Evaluation and refinement of tcps congestion control for performance enhancement in wired cum wireless environments

Abstract

Deployment of wireless links along with wired links has made expansion of newlinethe Internet feasible even in remote places. TCP/IP protocol suite is an newlineintegral part of the Internet. Congestion control of TCP plays a vital role in the newlineperformance of the Internet. TCP s unconditional flow control in case of a newlinepacket loss has always been a concern for researchers. Further, the halving newlinecongestion window in such conditions without taking into account the current newlinenetwork state is also considered inappropriate. The problem is compounded newlinein wireless networks where packet losses occur often due to channel errors newlinerather than the shortfall in the available bandwidth. In this situation, TCP s newlineconservative behaviour may underutilise the bandwidth. newlineWe, therefore, propose two approaches to address the issue of newlineunderutilisation of network resources. The first proposed approach, newlineDiscrete TCP (DTCP) differentiates slow start and congestion avoidance newlinephases while tuning the data flow over a transport connection. DTCP newlineevaluates ssthresh and cwnd before setting up parameters for flow control, newlinebased on the existing network condition to enhance the performance. The newlinesecond proposed approach, Composite TCP (CTCP) utilises the SACK newlineinformation available in a duplicate acknowledgement from a receiver along newlinewith round trip time to avoid flow control when the loss is because of a newlinerandom error. Treatment for losses are different for corruption and congestion newlineto improve efficiency. newlineThe proposed schemes are compared and analysed with various existing newlineschemes with the help of extensive simulations using ns-2. Results of newlinesimulation based experiments indicate significant performance improvement newlineof DTCP and CTCP on erroneous links over heterogeneous networks and newlineconfirm its suitability. Either of the approaches can be used alone to refine newlinecongestion control of TCP according to requirements. newline newline