Within the RTO period, then it assumes that the packet is lost. TCP updates the RTO period with the current round-trip delay calculated on the arrival of every ACK packet. Receiver window (which is advertised by the TCP receiver and carries the information about the receiver's buffer size), is called congestion avoidance, as it tries to avoid increasing the congestion window exponentially, which will surely worsen the congestion in the network. This linear growth, which continues until the congestion window reaches the Once it reaches the slow-start threshold (in Figure 9.2, the slow-start threshold is initially taken as 16 for illustration), it grows linearly, adding one MSS to the congestion window on every ACK received. Figure 9.2 shows the variation of the congestion window in TCP the slow start phase is between points A-B. Successful acknowledgment of all the segments in the current congestion window, is called slow-start (a more appropriate name would be exponential start, as it actually grows exponentially) and it continues until the congestion window reaches the slow-start threshold (the slow-start threshold has an initial value of 64 KB). This doubling of the congestion window with every Once the ACK is received within the retransmission timeout ( RTO) period, the congestion window is doubled and two MSSs are originated. It sends out one MSS and waits for the ACK. The TCP sender starts the session with a congestion window value of one MSS. TCP regulates the number of packets sent to the network by expanding and shrinking the congestion window. CongestionĬontrol deals with excess traffic in the network which may lead to degradation in the performance of the network, whereasįlow control controls the per-flow traffic such that the receiver capacity is not exceeded. The major responsibilities of TCP include congestion control, flow control, in-order delivery of packets, and reliable transportation of packets. The length of each segment limited by a maximum segment size ( MSS)]. Of bytes from the application layer is split into TCP segments, TCP is a reliable, end-to-end, connection-oriented transport layer protocol that provides a byte-stream-based service [the stream This section discusses the issues and challenges that TCP experiences when used in ad hoc wireless networks as well as some of the existing solutions for overcoming them. The seamless operation of application-level protocols such as FTP, SMTP, and HTTP across the integrated ad hoc wireless networks and the Internet. Possible, it is essential to have mechanisms that can improve TCP's performance in ad hoc wireless networks. Since TCP is widely used today and the efficient integration of an ad hoc wireless network with the Internet is paramount wherever Extensions of TCP that provide improved performance across wired and single-hop wireless networks were discussed in Chapter 4. TCP in its traditional form was designed and optimized only for wired networks. In the network has been an important feature leading to graceful degradation of the services offered by the network at times of extreme congestion. Its elegant and simple design have not only contributed to the success of the Internet, but also have made TCP an influencing protocol in the design of many of the other protocols and applications. Its reliability, end-to-end congestion control mechanism, byte-stream transport mechanism, and, above all, It transports more than 90% percent of the traffic The transmission control protocol ( TCP) is the most predominant transport layer protocol in the Internet today. Learn More Buy 9.5 TCP OVER AD HOC WIRELESS NETWORKS Ad Hoc Wireless Networks: Architectures and Protocols
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