Multi-domain routing techniques with topology aggregation in ASON networks

Thanks to the development of the automatic control plane (ASON and GMPLS standards) optical transport networks are able to provide bandwidth on demand service quickly and efficiently. But for this service to be really interesting to users the capability of seamlessly operating the network across multiple administrative domains should be developed. Multi-domain routing in ASON is a new challenging topic, especially if the target is a scalable solution. The paper investigates this topic and in particular it evaluates the effectiveness of the application of aggregation topology methods to the representation of network domains. These methods, initially devised for ATM networks, can be extended to ASON/GMPLS, as recommended by the Optical Interworking Forum (OIF). Topology aggregation limits the amount of topology information distributed throughout the network and the bandwidth occupation for control-plane signalling, improving scalability. On the other hand, concealing intra-domain topology details to other domains may limit the effectiveness of inter-domain routing. We analyze the behavior of the three topology-aggregation methods proposed by OIF (Simple Node, Full Mesh and Symmetric Star) comparing blocking probability in a multi-domain optical network under dynamic bandwidth-on-demand traffic. We further propose a new topology-aggregation scheme (Hybrid) with improved scalability and evaluate its performance in the case-study network compared to the other known schemes.