Distance Vector Multicast Routing Protocol
Encyclopedia
The Distance Vector Multicast Routing Protocol (DVMRP), defined in RFC 1075, is used to share information between routers to facilitate the transportation of IP Multicast
packets among networks. It forms the basis of the Internet's multicast backbone (MBONE).
protocol for forwarding packets: the router generates a routing table with the multicast group of which it has knowledge with corresponding distances (i.e. number of devices/routers between the router and the destination). When a multicast packet is received by a router, it is forwarded by the router's interfaces specified in the routing table.
DVMRP operates via a reverse path flooding technique, sending a copy of a received packet (specifically IGMP
messages for exchanging routing information with other routers) out through each interface except the one at which the packet arrived. If a router (i.e. a LAN which it borders) does not wish to be part of a particular multicast group, it sends a "prune message" along the source path of the multicast.
IP Multicast
IP multicast is a method of sending Internet Protocol datagrams to a group of interested receivers in a single transmission. It is often employed for streaming media applications on the Internet and private networks. The method is the IP-specific version of the general concept of multicast...
packets among networks. It forms the basis of the Internet's multicast backbone (MBONE).
Operation
The protocol is based on the RIPRouting Information Protocol
The Routing Information Protocol is a distance-vector routing protocol, which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from the source to a destination. The maximum number of hops allowed for RIP is 15....
protocol for forwarding packets: the router generates a routing table with the multicast group of which it has knowledge with corresponding distances (i.e. number of devices/routers between the router and the destination). When a multicast packet is received by a router, it is forwarded by the router's interfaces specified in the routing table.
DVMRP operates via a reverse path flooding technique, sending a copy of a received packet (specifically IGMP
Internet Group Management Protocol
The Internet Group Management Protocol is a communications protocol used by hosts and adjacent routers on IP networks to establish multicast group memberships....
messages for exchanging routing information with other routers) out through each interface except the one at which the packet arrived. If a router (i.e. a LAN which it borders) does not wish to be part of a particular multicast group, it sends a "prune message" along the source path of the multicast.
Criticisms
Like most distance-vector protocols, DVMRP has difficulties with network scaling, primarily due to periodic the reflooding necessary to detect new hosts. This was more prevalent in early versions of the protocol, prior to the implementation of pruning. DVMRP's flat unicast routing mechanism, which is used to determine the source interface of a data stream, also affects its ability to scale.External links
- RFC 1075 - Distance Vector Multicast Routing Protocol version 1
- Internet Draft http://tools.ietf.org/html/draft-ietf-idmr-dvmrp-v3-11 - proposal for Distance Vector Multicast Routing Protocol version 3
- DVMRP: Distance Vector Multicast Routing Protocol