Dynamic Congestion Control Mechanism in Mobile Adhoc Network: TCP Westwood-DCC

Transmission control protocol faces a problem of packet loss differentiation in the wireless and mobile adhoc network. Congestion control is not properly done here. It cannot manage the congestion window as per type of loss and it reduces Congestion window unnecessarily and that degrades the performance. TCP Westwood cannot identify congestion or link failure loss, and it cannot manage the congestion window as per available bandwidth. This paper discusses that TCP Westwood performs bandwidth estimation, setting up a congestion window and a slow start threshold. In mobile adhoc network, link failure may happen frequently, and it should be handled properly. Link failure can be detected with the help of retransmission timeout. Once timeout occurs Westwood performs congestion avoidance. Proposed Westwood manages three states of congestion 1) Avoidance 2) congestion and 3) No congestion, it updates congestion window and slow start threshold as per the status of network. It maintains congestion window dynamically. Network status is identified by estimated bandwidth and proportionality ratio. Proposed method is tested on NS2.35 and compared with the existing TCP variants. The proposed Westwood performs optimized link utilization and congestion control mechanism. Hence it gives significant performance for loss recovery.

Fairness and Friendliness Analysis of Most Reliable Transport Layer Protocol

Transport layer deals with process to process communication. It has reliable and non reliable services for communication. Transmission Control Protocol (TCP) is the most reliable protocol on transport layer. The basic version of TCP was designed by considering wired networks. Then other implementations could bring enhancement in basic design. The discussion is centered on one of the TCP version TCP Westwood with its New Reno implementation. Characteristics of fairness and friendliness with other competing connections have been evaluated and presented.