In Routing in Communication Networks (Editor Martha Steenstrup),
Prentice Hall, Englewood Cliffs, 1995. 13-47.
(ISBN 0 13 010752 2)
Dynamic call-routing strategies, which route calls according to current networks state, have been widely deployed in telephone networks over the past decade because of their ability to yield improved network performance at reduce network cost. This chapter describes an ingenious example of this type of routing strategy, Dynamic Alternative Routing (DAR), currently employed by British Telecom. DAR is an adaptive call-routing strategy that stochastically selects an alternative route when a direct route is not available and uses local information about the loading of outgoing trunks to determine the feasibility of selected routes. Dynamic routing strategies, such as DAR, which operate in a decentralized fashion and rely only on local information to make call-routing decisions, are particularly attractive because they are robust in the presence of failures, they consume a minimum of network resources, and they are simple to implement.
More material on Dynamic Alternative Routing.