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LinuxDig.com Request For Comments

RFC Number : 2855

Title : DHCP for IEEE 1394.






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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RFC 2855 DHCP for IEEE 1394 June 2000


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: fujisawa@sm.sony.co.jp










































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RFC 2855 DHCP for IEEE 1394 June 2000


Full Copyright Statement

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

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an
'AS IS' basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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



















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