Multicast Routing Protocols
- dense-mode : push model, flood traffic then prune (all 180 sec)
- sparse-mode : pull model, explicit join behavior
- PIM SM - Protocol Independent Multicast Sparse Mode, supports source, shared trees,pull model, uses RP (rendevouz point) RFC 2362, large scale, optimizations : Bi-directional mode, SSM (source-specific), PROS: traffic to only those who joined, dynamic switch to optimal path, unicast routing protocol independent, basis for interdomain (M-BGP,MSDP)
- DVMRP (v1 obsolet, v2 used on MBONE)
- MOSPF (Multicast OSPF) - uses OSPF LSAs
- CBT (Core Based Trees) - RFC2189 - like PIM - PROS:distribution tree bidirectional, CONS: experimental
Dense-Mode Protocols
- PIM DM - Protocol Independent Multicast Dense Mode, underlying unicast routing for RPF checks, flood and prune ( every 3 mins, 180 sec), designated forwarder on multiaccess networks, non-RPF-flows during inital flooding (discard), prune upstream if no downstream listener, Assert Message stops duplicates on multiaccess networks by comparing distance and metric if router receives (S,G)-packet on OIL (outgoing interface list) -> tie breaker highest IP wins, PRO : easy implement, simple flood and prune mechanism, CONS:inefficient flood and prune
- DVMRP Source Tree - on Multiaccess Networks only one forwarder -> designated Router (highest IP),
- MOSPF - Multicast Info included in OSPF LSAs, Group Membership flooded through OSPF Domain, Dijkstra on every change, scalability problems
Interdomain Multicast Routing
no standarized protocol
BGMP - Border Gateway Multicast Protocol - development
MBGP/MSDP - Multiprotocol BGP/Multicast Source Discovery Protocol - working solution
MSDP connects PIM SM domains
MBGP - multicast RPF NLRI (checking the source)
unicast NLRI (routing)
MSDP allows RPs (Rendevouz Points) in one domain to annouce their sources to other domains using Source Active (SA) Messages
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