Throughput and fairness of multiple TCP connections in wireless networks

TCP suffers from poor throughput performance in wireless networks. Furthermore, when multiple TCP connections compete at the base station, link errors and congestion lead to serious unfairness among the connections. Although the issue of TCP performance in wireless networks has attracted significant attention, most reports focus only on TCP throughput and assume that there is only a single connection in a congestion-free network. This paper studies the throughput and fairness of popular improvement mechanisms (the Snoop [8] and ELN [5]) and TCP variants with multiple TCP connections. Simulation results show that the improvement mechanisms under investigation are effective to improve TCP throughput in a wireless network. However, they cannot provide fairness among multiple TCP connections. From the studies presented, it is concluded that mechanisms to enhance TCP fairness are needed in wireless network

Enhancing TCP Performance In Wired-Cum-Wireless Networks

Increasing popularity for mobile devices has prompted industrial and academic research towards improving the performance of wireless applications. Transmission Control Protocol (TCP) plays an important role in defining a network’s performance, and its use in wireless networks has exposed several inadequacies in its operation. Tight coupling of TCP’s error and congestion control mechanisms has proven to be incompatible with the unique characteristics of wireless channels. TCP, designed for wired networks, assumes any loss of packet to be an indication of congestion in the network. Wireless networks exhibit a higher bit error rate, low and varying bandwidth, and disconnections of hosts due to mobility. All of the aforementioned reasons can result in random packet loss which is misinterpreted as a sign of congestion by TCP. Such erroneous triggering of congestion control measures can unnecessarily reduce TCP throughput. In this report, we will delve deeper into TCP’s operation, and discuss its performance issues in wired-cum-wireless networks. We also present a survey of existing schemes that tackle these issues, and introduce a new scheme called TCP-ECN to enhance TCP performance in wireless networks. The essence of the new scheme is to use Explicit Congestion Notification to enable the wireless host to distinguish between wired and wireless losses. Another facet of our scheme is to allow the base station to “freeze” the sender when it notices an imminent disconnection of the mobile host. The objective of TCP-ECN is to insulate the TCP sender from the idiosyncrasies of the wireless channel. We have both simulated and implemented the new scheme. This report details the new scheme in depth, and analyzes the test results obtained

G-Snoop: Enhancing TCP performance over wireless networks

Focusing on a general wireless network where a wireless link can be at any link along the sender-to-receiver path, a new TCP enhancement scheme, called Generalized-Snoop (G-Snoop), is proposed. Since many existing applications are built on top of TCP, it is essential that any TCP enhancement scheme should be transparent to the end-systems as well as the fixed networks. To achieve this, G-Snoop only needs to be implemented at the wireless gateways, no other parts of the network require modifications. With G-Snoop, TCP senders are shielded from non-congestion packet loss and thus no unnecessary congestion control mechanisms will be performed. Simulation results show that significant throughout gain can be obtained with G-Snoop.published_or_final_versio

TCP for Wireless Environments

Computer networks have experienced an explosive growth over the past few years, which has lead to some severe congestion problems. Reliable protocols like TCP works well in wired networks where loss occurs mostly because of congestion. However, in wireless networks, loss occurs because of bit rates and handoffs too. TCP responds all losses by congestion control and avoidance algorithms, which results in degradation of TCP\u27s End-To-End performance in wireless networks. This paper discusses different issues and problems regarding use of TCP in wireless networks and provides comprehensive survey of various schemes to improve performance of TCP in Wireless Networks

Different Transmission Control Protocol Variants in Wireless Environments

Computer networks have experienced an explosive growth over the past few years, which has lead to some severe congestion problems. Reliable protocols like TCP works well in wired networks where loss occurs mostly because of congestion. However, in wireless networks, loss occurs because of bit rates and handoffs too. TCP responds all losses by congestion control and avoidance algorithms, which results in degradation of TCP’s End-To-End performance in wireless networks. This paper discusses different issues and problems regarding use of TCP in wireless networks and provides comprehensive survey of various schemes to improve performance of TCP in Wireless Networks

Overcoming TCP Degradation in the Presence of Multiple Intermittent Link Failures Utilizing Intermediate Buffering

It is well documented that assumptions made in the popular Transmission Control Protocol\u27s (TCP) development, while essential in the highly reliable wired environment, are incompatible with today\u27s wireless network realities in what we refer to as a challenged environment. Challenged environments severely degrade the capability of TCP to establish and maintain a communication connection with reasonable throughput. This thesis proposes and implements an intermediate buffering scheme, implemented at the transport layer, which serves as a TCP helper protocol for use in network routing equipment to overcome short and bursty, but regular, link failures. Moreover, the implementation requires no modifications to existing TCP implementations at communicating nodes and integrates well with existing routing equipment. In a simulated six-hop network with five modified routers supporting four challenged links, each with only 60% availability, TCP connections are reliably established and maintained, despite the poor link availability, whereas 94% fail using standard routing equipment, i.e., without the TCP helper protocol