The Impact of Network Variabilities on TCP Clocking Schemes


TCP employs a self-clocking scheme that times the sending of packets. In that, the data packets are sent in a burst when the returning acknowledgement packets are received. This self-clocking scheme (also known as ack-clocking) is deemed a key factor to the burstiness of TCP traffic and the source of various performance problems --- high packet loss, long delay, and high delay jitter. Previous work has suggested contradictively the effectiveness of TCP pacing as a remedy to alleviate the traffic burstiness.

In this paper, we analyze systematically and in more robust experiments the impact of network variabilities on the behavior of TCP clocking schemes. We find that 1) aggregated packing traffic could be burstier than aggregated ack-clocking traffic. Physical explanation and experimental simulations are provided to support this argument. 2) The round-trip time heterogeneity and flow multiplexing significantly influence the behaviors of both ack-clocking and pacing schemes. Evaluating the performance of clocking schemes without considering these effects is prone to inconsistent results. 3) Pacing outperforms ack-clocking in more realistic settings from traffic burstiness point of view.


Kuan-Ta Chen, Polly Huang, Chun-Ying Huang, and Chin-Laung Lei, "The Impact of Network Variabilities on TCP Clocking Schemes," IEEE Global Internet, March 2005.


@inproceedings{chen05:clocking, author = {Kuan-Ta Chen and Polly Huang and Chun-Ying Huang and Chin-Laung Lei}, title = {The Impact of Network Variabilities on {TCP} Clocking Schemes}, booktitle = {Proceedings of the 8th Global Internet Symposium in conjunction with IEEE INFOCOM}, pages = {97--102}, year = {2005}, location = {Miami Florida USA} }