BUFFER AND BANDWIDTH ALLOCATION FOR TCP DATA TRAFFIC - EXPERIMENTAL RESULTS

This paper discusses the dimensioning of buffers and the bandwidth all ocation for data traffic in the ATM network. Data traffic is notorious ly complex and bursty, making such dimensioning a difficult task. Howe ver, the COMBINE project, when dimensioning their InterWorking Units ( IWUs), adopted a Poissonian packet arrival model, based upon the argum ent that burstiness at timescales higher than that of a packet arrival are a problem to be tackled by flow control at higher layers. This pa per presents experimental results from the COMBINE testbed that show t hat this hypothesis was justified and that good TCP goodput was obtain ed based upon this dimensioning approach, due to TCP's ability to adap t to network congestion. However, it is also shown that it was the TCP algorithm that was ultimately responsible for controlling the packet loss ratio in the network and not the bandwidth allocation or buffer s ize. The results highlight the importance of taking into account the m utual influence between the ATM layer and the transport layer congesti on control algorithms.