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Communications via satellite introduces a number of new technical problems for mobile networks and applications. Satellite links have fundamentally different properties from terrestrial wired or wireless networks. Some of the properties include larger latency, bursty error characteristics, asymmetric capability, and unconventional network architecture. These differences have far-reaching effects on many satellite communication issues.

Internetworking and Computing over Satellite Networks's emphasis is on data networking, internetworking and distributed computing issues. The material surveys recent work in the area of satellite networks, introduces certain state-of-the-art technologies, and presents recent research results in these areas. A variety of issues involving applications, network architecture, medium access controls, multicast routing, asymmetric routing, transport protocols, TCP performance enhancement techniques, data broadcast, and information disseminations, are addressed. This is one of the first books to be focused on the internetworking and computing aspect of satellite networks.



Chapter 1. The Role of Satellite Networks in the 21st Century

In the global information infrastructure (GII), satellite networks will play an increasingly important role because of their unique benefits. This chapter briefly introduces the architecture, the vision, and the challenge of future Internet-over- satellite services and applications.
Son K. Dao

Chapter 2. Satellite Constellation Networks

The path from orbital geometry through network topology to autonomous systems
Satellite constellations are introduced. The effects of their orbital geometry on network topology and the resulting effects of path delay and handover on network traffic are described. The design of the resulting satellite network as an autonomous system is then discussed.
Lloyd Wood

Chapter 3. Medium Access Control Protocols for Satellite Communications

This chapter surveys the medium access control (MAC) protocols for satellite networks. Many such protocols have been designed to handle different types of traffic and meet different performance requirements. This chapter gives a comprehensive comparison of these protocols.
Srikanth V. Krishnamurthy, Chen Liu, Vikram Gupta

Chapter 4. Direct Broadcast Satellites and Asymmetric Routing

Advances in digital satellite communication technologies have allowed the use of broadcast-only satellites to provide Internet services. These systems, while having many unique benefits, bring about a new type of link technology — unidirectional links. Traditionally, most Internet routing protocol designs and their implementations assume that every link is bi-directional. With these broadcast-based satellite systems, the assumption is no longer true. In this chapter, we describe the challenges of dynamic asymmetric routing with unidirectional links, and explain a practical solution that has been adopted by the IETF (Internet Engineering Task Force).
Yongguang Zhang

Chapter 5. Using Satellite Links in the Delivery of Terrestrial Multicast Traffic

Multicast has been deployed and operating in the Internet since 1992. Through the provisioning of a multicast delivery service, researchers have been learning how to deliver scalable, one-to-many content. While much of the focus on multicast research continues to be on addressing the deployment challenges for the traditional Internet, other “non-traditional” infrastructures, like satellite, cable, and wireless networks are beginning to be recognized as important environments in which to provide and use multicast communication. The inherent broadcast nature of these networks suggests that multicast might be easier to provide as compared to the traditional Internet. In this chapter, we first examine how to configure a satellite network to support IP multicast. Next, we examine how to bridge Internet-based multicast sessions to a satellite network. Then, we report on our efforts to demonstrate the basic feasibility of delivering multicast sessions over a satellite network. Further, we focus on a quantitative analysis of the impact of satellite links on three network performance metrics: loss, jitter, and delay. In the final analysis, we answer the question on how and when to use satellite links in combination with terrestrial multicast-based sessions.
Kevin C. Almeroth

Chapter 6. TCP Performance Over Satellite Channels

The Transmission Control Protocol (TCP) is an integral part of many popular Internet applications, including email, file transfer, and web browsing. Historically, the performance of TCP over satellite channels has been suboptimal due to a variety of protocol algorithm and configuration issues. In this chapter, we describe the challenges that the satellite environment poses to TCP performance. We then summarize a number of standard TCP options that, when applied to a connection, can improve performance. Finally, we survey additional proposals for further improvements that are still considered to be in the research phase.
Thomas R. Henderson

Chapter 7. TCP Performance Enhancement Proxy

The Industry’s Best Practice
It is commonly perceived that Internet applications, especially those based on TCP protocol, do not perform well over satellite networks. The root of this problem is the latency incurred in a satellite link. To stay competitive, the satellite industry has developed and deployed a practical solution, called TCP Performance-Enhancement Proxy (as known as “TCP Spoofing”) to solve this problem. Although it has gained tremendous success in today’s satellite networks, its use has always been controversial among the Internet community. Its critics blast it for breaking the end-to-end principle, an orthodox of the Internet. Lately, the increasingly pervasive IPsec applications have begun to threaten the performance of satellite networks by rendering TCP Performance-Enhancement Proxy useless for IPsec-protected traffic.
Yongguang Zhang

Chapter 8. Performance Evaluation of TCP Splitting Over Satellite

In this chapter we evaluate the performance of using TCP spoofing/splitting over satellite via a model-based study and a measurement-based study. Through analysis based on a few mathematical models we attempt to develop a basic understanding of the properties of TCP dynamics when connection spoofing is used, and further identify conditions under which using spoofing provides significant or marginal performance gain. Our measurement results are obtained from a commercial direct broadcast satellite system that uses TCP splitting at the network operating center (NOC). In particular these results show the performance of TCP splitting in combination with web caching. In both the model-based and the measurement-based studies we explore the effect of various factors including file size, congestion, and connection asymmetry. We use results and analysis from our models to better explain observations from the measurement. Finally we discuss the implications our findings and conclusions have on the design, deployment and provisioning of systems using TCP spoofing/splitting.
Mingyan Liu

Chapter 9. Scheduling Data Broadcast

Data broadcast is an effective method of information dissemination in satellite networks. Communications in satellite networks are usually asymmetric — the downstream communication capacity, from information server to clients, is much greater than the upstream communication capacity, from clients to server. It is not efficient (and sometimes not possible) for clients to send explicit requests to the server and for the server to serve requests individually. In data broadcast approach, the server broadcasts data items periodically over a broadcast channel that all clients listen to, serving a large number of clients demanding for same information simultaneously. One challenge in implementing this solution is to determine the broadcast schedule, such that the clients receive the best quality of service.
In this chapter, we study the optimal broadcast scheduling problem in a pure push data broadcast system. Our study is different from other researchers in that we assume both persistent user model and impatient user model. For each model, we define different performance metrics to address the most important user concerns. The properties of schedules that optimize each metric are derived through theoretical analysis. Based on theoretical results, we propose a heuristic algorithm for producing near-optimal schedules on-line. Performance evaluation results are also presented.
Shu Jiang, Nitin H. Vaidya

Chapter 10. Information Dissemination Applications

Satellite networks have unique advantage in applications like rapid deployment, situation awareness, and emergency response. The satellite network is often paired with terrestrial wireless networks to form a hybrid satellite-wireless infrastructure to support user mobility [Zhang and Dao, 1996; Dao and Perry, 1996]. However, the mismatches in characteristics of satellite and terrestrial wireless networks must be handled properly to allow effective utilization of available bandwidth, and timely delivery of highly relevant information. We have developed an Intelligent Information Dissemination Services (IIDS) model to address this. We believe it is the right model to support the dissemination and maintenance of extended situation awareness throughout such a network information infrastructure in a seamless manner.
Eddie C. Shek, Son K. Dao, Darrel J. Van Buer


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