Dynamic Host Configuration Protocol (DHCP) over InfiniBand
RFC 4390
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RFC - Proposed Standard
(April 2006; No errata)
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2015-10-14
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IETF
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plain text
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(None)
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IESG state |
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RFC 4390 (Proposed Standard)
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Unknown
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Responsible AD |
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Margaret Cullen
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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
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