THE INTERNET

1．What is the Internet？

　　Internet is the largest global internetwork，connecting tens of thousand of networks worldwide and having a“culture”that focuses on research and standardization based on real-life use．Many leading-edge network technologies come from the Internet community．The Internet evolved in part from ARPAnet．
ARPAnet is abbreviated from“Advanced Research Projects Agency Network”．Landmark packet-switching network established in 1969．ARPAnet was developed in the 1970s by BBN and funded by ARPA[1]．It eventually evolved into the Internet．The term ARPAnet was officially retired in 1990．

2．Internet services

　　From the user’s point of view，a TCP/IP internet[2] appears to be a set of application programs that use the network to carry out useful communication tasks．We use the term interoperability to refer to the ability of diverse computing systems to cooperate in solving computational problems．Internet application programs exhibit a high degree of interoperability．Most users that access the Internet do so merely by running application programs without understanding the TCP/IP technology，the structure of the underlying internet，or even the path the data travels to its destination；they rely on the application programs and the underlying network software to handle such details．Only programmers who write network application programs need to view the internet as a network and need to understand some of the technology．
The most popular and widespread Internet application services include：

1）WWW（word wide web）

WWW is a large network of Internet servers providing hypertext and other services to terminals[3] running client applications such as a browser．
WWW enables users to search，access，and download information from a worldwide series of networked servers where information is dynamically interlinked．A Web client passes a user’s request for information to a server，usually by way of a Web browser．The server and client communicate through a transfer protocol，usually the HyperText Transfer Protocol（HTTP）[4]．The server then accesses a Web page using a Uniform Resource Locator（URL）．Search engines are available to simplify access by enabling users to enter search criteria on a topic and have several URLs returned for Web pages that pertain to the desired information[5]．
　　Browser is a GUI-based hypertext client application，such as Internet explorer（IE），Mosaic，and Netscape Navigator，used to access bypertext documents and other services located on innumerable remote servers throughout the WWW and Internet．

2）Electronic mail

Electronic mail allows a user to compose memos and send them to individuals or groups．Another part of the mail application allows users to read memos that they have received．Electronic mail has been so successful that many Internet users depend on it for normal business correspondence[6]．Although many electronic mail systems exist，using TCP/IP makes mail delivery more reliable because it does not rely on intermediate computers to relay mail messages[7]．A TCP/IP mail delivery system operates by having the sender’s machine contact the receiver’s machine directly．Thus，the sender knows that once the message leaves the local machine，it has been successful received at the destination site．
　　There are two kinds of E-mail protocol used in the Internet．One is Simple Mail Transfer Protocol（SMTP）which accepts incoming connections and copies messages from them into the appropriate mailboxes[8]．Another is Post Office Protocol-3（POP3）which fetches E-mail from the remote mailbox and stores it on the user’s local machine to be read later．

3）File Transfer Protocol（FTP）

FTP is an application protocol，part of the TCP/IP protocol stack，used for transferring files between network nodes．Although users sometimes transfer files using electronic mail，mail is designed primarily for short text messages．The TCP/IP protocols include a file transfer application program that allows users to send or receive arbitrarily large files of programs or data．For example，using the file transfer program，one can copy from one machine to another a large database containing satellite images，a program written in Pascal or C＋＋，or even an English dictionary．The system provides a way to check for authorized users，or even to prevent all access．Like mail，file transfer across a TCP/1P internet is reliable because the two machines involved communicate directly，without relying on intermediate machines to make copies of the
file along the way．

4）Telecommunication network（Telnet）

　　Telnet is a standard terminal emulation protocol in the TCP/IP protocol stack．Telnet is used for remote terminal connection，enabling users to log in to remote systems and use resources as if they were connected to a local system．
　　Remote login allows a user sitting at one computer to connect to a remote machine and establish an interactive login session．The remote login makes it appear that a window on the user’s screen connects directly to the remote machine by sending each keystroke from the user’s keyboard to the remote machine and displaying each character the remote computer prints in the user’s window[10]．When the remote login session terminates，the application returns the user to the local system．

NOTES

[1] ARPA是Advanced Research Projects Agency的縮寫，指（美）高級研究計(jì)劃署。
[2] TCP/IP internet采用TCP/IP協(xié)議的互聯(lián)網(wǎng)。
[3] 此處，terminals是指連入因特網(wǎng)的各種終端。
[4] usually后面的是同位語。
[5] 由and連接的兩個并列成分，主語為Search engines。Search criteria搜索判據(jù)（關(guān)鍵字）。
[6] that引出的原因狀語從句。
[7] 此處TCP/IP是指由TCP/IP協(xié)議支持的電子郵件。relay此處意為轉(zhuǎn)發(fā)。
[8] 句中connections含有通信雙方先建立一個連接，然后再通信的意思；后面的them也代表connections。
[9] 由多個并列賓語構(gòu)成的長句。
[10]句中it為先行賓語，appear為賓語補(bǔ)語。由that引出的從句為真正的賓語，在這一從句中，by sending... and displaying...這兩個動名詞短語為狀語。

