Tcp westwood: adaptive rate estimation for enhanced congestion control over heterogeneous networks
Ren Wang, Mário Gerla · 2004
The rapid advancement in wired and wireless communication technology has spurred significant interest in the design and development of enhanced TCP protocols using more information from network feedback. The dissertation focuses on study and development of adaptive rate estimation schemes and their application on designing enhanced TCP (Transport Control Protocol) for wired/wireless networks. This dissertation proposes and studies TCP Westwood (TCPW), an enhanced transport based on adaptive rate estimation. TCPW is a sender side only modification to improve TCP performance particularly over heterogeneous networks. The key idea of TCPW is to use rate estimation methods to set the congestion window and slow start threshold after a packet loss, which could be due to random error as well as buffer overflow. The estimation method is also used during TCP's “Agile Probing” phase, a proposed modification to the well-known Slow Start phase to better handle large bandwidth delay product and dynamic pathes. TCPW estimation has evolved starting with a method we called Bandwidth Estimation (BE), which provides significant throughput gains but acts unfriendly toward legacy protocols under certain conditions. Then we have developed adaptive methods to manage the efficiency/friendliness tradeoffs, namely, Combined Bandwidth and Rate estimation (CRB) and Adaptive Bandwidth Share Estimation (ABSE). In this dissertation, we present TCPW algorithms: including estimation techniques, Load Gauge, and Agile Probing. We conduct simulation and measurement studies to evaluate our algorithms and strategies and compare with other similar or related approaches, showing the performance gains in efficiency, fairness, and friendliness. Significant efficiency gains can be obtained for large leaky dynamic pipes, while maintaining fairness. Under a more appropriate criterion for friendliness, i.e. “opportunistic friendliness”, TCPW is shown to have good, and controllable, friendliness.