Graduation Year

2004

Document Type

Thesis

Degree

M.S.C.S.

Degree Granting Department

Computer Science

Major Professor

Labrador, Miguel A.

Keywords

congestion control, high bandwidth-delay product network

Abstract

Next generation optical networks will soon provide users the capability to request and obtain end-to-end all optical 10 Gbps channels on demand. Individual users will use these channels to exchange large amounts of data and support applications for scientific collaborative work. These new applications, which expect steady transfer rates in the order of Gbps, will very likely use either TCP or a new transport layer protocol as the end-to-end communication protocol. This thesis investigates the performance of TCP and newer TCP versions over High Bandwidth Delay Product Channels (HBDPC), such as the on demand optical channels described above. In addition, it investigates the performance of these new TCP versions over wireless networks and according to old issues such as fairness. This is particularly important to make adoption decisions.

Using simulations, it is shown that 1) the window-based mechanism of current TCP implementations is not suitable to achieve high link utilization and 2) congestion control mechanisms, such as the one utilized by TCP Vegas and Westwood are more appropriate and provide better performance. Modifications to TCP Vegas and Scalable TCP are introduced to improve the performance of these versions over HBDPC. In addition, simulation results show that new TCP proposals for HBDPC, although they perform better than current TCP versions, still perform worse than TCP Vegas. Also, it was found that even though these newer versions improve TCP's performance over their original counterparts in HBDPC, they still have performance problems in wireless networks and present worse fairness problems than their old counterparts.

The main conclusion of this thesis is that all these versions are still based on TCP's AIMD strategy or similar and therefore continue to be fairly blind in the way they increase and decrease their transmission rates. TCP will not be able to utilize the foreseen optical infrastructure adequately and support future applications if not redesigned to scale.

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