InterNet Multicast Routing Internet Multicast Routing Algorithms that are already used to route non-multicast messages through an internet can be modified and extended to allow actual protocol support for multicasting. A lot of work has been done in this area and I intend to show this with reference to Spanning Tree routing. This information is taken from Stephen Deering's doctoral dissertation. Spanning Tree Routing ST routing is being adopted as the standard routing protocol for all types of IEEE 802 LAN's at the datalink layer. A distributed spanning tree algorithm is computed by all the routers in the internetwork.
Routers listen to all the packets that pass by on their parent and child sub-nets.
The time-left value indicates how long since the last packet for host was received. Stale values can be flushed from the cache after a certain period of quiet time. This helps to ensure that the routes in the cache do not become inaccurate, if a node crashes for example. The crashed node will originate no more messages and the cache will eventually discard the old route and have to locate a new route. Each message on a child or parent sub-net carries its source address.