Performance evaluation of Westwood+ TCP congestion control

Abstract

Westwood+ TCP is a sender-side only modification of the classic Tahoe/Reno TCP that has been recently proposed to improve fairness and efficiency of TCP. The key idea of Westwood+ TCP is to perform an end-to-end estimate of the bandwidth available for a TCP connection by properly counting and filtering the stream of ACK packets. This estimate is used to adaptively decrease the congestion window and slow start threshold after a congestion episode. In this way Westwood+ TCP substitutes the classic multiplicative decrease paradigm with the adaptive decrease paradigm. In this paper we report experimental results that have been obtained running Linux 2.2.20 implementations of Westwood+, Westwood and Reno TCP to ftp data over an emulated WAN and over Internet connections spanning continental and intercontinental distances. In particular, collected measurements show that the bandwidth estimation algorithm employed by Westwood+ nicely tracks the available bandwidth, whereas the TCP Westwood bandwidth estimation algorithm greatly overestimates the available bandwidth because of ACK compression. Live Internet measurements also show that Westwood+ TCP improves the goodput w.r.t. TCP Reno. Finally, computer simulations using ns-2 have been developed to test Westwood, Westwood+ and Reno in controlled scenarios. These simulations show that Westwood+ improves fairness and goodput w.r.t. Reno.

Performance evaluation of TcpHas: TCP for HTTP adaptive streaming

“…As indicated in [29], the result is a more accurate bandwidth measurement that ensures better performance when compared with NewReno and it is still fair when sharing the network with other TCP connections. Bwe is updated once per RT T .…”

“…Westwood+ estimation scheme [29]: To estimate correctly the bandwidth and alleviate the effect of ACK compression and clustering, a TCP source should observe its own link utilization for a time longer than the time needed for entire cluster transmission. For this purpose, Westwood+ modifies the bandwidth estimation (Bwe) mechanism to perform the sampling every RTT instead of every ACK reception as follows:…”

On the Use of SCTP in Wireless Networks

“…The former uses the sender-based packet pair technique, mentioned in the previous section, to estimate the bottleneck bandwidth of each path. The latter uses the same algorithm as in TCP Westwood (Mascolo et al, 2004) for the bandwidth estimation. Both aim at minimizing packet reordering.…”

Study on Westwood Algorithm Optimization

“…When data loss is detected from the destination end, congestion control will be functioned [1]. However, there are disadvantages such as high bit error rate, large latency, asymmetric bandwidth, limited mobility and energy, short-term flows existing in wireless networks, resulting in adaption problem of TCP congestion control to wireless network environment of relatively poor link quality [2].…”