Backward learning routing
is a routing
strategy for networks where the network
nodes acquire knowledge of the network state as packets are handled. The routing is originally random. A packet
with a hopcount
of one is from a directly connected node
. Thus, neighboring nodes are identified with their connecting links. A packet with a hop count of two is from a source two hops away, etc. As packets arrive, the IMP compares the hop count for a given source address with the minimum hop count already registered; if the new one is less, it is substituted for the previous one. In order to be able to adapt to deterioration of routes (e.g. link failures), the acquired information has to be "forgotten " periodically.