Research On The Scheme Of Quality-of-Service In Optical Burst Switching Networks Based On NS2

Optical Burst Switching(OBS) has been proposed as a new optical switching technology combining the advantages of Optical Circuit Switching(OCS) and Optical Packets Switching(OPS). As a low layer transmission technology, OBS must be able to provide QoS guarantee for many kinds of applications on high layer. So the QoS implementation on OBS network has become a hot research topic in this field.In OBS networks, Differentiated services(DiffServ) support is a very important issue. The dissertation has studied DiffServ support in OBS networks from the following aspects: the data channel scheduling, and resource reservation protocol. In this thesis we introduced the OBS network background, the basic concept and several key technologies. The research topics and our contributions are as follows.OBS simulation platform is obtained by extend each module of NS2 in this dissertation. After research the channel scheduling algorithm and wavelength grouping strategy, A new data channel scheduling mechanism (IWG-BFVF) is proposed to support relative DiffServ in Chapters 4. IWG is obtained by improved the wavelength grouping technology, it can adjust the number of wavelength for each priority traffics dynamically, according to the various changes in the business. This mechanism integrates Fiber Delay Line with BF-VF algorithm to schedule the data burst to the best channel void. So it can make better use of channel resources and reduce the overall loss rate.The existing resource reservation scheme for OBS networks is called just-enough-time (JET).The extra offset time is used in PJET scheme to reduce the data loss ratio of high-priority bursts markedly. To support absolute DiffServ in OBS networks, a new method using extra offset times is presented in Chpater5. This method can be used in JET-based OBS networks, and is called IAPJET(Improved Absolute PJET). IAPJET algorithm not only can ensure the data loss ratio of guaranteed traffic is not higher than the maximum, but also minimize the burst loss ratio of non-guaranteed traffic. And it has a good tolerance for high traffic load intensity.