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Versions: (draft-scskf-dhc-dhcpv4-over-dhcpv6) 00 01 02 03 04 05 06 07 08 09 RFC 7341

DHC Working Group                                                 Q. Sun
Internet-Draft                                                    Y. Cui
Intended status: Standards Track                     Tsinghua University
Expires: April 21, 2014                                     M. Siodelski
                                                                     ISC
                                                             S. Krishnan
                                                                Ericsson
                                                               I. Farrer
                                                     Deutsche Telekom AG
                                                        October 18, 2013


                      DHCPv4 over DHCPv6 Transport
                  draft-ietf-dhc-dhcpv4-over-dhcpv6-02

Abstract

   IPv4 connectivity is still needed as networks migrate towards IPv6.
   Users require IPv4 configuration even if the uplink to their service
   provider supports IPv6 only.  This document describes a mechanism for
   obtaining IPv4 configuration information dynamically in IPv6 networks
   by carrying DHCPv4 messages over DHCPv6 transport.  Two new DHCPv6
   messages as well as a new DHCPv6 option are defined for the purpose
   of conveying DHCPv4 messages through IPv6 networks.

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 April 21, 2014.

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



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   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
   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 . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Architecture Overview . . . . . . . . . . . . . . . . . . . .   3
   5.  New DHCPv6 Messages . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Message Types . . . . . . . . . . . . . . . . . . . . . .   5
     5.2.  Message Formats . . . . . . . . . . . . . . . . . . . . .   5
     5.3.  Boot-request-v6 Message Flags . . . . . . . . . . . . . .   6
     5.4.  Boot-reply-v6 Message Flags . . . . . . . . . . . . . . .   6
   6.  DHCPv6 Options  . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  BOOTP Message Option Format . . . . . . . . . . . . . . .   6
     6.2.  DHCPv4-over-DHCPv6 Enable Option Format . . . . . . . . .   7
     6.3.  4o6 Servers Address Option Format . . . . . . . . . . . .   8
   7.  Use of the Boot-request-v6 Unicast Flag . . . . . . . . . . .   8
   8.  Client Behavior . . . . . . . . . . . . . . . . . . . . . . .   9
   9.  Relay Agent Behavior  . . . . . . . . . . . . . . . . . . . .  10
   10. 4o6 Server Behavior . . . . . . . . . . . . . . . . . . . . .  11
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  11
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   13. Contributors List . . . . . . . . . . . . . . . . . . . . . .  11
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     14.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   As the migration towards IPv6 continues, IPv6-only networks will
   become more prevalent.  At the same time, IPv4 connectivity will
   continue to be provided as a service over 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).

   By conveying DHCPv4 messages over DHCPv6 transport, this document
   describes a mechanism for the dynamic provisioning of IPv4 addresses
   and other configuration parameters.  The mechanism leverages existing



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   infrastructure for DHCPv4, e.g. failover, DNS updates, leasequery,
   etc.  This mechanism is suitable for stateful allocation and
   management of IPv4 addresses (dynamic leasing) and other IPv4
   configuration parameters across IPv6-only networks.

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:

   DHCPv4-over-DHCPv6:   A protocol described in this document, which is
                         used to carry DHCPv4 messages encapsulated in
                         DHCPv6 messages.

   DHCP client:          The 'DHCP client' in this document consists of
                         both DHCPv4 and DHCPv6 client engines.  The
                         client is able to request IPv6 configuration
                         information through DHCPv6, as well as to
                         request IPv4 configuration information using
                         DHCPv4-over-DHCPv6 transport.

   4o6 Server:           A DHCP server capable of processing DHCPv4
                         packets wrapped in the DHCPv6 option: BOOTP
                         Message Option (defined below).

4.  Architecture Overview

   The architecture described in this document addresses a typical use
   case, where 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 mechanism
   that it describes does not restrict the transported messages types
   only to DHCPv4.  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 easier to modify compared to



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   those implemented on end hosts.  As a result, this document uses the
   CPE as an example for describing the mechanism.  This does not
   preclude any end-host, or other device requiring IPv4 configuration,
   from implementing the mechanism in the future.

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

   The DHCP client implements a new DHCPv6 message called Boot-
   request-v6, which contains a new option called BOOTP Message Option.
   The format of this option is described in Section 6.1.

