Internet Draft B. Nickless Document: draft-nickless-ipv4-mcast-unusable- Argonne National 00.txt Laboratory Expires: August 2002 February 2002 IPv4 Multicast Unusable Group Addresses 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. Abstract Due to the mapping of IPv4 Multicast addresses to Ethernet MAC addresses, and the prevalence of IGMP snooping switches, certain addresses in the IPv4 Multicast Group Address range 224.0.0.0/4 MUST NOT be used. Table of Contents Status of this Memo................................................1 Abstract...........................................................1 Conventions used in this document..................................2 Background.........................................................2 Group Address Restrictions.........................................2 IANA Considerations................................................3 Security Considerations............................................3 Acknowledgements...................................................3 References.........................................................3 Author's Address...................................................3 Nickless Informational - Expires August 2002 1 IPv4 Multicast Unusable Group Addresses February 2001 Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [RFC2119]. Background IPv4 multicast [MCAST] is an internetwork service that allows IPv4 datagrams sent from a source to be delivered to one or more interested receiver(s). That is, a given source sends a packet the network with a destination address 224/4 CIDR [CIDR] range. The network transports this packet to all receivers (replicated where necessary) that have registered their interest in receiving these packets. [MCAST] describes the mapping of IPv4 Multicast Group addresses to Ethernet MAC addresses, as follows: An IP host group address is mapped to an Ethernet multicast address by placing the low-order 23-bits of the IP address into the low-order 23 bits of the Ethernet multicast address 01-00-5E-00-00-00 (hex). Because there are 28 significant bits in an IP host group address, more than one host group address may map to the same Ethernet multicast address. Multicast group addresses in the 224.0.0.0/24 range are used for local subnetwork control. This maps to the Ethernet multicast address range 01-00-5E-00-00-XX, where XX is 00 through FF. Ethernet frames within this range are always processed in the control plane of many popular network devices, such as IGMP-snooping switches. Group Address Restrictions Because of the many-to-one mapping of IPv4 Multicast Group Addresses to Ethernet MAC addresses, it is possible to overwhelm the control plane of network devices by sending to group addresses that map into the 01-00-5E-00-00-XX (hex) range. The following IPv4 Multicast Group Address ranges MUST NOT be used in order to avoid overwhelming the control plane of network devices: Nickless Informational - Expires February 2002 2 IPv4 Multicast Unusable Group Addresses February 2001 224.128.0.0/24 225.0.0.0/24 225.128.0.0/24 226.0.0.0/24 226.128.0.0/24 227.0.0.0/24 227.128.0.0/24 228.0.0.0/24 228.128.0.0/24 229.0.0.0/24 229.128.0.0/24 230.0.0.0/24 230.128.0.0/24 231.0.0.0/24 231.128.0.0/24 232.0.0.0/24 232.128.0.0/24 233.0.0.0/24 233.128.0.0/24 234.0.0.0/24 234.128.0.0/24 235.0.0.0/24 235.128.0.0/24 236.0.0.0/24 236.128.0.0/24 237.0.0.0/24 237.128.0.0/24 238.0.0.0/24 238.128.0.0/24 239.0.0.0/24 239.128.0.0/24 IANA Considerations IANA SHALL permanently reserve these IPv4 Multicast Group Address ranges. These group addresses MUST NOT be allocated for any IPv4 multicast application. Security Considerations Low to moderate multicast traffic levels, using addresses within these IPv4 Multicast Group Address ranges, can result in severe denial of service on network devices that process frames with Ethernet MAC addresses in the 01-00-5E-00-00-XX (hex) range in the control plane. Acknowledgements This work was supported by the Mathematical, Information, and Computational Sciences Division subprogram of the Office of Advanced Scientific Computing Research, U.S. Department of Energy, under Contract W-31-109-Eng-38. References [RFC2119] RFC 2119: Key Words for use in RFCs to Indicate Requirement Levels. S. Bradner. March 1997. [MCAST] RFC 1112: Host extensions for IP multicasting. S.E. Deering. Aug-01-1989. [CIDR] RFC 1519: Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy. V. Fuller, T. Li, J. Yu, K. Varadhan. September 1993. Author's Address Bill Nickless Argonne National Laboratory 9700 South Cass Avenue #221 Phone: +1 630 252 7390 Argonne, IL 60439 Email: nickless@mcs.anl.gov Nickless Informational - Expires February 2002 3