1、朱龍 劉長(zhǎng)君 主編孫雅妮 謝宇 副主編趙克林 主審工業(yè)和信息化“十三五”高職高專人才培養(yǎng)規(guī)劃教材教學(xué)要求： 掌握專業(yè)關(guān)鍵詞匯（key words）；能閱讀本章所列英語(yǔ)短文；能識(shí)別計(jì)算機(jī)網(wǎng)絡(luò)的各組件。教學(xué)內(nèi)容： 計(jì)算機(jī)網(wǎng)絡(luò)英語(yǔ)；各相關(guān)硬件設(shè)備品牌、主要生產(chǎn)廠商；常用的專業(yè)術(shù)語(yǔ)。教學(xué)提示： 到學(xué)校機(jī)房或有關(guān)網(wǎng)絡(luò)公司參觀，感受本章內(nèi)容，以學(xué)到更多的專業(yè)知識(shí)和詞匯。ChapterFoundation of Computer Network （計(jì)算機(jī)網(wǎng)絡(luò)基礎(chǔ)）3.1 Network Concepts（網(wǎng)絡(luò)基礎(chǔ)）Networking arose from the need to share data in

2、 a timely fashion. Personal computers are wonderful business tools for producing data, spreadsheets, graphics, and other types of information, but do not allow you to quickly share the data you have produced.If the user were to connect his computer to other computers, he could share data on other co

3、mputers, including high-quality printers. A group of computers and other devices connected together are called a network, and the technical concept of connected computers sharing resources is called networking.Computers that are part of a network can share data, messages, graphics, printers, fax mac

4、hines, modems, CD-ROMs, hard disks, and other data storage equipment.According to the scope the network works and the distance for the mutual connection of computers, it has three categories: Wide Area Network, Local Area Network, and Metropolitan Area Network.計(jì)算機(jī)網(wǎng)絡(luò)的建立是為了滿足人們以即時(shí)方式共享數(shù)據(jù)的需求。個(gè)人計(jì)算機(jī)在處理數(shù)據(jù)、

5、電子表格、圖形以及其他類型的信息方面是理想的辦公設(shè)備，但卻不支持快速（用戶輸出的）數(shù)據(jù)共享。如果用戶能把他的計(jì)算機(jī)與其他計(jì)算機(jī)聯(lián)系在一起的話，他就可以共享其他計(jì)算機(jī)上的數(shù)據(jù)，包括高性能的打印機(jī)。一組計(jì)算機(jī)和其他的設(shè)備連接在一起構(gòu)成的系統(tǒng)叫作網(wǎng)絡(luò)，互連的計(jì)算機(jī)共享資源的技術(shù)（概念）叫作網(wǎng)絡(luò)技術(shù)。聯(lián)網(wǎng)的計(jì)算機(jī)可以共享數(shù)據(jù)、消息、圖形、打印機(jī)、傳真機(jī)、調(diào)制解調(diào)器、只讀光盤、硬盤以及其他數(shù)據(jù)存儲(chǔ)設(shè)備。按照網(wǎng)絡(luò)作用的范圍與計(jì)算機(jī)相互連接的距離分，有廣域網(wǎng)、局域網(wǎng)和城域網(wǎng)3種類型的網(wǎng)絡(luò)。 Key words: networking（網(wǎng)絡(luò)技術(shù)），spreadsheet（電子表格），share（共享），net

6、work（網(wǎng)絡(luò)），message（信息），graphics（圖形），fax machine（傳真機(jī)），modem（調(diào)制解調(diào)器），CD-ROM（只讀光盤），data storage equipment（數(shù)據(jù)存儲(chǔ)設(shè)備），Wide Area Network（廣域網(wǎng)），Local Area Network（局域網(wǎng)），Metropolitan Area Network（城域網(wǎng)）A computer network is a communication system connecting some computers that work together to exchange and share res

7、ources. Generally it is made up of two parts: network operation system (NOS) and hardware or nodes, referring to any devices that are connected to a network. Take LAN for example, the hardware system includes a microcomputer, which is used as file server and workstation, net interface card, T-shape

8、juncture, BNC joint, terminator, and cables etc.File Server is the soul of a whole network, so it must be the best. All the input and output of data are under control of the File Server on the network. A network must have a computer as the network File Server, and it provides the workstation its dat

