RFC 1054 (rfc1054) - Page 2 of 19
Host extensions for IP multicasting
Alternative Format: Original Text Document
RFC 1054 Host Extensions for IP Multicasting May 1988 attached multicast router completes delivery by transmitting the datagram as a local multicast. This memo specifies the extensions required of a host IP implementation to support IP multicasting, where a "host" is any internet host or gateway other than those acting as multicast routers. The algorithms and protocols used within and between multicast routers are transparent to hosts and will be specified in separate documents. This memo also does not specify how local network multicasting is accomplished for all types of network, although it does specify the required service interface to an arbitrary local network and gives an Ethernet specification as an example. Specifications for other types of network will be the subject of future memos. 3. LEVELS OF CONFORMANCE There are three levels of conformance to this specification: Level 0: no support for IP multicasting. There is, at this time, no requirement that all IP implementations support IP multicasting. Level 0 hosts will, in general, be unaffected by multicast activity. The only exception arises on some types of local network, where the presence of level 1 or 2 hosts may cause misdelivery of multicast IP datagrams to level 0 hosts. Such datagrams can easily be identified by the presence of a class D IP address in their destination address field; they should be quietly discarded by hosts that do not support IP multicasting. Class D addresses are described in section 4 of this memo. Level 1: support for sending but not receiving multicast IP datagrams. Level 1 allows a host to partake of some multicast-based services, such as resource location or status reporting, but it does not allow a host to join any host groups. An IP implementation may be upgraded from level 0 to level 1 very easily and with little new code. Only sections 4, 5, and 6 of this memo are applicable to level 1 implementations. Level 2: full support for IP multicasting. Level 2 allows a host to join and leave host groups, as well as send IP datagrams to host groups. It requires implementation of the Internet Group Management Protocol (IGMP) and extension of the IP and local network service interfaces within the host. All of the following sections of this memo are applicable to level 2 Deering
