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Title: Improving TCP Performance in the Mobile, High Speed, Heterogeneous and Evolving Internet
Keywords: Congestion Control, Intelligent TCP Implementation, Wireless Networks, High Speed Networks, The Heterogeneous and Evolving Internet
Issue Date: 12-Aug-2009
Source: WU XIUCHAO (2009-08-12). Improving TCP Performance in the Mobile, High Speed, Heterogeneous and Evolving Internet. ScholarBank@NUS Repository.
Abstract: As the de facto standard transport protocol, TCP has contributed to the enormous success of the Internet. However, in recent years, many new types of networks with different characteristics have been deployed in the Internet. Within these new types of networks, the original assumptions of TCP congestion control, such as reliable links with low/medium bandwidth and stationary hosts, are frequently undermined, and it is very important to improve the performance of TCP in these networks. In this thesis, three very important problems are addressed to improve the performance of TCP in the context of the mobile, high speed, heterogeneous and evolving Internet. Firstly, as we deploy many different kinds of wireless networks, the mobile Internet access through heterogeneous wireless networks will become more and more popular. Since TCP congestion control is designed for stationary hosts, TCP performs quite badly when users move around these heterogeneous wireless networks and handoff occurs frequently. This problem is investigated further in this thesis, and TCP-HO, a sender+receiver centric practical adaptation for handoff, is proposed to improve the performance of TCP in heterogeneous mobile environments through exploiting explicit cooperation between fixed servers and mobile hosts. Experimental results indicate that TCP-HO can improve TCP performance substantially without adversely affecting cross traffic, even while a mobile host has only a coarse estimation of new wireless link's bandwidth. Secondly, as bandwidth in the Internet continues to grow, there will be more and more long fat network pipes with abundant residual bandwidth. It is well known that TCP cannot work well on these network pipes and a new high speed congestion control (HSCC) algorithm is needed by bandwidth-greedy and elastic applications for efficient utilization of the abundant bandwidth. Considering that there are many different kinds of applications in the Internet, the tradeoff between efficiency and friendliness is investigated further in this thesis. In this thesis, Sync-TCP, a sender-centric delay-based HSCC algorithm, is also proposed to safely ramp up the throughput of bandwidth-greedy and elastic applications. Based on queue delay (a noisy and delayed network feedback), Sync-TCP is designed to drive the network to operate around the knee and to distribute residual bandwidth fairly among competing flows, even when the number of competing flows varies and their round trip propagation delays differ significantly. Sync-TCP has been implemented in NS-2 and FreeBSD. Extensive simulations and preliminary testbed evaluations show that Sync-TCP achieves its design goals and it performs better than existing HSCC approaches including Fast TCP, Compound TCP and Cubic-TCP, especially in the trade-off between throughput and friendliness. Thirdly, these new types of networks not only bring challenges to TCP protocol, they also bring challenges on how to implement TCP. With their deployment, the Internet is becoming a highly heterogeneous inter-network and it will keep evolving continuously. Hence, TCP implementation of a host needs to run on different kinds of network pipes, and the classical TCP implementation, that uses the same congestion control mechanism for all, cannot always achieve good performance. In this thesis, TCP KentRidge, a new TCP implementation framework, is proposed for the heterogeneous and evolving Internet. This new framework is carefully designed so that new congestion control mechanisms can be added conveniently for new types of networks, and the host can intelligently apply the most appropriate congestion control mechanism to each connection based on its current environment. An initial prototype of TCP KentRidge has been implemented in FreeBSD. At the end of this thesis, future works relating to Sync-TCP and TCP KentRidge are also discussed.
Appears in Collections:Ph.D Theses (Open)

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