Researches On Quality-of-Service Technologies In IP Networks

The reason why Internet can expand to such an enormous scale today mostly contributes to the Best-Effort design principle in TCP/IP protocol stack. This principle greatly brings down the complexity and the burden of the network core and makes it able to scale up quickly. As the fast expanding of network scale, various new network services emerge. Internet is now changing into an integrated network that transmits both data and multimedia flows. Also, the carrying foundation of traditional telecom applications is shifting into packet switching network based on IP technology. The shortcoming that original IP network lacks QoS (Quality of Service) warranty becomes increasingly critical. How to achieve QoS in IP network has become a key issue in next generation network development.This dissertation first reviews the elements of TCP/IP network and gives the definition of IP QoS together with the way to its realization. Then, on the basis of relative research works and progresses, the dissertation presents following innovative works:1. To deal with the particularity of Scavenger Service (SS) from Internet2 project, a logarithmically adaptive queue-scheduling algorithm named LAWRRQ is presented. In the algorithm, the number of active Scavenger Service flows is calculated by a time sliding window algorithm, and the bandwidth allocated for Best-Effort (BE) flows and SS flows is accordingly tuned in a logarithmical way. The tradeoff between flow number counting accuracy and cost is made by the characteristic of the logarithmic function. A looking-up table composed of flow number and total round robbing slice number resolves the computing complexity. A protection for BE queue in buffer management is also introduced. Simulation results show that compared with current algorithms recommended by Internet2, the algorithm provides more reliable bottom bandwidth guarantee for Scavenger Service flows when protecting BE flows well, and has better performance and robustness.2. The fairness between Scavenger Service micro-flows is studied. The problem that Scavenger Service is not applicable for non-adaptive flows is pointed out. Then, the study on performance of FRED queue management algorithm dealing with Scavenger Service shows the problem of many misidentifications with adaptive flows. Based on this, A MFRED algorithm is presented, in which a mechanism designed for misidentification correcting is added. Simulation results show that MFRED identifies non-adaptive flows and balances the bandwidth allocation effectively while misidentifications being greatly reduced. By means of study on therelationship between parameter nactive and actual active SS flow number in MFRED, a method of estimating SS flow number by nactive to tune the guarantee bottom bandwidth of Scavenger Service is presented and identified.3. An IE AM marking algorithm for proportional bandwidth distribution of Assured Service in DiffServ is presented. In the algorithm, the AIMD control thinking from TCP is introduced into the aggregate flow marking rate tuning. The core routers judge the congestion level according to the average length of IN queue and send out feedback information by marking the packets being forwarded to inverse direction at the moment of congestion. Based on the feedback information, the edge routers adjust their target rates in an AIMD way without communications with other edge routers. The presented algorithm is simple, adaptive and scalable. Simulations shows that the proposed algorithm realizes proportional bandwidth allocation according to committed information rate without communications between different edge routes under different network conditions.4^ Current research works on wireless mobile IP QoS are Summarized and the different schemes are compared with each other. These works are divided into four aspects: management of resource reservation, re-establishment of reservation path, design of mobile agent and integration of RSVP and mobility management. Based on some mechanisms mentioned in summarization, a QoS guarantee scheme in Fast Handovers for Mobile IPv6 architecture is presented. Finally, some basic simulations are made.