KEYWORDS
Internet 因特網(wǎng)
ARPAnet ARPA計(jì)算機(jī)網(wǎng)，阿帕網(wǎng)
packet-switching network 分組交換網(wǎng)，包交換網(wǎng)
interoperability 互操作性
WWW（world wide web） 　 萬維網(wǎng)，環(huán)球信息網(wǎng)
Hypertext 　　　 超文本
client 　　　 客戶
browser 　　　 瀏覽器
download 　　　 下載
HTTP（hypertext transfer protocol） 　　超文本傳送協(xié)議
URL（uniform resource locator） 　　　 統(tǒng)一資源定位地址
search engine 　　　 搜索引擎
search criteria 　　　搜索條件
Web page 　　　 網(wǎng)頁
GUI（graphical user interface） 　　 圖形用戶接口
IE（Internet Explorer） 　 （微軟公司的）瀏覽器軟件
Mosaic 　　　　　 美國計(jì)算機(jī)安全協(xié)會（NCSA）的公共WWW瀏覽器
Navigator （網(wǎng)景公司的）瀏覽器
electronic mail 電子郵件
SMTP（Simple Mail Transfer Protocol） 簡單郵件傳送協(xié)議
POP（Post Office Protocol） 郵局協(xié)議
FTP（File Transfer Protocol） 文件傳送協(xié)議
Telnet（Telecommunication network） 遠(yuǎn)程通信網(wǎng)
TCP/IP（Transmission Control Protocol/ Internet Protocol） 傳輸控制協(xié)議／互聯(lián)網(wǎng)協(xié)議

翻譯：

因特網(wǎng)

1．什么是因特網(wǎng)
因特網(wǎng)是最大的全球互聯(lián)網(wǎng)，連接了全世界范圍內(nèi)數(shù)以萬計(jì)的網(wǎng)絡(luò)，并已從真實(shí)生活出發(fā)形成了專注于研究和標(biāo)準(zhǔn)化的“文化”，許多前沿網(wǎng)絡(luò)技術(shù)都是來自因特網(wǎng)社會。因特網(wǎng)的前身是ARPAnet。
ARPAnet是Advanced Research Project Agency network的縮寫。它是1969年建立的分組交換網(wǎng)絡(luò)的里程碑，是由BBN公司開發(fā)和美國高級研究計(jì)劃署投資的。20世紀(jì)70年代ARPA網(wǎng)得到了發(fā)展，最終演變?yōu)橐蛱鼐W(wǎng)。“ARPAnet”一詞也于1990年正式停用。

2．因特網(wǎng)服務(wù)
從用戶的觀點(diǎn)來看，TCP/IP協(xié)議下的互聯(lián)網(wǎng)有一套通過網(wǎng)絡(luò)實(shí)現(xiàn)多種通信任務(wù)的應(yīng)用程序。術(shù)語互操作性用來表明各種計(jì)算系統(tǒng)解決計(jì)算問題時相互合作的能力。因特網(wǎng)應(yīng)用程序展示了高度的互操作性。大多數(shù)訪問因特網(wǎng)的用戶只是運(yùn)行應(yīng)用程序而不了解TCP/IP技術(shù)、互聯(lián)網(wǎng)基本結(jié)構(gòu)，甚至不了解數(shù)據(jù)到達(dá)目的站的路徑；他們依靠應(yīng)用程序和基本網(wǎng)絡(luò)軟件來處理這些細(xì)節(jié)。只有編寫網(wǎng)絡(luò)應(yīng)用程序的程序員，才需要把互聯(lián)網(wǎng)視為一個網(wǎng)絡(luò)并了解某些技術(shù)問題。

