Research And Implementation Of Load-balancing Technology Based On Content-oriented Switch

The "College Computer Teaching Platform" and the "Campus On-line Exam System" are two subprojects within "Construction and Reform of Core Computer Curriculum" project. Both of them are web applications built upon dynamic web technologies. Currently, we deploy them on a single web server using business machine. But in actual application environment, the single-machine architecture doesn't meet our requirements especially in such conditions like high concurrent transaction, extensibility, and high performance price ratio. A better solution is to build a load balancing cluster for web servers. The cluster consists of a group of interconnected and independent server nodes working cooperatively with the load balancer to provide a single system image.Load balance cluster technology can increase the quality of web service. The layer-4 switch method based on TCP/IP are widely deployed and used because of good forward performance. However, this method cannot make pertinent load balance decisions because it cannot recognize the real content in request packet. Meanwhile, it is inefficient if packets cannot be balanced according to the user's needs. It may even lead to serious errors. The existence of content-based switch method meets the requirement. In addition to the layer2-3-4 information available in the packet, a content-based switch uses application level information to route traffic in the network.Content-based switch is a new research thesis. At present, there are no mature products or research conclusion. In this paper, I describe the design and implementation of a prototype kernel content-based switch module in Linux kernel. The content-based switch module uses TCP handoff as packet forwarding mechanism. Also I cover two specific switch policies that I believe are ideal candidates for content-based switching: one is routing web content-based on Uniform Resource Locators (URL) and the other is session-aware switching of HTTP.This module validates the solution of content-based switch described in the paper, but further research and development are needed to solve the performance problem.