Resource sharing of TCP connections with different round trip times

The performance of TCP connections sharing a common link and the resulting link usage depends on the various round trip times along the connections. Expressions exist for these values only in the homogenous case and heuristics for the general case give uncertain results. In this paper we first derive an exact expression (in the setting of fluid models) for the window evolution of TCP connections with different round trip delays. We next apply this result in a particular context to derive expressions for the maximum window sizes and the throughput of TCP connections as well the idle periods and the utilization of the shared link. We show that a bias in favor of connections with short round trip delays persists even for large buffer sizes. First- and second-order approximations in buffer size are given respectively for small and large buffers. These expressions show that for small buffers small round trip times predominate in global performance while the opposite is true for large buffers