9、a on the hard disk. Workstation actually is a set of PC. When it has been connected with File Server and been logged on, it can access data from the File Server, and operates on the workstation with the documents needed.Net card (network interface card: NIC) is the interface between File Server and

10、Workstation.一個(gè)計(jì)算機(jī)網(wǎng)絡(luò)實(shí)際上是一個(gè)通信系統(tǒng)，它連接了若干一起工作并分享資源、交換信息的計(jì)算機(jī)。通常網(wǎng)絡(luò)系統(tǒng)由兩部分組成，即網(wǎng)絡(luò)操作系統(tǒng)和網(wǎng)絡(luò)硬件或節(jié)點(diǎn)，節(jié)點(diǎn)指的是連接在網(wǎng)絡(luò)上的任何設(shè)備。以局域網(wǎng)為例，硬件系統(tǒng)包括分別用作服務(wù)器與工作站的微型計(jì)算機(jī)、網(wǎng)卡、T形接頭、BNC接頭、終端電阻以及電纜線等。服務(wù)器（file server）是整個(gè)網(wǎng)絡(luò)的靈魂，所以它必須是最好的。網(wǎng)絡(luò)上所有數(shù)據(jù)的進(jìn)出都須通過(guò)服務(wù)器來(lái)控制。一個(gè)網(wǎng)絡(luò)必須有一臺(tái)計(jì)算機(jī)來(lái)做網(wǎng)絡(luò)服務(wù)器，由它將硬盤上的數(shù)據(jù)提供給工作站使用。工作站（workstation）實(shí)際上就是一臺(tái)PC，當(dāng)它與服務(wù)器連接并登錄后，就可以訪問(wèn)服務(wù)器上的

11、數(shù)據(jù)，在得到所需文件后就可以在工作站上運(yùn)行。網(wǎng)卡（network interface card: NIC）是服務(wù)器與工作站之間的接口。 Key words: resource（資源），network operating system（網(wǎng)絡(luò)操作系統(tǒng)），node（節(jié)點(diǎn)），workstation（工作站），T-shape juncture（T形頭），BNC joint（BNC接頭），terminator（終結(jié)器）， cable（電纜），file server（文件服務(wù)器），log on（登錄），network interface card（網(wǎng)卡），interface（界面，接口）3.2 Archit

12、ecture of Computer Networks（計(jì)算機(jī)網(wǎng)絡(luò)結(jié)構(gòu)）The configuration, or the physical layout, of the equipment in a communication network is called topology. Devices connected to a network, such as terminals, printers, or other computers, are referred to as nodes. The four configurations or Network are star, bus,

13、ring, and tree.Star NetworkA star network contains a central unit, a number of personal computers, terminals or peripheral devices. All of them are linked to the central unit either by point-to-point or multidrop cable lines. This central unit may be a host computer or a file server. All communicati

14、ons in the network are controlled through this central unit by polling. That is, before one user wants to send messages, he or she must be polled or asked if there is any message to be sent. One particular advantage of star network is that it provides a time-sharing system. This allows several users

15、 to share resources on a central computer simultaneously.拓?fù)洌竿ㄐ啪W(wǎng)中設(shè)備的配置或物理布局。節(jié)點(diǎn)，指連接在網(wǎng)絡(luò)上的設(shè)備，如終端、打印機(jī)或其他計(jì)算機(jī)。通信網(wǎng)絡(luò)的設(shè)備配置稱為拓?fù)洌饕?種配置方式：星形、總線形、環(huán)形和樹(shù)形。星形網(wǎng)絡(luò)星形網(wǎng)絡(luò)由一臺(tái)中央處理器、多臺(tái)個(gè)人計(jì)算機(jī)、終端或外圍設(shè)備構(gòu)成。所有這些設(shè)備都可以通過(guò)兩點(diǎn)連接或多點(diǎn)連接的方式和中央處理器連接，形成星形結(jié)構(gòu)。這臺(tái)中央處理器可以是一臺(tái)主機(jī)或是文件服務(wù)器。所有的網(wǎng)絡(luò)通信都必須通過(guò)訪問(wèn)這臺(tái)處理器來(lái)進(jìn)行控制。也就是說(shuō)，用戶在傳送信息之前將被詢問(wèn)是否有信息要傳送。星形網(wǎng)絡(luò)結(jié)構(gòu)的一個(gè)顯著

