TCP-M: Multiflow Transmission Control Protocol for Ad Hoc Networks
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TCP-M: Multiflow Transmission Control Protocol for Ad Hoc Networks Nagaraja Thanthry, Anand Kalamkar, and Ravi Pendse Department of Electrical and Computer Engineering, Wichita State University, 1845 N Fairmount, Wichita, KS 67260, USA Received 2 August 2005; Revised 18 February 2006; Accepted 13 March 2006 Recent research has indicated that transmission control protocol (TCP) in its base form does not perform well in an ad hoc environment. The main reason identified for this behavior involves the ad hoc network dynamics. By nature, an ad hoc network does not support any form of quality of service. The reduction in congestion window size during packet drops, a property of the TCP used to ensure guaranteed delivery, further deteriorates the overall performance. While other researchers have proposed modifying congestion window properties to improve TCP performance in an ad hoc environment, the authors of this paper propose using multiple TCP flows per connection. The proposed protocol reduces the influence of packet drops that occurred in any single path on the overall system performance. The analysis carried out by the authors indicates a significant improvement in overall performance. Copyright © 2006 Nagaraja Thanthry et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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INTRODUCTION
The transmission control protocol (TCP) is the most widely used transport layer protocol in the networking world. Many of the features supported by the TCP were developed based on a wired network environment, although now they are also being used in wireless networks. It has been observed that the TCP does not perform well in a wireless network environment due to such issues as link failures, collision, interference, and fading. Link failures are considered one of the major causes of performance degradation. The TCP works on the principle of guaranteed delivery. When a sender does not receive an acknowledgment for a packet being transmitted, the TCP assumes that the packet is dropped due to congestion and therefore attempts to retransmit it. In a wired network environment, packet drops generally result from network congestion, but in a wireless network, packet drops could also result from link failures. However, the TCP, by design, attributes packet drops to network congestion and attempts to avoid this by reducing the transmission rate. This further degrades network performance in a wireless network environment. Apart from the reduction in transmission rate, TCP behavior also results in an increase in the retransmission timeout period (RTO), which further delays packet delivery. This situation further deteriorates when the TCP is used in its base form in an ad hoc network environment. An ad
hoc network is formed on the fly and can be characterized by the absence of a centralized authority, random network topology, high mobility, and a high degree of link failures.
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