THE INTERNET

keywords:
internet 因特网
ARPAnet 阿帕网
packet switching network 分组交换网
interoperability 互操作性
www 万维网
hypertext 超文本
client 客户
browser 浏览器
download 下载
http 超文本传送协议
url 同一资源定位地址
search engine 搜索引擎
search criteria 搜索条件
web page 网页
GUI 图形用户接口
IE 浏览器软件
mosaic 美国计算机安全协会的公共www浏览器
navigator 网景的浏览器
electronic mail 电子邮件
smtp 简单邮件传送协议
pop 邮局协议
FTP 文件传送协议
telnet 远程通信网
tcp/ip 传输控制协议/互联网协议
overview the internet
1, what is intenet
internet is the largest global inter network connecting tens of thousand of networks worldwide and having a culture that focus on research and standardization based on real life use, mant leading edage network technologies come from the internet community, the internet evolved in part from ARPAnet
ARPANT is abbraviated from advanced research projects Agence network” landmark packet switching network established in 1969. arpanet was developed in the 1970s by bbn and fundedby arpa, it eventually evolved into the internet, the term arpanet was officaily retired in 1990.
2.internet services
from the user’ point of view, a tcp/ip internet 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 and underlying network software to handle sunch details , only programmers who write network application programs need to view the as a network and need to understand some of the technolugy.
The most popular and widespreaded internet application services include:
1, www
www is a large network of internet servers providing hypertext and other services to terminals run client applications sunch as browser.
www enables users to seatch, access and dowmload information from worldwide series of networks servers where information is dynamically iterlinked. A web client passes a user’s request for infromation to a server, usually by way of a web brower, the server and client communicate through a transfer protocol , usually the hyper text transfer protocol , the server when access a web page using a uniform resource locator, search engines are available to simplify access by enabling users to enter search criteria on a topic and have serval urls returned for web pages that pertain to the desired information.
Brower is a GUI based bypertext client application, sunch as internet explorer, mosaic, and netscape nacigator, used to access hypertext document and other services loacted on innumerable remote servers throught the www and internet
2) electronic mail
electronic mail allows a user to compse memos and send them to individuals or groups, another part of the mail application allow users to read memos that they have normal business corrrespondence, althogh mang electronic mail systems exist, using TCP/ip make mail delivery more reliable because it does not rely on intermediate computers to relay mail message, A tcp/ip mail delivery system operates by having the sender’s machine contract the reciever’s machine directly, thus , the sender knows the once the message leaves the local machine, it has been successful recieved at the destination site.
there are two kind of e mail protocol used in the internet, one is simple mail transfer protocol which accepts incoming connections and copies messages from them into the appropriate mailboxes, another is post office protocol 3 which feches e mail from the remote mialbox and stores it on the use’s local machine to be read.
3)file transfer protocol
FTP is an application protocol, part of the tcp/ip stack, used for teansferring files between network nodes ,Although users sometimes transfer files using electronic mail , mail is designed primarily for short text messages, the tcp/ ip protocals include a 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 image, a program written in pascal and C++ or even an english dictonary, the system provides a way to check for authorized users. or even to prevent all access. like mail , file transfer across a tcp/ip 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)Televommunication network
Telnet is a standard terminal emulation protocol in the tcp/IP protocol stack, telnet is used for remote teminal 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 amchine 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, when the remove login session reminates the application returns the user to the local system.