💾 Archived View for gmi.noulin.net › rfc › rfc4390.gmi captured on 2022-01-08 at 20:11:02. Gemini links have been rewritten to link to archived content
-=-=-=-=-=-=-
Keywords: [--------|p], bootstrap, boot, ipoib
Network Working Group Vivek Kashyap
Request for Comments: 4390 IBM
Category: Standards Track April 2006
Dynamic Host Configuration Protocol (DHCP) over InfiniBand
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 (2006).
Abstract
IP over Infiniband (IPoIB) link-layer address is 20 octets long.
This is larger than the 16 octets reserved for the hardware address
in a Dynamic Host Configuration Protocol/Bootstrap Protocol
(DHCP/BOOTP) message. The above inequality imposes restrictions on
the use of the DHCP message fields when used over an IPoIB network.
This document describes the use of DHCP message fields when
implementing DHCP over IPoIB.
Table of Contents
1. Introduction ....................................................2
2. The DHCP over IPoIB Mechanism ...................................2
2.1. IPoIB-specific Usage of DHCP Message Fields ................3
2.2. Use of the BROADCAST flag ..................................3
3. Security Considerations .........................................3
4. Acknowledgement .................................................4
5. References ......................................................4
5.1. Normative References .......................................4
5.2. Informative References .....................................4
Kashyap Standards Track [Page 1]
RFC 4390 DHCP Over Infiniband April 2006
1. Introduction
The Dynamic Host Configuration Protocol (DHCP) provides a framework
for passing configuration information to hosts on an IP network
[RFC2131]. DHCP is based on the Bootstrap Protocol (BOOTP) [RFC951]
adding the capability of automatic allocation of reusable network
addresses and additional configuration options [RFC2131,RFC2132].
The DHCP server receives a broadcast request from a client. The DHCP
server uses the client interface's hardware address to unicast a
reply when the client does not yet have an IP address assigned to it.
The "chaddr" field in the DHCP message carries the client's hardware
address.
The "chaddr" field is 16 octets in length. The IPoIB link-layer
address is 20 octets in length [RFC4391]. Therefore, the IPoIB
link-layer address will not fit in the "chaddr" field making it
impossible for the DHCP server to unicast a reply to the client.
To ensure interoperability, the usage of the fields and the method
for DHCP interaction must be clarified. This document describes the
IPoIB-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 [RFC2119].
2. The DHCP over IPoIB Mechanism
As described above, the link-layer address is unavailable to the DHCP
server because the link-layer address is larger than the "chaddr"
field length. As a result, the server cannot unicast its reply to
the client. Therefore, a DHCP client MUST request that the server
send a broadcast reply by setting the BROADCAST flag when IPoIB
Address Resolution Protocol (ARP) is not possible, i.e., in
situations where the client does not know its IP address.
[RFC1542] discourages the use of a broadcast reply. But in the case
of IPoIB, this is a necessity because the server does not receive the
link-layer address. To desynchronise broadcasts at subnet startup,
[RFC2131] suggests that a client wait a random time (1 to 10 seconds)
before initiating server discovery. The same timeout will spread out
the DHCP server broadcast responses generated due to the use of the
BROADCAST bit.
Kashyap Standards Track [Page 2]
RFC 4390 DHCP Over Infiniband April 2006
The client hardware address, "chaddr", is unique in the subnet and
hence can be used to identify a client interface. But in the absence
of a unique "chaddr", another unique client identifier must be used.
The DHCP protocol states that the "client identifier" option may be
used as the unique identifying value for the client [RFC2132]. This
value must be unique within the client's subnet.
The "client identifier" option includes a type and identifier pair.
The identifier included in the "client identifier" option may consist
of a hardware address or any other unique value such as the DNS name
of the client. When a hardware address is used, the type field
should be one of the ARP hardware types listed in [ARPPARAM].
2.1. IPoIB-specific Usage of DHCP Message Fields
A DHCP client, when working over an IPoIB interface, MUST follow the
following rules:
"htype" (hardware address type) MUST be 32 [ARPPARAM].
"hlen" (hardware address length) MUST be 0.
"chaddr" (client hardware address) field MUST be zeroed.
"client-identifier" option MUST be used in DHCP messages.
The "client identifier" used in DHCP messages MUST conform to
[RFC4361].
2.2. Use of the BROADCAST flag
A DHCP client on IPoIB MUST set the 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 the
client's IP address during BOUND, RENEWING or REBINDING states;
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 ARP.
3. Security Considerations
[RFC2131] describes the security considerations relevant to DHCP.
This document does not introduce any new issues.
Kashyap Standards Track [Page 3]
RFC 4390 DHCP Over Infiniband April 2006
4. Acknowledgement
This document borrows extensively from [RFC2855]. Roy Larsen pointed
out the length discrepancy between the IPoIB link address and DHCP's
"chaddr" field.
5. References
5.1. Normative References
[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.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP
Vendor Extensions", RFC 2132, March 1997.
[RFC951] Housley, R., Horting, T., and P. Yee, "TELNET
Authentication Using KEA and SKIPJACK", RFC 2951,
September 2000.
[RFC4391] Chu, J. and V. Kashyap "Transmission of IP over
InfiniBand (IPoIB)", RFC 4391, April 2006.
[ARPPARAM] http://www.iana.org/numbers.html
[RFC4361] Lemon, T. and B. Sommerfeld, "Node-specific Client
Identifiers for Dynamic Host Configuration Protocol
Version Four (DHCPv4)", RFC 4361, February 2006.
5.2. Informative References
[RFC2855] Fujisawa, K., "DHCP for IEEE 1394", RFC 2855, June
2000.
[RFC1542] Wimer, W., "Clarifications and Extensions for the
Bootstrap Protocol", RFC 1542, October 1993.
Kashyap Standards Track [Page 4]
RFC 4390 DHCP Over Infiniband April 2006
Author's Address
Vivek Kashyap
15350, SW Koll Parkway
Beaverton, OR 97006
USA
Phone: +1 503 578 3422
EMail: vivk@us.ibm.com
Kashyap Standards Track [Page 5]
RFC 4390 DHCP Over Infiniband April 2006
Full Copyright Statement
Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM 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.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Kashyap Standards Track [Page 6]