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Westwood+ is a sender-only modification of TCP Reno that optimizes the performance of TCP congestion control over both wired and wireless networks. TCP Westwood+ is based on end-to-end bandwidth estimation to set the congestion window and slow-start threshold after a congestion episode, that is, after three duplicate acknowledgments or a ...
Standard TCP recommendations as per RFC 2581 and RFC 5681 call for congestion window to be halved for each packet lost. Effectively, this process keeps halving the throughput until packet loss stops. Once the packet loss subsides, slow start kicks in to ramp the speed back up.
In TCP, after slow start, the additive increase parameter is typically one MSS (maximum segment size) per round-trip time, and the multiplicative decrease factor is typically 1/2. Protocols [ edit ]
TCP Westwood relies on mining the ACK stream for information to help it better set the congestion control parameters: Slow Start Threshold (ssthresh), and Congestion Window (cwin). In TCP Westwood, an "Eligible Rate" is estimated and used by the sender to update ssthresh and cwin upon loss indication, or during its "Agile Probing" phase, a ...
BIC TCP (Binary Increase Congestion control) is one of the congestion control algorithms that can be used for Transmission Control Protocol (TCP). BIC is optimized for high-speed networks with high latency: so-called long fat networks. For these networks, BIC has significant advantage over previous congestion control schemes in correcting for ...
Modern implementations of TCP contain four intertwined algorithms: slow start, congestion avoidance, fast retransmit, and fast recovery. [55] In addition, senders employ a retransmission timeout (RTO) that is based on the estimated round-trip time (RTT) between the sender and receiver, as well as the variance in this round-trip time. [56]
The slow-start protocol performs badly for short connections. Older web browsers created many short-lived connections and opened and closed the connection for each file. This kept most connections in the slow start mode. Initial performance can be poor, and many connections never get out of the slow-start regime, significantly increasing latency.
Most TCP congestion control algorithms rely on measuring the occurrence of packet drops to determine the available bandwidth between two ends of a connection. The algorithms speed up the data transfer until packets start to drop, then slow down the transmission rate.