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Network Working Group                                      Scott Bradner
Internet-Draft                                        Harvard University
                                                             Vern Paxson
                                                                   ACIRI
                                                            January 2000


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

                 <draft-bradner-iana-allocation-04.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
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   This document will expire in July 2000.


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.


Copyright Notice

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




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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].


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.


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.




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   4.2 IPv4 Type of Service field

      The Type of Service field described in [V4] has been superceded
      [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.

   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 values already
         assigned by the IETF for special functions or purposes. (For
         example, the private addresses defined in RFC 1918.) Further
         assignments in the 0/8 and 127/8 ranges require a Standards
         Action process since current IP implementations may break if
         this is done.

      4.4.2 IPv4 Multicast addresses

         IPv4 addresses that fall in the range from 224.0.0.0 through
         239.255.255.255 are known as multicast addresses.  The IETF has
         assigned a number of IPv4 multicast addresses for special
         purposes. For example, [ADSCP] assigned a number of IPv4
         multicast address to correspond to IPv6 scoped multicast
         addresses also, the values in the range from 224.0.0.0 to



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         224.0.0.255 , inclusive, are reserved by the IANA for the use
         of routing protocols and other low-level topology discovery or
         maintenance protocols, such as gateway discovery and group
         membership reporting. (See the IANA web page) New values in
         this range are assigned following an IESG Approval or Standards
         Action process.  Assignments of individual multicast address
         follow an Expert Review, IESG Approval or Standards Action
         process.  Until further work is done on multicast protocols
         large-scale assignments of IPv4 multicast addresses is not
         recommended.

         From time to time, there are requests for temporary assignment
         of multicast space for experimental purposes.  these will
         originate in an IESG Approval process and should be for a
         limited duration such as one year.

      4.4.3 IPv4 Reserved addresses

         IPv4 addresses in the range from 240.0.0.0 through
         255.255.255.255 are reserved [AN81, MULT] and compliant IPv4
         implementations will discard any packets that make use of them.
         Addresses in this range are not to be assigned unless an IETF
         Standards Action modifies the IPv4 protocol in such a way as to
         make these addresses valid.

   4.5 IPv4 Option Type field

      The IANA allocates values from the IPv4 Option Type name space
      following an IESG Approval, IETF Consensus or Standards Action
      process.


5. IANA Considerations for fields in the IPv6 header

   The IPv6 header [V6] contains the following fields that carry values
   assigned from IANA-managed name spaces: Version (by definition always
   6 in IPv6), Traffic Class, Next Header, Source and Destination
   Address.  In addition, the IPv6 Hop-by-Hop Options and Destination
   Options extension headers include an Option Type field with values
   assigned from an IANA-managed name space.

   5.1 IPv6 Version field

      The IPv6 Version field is always 6.

   5.2 IPv6 Traffic Class field

      The IPv6 Traffic Class field is described in [DIFF] as a 6-bit



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      Differentiated Services (DS) field and a 2-bit field which is
      currently reserved.  See Section 4.2 for assignment guidelines for
      these fields.

   5.3 IPv6 Next Header field

      The IPv6 Next Header field carries values from the same name space
      as the IPv4 Protocol name space. These values are allocated as
      discussed in Section 4.3.

   5.4 IPv6 Source and Destination Unicast Addresses

      The IPv6 Source and Destination address fields both use the same
      values and are described in [V6AD].  The addresses are divided
      into ranges defined by a variable length Format Prefix (FP).

      5.4.1 IPv6 Aggregatable Global Unicast Addresses

         The IANA was given responsibility for all IPv6 address space by
         the IAB in RFC 1881. Recently the IANA agreed to specific
         guidelines for the assignment of values in the Aggregatable
         Global Unicast Addresses FP (FP 001) formulated by the Regional
         Internet Registries.

      5.4.2 IPv6 Anycast Addresses

         IPv6 anycast addresses are defined in [V6AD].  Anycast
         addresses are allocated from the unicast address space and
         anycast addresses are syntactically indistinguishable from
         unicast addresses.  Assignment of IPv6 Anycast subnet addresses
         follows the process used described in [V6AD]. Assignment of
         other IPv6 Anycast addresses follows the process used for IPv6
         Aggregatable Global Unicast Addresses. (section 5.4.1)

      5.4.3 IPv6 Multicast Addresses

         IPv6 multicast addresses are defined in [V6AD]. They are
         identified by a FP of 0xFF.  Assignment guidelines for IPv6
         multicast addresses are described in [MASGN].

      5.4.4 IPv6 Unassigned and Reserved IPv6 Format Prefixes

         The responsibility for assigning values in each of the
         "unassigned" and "reserved" Format Prefixes is delegated by
         IESG Approval or Standards Action processes since the rules for
         processing these Format Prefixes in IPv6 implementations have
         not been defined.




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   5.5 IPv6 Hop-by-Hop and Destination Option Fields

      Values for the IPv6 Hop-by-Hop Options and Destination Options
      fields are allocated using an IESG Approval, IETF Consensus or
      Standards Action processes.