16、優(yōu)點(diǎn)是它提供分時(shí)服務(wù)，這使多個(gè)用戶可以同時(shí)分享中央計(jì)算機(jī)上的資源。 Key words: equipment（設(shè)備），topology（拓?fù)洌瑃erminal（終端），star network（星形網(wǎng)絡(luò)），peripheral device（外圍設(shè)備），host computer（主機(jī)），send message（傳送消息），time-sharing system（分時(shí)系統(tǒng)）Star NetworkBus NetworkIn bus network, each device in the network handles its own communications control. Ther

17、e is no host computer. All the devices are connected to and share a single cable. All communication travel along this common connection cable are called bus. As the information passes along the bus, its examined by each device to see if the information is intended for it.When only a few microcompute

18、rs are to be linked together, bus network is more preferable. This configuration is common in systems for electronic mail or for sharing data stored on different microcomputers. The bus network is as efficient as the star network for sharing resources, because it is not directly linked to the resour

19、ce.In bus network, any devices can be attached or detached from the network at any point without disturbing the network. In addition, if one computer fails, it doesnt affect the entire network.總線網(wǎng)絡(luò)在總線網(wǎng)絡(luò)中，每一個(gè)設(shè)備處理自己的通信管理，并沒(méi)有主機(jī)。所有的設(shè)備都由一根電纜線連接。所有的通信傳輸都沿著這根共同連接著的稱為總線的電纜進(jìn)行。當(dāng)信息沿總線傳送時(shí)，每個(gè)設(shè)備對(duì)它進(jìn)行檢查，看這條信息是否是對(duì)該設(shè)

20、備的。當(dāng)想要連接少數(shù)幾臺(tái)計(jì)算機(jī)時(shí)，總線網(wǎng)絡(luò)更加適合。這種配置的電子郵件或不同計(jì)算機(jī)上的數(shù)據(jù)共享系統(tǒng)是相同的。由于總線網(wǎng)絡(luò)并非直接和資源連接，因此在資源共享上和星形結(jié)構(gòu)一樣有效。總線網(wǎng)絡(luò)中的設(shè)備可以連接到網(wǎng)絡(luò)的任何一點(diǎn)，或從網(wǎng)絡(luò)上任何一點(diǎn)取下，而不影響其他部分。而且，一臺(tái)機(jī)器出故障，并不影響整個(gè)網(wǎng)絡(luò)。Key words: bus network（總線網(wǎng)絡(luò)），bus（總線），electronic mail（電子郵件）Bus NetworkRing Network and Tree NetworkA ring network doesnt use a central host computer. E

21、ach device is connected to two other devices, forming a ring. Messages are passed around the ring until they reach the destination.環(huán)形網(wǎng)絡(luò)和樹(shù)形網(wǎng)絡(luò)環(huán)形網(wǎng)絡(luò)也沒(méi)有主機(jī)，每個(gè)機(jī)器都和其他兩臺(tái)機(jī)器互相連接，形成一個(gè)環(huán)形。信息沿著環(huán)形線傳送直到到達(dá)目的地。A tree network consists of several computers linked to a central host computer, just like a star network. How

22、ever, these computers are also host to other smaller computers. It allows various computers to share database, processing power, and different output devices.如同星形網(wǎng)絡(luò)一樣，樹(shù)形網(wǎng)絡(luò)由若干計(jì)算機(jī)連接到一臺(tái)中央計(jì)算機(jī)上。然而，這些計(jì)算機(jī)同時(shí)又成為其他更小計(jì)算機(jī)的主機(jī)。樹(shù)形網(wǎng)絡(luò)允許各種計(jì)算機(jī)分享數(shù)據(jù)庫(kù)、字處理程序和其他不同的輸出設(shè)備。Key words: ring network（環(huán)形網(wǎng)絡(luò)），tree network（樹(shù)形網(wǎng)絡(luò)），datab

23、ase（數(shù)據(jù)庫(kù)）Ring NetworkTree Network3.3 LAN（局域網(wǎng)）A network is any collection of independent computers that communicate with one another over a shared network medium. LANs are networks usually confined to a geographic area, such as a single building or a college campus. LANs can be small, linking as few a

