| Since the E-Commerce has been widely adopted by many enterprises, the Internet service mode has transformed from conventional information browse to trade and service on-line, and this change made web server and web service to be a very important core facility. However, current web server did not supply us with satisfaction Quality of Service guarantee. Therefore, it would lost many of users and make great money losing when the web server overloaded. So a technology named Web QoS turned up. It faced to end web user and supplied the HTTP requests with performance guarantee.Based on reading and studying a lot of domestic and oversea papers and products about Web QoS, the key factors that affect the performance of web server are gotten, and the solution's check-point is held too. The reason that web server cannot achieve good quality target is the server did not distinguish the different request on applications and users, and did not control the usage of resource. So when designing and implementing Web QoS service mode, following questions: differentiate the requests, improve the utilization of resource, control the accepting of request and realize load-balance must be solved. Meanwhile the requirement of network system design -- high performance, scalable, manageability, transparence and customization must be considered. Based on this philosophy, a multi-level application differentiate Web QoS service mode is put forward. Because there is no one load-balancing algorithms can satisfy all application's demand, but it could find a suitable algorithms for one certain application, this paper's Web QoS service mode differentiates the requests of clients firstly, switch requests to corresponding load-balancer through high-level content-based switcher, and then the load-balancer assign a back-end web server, according to corresponding load-balancing algorithms, to deal with the request.In order to certify the validity of this mode, the develop history of web service is simulated by network simulation software OPNET Modeler 8.0, from few client and only one server, to because of the great increasing of client, one server cannot afford enormous requests, then lots of servers and cluster technology are adopted, and to the number of client is on the explosive increase, the Web QoS service mode is studied and adopted. From the compared result of OPNET simulation, it can find that the multi-level application differentiate Web QoS service mode can meet the increasing demand of web requests. Meanwhile, in order to certify mode's realizability, a kernel-space Layer-7 switcher, named KTCPVS--Kernel TCP Virtual Server, is improved and realized to supply high-level content-based switch function. It analyses the HTTP requests' content and switches requests to their corresponding load-balancer according to requests' content type. And the network load-balance technology is utilized to create web server cluster under Windows 2000 Advanced Server, and finally the back-end Web server in cluster serve the requests of users. Through analysing and testing, this Web QoS service mode archieves original design purpose, but there are still some problems that could not solve suitably, so great efforts should be made to make it perfect in the future study and practice. |
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