10_things_weve_learned_chapters_1_through_3 - Ten most...

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Ten most important ideas/concepts to take away 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, as well as 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 and wireless. Distributed applications: A computer network enables distributed applications. A distributed application runs on end systems and exchanges data via the computer network. Distributed applications include Web surfing, e-mail, instant messaging, Internet phone, distributed games, peer-to-peer file sharing, television distribution, and video conferencing. New distributed applications continue to be invented and deployed on the Internet. Packet switching: When one end system sends data to another the end system, the sending end system breaks the data into chunks, called packets. Similar to the process of delivering post-office mail, the Internet transports each packet separately, routing a packet to its destination using a destination address that is written into the packet. When a packet switch receives a packet, it uses the packet’s destination address to determine on which link it should forward the packet. Thus a packet switch performs “packet switching,” forwarding incoming packets to outgoing links on a packet by packet basis. Also, packet switches typically “store and forward” packets – that is, before a switch begins to forward a packet on an outgoing link, if first receives and stores the entire packet. Protocol: As defined on Page 8, a protocol defines the format and order of messages exchanged between two or more communication entities, as well as the actions taken on the transmission and/or receipt of a message or other event. Computer networks make extensive use of protocols. Figure 1.2 provides an analogy between a human protocol and a computer network protocol for messages exchanged between a Web browser and a Web server. In this example, the Web browser first sends an introductory message to the server; the server responds with its own introductory message; the browser then sends another message, requesting a specific Web page; finally, the server sends a last message, which includes the requested Web page. Circuit-switching: Computer networks constitute one major class of computer networks. Another major class of communication networks is traditional digital telephone networks. Traditional digital telephone networks do not use packet switching to move data from
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10_things_weve_learned_chapters_1_through_3 - Ten most...

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