Abstract:This paper investigates the problems in explicit rate congestion avoidance algorithms for ABR service in ATM networks. It is found that the performance of the existing algorithms [2, 3, 4] depend on network conditions which vary dramatically in the real condition such as number of traversing sessions, traffic characteristics and propagation delay. In addition, this paper proposes a novel efficient and robust ABR congestion avoidance algorithm called "Fast Rate Allocation Congestion Avoidance (FRACA)". Some simulation results are presented to illustrate performance in terms of computation accuracy and switch buffer occupancy of the proposed algorithm. Moreover, the simulation results are compared with Explicit Rate Indication Congestion Avoidance (ERICA+) and Enhanced Fast Max-Min Rate Allocation (E-FMMRA) which are the well-known explicit rate switch algorithms and also compatible with ATM Forum Traffic Management Specification 4.0. From comparison, the proposed algorithm works better than both algorithms for all configuration scenarios.

Abstract. The point-to-multipoint ABR service is a very important service in ATM networks. Recently, several researchers have studied the issues on multicast ABR services and have proposed a family of consolidation algorithms. All of the previous proposed algorithms have some drawbacks such as slow response, high consolidation noise and high implementation complexity etc. Hence, we propose a new efficient consolidation algorithm which overcomes all such drawbacks. We also recognize that in point-to-multipoint ATM n etworks, there is a possibility that the branch points will adopt different consolidation algorithms. We, therefore, investigate the interoperability issue and the impact of using different types of consolidation algorithm at the upper and lower stream branch points and show that the branch points with different consolidation algorithms can work interoperably. It is concluded from the simulation results that in order to avoid the consolidation noise and get a faster response in the network the most upper st ream branch point (the nearest one to the source) has to be implemented with a high accuracy consolidation algorithm and the lower stream branch point(s) should be implemented with a fast response consolidation algorithm. Moreover, using our proposed consolidation algorithm, fast response, low consolidation noise and low implementation complexity are achieved.

SUMMARYIn this paper we propose a performance analysis of the consolidation algorithms in point-to-multipoint ABR services in ATM network. We also present a new efficient consolidation algorithm, which overcomes some drawbacks of the previous works. The performance of the previous works and our proposed consolidation algorithms are analysed mathematically. General equations for calculating the response time and allowed cell rate of the source are derived. The derived equations show relatively good agreement with simulation results and can be applied for using in various network topologies. In addition, the interoperability issue in multicast available bit rate (ABR) is investigated. It is found that the branch points implemented with different consolidation algorithms can work interoperably. It is concluded from the simulation results that the performance of the point-to-multipoint ABR services is dominated by the most upper stream branch point (the nearest one to the source), therefore, in order to avoid the consolidation noise and get a faster response in the network, the most upper stream branch point has to be implemented with a high accuracy consolidation algorithm while the lower stream branch point(s) should be implemented with a fast response consolidation algorithm with a less degree of complexity.