3 research outputs found
A Comparative Study of QoS Routing Schemes That Tolerate Imprecise State Information
In large networks, maintaining precise global network state information is almost impossible. Many factors, including nonnegligible propagation delay, infrequent link state update due to overhead concerns, link state update policy, resource reservation, and hierarchical topology aggregation, have impacts on the precision of the global network state information. To achieve efficient Quality of Service (QoS) routing, a practical routing algorithm must be able to make effective routing decisions in the presence of imprecise global network state information. In this paper, we compare five QoS routing algorithms that were proposed to tolerate imprecise global network state information, safety-based routing, randomized routing, multi-path routing, localized routing, and static multi-path routing. The performance of these routing algorithms are evaluated under two link state update policies, the timer based policy and the threshold based policy. The strengths and limitations of each scheme are identified
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Novel localised quality of service routing algorithms. Performance evaluation of some new localised quality of service routing algorithms based on bandwidth and delay as the metrics for candidate path selection.
The growing demand on the variety of internet applications requires management of large scale networks by efficient Quality of Service (QoS) routing, which considerably contributes to the QoS architecture. The biggest contemporary drawback in the maintenance and distribution of the global state is the increase in communication overheads. Unbalancing in the network, due to the frequent use of the links assigned to the shortest path retaining most of the network loads is regarded as a major problem for best effort service. Localised QoS routing, where the source nodes use statistics collected locally, is already described in contemporary sources as more advantageous. Scalability, however, is still one of the main concerns of existing localised QoS routing algorithms.
The main aim of this thesis is to present and validate new localised algorithms in order to develop the scalability of QoS routing.
Existing localised routing, Credit Based Routing (CBR) and Proportional Sticky Routing (PSR), use the blocking probability as a factor in selecting the routing paths and work with either credit or flow proportion respectively, which makes impossible having up-to-date information. Therefore our proposed Highest Minimum Bandwidth (HMB) and Highest
Average Bottleneck Bandwidth History (HABBH) algorithms utilise bandwidth as the direct QoS criterion to select routing paths.
We introduce an Integrated Delay Based Routing and Admission Control mechanism. Using this technique Minimum Total Delay (MTD), Low Fraction Failure (LFF) and Low Path Failure (LPF) were compared against the global QoS routing scheme, Dijkstra, and localised High Path Credit (HPC) scheme and showed superior performance. The simulation with the non-uniformly distributed traffic reduced blocking probability of the proposed algorithms.
Therefore, we advocate the algorithms presented in the thesis, as a scalable approach to control large networks. We strongly suggest that bandwidth and mean delay are feasible QoS constraints to select optimal paths by locally collected information. We have demonstrated that a few good candidate paths can be selected to balance the load in the network and minimise communication overhead by applying the disjoint paths method, recalculation of candidate paths set and dynamic paths selection method. Thus, localised QoS routing can be used as a load balancing tool in order to improve the network resource utilization.
A delay and bandwidth combination is one of the future prospects of our work, and the positive results presented in the thesis suggest that further
development of a distributed approach in candidate paths selection may enhance the proposed localised algorithms.Umm AlQura University in Mecc