期刊名称：International Journal of Electronics and Computer Science Engineering
电子版ISSN：2277-1956
出版年度：2012
卷号：1
期号：1
页码：109-114
出版社：Buldanshahr : IJECSE
摘要：TCP is a window-based flow and congestion control protocol that uses a sliding window mechanism to manage its data transmission. The purpose of this scheme is to guarantee that the sender adjusts its transmission rate to meet both sender and receiver needs. Thus, the TCP sender contains a variable denoted window determining the amount of packets it can send into the network before receiving an ACK. This variable changes dynamically over time to properly limit the connection's sending rate. The sending rate of a TCP connection is regulated by two distinct mechanisms, the flow control and the congestion control. Although these mechanisms are similar, in the sense that both attempt to prevent the connection from sending at an excessive rate, they have specific purposes. Flow control is implemented to avoid that a TCP sender overflows the receiver's buffer. Thus, the receiver advertises in every ACK transmitted a window limit to the sender. This window is named receiver advertised window (rwin) and changes over time depending on both the traffic conditions and the application speed in reading the receiver's buffer. Therefore, the sender may not increase its window at any time beyond the value specified in rwin. In contrast to flow control, congestion control is concerned with the traffic inside the network. Its purpose is to prevent collapse inside the network when the traffic source (sender) is faster than the network in forwarding data. To this end, the TCP sender also uses a limiting window called congestion window (cwnd). Assuming that the receiver is not limiting the sender, cwnd defines the amount of data the sender may send into the network before an ACK is received. Considering flow control and congestion control, the sender faces two limiting factors for its window size, namely the rwin and the cwnd. To conform with both control schemes, the TCP sender adjusts its window to the minimum between rwin and cwnd. In general, however, cwnd is considered the limiting factor of a TCP sender because the receiver's buffer is mostly large enough not to constrain the sender's transmission rate. TCP congestion control has been evolving over the years to detect congestion inside the network and promptly react to that by properly slowing down
关键词：Wireless multihop networks; Mobility Management; Adaptive communication protocols
