On the impact of link layer retransmission schemes on TCP over 4G satellite links

We study the impact of reliability mechanisms introduced at the link layer on the performance of transport protocols in the context of 4G satellite links. Specifically, we design a software module that performs realistic analysis of the network performance, by utilizing real physical layer traces of a 4G satellite service. Based on these traces, our software module produces equivalent link layer traces, as a function of the chosen link layer reliability mechanism. We further utilize the link layer traces within the ns-2 network simulator to evaluate the impact of link layer schemes on the performance of selected Transmission Control Protocol (TCP) variants. We consider erasure coding, selective-repeat automatic request (ARQ) and hybrid-ARQ link layer mechanisms, and TCP Cubic, Compound, Hybla, New Reno and Westwood. We show that, for all target TCP variants, when the throughput of the transport protocol is close to the channel capacity, using the ARQ mechanism is most beneficial for TCP performance improvement. In conditions where the physical channel error rate is high, hybrid-ARQ results in the best performance for all TCP variants considered, with up to 22% improvements compared to other schemes

ResTP: A Configurable and Adaptable Multipath Transport Protocol for Future Internet Resilience

Motivated by the shortcomings of common transport protocols, e.g., TCP, UDP, and MPTCP, in modern networking and the belief that a general-purpose transport-layer protocol, which can operate efficiently over diverse network environments while being able to provide desired services for various application types, we design a new transport protocol, ResTP. The rapid advancement of networking technology and use paradigms is continually supporting new applications. The configurable and adaptable multipath-capable ResTP is not only distinct from the standard protocols by its flexibility in satisfying the requirements of different traffic classes considering the characteristics of the underlying networks, but by its emphasis on providing resilience. Resilience is an essential property that is unfortunately missing in the current Internet. In this dissertation, we present the design of ResTP, including the services that it supports and the set of algorithms that implement each service. We also discuss our modular implementation of ResTP in the open-source network simulator ns-3. Finally, the protocol is simulated under various network scenarios, and the results are analyzed in comparison with conventional protocols such as TCP, UDP, and MPTCP to demonstrate that ResTP is a promising new transport-layer protocol providing resilience in the Future Internet (FI)

Satellite Networks: Architectures, Applications, and Technologies

Since global satellite networks are moving to the forefront in enhancing the national and global information infrastructures due to communication satellites' unique networking characteristics, a workshop was organized to assess the progress made to date and chart the future. This workshop provided the forum to assess the current state-of-the-art, identify key issues, and highlight the emerging trends in the next-generation architectures, data protocol development, communication interoperability, and applications. Presentations on overview, state-of-the-art in research, development, deployment and applications and future trends on satellite networks are assembled

ARQ protocol for joint source and channel coding and its applications

Shannon\u27s separation theorem states that for transmission over noisy channels, approaching channel capacity is possible with the separation of source and channel coding. Practically, the situation is different. Infinite size blocks are needed to achieve this theoretical limit. Also, time-varying channels require a different approach. This leads to many approaches for source and channel coding. This dissertation will address a joint source and channel coding that suits Automatic Repeat Request (ARQ) application and applies it to packet switching networks. Following aspects of the proposed joint source and channel coding approach will be presented: The design of the proposed joint source and channel coding scheme. The approach is based on a variable length coding scheme which adapts the arithmetic coding process for joint source and channel coding. The protocol using this joint source and channel coding scheme in communication systems. The error recovery technique of the proposed scheme is presented. The application of the scheme and protocol. The design is applied to wireless TCP network and real-time video transmissions. The coding scheme embeds the redundancy needed for error detection in source coding stage. The self-synchronization property of lossless compression is utilized by decoder to detect channel errors. With this approach, error detection may be delayed. The delay in detection is referred to as error propagation distance. This work analyzes the distribution of error propagation distance. The error recovery technique of this joint source and channel coding for ARQ (JARQ) protocol is analyzed. Throughput is studied using signal flow graph for both independent channel and nonindependent channels. A packet combining technique is presented which utilizes the non-uniform distribution of error propagation distance to increase the throughput. The proposed scheme may be applied to many areas. In particular, two applications are discussed. A TCP/JARQ protocol stack is introduced and the coordination between TCP and JARQ layers is discussed to maximize system performance. By limiting the number of retransmission, the proposed scheme is applied to real-time transmission to meet timing requirement

An improved eifel algorithm for TCP over wireless links

Master'sMASTER OF SCIENC

End-to-End Resilience Mechanisms for Network Transport Protocols

The universal reliance on and hence the need for resilience in network communications has been well established. Current transport protocols are designed to provide fixed mechanisms for error remediation (if any), using techniques such as ARQ, and offer little or no adaptability to underlying network conditions, or to different sets of application requirements. The ubiquitous TCP transport protocol makes too many assumptions about underlying layers to provide resilient end-to-end service in all network scenarios, especially those which include significant heterogeneity. Additionally the properties of reliability, performability, availability, dependability, and survivability are not explicitly addressed in the design, so there is no support for resilience. This dissertation presents considerations which must be taken in designing new resilience mechanisms for future transport protocols to meet service requirements in the face of various attacks and challenges. The primary mechanisms addressed include diverse end-to-end paths, and multi-mode operation for changing network conditions

TECHNIQUES AND PROTOCOLS FOR DISTRIBUTED MEDIA STREAMING

Ph.DDOCTOR OF PHILOSOPH

Performance of Transmission Control Protocol (TCP) Congestion Control Over Wireless Links Using Modified Snoop Protocol

Because of the burgeoning increase for data communication and multimedia services over wireless links, and rapid growth of wireless communications, many researches have been undertaken to find effective integrated protocols that satisfy this demands. Since wireless links normally show higher bit error rate and temporal disconnections compared with wired links, the losses are greater, this may also be caused by the mobility like handoff, and many wireless channel impairment errors and not just congestion. TCP deals with packet losses by applying congestion control mechanisms, which tends to degrade its performance. Many protocols have been proposed including Snoop, to alleviate this problem. Our objectives here are to study and enhance the Snoop protocol using the modified ACK called Fake Acknowledgment under various network parameters. iv In this thesis, a Fake ACK technique proposed based on the Snoop Acknowledgment procedure; this reduces the waiting time of the Fixed Host waiting for the right Acknowledgment to be received, and hence reducing the probability of initiating congestion control mechanism. The results show that the throughput of our technique is increased and the losses are decreased compared to traditional Snoop protocol, under different parameter values