Document Type
Thesis - University Access Only
Award Date
2010
Degree Name
Master of Science (MS)
Department / School
Electrical Engineering and Computer Science
Abstract
Transmission control protocol (TCP) plays one of the most important parts in reliable network transmission scenario, so improving the performance of traditional TCP over modem network communication is an indispensable research field. In a heterogeneous (wired-cum-wireless) network environment, TCP performance is inefficient because it lacks the ability to recognize when a lost packet is caused by network congestion or bit errors. Among the TCP versions, TCP Vegas's ability to detect network congestion and prevent packet lost during transmission is superior; it also performs better than TCP Reno, which is the most popular version of TCP. However, TCP Vegas still cannot distinguish if the packet loss resulted from network congestion or link errors and, moreover, suffers serious performance decreases in a heterogeneous network. In this thesis, the common TCP packet losses recognition problems derived from wireless connections are stated and explained. Popular TCP congestion control mechanisms are reviewed and analyzed. A modified TCP Vegas congestion control mechanism is proposed which classifies the reason for packet loss by analyzing the queuing delay and packet interval. There are two major procedures added within TCP Vegas, the packet losses reasoning algorithm and packet losses interval observation. The packet losses reasoning algorithm analyzes transmission queuing delay and sets the congestion flag after a packet is dropped in order to distinguish wireless errors from congestion errors. The packet losses interval observation procedure evaluates the packets dropping condition and changes the size of congestion window for preventing throughput degradation. This modified TCP Vegas congestion control mechanism intends to overcome the performance degradation problem found in the original TCP Vegas. For validation, the modification is implemented on TCP Vegas module in NS-2 Network Simulator. The modified TCP Vegas is compared with the original TCP Vegas in each test scenario. At last, the simulation result is evaluated and analyzed to demonstrate the improvements.
Library of Congress Subject Headings
Network performance (Telecommunication)
Computer networks -- Workload -- Management
Computer network protocols
Format
application/pdf
Number of Pages
74
Publisher
South Dakota State University
Recommended Citation
Chao, Po-Sung, "Improving Heterogeneous Local Area Networks Performance by Modified TCP Vegas Congestion Control Mechanism" (2010). Electronic Theses and Dissertations. 1649.
https://openprairie.sdstate.edu/etd2/1649