HPIM-DM: A fast and reliable dense-mode multicast routing protocol

The Hard-state Protocol Independent Multicast—Dense Mode (HPIM-DM) multicast routing protocol is proposed. HPIM-DM is a hard-state version of PIM-DM that overcomes its poor convergence times and lack of resilience to replay attacks. Like PIM-DM, HPIM-DM is meant for dense networks and supports its operation on a unicast routing protocol and reverse path forwarding. However, routers maintain sense of the multicast trees at all times, allowing fast reconfiguration in the presence of network failures or unicast route changes. This is achieved by (i) keeping information on all upstream neighbours from which multicast data can be received, (ii) ensuring the reliable transmission and sequencing of control messages, and (iii) synchronizing the routing information immediately when a new router joins the network. The correctness of the protocol was extensively validated using model checking and logical reasoning. The protocol was fully implemented in Python, and the implementation is publicly available. Finally, we show both theoretically and experimentally that HPIM-DM has much better convergence times than PIM-DM.