Performance of TCP over ABR on ATM backbone and with various VBR background traffic patterns

We extend our earlier studies of buffer requirements of TCP over ABR in two directions. First, we study the performance of TCP over ABR in an ATM backbone. We find that the TCP queues are at the edge router and not inside the ATM network. The edge router requires buffering equal to the sum of the receiver window sizes of the participating TCP connections. Second, we study the performance when ABR capacity is variable due to the effect of various patterns of VBR background traffic. The key factors in this study are the VBR traffic pattern, ABR feedback delays and the sensitivity of the ABR switch scheme to variance. We present our experiences in refining the ERICA+ switch scheme to handle these conditions.