24、s three computers, but often link hundreds of computers used by thousands of people. The development of standard networking protocols and media has resulted in worldwide proliferation of LANs throughout business and educational organizations.LAN is possible for hardware resource sharing and informat

25、ion resource sharing on LANs. At the same time, each LAN can directly link to WANs, thus gains rich information.網(wǎng)絡(luò)就是連接在一起的獨(dú)立計(jì)算機(jī)，相互之間通過(guò)一個(gè)共享網(wǎng)絡(luò)媒介進(jìn)行通信的。局域網(wǎng)通常是指某一地域范圍內(nèi)的一個(gè)網(wǎng)絡(luò)，如一幢建筑物內(nèi)或一個(gè)大學(xué)校園內(nèi)。局域網(wǎng)可以很小，可以少到只連接3臺(tái)計(jì)算機(jī)，但通常會(huì)連接幾百臺(tái)計(jì)算機(jī)，供幾千人使用。標(biāo)準(zhǔn)網(wǎng)絡(luò)協(xié)議和網(wǎng)絡(luò)媒介的發(fā)展使得局域網(wǎng)在全世界快速發(fā)展，它遍及商業(yè)領(lǐng)域和各教育機(jī)構(gòu)。局域網(wǎng)可以實(shí)現(xiàn)硬件資源共享和信息資源共享。此外，局域網(wǎng)還能直接連接

26、到廣域網(wǎng)上，從而獲得上面的豐富信息。 Key words: communicate（通信），network medium（網(wǎng)絡(luò)媒介），network protocol（網(wǎng)絡(luò)協(xié)議），hardware resource（硬件資源），information resource（信息資源）What Is Wireless Computer Networking?Wireless networks utilize radio waves and/or microwaves to maintain communication channels between computers. Wireless netw

27、orking is a more modern alternative to wired networking that relies on copper and/or fiber optic cabling between network devices.什么是無(wú)線計(jì)算機(jī)網(wǎng)絡(luò)？無(wú)線網(wǎng)絡(luò)利用無(wú)線電波和（或）微波保持計(jì)算機(jī)之間的通信通道。無(wú)線網(wǎng)絡(luò)比依賴于銅線和（或）光纜來(lái)連接網(wǎng)絡(luò)設(shè)備的有線網(wǎng)絡(luò)更現(xiàn)代些。A wireless network offers advantages and disadvantages compared to a wired network. Advantages of

28、wireless include mobility and elimination of unsightly cables. Disadvantages of wireless include the potential for radio interference due to weather, other wireless devices, or obstructions like walls. Wireless is rapidly gaining in popularity for both home and business networking. Wireless technolo

29、gy continues to improve, and the cost of wireless products continues to decrease. Popular wireless local area networking (WLAN) products conform to the 802.11 “Wi-Fi” standards.The gear a person needs to build wireless networks includes network adapters (NICs), access points (APs), and routers.無(wú)線網(wǎng)絡(luò)與

30、有線網(wǎng)絡(luò)相比既有優(yōu)點(diǎn)也有缺點(diǎn)。其優(yōu)點(diǎn)是移動(dòng)性強(qiáng)，并且除去了難看的電纜線。其缺點(diǎn)是環(huán)境帶來(lái)的潛在的無(wú)線電干擾，如有天氣原因，或其他無(wú)線上網(wǎng)設(shè)備或障礙物（如墻）的阻擋都可能帶來(lái)干擾。無(wú)線網(wǎng)絡(luò)在家庭網(wǎng)絡(luò)和商業(yè)網(wǎng)絡(luò)兩方面迅速流行起來(lái)。無(wú)線技術(shù)還在繼續(xù)提高和完善，而無(wú)線產(chǎn)品的價(jià)格卻在不斷降低。一般的無(wú)線局域網(wǎng)（WLAN）產(chǎn)品都遵循802.11“Wi-Fi”標(biāo)準(zhǔn)。一個(gè)人要建立無(wú)線網(wǎng)絡(luò)必須有網(wǎng)絡(luò)適配器（NICs），訪問(wèn)端口和訪問(wèn)通道。 Key words: wireless computer networking（無(wú)線計(jì)算機(jī)網(wǎng)絡(luò)），radio wave（無(wú)線電波）， microwave（微波），commun

