Some simulation results about TCP connections in ATM networks

We discuss simulation results concerning the performance of the TCP protocol when running over high-speed ATM networks. Two network topologies are considered: a simple network topology, comprising just two ATM switches and supporting 3 TCP connections, and a candidate Italian ATM network topology comprising ten ATM switches and supporting 6 TCP connections. In all simulation scenarios the TCP traac is mixed with some background traac whose level is taken as a variable parameter. Both the background traf-c and the TCP traac are either unshaped, or shaped according to the GCRA algorithm. The eeect of the background traac on the TCP protocol performance is discussed, varying the buuering capacity within nodes as well as the peak bit rate that each TCP connection is allowed to use. Numerical results clearly show that shaping the TCP traac according to xed parameters signiicantly improves both the goodput and the eeciency of the TCP connections with respect to the case in which no traac shaping is implemented. Moreover, the performances achievable with an adaptive shaping of the TCP traac (using a simpliied version of the ABR ATM transfer capability) can be observed to be extremely satisfactory.