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TCP congestion control
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<p><a href="/facts/Transmission_Control_Protocol/WW4sPrt9">Transmission Control Protocol</a> (TCP) uses a <a href="/facts/Congestion_control/9ohkRMso">congestion control</a> algorithm that includes various aspects of an <a href="/facts/Additive_increase%2fmultiplicative_decrease/GmlKkQtu">additive increase/multiplicative decrease</a> (AIMD) scheme, along with other schemes including slow start and a congestion window (CWND), to achieve congestion avoidance. The TCP congestion-avoidance algorithm is the primary basis for <a href="/facts/Congestion_control/9ohkRMso">congestion control</a> in the Internet. Per the <a href="/facts/End-to-end_principle/6RkKmdUm">end-to-end principle</a>, congestion control is largely a function of <a href="/facts/Internet_host/HPNcFXHk">internet hosts</a>, not the network itself. There are several variations and versions of the algorithm implemented in <a href="/facts/Protocol_stack/Btj9FtwJ">protocol stacks</a> of <a href="/facts/Operating_system/8XTuvMh2">operating systems</a> of computers that connect to the <a href="/facts/Internet/Xw1rVvJU">Internet</a>. </p><p>To avoid <a href="/facts/Congestive_collapse/9ohkRMso">congestive collapse</a>, TCP uses a multi-faceted congestion-control strategy. For each connection, TCP maintains a CWND, limiting the total number of unacknowledged packets that may be in transit end-to-end. This is somewhat analogous to TCP's <a href="/facts/Sliding_window/TvkveH2L">sliding window</a> used for <a href="/facts/Transmission_Control_Protocol/WW4sPrt9">flow control</a>. </p>