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 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 other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This document will expire in January 2000. 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. Bradner & Paxson [Page 1] Internet-Draft IANA Assignments August 1999 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. Bradner & Paxson [Page 2] Internet-Draft IANA Assignments August 1999 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 Bradner & Paxson [Page 3] Internet-Draft IANA Assignments August 1999 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- Bradner & Paxson [Page 4] Internet-Draft IANA Assignments August 1999 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 Bradner & Paxson [Page 5] Internet-Draft IANA Assignments August 1999 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 This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Bradner & Paxson [Page 7]