Performance Evaluation of Scheduling Mechanisms for Broadband Networks
نویسنده
چکیده
While today's computer networks supports only best-effort service, future packet-switching integrated-services networks will have to support real-time communication services that allow clients to transport information with performance guarantees expressed in terms of delay, delay jitter throughput and loss rate. An important issue in providing guaranteed performance service is the choice of packet service discipline at the switching nodes. Recently, a number of new service disciplines that are aimed at providing per-connection performance guarantees have been proposed in the context of high-speed packet switching networks. Of these, fair queuing algorithms have gained significance in that they offer differentiated services to different classes of traffic and attempt to maintain fairness among competing users. Weighted Fair Queuing (WFQ) is one such fair queuing scheme. This thesis introduces a modification to the original WFQ and characterizes its delay and throughput performance in comparison with the traditional WFQ. The new queuing scheme is called Hybrid FIFO-Fair Queuing (HF 2 Q) since it exhibits both First-In First-Out (FIFO) and WFQ behaviors under different conditions. The modification introduced in the virtual time updation in WFQ results in packets getting ordered as in a FIFO queuing system when the total system load is less than unity. However, when the system is overloaded, HF 2 Q behaves as traditional WFQ. These conclusions have been established from via simulation studies. This thesis also analyses the performance of Data Over Cable Service Interface Specification 1.1 (DOCSIS 1.1). iv DOCSIS 1.1 is a standard interface for cable modems, on which the IEEE 802.16 standard for Broadband Wireless Access (BWA) systems was based. DOCSIS 1.1 provides Quality of Service (QoS) guarantees to different classes of traffic via new scheduling features like packet priorities and packet fragmentation. This thesis presents a detailed performance analysis via simulations of these QoS scheduling features applicable to specific classes of traffic. The performance of two classes of service namely Unsolicited Grant Service (UGS) and Best Effort introduced by DOCSIS was studied under different network conditions. The impacts of the different DOCSIS scheduling features on the different traffic classes are thoroughly investigated and analyzed. v Acknowledgements I would like to express my sincere gratitude to my advisor Dr.David W. Petr who is also my committee chair, for his constant guidance and patience throughout this thesis, and for his motivation and support during my graduate studies here at KU. He has always been willing to take the time to help …
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