Dynamically controlled routing in networks with non-DCR-compliant switches

The authors investigate the deployment of a state-dependent call routing scheme in a network where only a fraction of the switches can fully support it. The state-dependent routing scheme considered is dynamically controlled routing (DCR). Not all switches are assumed to be capable of supporting the feature that DCR requires. For switches that cannot support DCR, several alternative routing schemes are considered. These are: FHR, fixed routing (FR), and adaptive controlled routing (ACR). These schemes were selected on the basis of their modest switch requirements, which can be expected to be satisfied with no or minimal new development by the vast majority of existing switch products. The objective in the article is to define feasible interworking arrangements between DCR and these schemes and assess the performance that can be expected of a network operating under these arrangements. The authors begin by discussing DCR, and describe how it can be enhanced to interwork with non-DCR switches. They describe the routing schemes considered for the non-DCR switches, and how they can interwork with DCR. After that they analyze the performance that a network can expect to achieve when it supports DCR in its DCR switches in conjunction with one of the other routing schemes in its non-DCR switches