DVMRP

The term DVMRP is an acronym for Distance Vector Multicast Routing Protocol. This protocol is defined in the RFC 1075 and is used to provide a connectionless datagram delivery to the end nodes or a group of hosts across an internetwork. The DVMRP makes use of the RPM or Reverse Path Multicasting to generate an IP multicast delivery tree for the delivery of the data. This IP is generated dynamically by the program itself, without any interference with the user and this IP is used to forward the multicast traffic to downstream interfaces. This mechanism allows the formation of the shortest path trees to ensure that the data to the host can be sent as soon as possible.

The Distance Vector Multicast Routing Protocol is based on the RIP protocol and it is specifically designed to be used as the interior gateway protocol within a multicast domain. In the networking world, not all the routers present support the multicast routing, as there are certain old version of the routers too present in the network, so DVMRP is needed there, as it can tunnel the multicast IP datagram straight through the router, in simpler word, this protocol enables the sending of multicast IP, even over the routers that do not support multicast IP.

The way the DVMRP protocol brings this about is that it encapsulates the multicast transmission in the unicast packets of data which are then reassembled when they reach their destination. The reason the multicast is encapsulated to the unicast packet is that all the routers support the transportation or flow of the unicast data packets.

The main drawback about the DVMRP is that, it has problems with network scaling due to the periodic reflooding of the network which is necessary to detect and record the new host or hosts that join the network.