The Research Of Quality-of-Service In Optical Burst Switching Networks

In recent years, many novel high-speed transmission and switching technologies, such as optical circuit switching (OCS), optical packet switching (OPS) and optical burst switching (OBS), have been proposed. Among them, OBS is the most promising ones since it combines the advantages of OPS and OCS. Therefore, OBS is attracting more and more attentions of many researchers and institutes, and currently is regarded as a perfect backbone networking technology for the next-generation Internet.As a low layer transmission technology, OBS carries many kinds of high layer applications which have different quality of service (QoS) requirements, such as end-to-end delay, packet loss probability, would be different. How to provide QoS guarantee in OBS, and how to efficiently match with IP QoS mechanisms, is paid more attention in this dissertation. However, there are three major challenges for QoS in OBS: the limited burst header processing time in the core, the only available buffers based on FDL (Fiber Delay Line), and the one-way no-ack reservation protocol, such as Just-Enough-Time (JET). Based on the features, the dissertation has studied its QoS guarantee from the following aspects: the burst assembly and resource allocation, the contention resolution, and the data channel scheduling.In IP network, the packet classification acts as a way to guarantee QoS, and the similar one can be used to OBS networks. But the burst classification that OBS networks can support is limited, and so the QoS support in OBS faces a new challenge. Chapter 2 proposes a composite optical burst assembly technique to support QoS of OBS, which consists of the adaptive-threshold burst assembly algorithm and QoS-based random offset-time scheme. The algorithm is fit well to multi-class burst assembly, and not only matches with IP QoS mechanism based on packet classification, and also utilizes assembly capacity fairly and efficiently. The offset-time scheme can not only support OBS QoS, and also smooth the traffic's burstiness. The scheme is built on the token-bucket model and the modified Just-enough-time (JET) with burst segment selective discard (BSSD). In the scheme, the offset-time is divided into the QoS-based part, which is calculated on the basis of bursts priority and burst segment's class to support QoS, and the random part, which is determined by token bucket model to smooth the traffic burstiness The chapter also studies the performance of the technique in terms of packet loss probability (PLP), and some simulation results are shown.The mapping relationship between burst priority and packet class in literatures [62,63] and Chapter 2 cannot real-time and exactly reflect the differences of QoS requirement of packet classes, and the time-variance of their traffic. Meanwhile, it is required the burst assembly resource allocation among packet classes to be differential but fair. Hence, Chapter 3 proposes a novel optical burst assembly technique ATQ-DT+ TQ-Map, which is based on map rules and a dynamic threshold mechanism called ATQ-DT. How to map the IP QoS to burst priority is resolved by the map rules, and how to efficiently allocate assembly capacity among classes belonging to the same priority is answered by ATQ-DT, which determines the maximum share for each class, which is proportional to the current unused capacity. Among the proposed map rules, the mapping relation TQ-Map establishes is most reasonable because it considers both traffic condition and QoS requirement. Shown by simulation results, ATQ-DT with TQ-Map can most remarkably improve the packets loss probability (PLP) to support QoS.Chapter 4 simultaneously takes mapping relationship and assembly resource allocation into consideration, and proposes a novel assembly mapping mechanism, called Optimized TQ-MAP, in which the most important feature is adaptivity. In other words, it can adaptively adjust the mapping relationship with the variation of traffic load and the QoS requirements of each class. Based on nonlinear programming and differential calculus, it allocate...