Wi TCP Performance Enhancement of Transmission Control Protocol in Mobile IP based Networks

Abstract

Most of the Internet applications such as file transfer, web browsing, and e-mail use TCP as a transport layer protocol which controls large fraction of traffic that travelling over Internet. TCP is designed to perform well in traditional wire line networks with the assumptions that packet losses are mainly due to network congestion where random bit error rate (BER) is negligible. Today mobile wireless access to Internet is experiencing a great deal of popularity, but TCP performs poorly in this environment because it treats any packet loss in the network as a result of network congestion and slows down its transmission rate, or even cause the TCP sender to experience series of unnecessary timeouts. As a consequence, it is important to study the TCP behavior in mobile wireless environment during handoff. However in the conventional Internet architecture mobile host can never inherently avoid the degradation of communication quality during handover. newlineWi-TCP is a new wireless end to end transmission control protocol, has been designed to support TCP handoffs in mobile IP based network by utilizing the basic features of Mobile IP, Route Optimized Mobile IP and TCP. It comprises of two modules one is implemented on sender side while other on intermediate node. In order to implement a concept, cross layer feedback module and schemes (HF_H, FF_H and FH_H) are introduced at IEEE 802.11 WLAN base stations to initiate handoff notifications. While implementing cross layer feedback module, MAC layer self s information has been considered as a decisive factor to detect handoff. Further on the basis of feedback from MAC layer, EHO-ACK and EHC-ACK are initiated at home agent/foreign agent which enabling the TCP sender to exclusively identify the handoff. newlineFurther module designed at sender which exclusively identifies the handoff. On receiving handoff notification, sender avoids retransmission and reduction in congestion window consequently, suspends transmissions, and stores congestion window and slow start threshold value.