應(yīng)用最廣的因特網(wǎng)應(yīng)用服務(wù)包括如下諸方面。
1）萬維網(wǎng)
萬維網(wǎng)是一種提供因特網(wǎng)服務(wù)的大型網(wǎng)絡(luò)，它同運(yùn)行客戶應(yīng)用程序，如瀏覽器軟件的終端提供超文本和其他服務(wù)。
萬維網(wǎng)允許用戶從動態(tài)鏈接信息的全球服務(wù)器系列中搜索、訪問和下載信息。 Web客戶通常通過Web瀏覽器，向服務(wù)器傳送用戶需要信息的請求。服務(wù)器與客戶通過傳輸協(xié)議。通常是超文本傳輸協(xié)議（HTTP）進(jìn)行通信。然后，服務(wù)器用統(tǒng)一資源地址（URL）訪問網(wǎng)頁，搜索引擎可用來簡化訪問允許用戶輸入有關(guān)專題的搜索條件，從而使若干（URL）返回有關(guān)所需信息的網(wǎng)頁。
瀏覽器是一種基于圖形用戶界面的超文本客戶程序，如IE，Mosaic和Netscape公司的Navigator等。通過瀏覽器可以對萬維網(wǎng)和因特網(wǎng)上無數(shù)個遠(yuǎn)程服務(wù)器上的超文本文件和其他服務(wù)進(jìn)行訪問。
2）電子郵件
電子郵件讓用戶能撰寫信函并將其發(fā)送給一個人或一群人。郵件應(yīng)用程序的另一功能是允許用戶去閱讀已經(jīng)收到的信函。電子郵件之所以如此成功，是因?yàn)楹芏嘁蛱鼐W(wǎng)用戶依靠它進(jìn)行正常的通信。雖然現(xiàn)在有很多電子郵件系統(tǒng)，但采用TCP/IP使得郵件的發(fā)送更可靠。這是因?yàn)門CP/IP不依靠中間的計(jì)算機(jī)去轉(zhuǎn)發(fā)郵件報文。TCP/IP郵件發(fā)送系統(tǒng)是發(fā)送方機(jī)器與接受方機(jī)器直接進(jìn)行通信的。因而發(fā)送者知道一旦報文離開本地機(jī)器，就能被目的站點(diǎn)成功地接收到。
在因特網(wǎng)上有兩種電子郵件協(xié)議，一是簡單郵件傳送協(xié)議SMTP，它接收送達(dá)的郵件并從中復(fù)制報文到相應(yīng)的郵箱，另一個郵件協(xié)議是郵局協(xié)議POP3，它從遠(yuǎn)程郵箱中取出電子郵件并將其存儲在用戶本地機(jī)器上，以便以后閱讀。
3）文件傳送協(xié)議（FTP）
FTP是TCP/IP協(xié)議棧中的應(yīng)用協(xié)議，用來在網(wǎng)絡(luò)結(jié)點(diǎn)間傳送文件。
雖然用戶有時用電子郵件傳送文件，但郵件主要用來傳送短的文本報文。TCP/ IP協(xié)議包含一種文件傳送應(yīng)用程序，它允許用戶發(fā)送和接收任意規(guī)模的程序或數(shù)據(jù)文件。例如，利用文件傳輸程序，可將含有衛(wèi)星圖像的大型數(shù)據(jù)庫，用Pascal或C++語言寫的程序或一本英語字典從一臺機(jī)器復(fù)制到另一臺機(jī)器上。該系統(tǒng)提供一種對授權(quán)用戶的檢查方法，甚至可阻止所有的訪問。與郵件一樣，文件傳輸跨越TCP/IP協(xié)議下的互聯(lián)網(wǎng)是可靠的，因?yàn)樗婕暗膬膳_機(jī)器直接通信，在一條通路上進(jìn)行文件復(fù)制，而不依靠中間的機(jī)器。
4）遠(yuǎn)程通信網(wǎng)（Telnet）
它是TCP/ IP協(xié)議棧中的標(biāo)準(zhǔn)終端仿真協(xié)議。Telnet用于遠(yuǎn)程終端連接，允許用戶登錄到遠(yuǎn)程系統(tǒng)上，并像連接到本地系統(tǒng)那樣使用資源。遠(yuǎn)程登錄使一臺計(jì)算機(jī)上的用戶連到一臺遠(yuǎn)程機(jī)器上并建立一個交互式登錄會話。遠(yuǎn)程登錄將用戶屏幕窗口直接連接到遠(yuǎn)程機(jī)器上，于是，用戶鍵盤上的每一個擊鍵都發(fā)送到遠(yuǎn)程機(jī)器上，而遠(yuǎn)程計(jì)算機(jī)在該用戶窗口上輸出的每一個字符都會顯示出來。當(dāng)遠(yuǎn)程登錄會話終止時，該應(yīng)用程序再將用戶返回到本地系統(tǒng)。

EXERCISES
1．Fill in the blanks with appropriate words or phrases．
（1）＿＿＿is a large network of Internet servers．
（2）＿＿＿is the largest global internetworks．
（3）＿＿＿is the landmark packet-switching network．
（4）GUI is abbreviated from＿＿＿．
（5）Many business correspondences are transferred via＿＿＿．
（6）IE is produced by＿＿＿．
（7）We access a Web page by using a ．
（8）We can use the＿＿＿to send or receive arbitrarily large files．
（9）Many leading-edge network technologies come from＿＿＿．
（10）＿＿＿is a standard terminal emulation protocol．
　 a．electronic mail b．Telnet
c．WWW d．Graphical User Interface
e．Internet community f．Internet
g．URL h．Microsoft corp．
i．FTP j．ARPAnet

2．True / False．
（1）A“culture”of Internet focuses on research and standardization based on real-life use．
（2）Electronic mail is designed for transferring very large file．
（3）The term ARPAnet was officially retired in 1980s．
（4）We can use POP3 to send a E-mail．
（5）Using Telnet we can login to remote systems as if we were connected to a local system．
（6）The term interoperability means the ability of the same computing syste-ms．
（7）To use the electronic mail we must establish a mailbox on a mail server．
（8）Most Internet users must understand the TCP/IP technology．
（9）Two sites of using FTP rely on intermediate machines．
（10）Search engines require users to enter search criteria．


答案：
1．
（1）c （2）f （3）j （4）d
（5）a （6）h （7）g （8）i
（9）e （10）b
2．
（1）t （2）f （3）f （4）f
（5）t （6）f （7）t （8）f
（9）f （10）t