RFC 1075 (rfc1075) - Page 2 of 24
Distance Vector Multicast Routing Protocol
Alternative Format: Original Text Document
RFC 1075 Distance Vector Multicast Routing Protocol November 1988 DVMRP differs from RIP in one very important way. RIP thinks in terms of routing and forwarding datagrams to a particular destination. The purpose of DVMRP is to keep track of the return paths to the source of multicast datagrams. To make explanation of DVMRP more consistent with RIP, the word "destination" is used instead of the more proper "source", but the reader must remember that datagrams are not forwarded to these destinations, but originate from them. This memo is organized into the following sections: - A description of DVMRP is presented. - Tunnels are explained. - The routing algorithm is shown. - The forwarding algorithm is shown. - The various time values are listed. - Configuration information is specified. This memo does not analyze distance-vector routing, nor fully explain the distance-vector algorithm; see [1] for more information on these topics. The process or processes that perform the routing and forwarding functions are called "routers" in this memo. 3. Protocol Description DVMRP uses the Internet Group Management Protocol (IGMP) to exchange routing datagrams [2]. DVMRP datagrams are composed of two portions: a small, fixed length IGMP header, and a stream of tagged data. The fixed length IGMP header of DVMRP messages is: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Type | Subtype | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The version is 1. The type for DVMRP is 3. The subtype is one of: 1 = Response; the message provides routes to some destination(s). 2 = Request; the message requests routes to some destination(s). 3 = Non-membership report; the message provides non-membership report(s). Waitzman, Partridge & Deering
