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Title: Providing absolute QoS in OBS networks through virtual channel reservation
Authors: GUAN XIN
Keywords: Quality of Service, IP-over-WDM networks, Priority, Conservation law,Preemptive
Issue Date: 19-Sep-2004
Citation: GUAN XIN (2004-09-19). Providing absolute QoS in OBS networks through virtual channel reservation. ScholarBank@NUS Repository.
Abstract: Optical Burst Switching (OBS) networks provide good features to support IP-over-photonics for the next generation Internet. As OBS networks are built with huge bandwidth capacity and very high speed transmission technology, it is critical and challenging to satisfy their requirements on quality of service. This thesis proposes a new absolute QoS differentiation scheme call Virtual Channel Reservation (VCR) scheme for Optical Burst Switching (OBS) networks. The scheme provides worst case guarantee on the dropping probability of higher priority classes. In existing literature, there are very few contributions that support efficient absolute QoS guarantee in OBS networks, which is critical for burst drop sensitive applications. The service differentiation among each priority class in VCR is achieved by applying the concepts of virtual channel reservation and preemption, rather than by implementing optical buffer or extra offset time. Preemption in OBS literature often means that discard of a scheduled burst or a burst in service. One potential side effect of preemption, however, is bandwidth underutilization in multi-node scenarios. To address this problem, we also contribute a new informing header (i-header) mechanism. Simulations are conducted to evaluate the performance of VCR, both with and without i-headers. Results show that VCR without i-headers is able to meet the absolute QoS requirements in both single-node and multi-node scenarios. In addition, the introduction of i-header effectively reduces downstream bandwidth wastage caused by preemption in the multi-node scenario. The contribution of VCR and i-header is significant for the following practical reasons. Firstly, VCR does not use optical buffers or extra offset time to achieve service differentiation; hence the problem of path length priority effect or long end-to-end delay problems will not arise. Secondly, VCR conforms theoretically to the Conservation Law; hence as far as overall dropping probability is concerned, VCR will outperform other QoS techniques like Guard Channel (GC) and JET QoS schemes. The last statement will be verified both theoretically and by the many simulation scenarios presented in the thesis.
Appears in Collections:Master's Theses (Open)

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