Computer Networking Chapter 1.Pdf Essay

8592 Words Apr 10th, 2011 35 Pages
CHAPTER

1
Computer Networks and the Internet

1

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STUDY COMPANION FOR COMPUTER NETWORKING, THIRD EDITION

Most Important Ideas and Concepts from Chapter 1
Nuts and bolts of computer networks. Computer networks consist of end systems, packet switches, and communication links. End systems—also called hosts—include desktop PCs, laptops, hand-held network devices (including cell phones, PDAs, and BlackBerries), sensors, and servers (such as Web and mail servers). Just as cities are interconnected by a network of roads and intersections, end systems of a computer network are interconnected by a network of communication links and packet switches. Communication links can be wired or wireless. Distributed applications. A computer
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Each ISP is a network of packet switches and communication links. Thus, the Internet is a network of networks. ISPs are roughly organized in a hierarchy. ISPs at the bottom of the hierarchy access ISPs such as residential ISPs, university ISPs, and enterprise ISPs. ISPs at the top of the hierarchy are called tier-1 ISPs and typically include long-haul intra- and intercontinental fiber links. Tier-n ISPs provide service—for a price—to tier-(n+1) ISPs. Each ISP is independently managed. However, ISPs employ a common protocol suite called the Internet Protocol, which is better known as IP. Transmission and propagation delays. Transmission and propagation delays play a critical role in the performance of many distributed applications. Perhaps the best way to understand transmission and propagation delays and their differences is to work with the Transmission versus Propagation delay applet on the textbook’s Web site. The propagation delay over a link is the time it takes a bit to travel from one end of the link to the other. It is equal to the length of the link divided by the propagation speed of the link’s physical medium. The transmission delay is a quantity that relates to packets and not bits. The transmission delay for a link is equal to the number of bits in the packet divided by the transmission rate of the link. It is the amount of time it takes to push the packet onto the link. Once a bit is pushed onto a link it needs to propagate

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