Editing Distance Vector Multicast Routing Protocol

The '''Distance Vector Multicast Routing Protocol''' ('''DVMRP'''), defined in {{IETF RFC|1075}}, is a [[routing protocol]] used to share information between [[router (computing)|router]]s to facilitate the transportation of [[IP multicast]] packets among networks. It formed the basis of the Internet's historic multicast backbone, [[Mbone]].

==Operation==
The protocol is based on the [[Routing Information Protocol]] (RIP).<ref>[http://www.javvin.com/protocolDVMRP.html DVMRP: Distance Vector Multicast Routing Protocol] {{webarchive |url=https://web.archive.org/web/20090622072943/http://www.javvin.com/protocolDVMRP.html |date=June 22, 2009 }}</ref> 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 [[Internet Group Management Protocol|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.

==Criticisms==
Being a naïve distance-vector protocol, DVMRP has difficulties with network scaling in some topologies,<ref name="Scaling">[http://www.savetz.com/mbone/apc_13.html What is DVMRP?]</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.<ref name="Why">[http://www.cisco.com/en/US/tech/tk828/technologies_white_paper09186a00800a43ee.shtml Multicast Routing May 5, 1995]</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]]
* [[Router Information Protocol]]

==References==
{{reflist}}

==External links==
*[http://tools.ietf.org/html/draft-ietf-idmr-dvmrp-v3-11 Proposal for Distance Vector Multicast Routing Protocol version 3]

[[Category:Routing protocols]]