Congestion Control Approach for TCP by Differentiating NCL and PR upon the ERT in Wireless Mesh Networks

The main concern of wireless network is communication. Basically communication is influenced by traffic overloading. Communication congestion is one of the major issues of networks. Congestion degrades the performance of Transmission Control Protocol (TCP). TCP regulates the amount of data traffic injected by nodes into communication networks, preventing persistent network overload. In the network it is typically realized by Transmission Control Protocol (TCP), which backs off transmission of end systems upon detecting packet loss, with the assistance of active queue management algorithms, which probabilistically drop packets at the intermediate routers based on the buffer occupancy. To control congestion and improve the performance of TCP, several methods are devised and some more needed. In this paper a scheme is advised to control the congestion of TCP by differentiating Non-congestion loss and packet reordering upon the expirations of retransmission timeouts. KeywordsWireless Mesh Network, Congestion Control, TCP, Packet Reordering I. INTRODCUTION WMN is a potential network infrastructure for cheap, fast wireless access to the Internet [1]. WMNs is dynamically self-organized and automatically configured, along with the nodes in the network without extra efforts establishing and maintaining mesh connectivity among themselves. One of the main characteristicsn of WMNs is multi-hop transmission and the number of wireless hops between the sender and receiver is variable. End-to-end performance can be very poor due to variable links, because of interference and various disturbing factors in environment. This is especially true for wireless mesh networks where packets traverse several consecutive links [2]. The main design challenge is to schedule links and route packets in order to efficiently use network resources while guaranteeing fairness among users. Wireless mesh networks typically provide several paths from a source to a destination, and using paths efficiently, makes aggregation of the available resources. To improve both capacity and reliability in such networks each node can be equipped with multiple radio interfaces using a set of orthogonal channels. This channel diversity improves the performance of a single-path, while at the same time increases the possibility to create multiple interference-free paths between the sender and the receiver II. TRANSMISSION CONTROL PROTOCOL Transmission Control Protocol is the most popular connection oriented transport layer protocol used in the current internet and its congestion control algorithms are very essential for the stability of the internet. TCP has severe performance problems when operated over WMNs [3]. The principal problem of TCP lies in the congestion control mechanism. With TCP congestion control mechanism, multiple TCP connections can share network and link resources simultaneously. The quality of TCP connections degrades rapidly with the number of wireless hops in WMNs due to its inability to distinguish noncongestion losses from congestion losses. Several loss differentiation algorithms [4] are proposed to improve the performance of TCP over wireless networks. However, these algorithms have no mechanism to detect and differentiate non-congestion losses from packet reordering. TCPs inability to distinguish non-congestion loss from packet reordering may causes unnecessary retransmissions, results in slow down of the progress of cwnd and decreases the efficiency of the receiving TCP. As an output, it is an important consideration of TCP to guide the TCP sender for triggering the congestion control algorithms properly by distinguishing non-congestion losses from packet reordering in addition to network congestion when the sender receives three dupacks. TCP Congestion Control and FairnessOne of the goals of TCP is to detect and avoid network congestion. Another goal is to guarantee fairness among flows. TCP achieves both these goals by reacting to packet losses. Each packet loss is treated as a congestion loss, and the congestion window is halved. Faster flows see more congestion losses, which guarantee a certain form of fairness Packet ReorderingPacket reordering is a rather common event that poses negative effects on applications and protocols that require in-order data delivery. For TCP, the reordering of both data and acknowledgments affects performance [5]. Previous research has shown the possibility to mitigate reordering effects in a reactive and/or proactive manner Neha Patil et al, / (IJCSIT) International Journal of Computer Science and Information Technologies, Vol. 5 (6) , 2014, 7427-7429