Two types of transport are used by store and forward networks:-
- For datagram transport the network selects the path for each packet individually.
- For virtual circuit transport the network makes one path selection for all the packets of the same connection.
Usefull Routing Algorithm Characteristics:
Robustness - it should adapt the routing decisions to changing conditions (i.e . network traffic and topology).
Stability - a small change in conditions should result in a small change in routing decisions.
Fairness - different users should experience equitable delays and transmission rates.
Optimality - maximizing the network designers objective function while satisfying the design constraints.
Classes of routing algorithm:-
Routing algorithms can be classified as non-adaptive and adaptive. If a network is stable in its topology and traffic flow a non-adaptive algorithm. In this case all routes are computed initially and never change. This relieves the nodes from havin to monitor changes and compute new routes.
Alternately adaptive algorithms attempt to make routing decisions based on current traffic and topology. These algorithms can be divided into 3 sub-classes.
- centralised routing
- isolated routing
- distributed routing