31、ication channel（通信通道），wired networking（有線網(wǎng)絡(luò)），network device（網(wǎng)絡(luò)設(shè)備），wireless device（無(wú)線設(shè)備），wireless product（無(wú)線產(chǎn)品），wireless local area networking（WLAN，無(wú)線局域網(wǎng)） 無(wú)線網(wǎng)關(guān)鍵字 802.11x：定義了無(wú)線局域網(wǎng)技術(shù)的一系列標(biāo)準(zhǔn)。此標(biāo)準(zhǔn)由電氣電子工程協(xié)會(huì)（IEEE）制定，它包括802.11a、802.11b、802.11g和新興802.11n。802.11ac標(biāo)準(zhǔn)在本文發(fā)布時(shí)仍在開(kāi)發(fā)中。Wi-Fi：代表“無(wú)線保真”，指802.11標(biāo)準(zhǔn)的IEEE802.1

32、1b子集。Wi-Fi支持高達(dá)11Mbit/s的數(shù)據(jù)傳輸率，是迄今為止最常用的標(biāo)準(zhǔn)。WLAN：無(wú)線局域網(wǎng)的縮寫，指采用802.11無(wú)線技術(shù)進(jìn)行互連的一組計(jì)算機(jī)和相關(guān)設(shè)備。也稱為L(zhǎng)AWN。WAN：廣域網(wǎng)，指覆蓋主要城市中心或整個(gè)國(guó)家的網(wǎng)絡(luò)，如GPRS、CDMA和GSM等。無(wú)線熱點(diǎn)：通過(guò)無(wú)線接入點(diǎn)為移動(dòng)用戶提供連網(wǎng)或互聯(lián)網(wǎng)服務(wù)的區(qū)域。公共熱點(diǎn)建立在圖書館、機(jī)場(chǎng)、酒店甚至咖啡廳和餐館中。藍(lán)牙：一種低成本、低功率無(wú)線“線纜替代”技術(shù)，使電話、筆記本電腦、PDA和外設(shè)等設(shè)備能夠通過(guò)短程（10米）無(wú)線信號(hào)進(jìn)行互連。3.4 WAN（廣域網(wǎng)）As the geographical scope of the ne

33、twork grows by connecting users in different cities or different states, the LAN grows into a wide area network (WAN). WAN (wide area network) is also called RCN (remote computer network). Its effective scope can reach from tens of kilometers to ten thousands of kilometers. A wide area network uses

34、telephone lines, microwaves, satellites, or a combination of communi-cation channels. The network between nations belongs to wide area network. At present the biggest wide area network in the world is Internet and it has covered more than 220 nations. It is like a giant highway that connects you to

35、millions of other people and organizations located throughout the world. The Internet is a huge computer network available to nearly everyone with a microcomputer and a means to connect to it. The Web, also known as the World Wide Web or WWW, is an Internet service that provides a multimedia interfa

36、ce to numerous resources available on the Internet.隨著各個(gè)城市、各個(gè)國(guó)家的用戶被連接在一起，網(wǎng)絡(luò)的地理覆蓋范圍不斷擴(kuò)展，局域網(wǎng)（LAN）已經(jīng)發(fā)展成了廣域網(wǎng)（WAN）。廣域網(wǎng)也稱遠(yuǎn)程網(wǎng)RCN（remote computer network），其作用范圍可以達(dá)幾十公里到幾萬(wàn)公里。廣域網(wǎng)使用電話線、微波、衛(wèi)星或這些通信信道的組合來(lái)傳送信息。國(guó)家與國(guó)家之間的網(wǎng)絡(luò)就屬于廣域網(wǎng)。目前世界上最大的廣域網(wǎng)就是互聯(lián)網(wǎng)，其范圍已經(jīng)覆蓋了全球220多個(gè)國(guó)家。它像一條高速公路一樣將你與遍布全世界的多達(dá)幾百萬(wàn)的人和機(jī)構(gòu)連接起來(lái)。互聯(lián)網(wǎng)是一個(gè)巨大的計(jì)算機(jī)網(wǎng)絡(luò)，它適合幾乎

