大学计算机基础英语教学 (2)

Structure of LAN

The structure of LAN is following the structure of network, also been called topology of network. Network topology is the arrangement of the various elements (links, nodes, etc.) of a computer network. Essentially, it is the topological structure of a network and may be depicted physically or logically. Physical topology is the placement of the various components of a network, including device location and cable installation, while logical topology illustrates how data flows within a network, regardless of its physical design. Distances between nodes, physical interconnections, transmission rates, or signal types may differ between two networks, yet their topologies may be
Wired
technologies Wireless technologies
By Scale

computer networks may be classified according to the scale, in Local Area Network (LAN), Metropolitan Area Network (MAN), and Wide Area Network (WAN).
7 Layers
Data transmission
local area network

A LAN is a group of computers and associated devices that share a common communications line or wireless link to a server. Typically, a LAN encompasses computers and peripherals connected to a server within a distinct geographic area such as an office or a commercial establishment. Computers and other mobile devices use a LAN connection to share resources such as a printer or network storage.
characteristics of a Computer Network

People can play a CD music from one computer while sitting on another computer. They may have a computer that does not have a DVD or BluRay (BD) player. In this case, people can place a movie disc (DVD or BD) on the computer that has the player, and then view the movie on a computer that lacks the player. People may have a computer with a CD/DVD/BD writer or a backup system but the other computer(s) does not (don't) have it. In this case, people can burn discs or make backups on a computer that has one of these but using data from a computer that does not have a disc writer or a backup system. People can connect a printer (or a scanner, or a fax machine) to one computer and let other computers of the network print (or scan, or fax) to that printer (or scanner, or fax machine). People can place a disc with pictures on one computer and let other computers access those pictures.
Network Classification

Computer network can be classified on the different criteria, such as scale, Connection Method, Functional Relationship (Network Architectures), or Network Topology.


In 1984, Apple Macintosh is launched and the first domain is registered in 1985. By 1995, the bulk of US internet traffic is routed through interconnected network service providers and Microsoft Windows 95 is launched.
Network Concept

Computer networking may be considered a branch of electrical engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of the related disciplines.
Network Protocol


A network protocol defines rules and conventions for communication between network devices. Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets. OSI protocols are a family of standards for information exchange. These were developed and designed by the International Organization of Standardization (ISO). In 1977 the ISO model was introduced, which consisted of seven different layers. This model has been criticized because of its technicality and limited features.




History of Network

Around 1960s-1970s, ARPANET commonly thought of as the predecessor to the Internet and created by the US Department of Defenses Advanced Research Projects Agency (ARPA). The first known fully operational packet-switching network, the ARPANET was designed to facilitate communication between ARPA computer terminals during the early 1960s, at a time when computers where far too expensive for widespread usage.
CHAPTER 6 ONLINE CONNECTION
introduction

A network is the collection of devices that have the ability to communicate with each other.A basic understanding of networking is important for anyone managing a server. Not only is it essential for getting the services online and running smoothly, it also gives the insight to diagnose problems.