agents_and_Servers multicast address on the
   DHCPv6 server port (UDP port 547).




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   The DHCPv6 packet can be transmitted either via Relay Agents or
   directly to the server.  The server is referred in this document as a
   "Unified Server" for its capability of processing regular DHCPv6
   traffic as well as DHCPv4 packets wrapped in the BOOTP Message
   Option.  Server replies with a relevant DHCPv6 packet carrying DHCPv4
   response wrapped with the BOOTP Message Option.  Clients receive a
   response on UDP port 546.






                  _____________             _____________
                 /             \           /             \
                 |             |           |             |
        +--------+-+  IPv6   +-+-----------+-+  IPv6   +-+--------+
        |   DHCP   | network |     DHCP      | network | Unified  |
        |  Client  +---------+  Relay Agent  +---------+  Server  |
        | (on CPE) |         |               |         |          |
        +--------+-+         +-+-----------+-+         +-+--------+
                 |             |           |             |
                 \_____________/           \_____________/


                      Figure 1: Architecture Overview

5.  BOOTP Message Option Format

   The BOOTP Message option carries a BOOTP message that is sent by the
   client or the server.  Such BOOTP messages exclude any IP or UDP
   headers.

   The format of the BOOTP Message 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_BOOTP_MSG       |           option-len          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                         BOOTP-message                         .
     .                                                               .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   Figure 2: BOOTP Message Option Format



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   option-code     OPTION_BOOTP_MSG (TBD)

   option-len      Length of BOOTP message

   BOOTP-message   The BOOTP message sent by the client or the server.
                   In a BOOTREQUESTV6 message it contains a BOOTREQUEST
                   message sent by client.  In a BOOTREPLYV6 message it
                   contains a BOOTREPLY message sent by a server in
                   response to a client.

6.  Client Behavior

   When a client requires an IPv4 address and/or other IPv4
   configuration parameters, it MUST generate a DHCPv4 message to obtain
   them from a DHCP server.  This message is stored verbatim in the
   BOOTP Message Option carried by the BOOTREQUESTV6 message.  A Client
   MUST put exactly one BOOTP Message Option into a single BOOTREQUESTV6
   message.  The Client sends out the BOOTREQUESTV6 message to the Well-
   Known multicast address, i.e.  All_DHCP_Relay_Agents_and_Servers on
   multicast address defined in [RFC3315].

   When a client receives a BOOTREPLYV6 message, it MUST look for the
   BOOTP Message Option within this message.  If this option is not
   found, the BOOTREPLYV6 message is discarded.  If the BOOTP Message
   Option is found, the client extracts the DHCPv4 message it contains
   and processes it as described in section 4.4 of [RFC2131].

   As the DHCPv4 and DHCPv6 clients are running on the same host, the
   client MUST implement [RFC4361] to ensure that the device correctly
   identifies itself.

7.  Relay Agent Behavior

   When a DHCPv6 relay agent receives a BOOTREQUESTV6 message, it MUST
   handle the message as described in section 20.1.1 of [RFC3315].

   A DHCPv6 relay agent MUST implement the Relay behaviour described in
   section 20.1.1 of [RFC3315].

   Additionally, the DHCPv6 relay agent MAY allow the configuration of a
   dedicated DHCPv4 over DHCPv6 specific destination addresses,
   differing from the addresses of the DHCPv6 only server(s).  To
   implement this function, the relay checks the received DHCPv6 message
   type and forwards according to the following logic:

   1.  If the message type is BOOTREQUESTV6, then the DHCPv6 request is
       relayed to the configured DHCPv4 aware unified server's
       address(es).



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   2.  For any other DHCPv6 message type, forward according to section
       20 of [RFC3315].

   The above logic only allows for separate relay destinations
   configured on the relay agent closest to the client (single relay
   hop).  Multiple relaying hops are not considered in this document.

8.  Server Behavior

   When a Unified Server receives a BOOTREQUESTV6 message from a client,
   it searches for a BOOTP Message Option.  If this option is missing,
   the server discards the packet.  The Server MAY notify an
   administrator about the receipt of a malformed packet.  The mechanism
   for this notification is out of scope for this document

   If the server finds a valid BOOTP Message Option, it extracts the
   original DHCPv4 message sent by the client.  This message is passed
   to the DHCPv4 server engine, which generates a response to the as
   specified in [RFC2131].  The server places the DHCPv4 response
   message, in the payload of a BOOTP Message Option, which it puts into
   the BOOTREPLYV6 message.

   If the BOOTREQUESTV6 message was received directly by the server, the
   BOOTREPLYV6 message MUST be unicast from the interface on which the
   original message was received.

   If the BOOTREQUESTV6 message was received in a Relay-forward message,
   the server creates a Relay-reply message with the BOOTREPLYV6 message
   in the payload of a Relay Message Option.  This is analogous to other
   types of DHCPv6 messages as described in [RFC3315].  The server
   unicasts the Relay-reply message directly to the IP address of the
   relay agent from which the Relay-forward message was received.

9.  Security Considerations

   In this specification, DHCPv6 is made a 'transport protocol' for
   DHCPv4 messages over an IPv6 network.  In order to bypass firewalls
   or network authentication gateways, a malicious attacker may leverage
   this feature to convey other messages using DHCPv6, i.e.  use DHCPv6
   as a type of tunnel.  However, the potential risk from this is no
   greater than with current DHCPv4 and DHCPv6 practice.

10.  IANA Considerations

   IANA is kindly requested to allocate one DHCPv6 option code to the
   OPTION_BOOTP_MSG and two DHCPv6 message type codes to the
   BOOTREQUESTV6 and BOOTREPLYV6.




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11.  Contributors List

   Many thanks to Ted Lemon, Bernie Volz, Tomek Mrugalski, Yuchi Chen
   and Cong Liu, for their great contributions to the draft.

12.  References

12.1.  Normative References

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol", RFC
              2131, 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.

   [RFC4361]  Lemon, T. and B. Sommerfeld, "Node-specific Client
              Identifiers for Dynamic Host Configuration Protocol
              Version Four (DHCPv4)", RFC 4361, February 2006.

12.2.  Informative References

   [I-D.ietf-dhc-dhcpv4-over-ipv6]
              Cui, Y., Wu, P., Wu, J., and T. Lemon, "DHCPv4 over IPv6
              Transport", draft-ietf-dhc-dhcpv4-over-ipv6-06 (work in
              progress), March 2013.

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

Authors' Addresses

   Qi Sun
   Tsinghua University
   Department of Computer Science, Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6278-5822
   Email: sunqi@csnet1.cs.tsinghua.edu.cn











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   Yong Cui
   Tsinghua University
   Department of Computer Science, Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6260-3059
   Email: yong@csnet1.cs.tsinghua.edu.cn


   Marcin Siodelski
   950 Charter Street
   Redwood City, CA  94063
   USA

   Phone: +1 650 423 1431
   Email: msiodelski@gmail.com


   Suresh Krishnan
   Ericsson

   Email: suresh.krishnan@ericsson.com


   Ian Farrer
   Deutsche Telekom AG
   GTN-FM4,Landgrabenweg 151
   Bonn, NRW  53227
   Germany

   Email: ian.farrer@telekom.de


















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