A split protocol technique for web server migration

Reliability, availability and survivability are important characteristics of Web servers that enable them to provide continual service to clients. Server migration is one of the many approaches used to improve the reliability of Web servers. We propose a novel technique for migrating Web servers that is based on protocol splitting, wherein two servers, a connection server and a data server, function as a single logical server. The technique extends splitting by having the connection server dynamically transfer a TCP connection to another connection server with no client involvement. We describe an implementation of the migration technique and present preliminary performance results using bare PC Web servers in a LAN environment with Linux routers. The connection transfer is achieved by means of an additional inter-server packet and a script to modify a routing table. The results indicate the feasibility of adapting this approach in the future to work with conventional (non-bare) servers on the Internet.