Distance-Vector Multicast Routing Protocol (DVMRP) is the multicast routing algorithm that is used in the MBONE routers. DVMRP is based on a combination of RIP and RPM. One main difference between RIP and DVMRP is that RIP determines the next hop toward the destination, whereas DVMRP determines the previous hop toward the source. DVMRP uses a tunneling mechanism to traverse networks that do not support multicasting. Tunnels are manually configured between two multicast router (mrouters).
One of the severe shortcomings of DVMRP is its inability to operate in a large internetwork. The first reason for this shortcoming is that the maximum number of hops is limited to 15. Second, it is not desirable to flood the entire Internet's leaf routers with the first multicast packet for a particular (source, group). Periodic refloodings due to the soft state mechanism associated with the prune information compound the problem. Also, the flat nature of the routing domain make it unsuitable for a large network.
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