The Distance Vector Multicast Routing Protocol (DVMRP), defined in , is a
routing protocol
A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network. Routers perform the traffic directing functions on the Internet; data packets ...
used to share information between
routers to facilitate the transportation of
IP multicast
IP multicast is a method of sending Internet Protocol (IP) datagrams to a group of interested receivers in a single transmission. It is the IP-specific form of multicast and is used for streaming media and other network applications. It uses speci ...
packets among networks. It formed the basis of the Internet's historic multicast backbone,
Mbone
Mbone (short for "multicast backbone") was an experimental backbone and virtual network built on top of the Internet for carrying IP multicast traffic on the Internet. It was developed in the early 1990s and required specialized hardware and soft ...
.
Operation
The protocol is based on the
Routing Information Protocol
The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols 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 sourc ...
(RIP).
DVMRP: Distance Vector Multicast Routing Protocol
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
The Internet Group Management Protocol (IGMP) is a communications protocol used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships. IGMP is an integral part of IP multicast and allows the network to direct m ...
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
Being a naïve distance-vector protocol, DVMRP has difficulties with network scaling in some topologies,[What is DVMRP?](_blank)
/ref> primarily due to the periodic reflooding necessary to detect new hosts. This was more prevalent in early versions of the protocol, prior to the implementation of pruning.[Multicast Routing May 5, 1995](_blank)
/ref> DVMRP's flat unicast routing mechanism, which is used to determine the source interface of a data stream, also affects its ability to scale.
See also
* Protocol Independent Multicast
400px, Example of a multicast network architecture
Protocol-Independent Multicast (PIM) is a family of multicast routing protocols for Internet Protocol (IP) networks that provide one-to-many and many-to-many distribution of data over a LAN, ...
* Router Information Protocol
The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols 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 sour ...
References
{{reflist
External links
Proposal for Distance Vector Multicast Routing Protocol version 3
Routing protocols