DVMRP

DVMRP stands for Distance Vector Multicast Routing Protocol. It is one of the earliest multicast routing protocols used in IP networks and was designed for IPv4 networks. The protocol is described in RFC 1075 as DVMRP Version 3 and was implemented in several Unix-based router daemons, notably mrouted.

DVMRP uses a distance-vector approach in which routers periodically exchange information about reachable subnets and associated metrics with their directly connected neighbors. To forward multicast traffic, DVMRP floods the traffic within the network and builds a distribution tree using Reverse Path Forwarding (RPF) along the shortest-path toward the source. This flooding is then pruned on branches that do not have receivers, using prune messages. If a new receiver appears on a previously pruned branch, graft messages can rejoin that branch to the distribution tree.

The protocol operates primarily over IPv4 and was historically associated with dense-mode deployments where receivers are relatively abundant. DVMRP’s flooding and prune/graft mechanism offered a straightforward way to deliver multicast but did not scale as well as later approaches in large or sparse networks. As a result, Protocol Independent Multicast (PIM) variants, especially PIM Sparse Mode, and other multicast architectures were developed to improve scalability and flexibility.

In modern networks, DVMRP is largely superseded by PIM variants and source-specific multicast approaches. Some legacy or compatibility-focused networks may still run DVMRP using established software implementations, but it is less common in new deployments.