The Research Of Time Performance And Scheduling Mechanism About Three Kinds Of Primary Network Services

With the development of the network and communication technology,there are not only some users who need the service of the Internet,but also people who need providing real-time requirements and bandwidth assurance in many network applications.In this way,we have three kinds of primary network businesses:real-time,bandwidth assurance and best- effort bussinesses.With the expanding of network scale and the increasing of the bussiness class and quality requirement, how to realize the control of Quality of Service(QoS) for multi-service is a problem worthing reseach.In the control mechanisms of QoS,the scheduling algorithms decide the order of the serviced packets and make data transferring devices control some characteristics intelligently,which include the priority of data transferring,individual link bandwidth and average delay.These can satisfy QoS in a certain extent.To improve network QoS and satisfy the users,many researches on scheduling algorithms are emerged.Firstly,this paper introduces associated definitions and technique performances from the current reseach status of QoS.And then,it analyzes the control mechanism of QoS.Also,the development of several important mechanisms is described,including the packet scheduling algorithms.Secondly,the paper points out three kinds of primary network businesses and lists the application environment owning the three businesses.After this,the time performances based on the TCP and UDP in the network with three primary businesses are researched;the formulas for calculating the maximum delay of bandwidth assurance and real-time services are given out.Lastly,according to the classical uni-processor schedule algorithm named the Earliest-Deadline-First algorithm,the paper puts forward the improved EDF algorithm based on the real-time,bandwidth guarantee and best-effort sevices regarding the need of network users in the current stage.In this algorithm,a new bandwidth assurance strategy and the schedule process based on three different models are provided.And then, the presented algorithm is simulated with the experiment tool SIM.In this paper,the formulas of the maximum delay provide the basis for the improved EDF scheduling mechanism which is based on the exchange queues and the priority bandwidth assurance strategy. Simulation results show that the improved algorithm can reduce the delay and increase the bandwidth assurance rate of the relevant flow.As a whole,the performances of network QoS are improved.