  ATM (asynchronous transfer mode) is the technology chosen for the Broadband
Integrated Services Digital Network (B-ISDN). The ATM ABR (available bit rate)
service can be used to transport ``best-effort'' traffic. In this paper, we
extend our earlier work on the buffer requirements problem for TCP over ABR.
Here, a worst case scenario is generated such that TCP sources send a burst of
data at the time when the sources have large congestion windows and the ACRs
(allowed cell rates) for ABR are high. We find that ABR using the ERICA+ switch
algorithm can control the maximum queue lengths (hence the buffer requirements)
even for the worst case. We present analytical arguments for the expected queue
length and simulation results for different number of sources values and
parameter values.
