On the Interaction between TCP and the Wireless Channel in CDMA2000 Networks

In this work, we conducted extensive active measurements on a large nationwide CDMA2000 1xRTT network in order to characterize the impact of both the Radio Link Protocol and more importantly, the wireless scheduler, on TCP. Our measurements include standard TCP/UDP logs, as well as detailed RF layer statistics that allow observability into RF dynamics. With the help of a robust correlation measure, normalized mutual information, we were able to quantify the impact of these two RF factors on TCP performance metrics such as the round trip time, packet loss rate, instantaneous throughput etc. We show that the variable channel rate has the larger impact on TCP behavior when compared to the Radio Link Protocol. Furthermore, we expose and rank the factors that influence the assigned channel rate itself and in particular, demonstrate the sensitivity of the wireless scheduler to the data sending rate. Thus, TCP is adapting its rate to match the available network capacity, while the rate allocated by the wireless scheduler is influenced by the sender's behavior. Such a system is best described as a closed loop system with two feedback controllers, the TCP controller and the wireless scheduler, each one affecting the other's decisions. In this work, we take the first steps in characterizing such a system in a realistic environment

TCP over CDMA2000 Networks: A Cross-Layer Measurement Study

Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport layer, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler and the radio link protocol in a commercial CDMA2000 network and assess their impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, with the help of a robust correlation measure, Normalized Mutual Information, we were able to quantify the impact of the wireless scheduler and the radio link protocol on various TCP parameters such as the round trip time, throughput and packet loss rate

The Performance of a Second Generation Service Discovery Protocol In Response to Message Loss

We analyze the behavior of FRODO, a second generation service discovery protocol, in response to message loss in the network. Earlier protocols, like UPnP and Jini rely on underlying network layers to enhance their failure recovery. A comparison with UPnP and Jini shows that FRODO performs more efficiently in maintaining consistency, with shorter latency, not relying on lower network layers for robustness and therefore functions correctly on a simple lightweight protocol stack

Design of SNACK mechanism for wireless TCP with New Snoop

TCP is the most widely adopted transport layer communication protocol. In heterogeneous wired/wireless networks, however, the high packet loss rate over wireless links can trigger unnecessary execution of TCP congestion control algorithms, resulting in performance degradation. TCP performs poorly on wireless links with bursts losses, when it is forced to rely on limited information available from batched acknowledgements, (i.e., multiple packets are acknowledged with one acknowledgment packet). In this paper, a Selective Negative Acknowledgement (SNACK) mechanism is designed to overcome the limitation of batched acknowledgments. A new link layer retransmission protocol, called, SNACK-NS (New Snoop), is proposed. Through the detection and retransmission functions that are provided by the two protocol components of SNACK-NS, namely, SNACK-Snoop and SNACK-TCP, the transmission performance of TCP over wireless network is greatly enhanced in both fixed host (FH) to mobile host (MH) and MH to FH transmissions.published_or_final_versio

Simulation based Study of TCP Variants in Hybrid Network

© ASEE 2011Transmission control protocol (TCP) was originally designed for fixed networks to provide the reliability of the data delivery. The improvement of TCP performance was also achieved with different types of networks with introduction of new TCP variants. However, there are still many factors that affect performance of TCP. Mobility is one of the major affects on TCP performance in wireless networks and MANET (Mobile Ad Hoc Network). To determine the best TCP variant from mobility point of view, we simulate some TCP variants in real life scenario. This paper addresses the performance of TCP variants such as TCP-Tahoe, TCP-Reno, TCP-New Reno, TCPVegas, TCP-SACK and TCP-Westwood from mobility point of view. The scenarios presented in this paper are supported by Zone routing Protocol (ZRP) with integration of random waypoint mobility model in MANET area. The scenario shows the speed of walking person to a vehicle and suited particularly for mountainous and deserted areas. On the basis of simulation, we analyze Round trip time (RTT) fairness, End-to-End delay, control overhead, number of broken links during the delivery of data. Finally analyzed parameters help to find out the best TCP variant

TCP-Swift: An end-host enhancement scheme for TCP over satellite IP networks

A new transport layer protocol called TCP-Swift is proposed for enhancing the TCP performance over satellite IP networks. TCP-Swift replaces the conventional TCP slow start and fast recovery algorithms by speedy start and speedy recovery. With speedy start, a TCP-Swift sender opens up its congestion window in only two round trip times. This significantly shortens the time needed in probing the network for equilibrium state. With speedy recovery, we can infer the cause of a packet loss by observing the ACK stream received at the sender. If the loss is due to wireless transmission error, the sender's congestion window can be re-opened up more aggressively to fully utilize the available satellite link bandwidth. We show that TCP-Swift outperforms existing TCP schemes by simulations.published_or_final_versio