Network Working Group Scott Bradner
Internet-Draft Harvard University
Vern Paxson
ACIRI
July 1999
IANA Allocation Policies For Values In
the Internet Protocol and Related Headers
<draft-bradner-iana-allocation-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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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 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 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The Type of Service field described in [V4] has been superceded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
currently unused field. The IANA allocates values in the DS field
following the IANA Considerations section in [DIFF]. The values in
the 2-bit unused field are allocated following a Standards Action
process.
IANA allocates values from the IPv4 Protocol name space following an
Expert Review, IESG Approval or Standards Action process. The Expert
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Review process should only be used in those special cases where non-
disclosure information is involved. In these cases the expert should
be designated by the IESG.
The IPv4 Source and Destination addresses use the same values. These
values fall into a number of ranges (called "Classes") defined in
[V4] and [MULT]. The guidelines for the allocation of the values
from the IPv4 Class A, Class B and Class C unicast addresses are
under the control of Internet Corporation for Assigned Names and
Numbers (ICANN) 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 an Standards Action process. The IETF has also assigned a
number of IPv4 Class D (multicast) addresses for special purposes.
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) 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.
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
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
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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
guidelines for the assignment of values in the Aggregatable Global
Unicast Addresses FP (FP 001) are under the control of the Internet
Corporation for Assigned Names and Numbers (ICANN). 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-
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.
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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.
[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.
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[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
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