Estudo comparativo de desempenho das categorias de serviço ABR e GFR com aplicações TCP/IP sobre uma rede de acesso baseada em ATM sobre ADSL

Abstract

This work presents a comparative performance study of the ATM traffic control, realized using the ABR and GFR Service categories, in the decreasing of the ADSL bandwidth variations, which are provoked by alterations in the operational conditions and physical properties of the related ADSL link during its use. Such study, which was realized by means of modeling and simulation, considered the applications of the TCP/IP architecture. The control done by the ABR category used the ERICA and EPRCA algorithms for the ER (Explicit Rate) control, trying to extinguish problems like the discarding of cells, caused by factors like queuing delay. On the other hand, the GFR Service category implementation was realized by using the Per-VC-WRR technique, which is a combination of the FBA buffer management mechanism and the WRR scheduling mechanism. The implementation of the GFR category using an ABR control mechanism, was still considered. As result of the employment of the ATM traffic control, the ABR Service category, more specifically the ABR-ER technique that uses the ERICA+ algorithm, presented the best performance in general terms if compared with the others techniques used, considering the leveis of TCP throughput and fairness between the VCs, that had been reached.