   The DHCPv6 packet can be transmitted either via Relay Agents or
   directly to the 4o6 Server.  The server replies with a DHCPv6
   response, which is a new DHCPv6 message called Boot-reply-v6.  This
   message carries DHCPv4 response wrapped with the BOOTP Message
   Option.

                  _____________             _____________
                 /             \           /             \
                 |             |           |             |
        +--------+-+  IPv6   +-+-----------+-+  IPv6   +-+--------+
        |   DHCP   | network |     DHCP      | network |   4o6    |
        |  Client  +---------+  Relay Agent  +---------+  Server  |
        | (on CPE) |         |               |         |          |
        +--------+-+         +-+-----------+-+         +-+--------+
                 |             |           |             |
                 \_____________/           \_____________/


                      Figure 1: Architecture Overview

   By default, the DHCPv4-over-DHCPv6 is disabled on the client.  Before
   a client can use this protocol it MUST obtain the necessary IPv6
   configuration.  If the client is configured to use DHCPv6 to obtain
   its IPv6 configuration, the DHCPv6 server MAY include the DHCPv4
   -over-DHCPv6 Enable Option in its Reply message to indicate that
   client SHOULD use the DHCPv4-over-DHCPv6 protocol to obtain
   additional configuration.  The format of the DHCPv4-over-DHCPv6
   Enable Option is described in Section 6.2.

   Typically, a client communicates with the 4o6 Servers using well
   known All_DHCP_Relay_Agents_and_Servers multicast address.  If a
   DHCPv6 server is configured to do so, it MAY send unicast addresses
   of the 4o6 Servers to the client during the client's configuration
   using DHCPv6.  The unicast addresses are carried in the 4o6 Server
   Addresses Option encapsulated in the Reply message.  The 4o6 Server



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   Addresses Option's format is defined in Section 6.3.

5.  New DHCPv6 Messages

   There are two new DHCPv6 messages defined in this document which
   carry DHCPv4 messages between a client and a server using DHCPv6
   protocol: Boot-request-v6 and Boot-reply-v6.  This section describes
   structures of these messages.

5.1.  Message Types

   The following new message types are defined in this document:

   BOOTREQUESTV6 (TBD):  Identifies a Boot-request-v6 message.  A client
                         sends this message to a server.  The BOOTP
                         Message Option carried by this message contains
                         a BOOTREQUEST message that the client uses to
                         request IPv4 configuration parameters from the
                         server.

   BOOTREPLYV6 (TBD):    Identifies a Boot-reply-v6 message.  A server
                         sends this message to a client.  It contains a
                         BOOTP Message Option carrying a BOOTREPLY
                         message in response to a BOOTREQUEST received
                         by the server in the BOOTP Message Option of
                         the Boot-request-v6 message.

5.2.  Message Formats

   Both DHCPv6 messages defined in this document share the following
   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    msg-type   |                     flags                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                            options                            .
     .                           (variable)                          .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 2: Architecture Overview

   msg-type        Identifies message type.  It can be either
                   BOOTREQUESTV6 (TBD) or BOOTREPLYV6 (TBD) which
                   corresponds to the Boot-request-v6 or Boot-reply-v6



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                   respectively.

   flags           Specifies flags which provide additional information
                   required by the server to process a DHCPv4 message
                   wrapped in Boot-request-v6 Message, or required by
                   the client to process DHCPv4 message wrapped in Boot-
                   reply-v6 Message.

   options         Options carried by the message and described in
                   Section 6.

5.3.  Boot-request-v6 Message Flags

   The "flags" field of the Boot-request-v6 is used to carry additional
   information which may be used by the server to process the
   encapsulated DHCPv4 message.  Currently only one bit of this field is
   used.  Remaining bits are reserved for the future use.  Currently the
   "flags" field has the following format:

             0                   1                   2
             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
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |U|                 Reserved                    |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 3: Boot-request-v6 flags format

   U               Unicast Flag.  If it is set to 1, it indicates that
                   the DHCPv4 message encapsulated with the Boot-
                   request-v6 message would be sent to a unicast address
                   if it was sent using IPv4.  If this flag is set to 0
                   it indicates that the DHCPv4 message would be sent to
                   broadcast address if it was sent using IPv4.

   Reserved        Bits reserved for future use.  A client which doesn't
                   implement future extensions using these bits MUST set
                   them to 0.

5.4.  Boot-reply-v6 Message Flags

   This document introduces no flags to be carried in the "flags" field
   of the Boot-reply-v6 message.  They are all reserved for the future
   use.  Server MUST set all bits of this field to 0.

