Some simulation results about TCP connections in ATM networks
We discuss simulation results concerning the performance of the TCP protocol when run—ning 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 sup—porting 6 TCP connections. In all simulation scenarios the TCP traffic is mixed with some background traffic whose level is taken as a variable parameter. Both the background traf—fic and the TCP traffic are either unshaped, or shaped according to the GCRA algorithm.
The effect of the background traffic on the TCP protocol performance is discussed,varying the buffering 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 traffic according to fixed parameters significantly improves both the goodput and the efficiency of the TCP connections with respect to the case in which no traffic shaping is implemented.Moreover, the performances achievable with an adaptive shaping of the TCP traffic (using a simplified version of the ABR ATM transfer capability) can be observed to be extremely satisfactory.
KeywordsATM simulation TCP traffic control traffic shaping ABR
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