Demonstration of the Functioning of TCP Protocol Used for Network Congestion Control

Congestion can occur when the quality of service in a network reduces as a result of a node orlink   conveying   too   many   data.   TCP   is   the   most   widely   used   protocol   for   Internet   traffic,including email, web browsing, data and an increasing portion of multimedia content deliveredin real time using the HTTP/TCP protocols. Performances of existing TCP congestion controlalgorithms   degrade significantly   when deployed over wireless   networks.  TCP was   designedprimarily for reliability as opposed to real time delivery, but the problem is particularly severefor real time applications, such as, HTTP/TCP based streaming. In this paper, we carried out aresearch on the TCP’s four related congestion control algorithms, namely: slow-start, congestionavoidance, fast retransmit and fast recovery. We studied the behaviour and implementation ofslow-start   and   congestion   avoidance   algorithms,   as   well   as   the   modifications   to   the   fastretransmit and fast recovery. We used the OPNET Network Model as our methodology. The TCPperformance   on   the   network   was   modeled,   first   without   background   traffic   and   then   withbackground   traffic.   We   compared   these   algorithms  using   the   same   network   model   todeterministically   check   several   scenarios;   and   simulations   were conducted   to   ascertain   thedifferences   between   the   congestion   control   algorithms   studied   and   OPNET’s  software.  Theresults gotten showed that using different algorithms, traffic could actually be fine tuned in thenetwork being modeled so as to achieve higher Performance. The adjustments were done in theOPNET simulator