Distributed routing using topology database in large computer networks

The authors develop distributed routing algorithms for large computer networks that provide virtual circuit connections to end users. One routing scheme in computer networks is to use a topology database maintained at each node that contains information about nodes and link cost. Using this information, each node finds shortest routes to other nodes. This scheme may be inefficient in large networks since the overhead associated with topology database update and shortest path computation may become large. One way of solving this problem is to partition the network into subnetworks or clusters. After partitioning, each node in a cluster only maintains a topology database of nodes and links in its own cluster and possibly marginal information about the entire network. For intracluster communication, shortest path routes are provided. For intercluster communication the source node collaborates with other nodes to find a path to the destination node. The authors propose two collaboration schemes that use simple protocols among network nodes. In one scheme, a broadcast search is used to find a path to the destination node in other clusters. In the other scheme each node maintains information about intercluster links on an up/down basis as well as complete topology database of its own cluster. Using this information, it finds a path to the destination node with the help of border nodes (nodes sharing intercluster links) in the intermediate clusters