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Chapter 1 Introduction

Chapter 1 Introduction. Two Advances in Technology. Development of Powerful Microprocessors Moore ’ s Law: The performance and capabilities of semiconductors was growing exponentially and would continue to. In 1975, Moore stated that the number of transistors doubled about every 18 months.

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Chapter 1 Introduction

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  1. Chapter 1 Introduction

  2. Two Advances in Technology • Development of Powerful Microprocessors • Moore’s Law: The performance and capabilities of semiconductors was growing exponentially and would continue to. In 1975, Moore stated that the number of transistors doubled about every 18 months. • High-speed computer networks • High-speed LANs and WANs • Gilder’s Law • George Gilder, visionary author of Telecosm • Bandwidth grows at least three times faster than computer power

  3. Definition of a Distributed System • A. Tanenbaum and M. Steen: • A collection of independent computers that appears to its users as a single coherent system • G. Coulouris, J. Dollimore, T. Kindberg: • A system in which hardware and software components located at networked computers communicated and coordinate their actions only by message passing • Motivation: resource sharing • Important aspects: • Components are autonomous • Virtually single systems (transparency)

  4. A Distributed System …

  5. Kinds of Systems

  6. Why Distributed?

  7. The Internet • Collection of computer networks • Enables programs to communicate over arbitrary distance • Makes available services • mail, file transfer, documents, telephony, ... • Communication via message passing according to Internet protocols • (IP, UDP, TCP, ICMP, SMTP, FTP, ...) • Infrastructure: backbones, routing, naming • Extensible (new services, new protocols) • Open communication channels (security!) • Technology applicable to other distributed systems

  8. intranet % % ISP % % backbone satellite link desktop computer: server: network link: A Typical Portion of the Internet

  9. Intranets • Autonomous network running Internet protocols • independent administration • boundary, where security policies are enforced • access via router/firewall • Consists of one or more LANs • Firewall • filters incoming and outgoing messages • ... sometimes too many • File services • Other servers

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