Network Working Group                                        K. Fujisawa
Request for Comments: 2855                              Sony Corporation
Category: Standards Track                                      June 2000


                          DHCP for IEEE 1394

Status of this Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

  IEEE Std 1394-1995 is a standard for a High Performance Serial Bus.
  Since 1394 uses a different link-layer addressing method than
  conventional IEEE802/Ethernet, the usage of some fields must be
  clarified to achieve interoperability.  This memo describes the 1394
  specific usage of some fields of DHCP messages.

1. Introduction

  IEEE Std 1394-1995 is a standard for a High Performance Serial Bus.
  IETF IP1394 Working Group specified the method to carry IPv4
  datagrams and 1394 ARP packets over an IEEE1394 network [RFC2734].

  The Dynamic Host Configuration Protocol (DHCP) [RFC2131] provides a
  framework for passing configuration information to hosts on a TCP/IP
  network.

  Since 1394 uses a different link-layer addressing method than
  conventional IEEE802/Ethernet, the usage of some fields must be
  clarified to achieve interoperability.  This memo describes the 1394
  specific usage of some fields of DHCP.  See [RFC2131] for the
  mechanism of DHCP and the explanations of each field.

  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 RFC 2119 [RFC2119].





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RFC 2855                   DHCP for IEEE 1394                  June 2000


2. Issues related to 1394 link address

  With conventional link-layer protocols, such as an Ethernet, the
  'chaddr' (client hardware address) field may be used to return a
  reply message from a DHCP server (or relay-agent) to a client.  Since
  a 1394 link address (node_ID) is transient and will not be consistent
  across the 1394 bridge, we have chosen not to put it in the 'chaddr'
  field.  A DHCP client should request that the server sends a
  broadcast reply by setting the BROADCAST flag when 1394 ARP is not
  possible yet.

     Note: In general, the use of a broadcast reply is discouraged, but
     we consider the impact in a 1394 network as a non issue.

3. 1394 specific usage of DHCP message fields

  Following rules should be used when a DHCP client is connected to an
  IEEE1394 network.

  'htype' (hardware address type) MUST be 24 [ARPPARAM].

  'hlen' (hardware address length) MUST be 0.

  The 'chaddr' (client hardware address) field is reserved.  The sender
  MUST set this field to zero, and the recipient and the relay agent
  MUST ignore its value on receipt.

  A DHCP client on 1394 SHOULD set a BROADCAST flag in DHCPDISCOVER and
  DHCPREQUEST messages (and set 'ciaddr' to zero) to ensure that the
  server (or the relay agent) broadcasts its reply to the client.

     Note: As described in [RFC2131], 'ciaddr' MUST be filled in with
     client's IP address during BOUND, RENEWING or REBINDING state,
     therefore, the BROADCAST flag MUST NOT be set.  In these cases,
     the DHCP server unicasts DHCPACK message to the address in
     'ciaddr'. The link address will be resolved by 1394 ARP.

  'client identifier' option MUST be used in DHCP messages from the
  client to the server due to the lack of the 'chaddr'.  'client
  identifier' option may consist of any data.  Because every IP over
  1394 node has an EUI-64 (node unique ID), the EUI-64 makes an obvious
  'client identifier'.  1394 clients SHOULD include an EUI-64
  identifier in the 'client identifier' option. The type value for the
  EUI-64 is 27 [ARPPARAM], and the format is illustrated as follows.







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   Code  Len   Type  Client-Identifier
  +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
  |  61 |  9  | 27  |           EUI-64 (node unique ID)             |
  +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

  Note that the use of other 'client identifier' type, such as a fully
  qualified domain name (FQDN), is not precluded by this memo.

  For more details, see "9.14. Client-identifier" in [RFC2132].

4. Security Considerations

  DHCP currently provides no authentication or security mechanisms.
  Potential exposures to attack are discussed in section 7 of the DHCP
  protocol specification [RFC2131].

  A malicious client can falsify its EUI-64 identifier, thus
  masquerading as another client.

Acknowledgments

  The author appreciates the members of the Dynamic Host Configuration
  Working Group for their review and valuable comments.

References

  [RFC2734]  Johansson, P., "IPv4 over IEEE 1394", RFC 2734, December
             1999.

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

  [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol", RFC
             2131, March 1997.

  [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
             Extensions", RFC 2132, March 1997.

  [ARPPARAM] http://www.iana.org/numbers.html












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RFC 2855                   DHCP for IEEE 1394                  June 2000


Author's Address

  Kenji Fujisawa
  Sony Corporation
  6-7-35, Kitashinagawa,
  Shinagawa-ku, Tokyo, 141-0001 Japan

  Phone: +81-3-5448-8507
  EMail: [email protected]










































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RFC 2855                   DHCP for IEEE 1394                  June 2000


Full Copyright Statement

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Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.



















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