Load-balanced anycast routing

For fault-tolerance and load-balance purposes, many modern Internet applications may require that a group of replicated servers dispersed widely over the world. The anycast as a new communication style defined in IPv6 provides the capability to route packets to the nearest server. Better quality of service (QoS) can be achieved by this kind of computing paradigm. DNS, Web service, and distributed database system are three most well known examples. However, before anycasting can be realized, more researches need to be done. The anycast routing scheme is one of the most important issues. In this paper, we propose a load-balanced anycast routing scheme based on the WRS (weighted random selection) method. We suggest that the server capability should be propagated along with other fields in the routing tables. An anycast routing algorithm should take into account the network transmission capability as well as the server processing capability for the selection of a target server. Three weight determination strategies are given. We also develop a simple algorithm to calculate the weights of WRS to achieve optimization under both the heavy and the light system traffic environment. Our approach is locally optimized to minimize the average total delay and well balanced for the server load.