6.  DHCPv6 Options

6.1.  BOOTP Message Option Format




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   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 4: BOOTP Message Option Format

   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 Boot-request-v6 message it contains a
                   BOOTREQUEST message sent by a client.  In a Boot-
                   reply-v6 message it contains a BOOTREPLY message sent
                   by a server in response to a client.

6.2.  DHCPv4-over-DHCPv6 Enable Option Format

   The DHCPv4-over-DHCPv6 Enable Option indicates that the client SHOULD
   enable the DHCPv4-over-DHCPv6 function.

   The format of the DHCPv4-over-DHCPv6 Enable 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_DHCP4_O_DHCP6_ENABLE  |           option-len          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


             Figure 5: DHCPv4-over-DHCPv6 Enable Option Format

   option-code     OPTION_DHCP4_O_DHCP6_ENABLE (TBD)




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   option-len      0

6.3.  4o6 Servers Address Option Format

   The 4o6 Servers Address Option carries unicast IPv6 addresses of the
   4o6 Servers.

   The format of the 4o6 Servers Address 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_DHCP4_O_DHCP6_SERVERS  |           option-len          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                        IPv6 Address(es)                       .
     .                                                               .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                Figure 6: 4o6 Servers Address Option Format

   option-code     OPTION_DHCP4_O_DHCP6_SERVERS (TBD)

   option-len      Length of the IPv6 address(es), i.e.  integer times
                   of 16.

   IPv6 Address    The IPv6 address(es) of the 4o6 Server(s).

7.  Use of the Boot-request-v6 Unicast Flag

   A DHCPv4 client conforming to the [RFC2131] may send its DHCPREQUEST
   message to either broadcast or unicast address depending on its
   state.  For example, the client in the RENEWING state will use a
   unicast address to contact a server and renew its lease.  The client
   in the REBINDING state MUST use a broadcast address.  If there is a
   relay agent in the middle, a client in the RENEWING state may send a
   DHCPREQUEST message to the unicast address of the relay agent.  In
   such case the server can't find out whether client sent a message to
   a unicast or broadcast address and thus it can't determine the
   client's state.  [RFC5010] introduced the "Flags Suboption" which
   relay agents add to relayed messages to indicate whether broadcast or
   unicast was used by the client.

   The DHCPv4-over-DHCPv6 protocol uses IPv6 to deliver DHCPv4 messages
   to the server.  There is no relation between the outer IPv6 address
   and the inner DHCPv4 message.  So the server is not able to know



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   whether the DHCPv4 messages should have been sent using broadcast or
   unicast in IPv4 by checking the IPv6 address.  This is similar to the
   case [RFC5010] handled.

   In order to allow the server to determine the client's state, the
   "Unicast" flag is carried in the Boot-request-v6 message.  Client
   MUST set this flag to 1 when the DHCPv4 message would have been sent
   to the unicast address if using DHCPv4 over IPv4.  This flag MUST be
   set to 0 if the DHCPv4 client would have sent the message to the
   broadcast address in IPv4.  The choice whether a given message should
   be sent to a broadcast or unicast address MUST be made based on the
   [RFC2131] and its extensions.

8.  Client Behavior

   The DHCP client by default doesn't use DHCPv4-over-DHCPv6 protocol to
   obtain its DHCPv4 configuration.  Client MUST obtain its IPv6
   configuration before it MAY use DHCPv4-over-DHCPv6 to obtain DHCPv4
   configuration.  If IPv6 configuration is obtained using DHCPv6 as
   described in [RFC3315], client SHOULD request the DHCPv4-over-DHCPv6
   Enable Option and the 4o6 Server Addresses Option in the Option
   Request Option (ORO) to check if it SHOULD use DHCPv4-over-DHCPv6.

   The DHCPv6 server MAY include these options in the Reply message sent
   to the client.  The client determines how to launch the DHCPv4-over-
   DHCPv6 function based on the presence / absence of these two options:

   o  If the client doesn't receive the DHCPv4-over-DHCPv6 Enable
      Option, it SHOULD NOT enable the DHCPv4 over DHCPv6 function.

   o  If the client receives the DHCPv4-over-DHCPv6 Enable Option but no
      4o6 Servers Address Option, it SHOULD enable the DHCPv4-over-
      DHCPv6 function, but use IPv6 All_DHCP_Relay_Agents_and_Servers
      multicast address to communicate with the servers or relays as
      described above.

   o  If the client receives both options, it SHOULD enable the DHCPv4
      -over-DHCPv6 function, and send requests to all unicast addresses
      conveyed by the 4o6 Server Addresses Option.

