Load-Balanced Anycast with Minimal Average Delay

Abstract

To achieve load-balance and fault-tolerance, a lot of current Internet applications will need a group of replicated servers spread all over the world. In IPv6, a new communication style, anycast provides the capability of routing packets to the nearest server. An enhanced Qos (Quality of Service) can be satisfied with such kind of computing paradigm. Web service, Distributed Database System and DNS are the most well-known examples. However, we still need further investigations before anycasting can be realized. 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.