Enhanced Ticket - Based Qos Routing Algorithms

Quality of Service (QoS) routing in computer networks is an important component in QoS architectures in order to provide end-to-end QoS support. Two major issues make QoS routing difficult: (1) Most of the QoS routing problems are NP-hard, such as the Delay Constraint Least Cost Routing (DCLCR) problem; (2) Imprecise network information degrades the routing performance. Using DCLCR problem as an example, we investigate the techniques for improving the performance of the existing ticket-based routing (TBR) algorithm, so that the negative impacts from the above two difficulties are reduced. There exist two major limitations in the existing TBR algorithm. First, the probing strategies are not optimized. For example, there are unnecessary ticket dropping and redundant probing in some network scenarios. Second, the decision of the ticket numbers does not take topology information into consideration. We extend TBR to address these limitations. The main achievements of this thesis are as follows: 1. Enhanced Ticket-based Routing (ETBR) algorithm is proposed to optimize the ticket probing process. Two optimization techniques are used. First, the color-based ticket distribution sets avoid incorrect ticket dropping. Second, the historical probing records optimize the ticket states, so that the redundant probing is removed. 2. Generalized Ticket-based Routing (GTBR) algorithm is proposed to allow any number of ticket types to be used to find the route, which makes the ticket-based routing algorithm more flexible.