Limited Distribution Updates to Reduce Overhead in

The increasing transmission speed and the growing size of computer networks are creating new challenges for network routing. Increased transmission speed enables new, integrated, applications that require service guarantees from the network. In order to provide these guarantees, routes with suucient resources must be located. The ability of a particular route to support performance-sensitive applications will vary over time as the utilization of the resources along that route changes. Therefore, routing performance can improve with the distribution of dynamic information about the state of the network. At the same time, the increasing size of networks argues against the global distribution of dynamic routing information and against requiring consistent dynamic routing information at all nodes in the network. These connicting constraints motivate us to consider schemes that allow partial distribution of dynamic routing information. In this paper we present a protocol for the distribution of routing updates, called Reverse Path Update (RPU). RPU distributes routing updates only along active routes, as an alternative to global ooding. Using RPU, a node receives updates about those areas of the network through which it sends its traac. Thus, the overhead associated with update distribution is not a function of network size. Rather, distribution overhead depends on the average number of transit nodes through which the source nodes send their traac. This important characteristic of RPU makes it a promising strategy for the dissemination of routing information in large networks. We measure the overhead associated with RPU using simulation. When compared to global ood-ing, we nd that RPU signiicantly reduces the number of dynamic updates distributed in the network. The magnitude of the savings depends on the traac patterns, with greater savings realized when network traac, measured by the percentage of communicating source-destination pairs, is sparse.