Network Working Group J. Arkko
Request for Comments: 5494 Ericsson
Updates: 826, 951, 1044, 1329, 2131, C. Pignataro
2132, 2176, 2225, 2834, 2835, Cisco Systems
3315, 4338, 4361, 4701 April 2009
Category: Standards Track
IANA Allocation Guidelines for the Address Resolution Protocol (ARP)
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 (c) 2009 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
Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
This document specifies the IANA guidelines for allocating new values
in the Address Resolution Protocol (ARP). This document also
reserves some numbers for experimentation purposes. The changes also
affect other protocols that employ values from the ARP name spaces.
Arkko & Pignataro Standards Track [Page 1]
RFC 5494 ARP IANA Rules April 2009
This document specifies the IANA guidelines [RFC5226] for allocating
new values for various fields in the Address Resolution Protocol
(ARP) [RFC0826]. The change is also applicable to extensions of ARP
that use the same message format, such as [RFC0903], [RFC1931], and
The change also affects other protocols that employ values from the
ARP name spaces. For instance, the ARP hardware address type
(ar$hrd) number space is also used in the "htype" (hardware address
type) fields in the Bootstrap Protocol (BOOTP) [RFC0951] and Dynamic
Host Configuration Protocol (DHCP) [RFC2131], as well as in the
"hardware type" field in the DHCP Unique Identifiers in DHCPv6
[RFC3315]. These protocols are therefore affected by the update in
the IANA rules. Other affected specifications include the
specialized address resolution mechanisms in:
o HYPERchannel [RFC1044]
o DHCP options [RFC2132] [RFC4361]
o ATM (Asynchronous Transfer Mode) ARP [RFC2225]
o HARP (High-Performance Parallel Interface ARP) [RFC2834] [RFC2835]
o Dual MAC (Media Access Control) FDDI (Fiber Distributed Data
Interface) ARP [RFC1329]
o MAPOS (Multiple Access Protocol over Synchronous Optical Network/
Synchronous Digital Hierarchy) ARP [RFC2176]
o FC (Fibre Channel) ARP [RFC4338]
o DNS DHCID Resource Record [RFC4701]
The IANA guidelines are given in Section 2. Previously, no IANA
guidance existed for such allocations. The purpose of this document
is to allow IANA to manage number assignments based on these
guidelines in a consistent manner.
This document also reserves some numbers for experimentation
purposes. These numbers are given in Section 3.
Arkko & Pignataro Standards Track [Page 2]
RFC 5494 ARP IANA Rules April 2009
2. IANA Considerations
The following rules apply to the fields of ARP:
ar$hrd (16 bits) Hardware address space
Requests for ar$hrd values below 256 or for a batch of more than
one new value are made through Expert Review [RFC5226].
Note that certain protocols, such as BOOTP and DHCPv4, employ
these values within an 8-bit field. The expert should determine
that a need to allocate the new values exists and that the
existing values are insufficient to represent the new hardware
address types. The expert should also determine the applicability
of the request and assign values higher than 255 for requests that
do not apply to BOOTP/DHCPv4. Similarly, the expert should assign
1-octet values for requests that apply to BOOTP/DHCPv4, as for
example the "IPsec tunnel" with value 31 [RFC3456]. Conversely,
ARP-only uses, without a foreseeable reason to use the same value
in BOOTP/DHCPv4, should favor 2-octet values.
Requests for individual new ar$hrd values that do not specify a