37、每一個(gè)有計(jì)算機(jī)和上網(wǎng)條件的人去使用它。環(huán)球網(wǎng)，也就是眾所周知的萬(wàn)維網(wǎng)，是互聯(lián)網(wǎng)的一項(xiàng)服務(wù)，它為互聯(lián)網(wǎng)上大量的可用資源提供一個(gè)多媒體的界面。 Key words: RCN（remote computer network，遠(yuǎn)程網(wǎng)），telephone line（電話線），communication channel（通信信道），Internet（互聯(lián)網(wǎng)），Web（環(huán)球網(wǎng)），World Wide Web（萬(wàn)維網(wǎng)），Internet service（互聯(lián)網(wǎng)服務(wù)）InternetThe Internet is a system of linked networks that are worldwide i

38、n scope and facilitate data communication services such as remote login, file transfer, electronic mail, the World Wide Web, and newsgroups.With the meteoric rise in demand for connectivity, the Internet has become a communication highway for millions of users. The Internet was initially restricted

39、to military and academic institutions, but now it is a full- fledged conduit for any and all forms of information and commerce. Internet websites now provides personal, educational, political, and economic resources to every corner of the planet.互聯(lián)網(wǎng)互聯(lián)網(wǎng)是一個(gè)全球網(wǎng)絡(luò)系統(tǒng)，它有許多方便的數(shù)據(jù)通信服務(wù)，如遠(yuǎn)程登錄、文件傳輸、電子郵件、萬(wàn)維網(wǎng)和新聞組等

40、。隨著聯(lián)網(wǎng)需求的迅速上升，互聯(lián)網(wǎng)已成為幾百萬(wàn)用戶間的信息通信高速公路。互聯(lián)網(wǎng)最初僅限于軍事部門和學(xué)術(shù)機(jī)構(gòu)使用，而現(xiàn)在它已經(jīng)是一個(gè)完全成熟的通信通道以及信息和商業(yè)的窗口。現(xiàn)在互聯(lián)網(wǎng)各網(wǎng)絡(luò)站點(diǎn)向全球每一個(gè)角落提供個(gè)人、教育、政治和經(jīng)濟(jì)等資源。Key words: remote login（遠(yuǎn)程登錄），file transfer（文件傳輸），newsgroups（新聞組），website（網(wǎng)絡(luò)站點(diǎn)）國(guó)內(nèi)主干網(wǎng)絡(luò)分布圖 中國(guó)的計(jì)算機(jī)網(wǎng)絡(luò)主要有六大互聯(lián)網(wǎng)絡(luò)：中國(guó)科學(xué)技術(shù)網(wǎng)（CSTNet）、郵電部中國(guó)公用計(jì)算機(jī)互聯(lián)網(wǎng)（ChinaNet）、中國(guó)教育和科研計(jì)算機(jī)網(wǎng)（CERNet）、中國(guó)金橋信息網(wǎng)（ChinaG

41、BN）、中國(guó)聯(lián)通工聯(lián)網(wǎng)（UNINET）和中國(guó)網(wǎng)通（CNCNET），并實(shí)現(xiàn)了網(wǎng)絡(luò)間的互聯(lián)互通。中國(guó)互聯(lián)網(wǎng)就是以這六大互聯(lián)網(wǎng)為依托而產(chǎn)生和發(fā)展起來(lái)的。3.5 Hardware Concepts of Computer Network（計(jì)算機(jī)網(wǎng)絡(luò)硬件設(shè)備基礎(chǔ)）3.5.1 Network Interface Card（網(wǎng)卡）A network interface card (NIC) is a computer circuit board or card that is installed in a computer so that it can be connected to a network.

42、Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or Token Ring. Network interface cards provide a dedicated, full-time connection to a network. Most home and portab

43、le computers are connected to the Internet through as-needed dial-up connection. The modem provides the connection interface to the Internet service provider.網(wǎng)卡是安裝在計(jì)算機(jī)內(nèi)的一塊電路板（或插卡），計(jì)算機(jī)通過(guò)它連接到網(wǎng)絡(luò)上。在局域網(wǎng)中的個(gè)人計(jì)算機(jī)和工作站中都會(huì)有一塊專為局域網(wǎng)傳輸技術(shù)而設(shè)計(jì)的網(wǎng)卡，如以太網(wǎng)或令牌環(huán)網(wǎng)。網(wǎng)卡專用于全時(shí)連接網(wǎng)絡(luò)。絕大多數(shù)家用電腦和手提電腦通過(guò)撥號(hào)連接上網(wǎng)。調(diào)制解調(diào)器為互聯(lián)網(wǎng)服務(wù)提供商提供了一個(gè)連接接口。 K

