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Network Working Group                                          B. FennerRequest for Comments: 3228                                 AT&T ResearchBCP: 57                                                    February 2002Category: Best Current PracticeIANA Considerations forIPv4 Internet Group Management Protocol (IGMP)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 (2002).  All Rights Reserved.Abstract   This memo requests that the IANA create a registry for fields in the   IGMP (Internet Group Management Protocol) protocol header, and   provides guidance for the IANA to use in assigning parameters for   those fields.Table of Contents1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . .12. IANA Considerations for fields in the IPv4 IGMP header. . . .23. Assignments for testing and experimentation . . . . . . . . .24. Security Considerations . . . . . . . . . . . . . . . . . . .25. Normative References. . . . . . . . . . . . . . . . . . . . .26. Informative References. . . . . . . . . . . . . . . . . . . .37. Author's Address. . . . . . . . . . . . . . . . . . . . . . .38. Full Copyright Statement. . . . . . . . . . . . . . . . . . .41.  Introduction   This memo requests that the IANA create a registry for fields in the   IGMP protocol header.   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 [2].Fenner                   Best Current Practice                  [Page 1]

RFC 3228           IANA Considerations for IPv4 IGMP       February 20022.  IANA Considerations for fields in the IPv4 IGMP header   The IPv4 IGMP header [1] contains the following fields that carry   values assigned from IANA-managed name spaces: Type and Code.  Code   field values are defined relative to a specific Type value.   Values for the IPv4 IGMP Type fields are allocated using an IESG   Approval or Standards Action processes.  Code Values for existing   IPv4 IGMP Type fields are allocated using IESG Approval or Standards   Action processes.  The policy for assigning Code values for new IPv4   IGMP Types should be defined in the document defining the new Type   value.3.  Assignments for testing and experimentation   Instead of suggesting temporary assignments as in [3], this document   follows the lead of [4] and assigns a range of values for   experimental use.  The IGMP Code values 240-255 inclusive (0xf0 -   0xff) are reserved for protocol testing and experimentation.   Systems should silently ignore IGMP messages with unknown Code   values.4.  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.5.  Normative References   [1]   Fenner, W., "Internet Group Management Protocol, Version 2",RFC 2236, November 1997.   [2]   Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA         Considerations Section in RFCs",BCP 26,RFC 2434, October         1998.Fenner                   Best Current Practice                  [Page 2]

RFC 3228           IANA Considerations for IPv4 IGMP       February 20026.  Informative References   [3]   Bradner, S. and V. Paxson, "IANA Allocation Guidelines For         Values In the Internet Protocol and Related Headers",BCP 37,RFC 2780, March 2000.   [4]   Narten, T., "Assigning Experimental and Testing Numbers         Considered Useful", Work in Progress.7.  Author's Address         Bill Fenner         AT&T Labs -- Research         75 Willow Rd         Menlo Park, CA 94025         USA         EMail: fenner@research.att.comFenner                   Best Current Practice                  [Page 3]

RFC 3228           IANA Considerations for IPv4 IGMP       February 20028.  Full Copyright Statement   Copyright (C) The Internet Society (2002).  All Rights Reserved.   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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Fenner                   Best Current Practice                  [Page 4]