Multicast Routing Algorithms; Flooding; Spanning Tree - 3Com CoreBuilder 2500 User Manual

Multicast Routing
Algorithms

Flooding

Spanning Tree

The CoreBuilder 2500 system uses three multicast routing algorithms:
Flooding
Spanning Tree
Reverse Path Forwarding
In most flooding algorithms, a network node receives a packet that was
sent to a multicast destination. The node determines whether the packet
is an original that it has not received before or a duplicate of a packet
that it has received before. If the packet is original, the node forwards the
packet on all interfaces except the incoming interface. If the packet is a
duplicate, the node discards it.
This flooding algorithm is useful when network robustness is important.
The algorithm does not depend on routing tables. Multicast destinations
receive packets as long as at least one path to the destinations exists and
no errors occur during transmission.
The Spanning Tree algorithm detects loops and logically blocks redundant
paths within the network. The paths form a loopless graph, or tree,
spanning all the nodes in the network. A port in the Spanning Tree
blocking state does not forward or receive data packets.
After the algorithm eliminates redundant paths, the network
configuration stabilizes. When one or more of the paths in the stable
topology fail, the protocol automatically recognizes the changed
configuration and activates redundant links. This strategy ensures that all
nodes remain connected.
Figure 5-1 shows a simple network with six links.
1
A
B
3 4
D E
6
Figure 5-1 Simple Network Implemented Without Using Spanning Tree

Multicast Routing Algorithms

2
C
5
5-3