Network Working Group Scott Bradner
Internet-Draft Harvard University
Vern Paxson
ACIRI
August 1999
IANA Allocation Policies For Values In
the Internet Protocol and Related Headers
<draft-bradner-iana-allocation-01.txt>
Status of this Memo
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Abstract
This memo provides guidance for the IANA to use in assigning
parameters for fields in the IPv4, TCP, UDP, ICMP and IPv6 protocol
headers.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
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1. Introduction
For many years the Internet Assigned Numbers Authority (IANA) has
allocated parameter values for fields in the the headers of network
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 header
fields in protocols developed before 1998. This memo provides the
IANA with guidance to be used in the assignment of parameters in some
of these protocols. It is expected that additional memos will be
developed in the future to provide guidance in other cases.
This memo addresses the fields within the IPv4, TCP, UDP, ICMP and
IPv6 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. IANA Considerations for fields in the IPv4 header
The IPv4 header [V4] contains the following fields that carry values
assigned by the IANA: Version (by definition always 4 in IPv4), Type
of Service, Protocol, Source Address, Destination Address, and Option
Type.
The IANA allocates values from the IP Version name space following a
Standards Action process.
The Type of Service field described in [V4] has been superceded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 reserved 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.
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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.
The IPv4 Source and Destination addresses use the same namespace.
The values fall into a number of ranges (called "Classes" in [V4] and
[MULT].) 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 what used
to be refereed to as the IPv4 Class A, Class B and Class C unicast
address spaces 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. The IETF has also assigned a
number of IPv4 Class D (multicast) addresses for special purposes.
For example, the values in the range from 224.0.0.0 to 224.0.0.255 ,
inclusive, are reserved 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 http://www.iana.org ) New values in this range are assigned
following an IESG Approval or Standards Action process. Assignments
of individual Class D address follow an Expert Review, IESG Approval
or Standards Action process. Until further work is done on multicast
protocols large scale assignments of IPv4 Class D addresses is not
recommended. IPv4 Class E addresses are reserved [MULT] and not to
be assigned unless an IETF Standards Action modifies the IPv4
protocol in such a way as to make Class E addresses valid. From time
to time, there are requests for temporary assignment of multicast
space for experimental purposes. Such requests will originate from
an IESG Approval, IETF Standards Action or Expert Review process.
Any such assignments should be for a limited duration such as one
year.
The IANA allocates values from the IPv4 Option Type name space
following an IESG Approval, IETF Consensus or Standards Action
process.
4. 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
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Options extension headers include an Option Type field with values
assigned from an IANA-managed name space.
The Version field in the IPv6 header uses the same name space as the
Version field in the IPv4 header. Values in this field are allocated
as described in Section 2.
The IPv6 Traffic Class uses the same namespace as the IPv4 6-bit DS
field and 2-bit unused field. Values in these fields are allocated as
described in Section 2.
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 2.
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). The Internet
Corporation for Assigned Names and Numbers (ICANN) recently accepted
responsibility for the formulation of specific guidelines for the
assignment of values in the Aggregatable Global Unicast Addresses FP
(FP 001). The responsibility for assigning values in each of the
"unassigned" and "reserved" FPs is delegated by IESG Approval or
Standards Action processes.
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. IANA Considerations for fields in the ICMP header
The ICMP header [ICMP] contains the following fields that carry
values assigned from IANA-managed name spaces: Type and Code.
Values for the ICMP Type and Code fields are allocated using an IESG
Approval or Standards Action processes.
6. 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-
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disclosure information.
7. IANA Considerations for fields in the TCP header
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.
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.
The reserved bits in the TCP header are assigned following a
Standards Action process.
Values in the Option Kind field are assigned following an IESG
Approval or Standards Action process.
8. 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.
9. References
[AN80] Postel, J., "Assigned numbers", RFC 758, August 1979
[CONS] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, October 1998.
[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
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Congestion Notification (ECN) to IP", RFC 2481, January 1999
[ICMP] Postel, J., "Internet Control Message Protocol", RFC 792,
September 1981.
[MULT] Deering, S. E., "Host extensions for IP multicasting", RFC
988, July 1986
[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
10. Author's Addressees
Scott Bradner
Harvard University
1350 Mass Ave - rm 876
Cambridge MA - USA
02138
sob@harvard.edu
+1 617 495 3864
Vern Paxson
ACIRI / ICSI
1947 Center Street, Suite 600
Berkeley, CA - USA
94704-1198
vern@aciri.org
+1 510/642-4274 x302
Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
Bradner & Paxson [Page 6]
Internet-Draft IANA Assignments August 1999
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