   5.6 IPv6 Neighbor Discovery Fields

      The IPv6 Neighbor Discovery header [NDV6] contains the following
      fields that carry values assigned from IANA-managed name spaces:
      Type, Code and Option Type.

      Values for the IPv6 Neighbor Discovery Type, Code, and Option Type
      fields are allocated using an IESG Approval or Standards Action
      process.


6. IANA Considerations for fields in the IPv4 ICMP header

   The IPv4 ICMP header [ICMP] contains the following fields that carry
   values assigned from IANA-managed name spaces: Type and Code.

   Values for the IPv4 ICMP Type and Code fields are allocated using an
   IESG Approval or Standards Action processes.


7. IANA Considerations for fields in the IPv6 ICMP header

   The IPv6 ICMP header [ICMPV6] contains the following fields that
   carry values assigned from IANA-managed name spaces: Type and Code.

   Values for the IPv6 ICMP Type and Code fields are allocated using an
   IESG Approval or Standards Action processes.


8. IANA Considerations for fields in the UDP header

   The UDP header [UDP] contains the following fields that carry values
   assigned from IANA-managed name spaces: Source and Destination Port.

   Both the Source and Destination Port fields use the same namespace.
   Values in this namespace are assigned following a Specification
   Required, Expert Review, IESG Approval, IETF Consensus, or Standards
   Action process.  Note that some assignments may involve non-
   disclosure information.


9. IANA Considerations for fields in the TCP header



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   The TCP header [TCP] contains the following fields that carry values
   assigned from IANA-managed name spaces: Source and Destination Port,
   Reserved Bits, and Option Kind.

   9.1 TCP Source and Destination Port fields

      Both the Source and Destination Port fields use the same
      namespace.  Values in this namespace are assigned following a
      Specification Required, Expert Review, IESG Approval, IETF
      Consensus, or Standards Action process.  Note that some
      assignments may involve non-disclosure information.

   9.2 Reserved Bits in TCP Header

      The reserved bits in the TCP header are assigned following a
      Standards Action process.

   9.3 TCP Option Kind field

      Values in the Option Kind field are assigned following an IESG
      Approval or Standards Action process.


10. Security Considerations

   Security analyzers such as firewalls and network intrusion detection
   monitors often rely on unambiguous interpretations of the fields
   described in this memo.  As new values for the fields are assigned,
   existing security analyzers that do not understand the new values may
   fail, resulting in either loss of connectivity if the analyzer
   declines to forward the unrecognized traffic, or loss of security if
   it does forward the traffic and the new values are used as part of an
   attack.  This vulnerability argues for high visibility (which the
   Standards Action and IETF Consensus processes ensure) for the
   assignments whenever possible.

11. References

   [ADSCP] Meyer, D., "Administratively Scoped IP Multicast", RFC 2365,
      July 1998

   [AN80] Postel, J., "Assigned numbers", RFC 758, August 1979

   [AN81] Postel, J., "Assigned numbers", RFC 790, September 1981

   [CONS] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
      Considerations Section in RFCs", RFC 2434, October 1998.




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   [DIFF] Nichols, K., S. Blake, F. Baker, D. Black, "Definition of the
      Differentiated Services Field (DS Field) in the IPv4 and IPv6
      Headers", RFC 2474, December 1998.

   [ECN] Ramakrishnan, K., S. Floyd, "A Proposal to add Explicit
      Congestion Notification (ECN) to IP", RFC 2481, January 2000

   [ICMP] Postel, J., "Internet Control Message Protocol", RFC 792,
      September 1981.

   [ICMPV6] Conta, A., S. Deering, "Internet Control Message Protocol
      (ICMPv6) for the Internet Protocol Version 6 (IPv6)", RFC 2463,
      December 1998.

   [MASGN] Hinden, R., and S. Deering, "IPv6 Multicast Address
      Assignments", RFC 2375, July 1998.

   [MULT] Deering, S. E., "Host extensions for IP multicasting", RFC
      988, July 1986

   [NDV6] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery for
      IP Version 6 (IPv6)", RFC 2461, December 1998.

   [TCP] Postel, J., "Transmission Control Protocol", RFC 793, September
      1981.

   [UDP] Postel, J., "User Datagram Protocol", RFC 768, August 1980.

   [V4] Postel, J., "Internet Protocol", RFC 791, September, 1981.

   [V6] Deering, S., R. Hinden, "Internet Protocol, Version 6 (IPv6)
      Specification", RFC 2460, December 1998.

   [V6AD] Hinden, R., S. Deering, "IP Version 6 Addressing
      Architecture", RFC 2373, July 1998


12. Author's Addresses

   Scott Bradner
   Harvard University
   Cambridge MA - USA
   02138

   sob@harvard.edu
   +1 617 495 3864





Bradner & Paxson                                                [Page 8]

Internet-Draft              IANA Assignments                January 2000


   Vern Paxson
   ACIRI / ICSI
   1947 Center Street, Suite 600
   Berkeley, CA - USA
   94704-1198

   vern@aciri.org
   +1 510/642-4274 x302


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