Alternate path routing (APR) can be used to achieve efficient routing in communications networks. We describe several approaches to APR in connection-oriented networks running link-state routing protocol, and evaluate their performance using call-level simulations. We assume source routing paradigm where primary paths for calls are computed only at source nodes. However, depending on the approach, alternate paths can be computed at source, intermediate or even destination nodes. We present simulation results to show that, if not carefully used, APR may degrade network performance under heavy load. Finally, we describe two mechanisms for improving APR, and address some of their implementation issues.
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