UMA PLATAFORMA DE TESTES COM SERVIÇOS DIFERENCIADOS PARA MODELAGEM DE TRÁFEGO DE VOZ SOBRE IP: análises de desempenho e de impacto

Abstract

This work presents a platform of tests (testbed) inexpensive, constructed in a controlled environment composed by microcomputers and free softwares. It is implemented, in such platform, the differentiated service model (DiffServ), with expedited forwarding (PHB EF). It is basically considered, from the collection of metrics main of QoS (delay, jitter, loss and throughtput), the performance analysis of voice characteristic traffics, when submitted to experimental tests in some scenes and conditions. Initially, in an environment capable to differentiate traffics, flows generated by standardized voice coder/decoder (G.711 and G.726) are modeled, in which the packets size and the amount of aggregate flows are varied, in scenes with and without QoS. It is compared, after that, the behavior of flows generated by activity-silence (ON-OFF) and continuous (CBR) sources. Can be perceived in this study how much the packets size variation influence in the performance of the most priority packets. It is carried, in the sequence, a specific analysis of the aggregation factor in flows generated by ON-OFF sources, in which can be observed the action of the basic principle of the model DiffServ, where aggregate flows receive differentiated treatment. It is studied, finally, through the use of transport protocols (UDP and TCP) and of elastic flows of FTP type, how much the best effort traffic confuses the performance of voice modeled flows.