Source Tree Characteristics Source tree More memory o (G Xs)in routers Optimal path from source to receiver, minimizes delay Good for small number of senders, many receivers such as Radio broadcasting application 2021/2/11
Source Tree Characteristics Source tree More memory O (G x S ) in routers Optimal path from source to receiver, minimizes delay Good for small number of senders, many receivers such as Radio broadcasting application 2021/2/11 27
Shared Tree characteristics Shared tree Less memory o(G)in routers Sub-optimal path from source to receiver, may introduce extra delay(source to root May have duplicate data transter(possible duplication of a path from source to root and a path from root to receivers) Good for k Environments where most of the shared tree is the same as the source tree Many senders with low bandwidth(e.g. shared whiteboard 2021/2/11
Shared Tree Characteristics Shared tree Less memory O (G) in routers Sub-optimal path from source to receiver, may introduce extra delay (source to root) May have duplicate data transfer (possible duplication of a path from source to root and a path from root to receivers) Good for Environments where most of the shared tree is the same as the source tree Many senders with low bandwidth (e.g. shared whiteboard) 2021/2/11 28
Multicast Forwarding Multicast Forwarding is backwards from Unicast Forwarding k Unicast Forwarding is concerned about where the packet is going k Multicast Forwarding is concerned about where the packet came from Multicast Forwarding uses "Reverse Path Forwarding”" 2021/2/11
Multicast Forwarding Multicast Forwarding is backwards from Unicast Forwarding Unicast Forwarding is concerned about where the packet is going Multicast Forwarding is concerned about where the packet came from Multicast Forwarding uses “Reverse Path Forwarding” 2021/2/11 29
Reverse Path Forwarding(RPF) What is RPF? A router forwards a multicast datagram only if received on the up stream interface to the source (i.e. it follows the distribution tree the rpf check The routing table used for multicasting is checked against the "source"IP address in the packet If the datagram arrived on the interface specified in the routing table for the source address; then the RPF check succeeds Otherwise, the rpf check fails 2021/2/11 30
Reverse Path Forwarding (RPF) What is RPF? A router forwards a multicast datagram only if received on the up stream interface to the source (i.e. it follows the distribution tree) The RPF Check The routing table used for multicasting is checked against the “source” IP address in the packet If the datagram arrived on the interface specified in the routing table for the source address; then the RPF check succeeds Otherwise, the RPF Check fails 2021/2/11 30
EXample: RPF Checking Source 151.10.3.21 RPF Check Fails Packet arrived on wrong interface Mcast packets 2021/2/11 31
Example: RPF Checking 2021/2/11 31 Source 151.10.3.21 Mcast Packets RPF Check Fails Packet arrived on wrong interface!