IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers
RFC 2780

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Network Working Group                                         S. Bradner
Request for Comments: 2780                            Harvard University
BCP: 37                                                        V. Paxson
Category: Best Current Practice                                    ACIRI
                                                              March 2000

                IANA Allocation Guidelines For Values In
               the Internet Protocol and Related Headers

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

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

Abstract

   This memo provides guidance for the IANA to use in assigning
   parameters for fields in the IPv4, IPv6, ICMP, UDP and TCP protocol
   headers.

1. Introduction

   For many years the Internet Assigned Numbers Authority (IANA)
   (www.iana.org) has allocated parameter values for fields in protocols
   which have been created or are maintained by the Internet Engineering
   Task Force (IETF).  Starting a few years ago the IETF began to
   provide the IANA with guidance for the assignment of parameters for
   fields in newly developed protocols.  Unfortunately this type of
   guidance was not consistently provided for the fields in protocols
   developed before 1998.  This memo attempts to codify existing IANA
   practice used in the assignment of parameters in the specific case of
   some of these protocols.  It is expected that additional memos will
   be developed in the future to codify existing practice in other
   cases.

   This memo addresses the fields within the IPv4, IPv6, ICMP, UDP and
   TCP protocol headers for which the IANA assigns values.

   The terms "Specification Required", "Expert Review", "IESG Approval",
   "IETF Consensus", and "Standards Action", are used in this memo to
   refer to the processes described in [CONS].

Bradner & Paxson         Best Current Practice                  [Page 1]
RFC 2780                    IANA Assignments                  March 2000

2. Temporary Assignments

   From time to time temporary assignments are made in the values for
   fields in these headers for use in experiments.  IESG Approval is
   required for any such temporary assignments.

3. Version field in the IP header.

   The first field in the IP header of all current versions of IP is the
   Version field.  New values in the Version field define new versions
   of the IP protocol and are allocated only after an IETF Standards
   Action.  It should be noted that some of the Version number bits are
   used by TCP/IP header compression schemes. Specifically, the hi-order
   bit of the Version field is also used by TCP/IP header compression
   [HC], while the three hi-order bits are used by IP Header Compression
   [IPHC].

4. IANA Considerations for fields in the IPv4 header

   The IPv4 header [V4] contains the following fields that carry values
   assigned by the IANA: Version, Type of Service, Protocol, Source
   Address, Destination Address, and Option Type.

4.1 IPv4 IP Version field

   The IPv4 Version field is always 4.

4.2 IPv4 Type of Service field

   The Type of Service field described in [V4] has been superseded[DIFF]
   by the 6-bit Differentiated Services (DS) field and a 2-bit field
   which is currently reserved.  The IANA allocates values in the DS
   field following the IANA Considerations section in [DIFF].  [ECN]
   describes an experimental use of the 2-bit "currently unused" field.
   Other experimental uses of this field may be assigned after IESG
   Approval processes.  Permanent values in this field are allocated
   following a Standards Action process.

4.3 IPv4 Protocol field

   IANA allocates values from the IPv4 Protocol name space following an
   Expert Review, IESG Approval or Standards Action process.  The Expert
   Review process should only be used in those special cases where non-
   disclosure information is involved.  In these cases the expert(s)
   should be designated by the IESG.

Bradner & Paxson         Best Current Practice                  [Page 2]
RFC 2780                    IANA Assignments                  March 2000

4.4 IPv4 Source and Destination addresses

   The IPv4 source and destination addresses use the same namespace but
   do not necessarily use the same values.  Values in these fields fall
   into a number of ranges defined in [V4] and [MULT].

4.4.1 IPv4 Unicast addresses

   The Internet Corporation for Assigned Names and Numbers (ICANN)
   recently accepted responsibility for the formulation of specific
   guidelines for the allocation of the values from the IPv4 unicast
   address space (values 0.0.0.0 through 223.255.255.255 ) other than
   values from the ranges 0/8 (which was reserved in [AN80]) and 127/8
   (from which the loopback address has been taken) along with other