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Computer Networking Chapter 1.Pdf

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CHAPTER 1 Computer Networks and the Internet 1 2 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 …show more content…

Queuing delay and packet loss. Many packets can arrive at a packet switch roughly at the same time. If these packets need to be forwarded on the same outbound link, all but one will have to “queue,” that is, wait to be transmitted. This waiting introduces a queuing delay. Furthermore, if the queue of packets becomes very large, the packet switch’s buffer may become exhausted, causing packets to be dropped or “lost.” Queuing delay and packet loss can severely impact the performance of an application. Protocol layers. A typical computer network makes use of many protocols—easily hundreds. To deal with this complexity, the protocols are organized into layers. These protocol layers are arranged in a “stack.” For example, the Internet organizes its protocols into five layers—namely, from top to bottom: application layer, transport layer, network layer, link layer, and physical layer. The protocols of layer n use the services provided by the protocols at the layer n - 1 (the layer below). This abstract concept, 4 STUDY COMPANION FOR COMPUTER NETWORKING, THIRD EDITION often difficult to grasp at first, will become clearer as we delve into the different protocol layers. With the application-layer as the highest layer in the protocol stack, one can say that all other layers in the stack exist only to provide services to the application. Indeed this is the case, as applications are the raison d’être for computer networks. Without networked applications,

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