Abstract: The purpose of this work consists in the evaluation of the TCP streams performance, when the link that causes bottleneck is also shared by the background traffic. Standard TCP is the most used protocol which sustains the majority of Internet traffic. Nevertheless TCP manifests some problems when using almost all of the available bandwidth. Based on this problems are realized different versions of TCP. The aim of this paper is to test the conflict between TCP flows bandwidth allocation. We have implemented a network which includes FTP traffic and background traffic. TCP flows are simulated so that they begin transmitting at different time. Background traffic is added besides TCP flows so that we approach a real network model. Besides studying how TCP flows compete with each other, we will evaluate if the background traffic has an impact on the behaviour of TCP flows and if it influences how the available bandwidth is shared equally among flows. We compare standard TCP Tahoe and TCP Reno, which do not differ much between each-other, but they use different algorithms so through simulation we will evaluate the changes between the bandwidth they use, even though we expect TCP flows to be more aggressive in getting the bandwidth from other TCP flows.