44、ey words: NIC（網(wǎng)卡），transmission technology（傳輸技術(shù)），Ethernet（以太網(wǎng)），Token Ring（令牌環(huán)網(wǎng)），portable computer（手提電腦），dial-up connection（撥號(hào)連接），Internet service provider（互聯(lián)網(wǎng)服務(wù)提供商） 常見(jiàn)的網(wǎng)卡（NIC）品牌有：Intel、Winyao（萬(wàn)耀）、TP-LINK（普聯(lián)）、D-Link（友訊）、LR-LINK（聯(lián)瑞）、Tenda（騰達(dá)）、DIEWU（蝶舞）、GRT（光潤(rùn)通）、B-LINK（必聯(lián)）、Unicaca（眾力）等。3.5.2 Modem（調(diào)制解調(diào)器

45、）Modem is short for “modulator-demodulator”. A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves.

46、 A modem converts between these two forms.Fortunately, there is one standard interface for connecting external modems to computers called RS-232. Consequently, any external modem can be attached to any computer that has an RS-232 port, which almost all personal computers have. There are also modems

47、that come as an expansion board that you can insert into a vacant expansion slot. These are sometimes called onboard or internal modems.調(diào)制解調(diào)器（Modem）是“調(diào)制解調(diào)（modulator，demodulator）”的縮寫。調(diào)制解調(diào)器是一個(gè)幫助計(jì)算機(jī)轉(zhuǎn)換（比如電話線、電纜線）數(shù)據(jù)的設(shè)備或程序。計(jì)算機(jī)中的信息是以數(shù)字方式存儲(chǔ)的，而在電話線中傳輸?shù)膮s是模擬信號(hào)。調(diào)制解調(diào)器就將這兩種信號(hào)互相轉(zhuǎn)換。幸好，外置調(diào)制解調(diào)器都有一個(gè)叫作RS-232的標(biāo)準(zhǔn)接口與計(jì)算機(jī)相聯(lián)

48、，因此，任何一個(gè)外置調(diào)制解調(diào)器都能連接到任何一臺(tái)有RS-232端口的計(jì)算機(jī)上，而幾乎所有的個(gè)人計(jì)算機(jī)都有這種端口。也有的調(diào)制解調(diào)器以擴(kuò)展板的形式插入空的擴(kuò)展槽當(dāng)中。有時(shí)它們被稱為內(nèi)置調(diào)制解調(diào)器。 Key words: modulator-demodulator（調(diào)制解調(diào)器），digitally（數(shù)字地），standard interface（標(biāo)準(zhǔn)接口），external modem（外置調(diào)制解調(diào)器），expansion board（擴(kuò)展板），expansion slot（擴(kuò)展槽），internal modem（內(nèi)置調(diào)制解調(diào)器）Modem3.5.3 Hubs（集線器）A hub is a com

49、mon connection point for devices in a network, which is commonly used to connect segments of a LAN. A hub contains multiple ports.When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.A passive hub serves simply as a conduit for the da

50、ta, enabling it to go from one device (or segment) to another. So-called intelligent hubs include additional features that allow an administrator to monitor the traffic passing through the hub and to configure each port in the hub. Intelligent hubs are also called manageable hubs.A third type of hub

51、, called a switching hub, actually reads the destination address of each packet and then forwards the packet to the correct port.集線器是網(wǎng)絡(luò)設(shè)備的一個(gè)普通連接點(diǎn)，它通常用于連接局域網(wǎng)中的各網(wǎng)段。一個(gè)集線器有若干個(gè)端口。當(dāng)一個(gè)數(shù)據(jù)包到達(dá)一個(gè)端口時(shí)，它將被復(fù)制到其他端口，因此局域網(wǎng)中所有網(wǎng)段都能看到所有的數(shù)據(jù)包。一個(gè)被動(dòng)集線器僅僅是一個(gè)數(shù)據(jù)通道，它使數(shù)據(jù)從一個(gè)設(shè)備（或網(wǎng)段）傳輸?shù)搅硪粋€(gè)上面。所謂的智能集線器，還包括其他的特征，即允許管理員監(jiān)控通過(guò)集線器的流量和配置集線器

