Web Differentiated Services, Technology And Strategy Research

With the explosive use of Internet and rapid development of e-commerce,it becomes more urgent for web sites to provide quality of services (QoS) guarantees for client requests to reduce the response delays and response failures. Internet Engineering Task Force (IETF) has proposed two transports mode - IntServ and DiffServ - to improve QoS on Internet,but it is not enough to meet the QoS demands since QoS may be affected by network or/and server. With more bandwidth added to Internet and the bottleneck moved to server side,how to assure QoS in web servers becomes the major problem.Differentiated service in web servers is brought forth timely,and becomes a new research field and important scientific division rapidly. To support differentiated services in web servers,the methods of technologies and implementation of policies should be deeply studied. This dissertation makes a lot of researches on these aspects and puts forth a number of novel policies and methods. The main contributions of the dissertation are concluded as follows:1 . Web differentiated service is inherited from traditional web technology and integrated with Internet differentiated service to provide QoS management. As the foundation of our researches,the dissection studies the web technologies,web cluster technologies,web access characteristics and Internet differentiated service policies,and presents the concerned problems on technologies and policies.2. Web server architectures based upon traditional web server and web cluster with embedded modules have been constructed,and the implementation methods of differentiated services are provided. The critical functions which include class identification,resource management,requests scheduling ar.d admission control are specifically analyzed,and the works on improving resource utility and reducing resource overhead on refused requests are also discussed.3 . The premise to assure QoS is to provide sufficient resource to meet demands. We come up with a method to partition the resources of web cluster for each class with its resource demand and priority requirement taken for granted,where system processing time or average access rates is summed up for each class periodically and resource demands is evaluated with stretch factor as performance metric. Also the nodes marked in number will be orderly assigned to the classes ordered in priorities,which helps to maintain data locality and improves memory Cache hits.4. The definitions of absolute differentiated service and relative differentiated service have been extended to web sen-ices in this dissertation. We design a method,SLADS,to support absolute differentiated service in web clusters. With resource repartitioned periodically and having resource utility controlled in each period,the QoS demands of each class can be meet. Based onSLADS,we construct a web cluster prototype that can support absolute differentiated services.5. As efficient resource allocation approaches,economic models are widely adopted in computer network systems. We have the economic models introduced in web services. First,we have the resource of web cluster allocated among the classes with pareto optimal method in microeconomic1 model,and have the resource load of each class controlled not to be overused. Then a policy for supporting service level agreement (SLA) is proposed to optimize the resource utility among the web hosting users who may have idle resources or lack resources. Combinedwith economic models,web differentiated services is more practical.6. In e-commerce web sites,majority of the requests in web traffic are session-based. With the transactional characteristics of sessions,a session once accepted will experience a few stages such as main menu,Browsing-Empty-Cart,Brbwsing-Articles-in-Cart and Checkout before completed. We have the session priority maintained on the basis of the client who issues the session and the stage which the session resides in,and propose a differentiated service policy to assure the integrity for the sessions with hi...