Congestion control in TCP: performance of binary congestion notification enhanced TCP compared to Reno and Tahoe TCP
Dorgham Sisalem, Henning G. Schulzrinne · 2002
In previous work, we proposed to enhance TCP's congestion control mechanisms using binary congestion notification (BCN). With this combined scheme called BCN-TCP congestion is indicated both by packet losses and by having switches inform sources about their congestion state by setting a congestion bit. Unlike other studies, our approach maintains the basic elements of TCP's congestion control mechanisms and models the response of TCP to the congestion bit to that of the ATM available bit rate service (ABR). We compared the performance of BCN-TCP to the versions currently implemented in hosts (Tahoe and Reno TCP). However BCN-TCP only offered significant performance improvements if part of the path contained ATM ABR services. In this paper we present further results on the performance of BCN-TCP when used in heterogeneous environments, i.e., Internet paths where only some end systems support BCN-TCP. We also consider the fairness between long and short-haul connections and discover that BCN-TCP treats long-haul connections worse than Tahoe and Reno TCP. We investigate the cause of this unfairness and suggest possible remedies.