7.1 Future directions

One important aspect of circuit switching that has not been addressed in this thesis is the routing of circuits in the backbone. Routing has important implications in the performance and scalability of a circuit-switched network. For example, a network can increase its throughput without increasing the total capacity if the traffic load is balanced across multiple parallel paths. Even if the set of routes is not optimal, the throughput can be much higher than the trivial shortest-path-first solution. Routing decisions need to be fast so as to be reactive to changes in the network traffic. Routing also performs an important role in the robustness of the network because in case of a failure, the routing mechanism has to restore the broken paths as soon as possible. One can speed up recovery if a disjoint backup path has been pre-computed and perhaps even pre-provisioned before any failure occurs.

Finally, the analysis of circuit and packet switching can have many other applications; especially, when comparing preemptive and non-preemptive systems with several parallel channels or servers. A short list of applications include:

• Router and switch crossconnects with few or no buffers. These crossconnects resemble a bufferless optical network where most or all buffers are at the ingress and egress points. The approaches that have been presented in this thesis could be applicable in this situation.

• Wireless access networks, in which orthogonal channels are used to increase the capacity of the access network.

• HTTP 1.1, where a client pipelines its requests through several parallel connections to a proxy server.

• Computer clusters, in which workloads are so large that it becomes very expensive to switch contexts, and so tasks need to be executed to completion.