因特网(中英对照)[1]

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．
  
  
   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 running client applications such as a browser．
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．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．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．

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

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．