Abstract:
This dissertation investigates and improves the performance of the point-to-multipoint Available Bit Rate (ABR) service in ATM networks. We propose two new consolidation algorithms called "Rate-Queue Balanced" (RQB) and "Selective Backward Resource Management Feedback" (SBF). The RQB employs the Explicit Rate (ER) and Queue Length (QL) field in Backward Resource Management (BRM) cell as parameters to compute a Response-Accuracy Index (RAI) at a branch point. The RQB algorithm is adaptive to the network condition and the branch point uses it as an indication rather to work in a fast response or high accuracy way, however, at a little more expenses of buffer size in branch point nodes. SBF is an effective capacity tracking algorithm that can function in dynamic network scenarios. It achieves a fast response and low consolidation noise by selectively forwarding BRM cell from the most congested branch to the source instead of waiting for BRM cell from all branches. Simulation results show that the proposed algorithms outperform the already existed schemes in terms of response time and consolidation noise. The performance, i.e. the response time and Allowed Cell Rate (ACR) of the source is mathematically analyzed. They show relatively good agreement with the simulation results and can be applied for using in various network topologies. In addition, in this dissertation, the interoperability issue for the multicast ABR services is investigated. We address on a response time, a consolidation noise and an effect of asymmetrical Round Trip Delay (RTD) from branch point to destinations aspects. We found from the simulation results that the consolidation algorithm used at the most upper stream branch point (the nearest one to the source), especially in WAN configuration, plays an important role in determining the performance of the network. While consolidation algorithm used at the lower stream branch point affects the network performance insignificantly In LAN/MAN environment, due to a small difference in time delay, we can say that the consolidation algorithm insignificantly affects the network performance. Therefore, implementation simplicity of the consolidation algorithms should be a major consideration issue for employing to this kind of network.
