Border Gateway Multicast Protocol
|Document||Charter||Border Gateway Multicast Protocol WG (bgmp)|
|Title||Border Gateway Multicast Protocol|
|Charter edit AD||(None)|
|Send notices to||(None)|
As IP multicast is being more widely deployed and used, the existing multicast routing algorithms have demonstrated several limitations which make them unsuitable for deployment globally or among multiple provider domains. Protocols like DVMRP and PIM Dense Mode that rely on broadcasting and pruning leave state in parts of the network that are not on the multicast delivery tree. Protocols like CBT and PIM Sparse Mode use a centralized resource to learn of multicast sources. Service providers are reluctant to maintain state for multicast groups that have no receivers in their domain or use a centralized resource in another domain that they cannot control. BGMP is a scalable multicast routing protocol which addresses these problems. Like CBT and PIM Sparse Mode, BGMP chooses a global root for a delivery tree. However, the root is a domain, not a single router, so if there is any path available to the domain connectivity can be maintained. BGMP builds a bidirectional, shared tree of domains. Similarly to the unicast EGP/IGP split, BGMP is used as the inter-domain or external protocol, while domains can run any multicast IGP internally (such as CBT or PIM Sparse Mode), and can build source-specific shortest-path distribution branches to supplant the shared tree where needed. The BGMP working group is chartered to complete the protocol specification and follow it through the Internet standards track. It will also help to design a transition mechanism from MSDP (the Multicast Source Distribution Protocol, an interim interdomain solution that is unlikely to scale for the long term) to Internet-wide BGMP.