52、的每個(gè)端口。智能集線器也被稱為可控集線器。第三種集線器被稱為交換集線器，事實(shí)上是先讀取每個(gè)數(shù)據(jù)包中的目的地址，然后將數(shù)據(jù)包傳送到正確的端口。Key words: hub（集線器），connection point（連接點(diǎn)），segment of a LAN（局域網(wǎng)段），packet（信息包，數(shù)據(jù)包），port（端口），passive hub（被動(dòng)集線器），intelligent hub（智能集線器），traffic（通信量，流量），configure（配置），manageable hub（可控集線器），switching hub（交換集線器），destination address（目的地址）

53、常見(jiàn)的集線器（HUB）品牌：高檔HUB主要由美國(guó)品牌占領(lǐng)，如3COM、INTEL、BAY等；我國(guó)的D-LINK和ACCTON占有中低端HUB的主要份額；其他的有TP-LINK/普聯(lián)集線器（HUB）、優(yōu)越者集線器（HUB）、水星集線器（HUB）、阿爾法集線器（HUB）、SSK/飚王集線器（HUB）、ECOM集線器（HUB）、HP/惠普集線器（HUB）、LANVOLAN集線器（HUB）、TCL集線器（HUB）、TENDA/騰達(dá)集線器（HUB）、UGR/聯(lián)合金彩虹集線器（HUB）、WG集線器（HUB）、XINGNET集線器（HUB）、頂聯(lián)網(wǎng)絡(luò)集線器（HUB）、頂星集線器（HUB）、捷訊數(shù)碼集線器（H

54、UB）、奇勝集線器（HUB）、全碼集線器（HUB）、神州數(shù)碼集線器（HUB）等。Hub3.5.4 Network Medium（網(wǎng)絡(luò)介質(zhì)）Twisted-pair cable, a type of cable that consists of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. While twisted-pair ca

55、ble is used by older telephone networks and is the least expensive type of local-area network (LAN) cable. Most networks contain some twisted-pair cabling at some point along the network. Other types of cables used for LANs include coaxial cables and fiber optic cables.雙絞線，一種由兩根獨(dú)立的絕緣金屬絲相互纏繞在一起構(gòu)成的電纜。

56、兩根金屬絲相互纏繞在一起是為了降低相互間的信號(hào)串?dāng)_和電磁感應(yīng)。雖然雙絞線常用于老的電話網(wǎng)和費(fèi)用低廉的局域網(wǎng)中，但在絕大多數(shù)的網(wǎng)絡(luò)分支上也用到了雙絞線。局域網(wǎng)中用到的其他類型的電纜還有同軸電纜和光纜。Coaxial cable, a high-frequency transmission cable, replaces the multiple wires of telephone lines with a single solid-copper core. In terms of number of telephone connections, a coaxial cable has over

57、 80 times the transmission capacity of twisted pair. Coaxial cable is used to deliver television signals as well as to connect computers in a network.同軸電纜，一種高頻傳輸電纜，用一根單一的銅芯取代了多金屬絲的電話線。如果在相同的電話線路中，同軸電纜的傳輸速度是雙絞線的80倍。同軸電纜也常被用于傳送電視信號(hào)，以及在網(wǎng)絡(luò)中連接計(jì)算機(jī)。Key words: twisted-pair cable（雙絞線），crosstalk（串音干擾，交調(diào)失真），el

58、ectromagnetic induction（電磁感應(yīng)），telephone networks（電話網(wǎng)），coaxial cable（同軸電纜），fiber optic cable（光纜），transmission capacity（傳輸量）Fiber-optic cable transmits data as pulses of light through tiny tubes of glass. In terms of number of telephone connections, fiber-optic cable has over 26000 times the transmiss

59、ion capacity of twisted pair. However, it is significantly smaller. Indeed, a fiber-optic tube can be half the diameter of a human hair. Although limited in the distance they can carry information, fiber-optic cable have several advantages. Such cables are immune to electronic interference, which ma

60、kes them more secure. They are also lighter and less expensive than coaxial cable and are more reliable at transmitting data. They transmit information using beams of light at light speeds instead of pulses of electricity, making them far faster than copper cable. Fiber-optic cable is rapidly replac