Research On Marking Policy And Controlling Ill-Behaved Flows In DiffServ

The current Internet only provides the service called best-effort, in which, all traffcis are treated indistingguishably and compete for the network resources equally. This service model is insufficient for those multimedia applications that have special requirements of transmission quality for bandwidth, delay and delay jitter. In order to supply better end to end QoS controll, IETF advaced Intergrated and Differentiated sevices model. Comparing to InSterv model, Diffserv doesn't need to keep flow states and deal with complicated message protocol. So it has better expansibility and is considered as the foundation for future IP QoS framework.This dissertation makes a research on the strcture and IP QoS controlling policy of DiffServ model. Based on this, this disserttion imporves the packets marking and ill-behaved flows controlling policy for resolving the unfairness problems in DiffServ AF service and supplies better scheme for end to end IP QoS controlling and different services for different QoS request. In summarize, this paper includes following outcomes:Firstly, this dissertation made a summarizaiton of the current research on QoS and two main service modeles, then pointed out the problems in the QoS controlling of the AF service through making research emphasizly on the policy of IP QoS controlling of Diffserv.Seondly, this dissertation studied the packet marking policies and put forward a self-adjusting fair marking approach. This approach improved the fairness between aggregate flows through remarking or dropping packets according the history information of forwarding packets through the edge router.Thirdly, analyse the impact of ill-behaved flows to IP network and methods for identifying ill-behaved flows. Base on this, advanced a dynamic service profiles based method for controlling ill-behaved flows. This method could improve the performance of normal flows and prevent the global max-min unfairness problem caused by ill-behaved flows in DS domain.Finally, make simulation experiments for analysing the new marking policy (SAFM) and ill-behaved controlling method (DSP-IFC) advanced by this dissertation through improving the DiffServ model in NS and building simulation environment under Linux.