   If the client is instructed by the DHCPv6 server to use DHCPv4-over-
   DHCPv6 function it SHOULD generate a DHCPv4 message to obtain
   configuration from the 4o6 Server.  This message is stored verbatim
   in the BOOTP Message Option carried by the Boot-request-v6 message.
   The client MUST put exactly one BOOTP Message Option into a single
   Boot-request-v6 message.

   A client MUST set the Unicast flag as specified in Section 7.



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   If the client has not received a 4o6 Server Addresses Option from the
   DHCPv6 server, it transmits the Boot-request-v6 message as specified
   in Section 13 of [RFC3315].  If the client received this option, it
   MUST send Boot-request-v6 message to all unicast addresses listed in
   the received option.

   When a client receives a Boot-reply-v6 message, it MUST look for the
   BOOTP Message Option within this message.  If this option is not
   found, the Boot-reply-v6 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].

   DHCP clients are responsible for the retransmission of messages.
   When requesting IPv4 configuration, the client SHOULD follow the
   normal DHCPv4 retransmission requirements and strategy as specified
   in section 4.1 of [RFC2131].  As a result there are no explicit
   transmission parameters associated with a Boot-request-v6 message.

   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.

9.  Relay Agent Behavior

   When a DHCPv6 relay agent receives a Boot-request-v6 message, it MUST
   handle the message as described in section 4 of
   [I-D.ietf-dhc-dhcpv6-unknown-msg].

   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
   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 Boot-request-v6, then the DHCPv6 request
       is relayed to the configured DHCPv4 aware 4o6 Server's
       address(es).

   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 the case of
   separate relay destinations.



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10.  4o6 Server Behavior

   When the server receives a Boot-request-v6 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 client
   as specified in [RFC2131].  This engine can be implemented as a
   built-in DHCPv4 server function of the 4o6 Server, or it can be a
   separate DHCPv4 server instance.  Discussion regarding communication
   between the 4o6 Server and a DHCPv4 server engine is out of scope for
   this document.

   When appropriate DHCPv4 response is generated, 4o6 Server places it
   in the payload of a BOOTP Message Option, which it puts into the
   Boot-reply-v6 message.

   If the Boot-request-v6 message was received directly by the server,
   the Boot-reply-v6 message MUST be unicast from the interface on which
   the original message was received.

   If the Boot-request-v6 message was received in a Relay-forward
   message, the server creates a Relay-reply message with the Boot-
   reply-v6 message in the payload of a Relay Message Option, and
   responds as described in section 20.3 of [RFC3315].

11.  Security Considerations

   In this specification, DHCPv4 messages are encapsulated in the newly
   defined option and messages.  This is similar to the handling of the
   current relay agent messages.  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 form of encapsulation.  However, the potential risk from this is
   not seen to be greater than that with current DHCPv4 and DHCPv6
   practice.

12.  IANA Considerations

   IANA is requested to allocate three DHCPv6 option codes for use by
   OPTION_BOOTP_MSG, OPTION_DHCP4_O_DHCP6_ENABLE and
   OPTION_DHCP4_O_DHCP6_SERVERS, and two DHCPv6 message type codes for
   the BOOTREQUESTV6 and BOOTREPLYV6.




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13.  Contributors List

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

14.  References

14.1.  Normative References

   [I-D.ietf-dhc-dhcpv6-unknown-msg]
              Cui, Y., Sun, Q., and T. Lemon, "Handling Unknown DHCPv6
              Messages", draft-ietf-dhc-dhcpv6-unknown-msg-02 (work in
              progress), September 2013.

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

   [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.

14.2.  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-ipv6-07 (work in
              progress), September 2013.

   [RFC5010]  Kinnear, K., Normoyle, M., and M. Stapp, "The Dynamic Host
              Configuration Protocol Version 4 (DHCPv4) Relay Agent
              Flags Suboption", RFC 5010, September 2007.

Authors' Addresses











Sun, et al.              Expires April 21, 2014                [Page 12]


Internet-Draft             DHCPv4 over DHCPv6               October 2013


   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


   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









Sun, et al.              Expires April 21, 2014                [Page 13]


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