BASICS OF THE INTERNET
Connect to the Internet
Minchelle wants to begin her talk with an overview of the technology that enables people to communicate with each other using their computers.She also wants to familiarize her audience with common network terms that will help them understand how the Internet operates.Two or more computers linked together so that they can exchange information an share resoures create a structure known as a network.Some computers,called servers,provide specific resources for the network,such as print capabilities or file storage.
Networks can also be connected to each other so computers on different networks can share information.The Internet,the largest and most famous example of a “network of network,”is made up of millions of computers and networks all over the world.Fiber potic cables,satellites,phone lines,and other communication systems connect computers and networks on the Internet.Computers on a network are often called hosts,and thus computers on the Internet are sometimes called Internet hosts.
The Internet,by design,is a decentralized structure.There is no Internet “company,”Instead,the Internet is a collection of different organizations,such as universities and companies,that organize their own information.There are no rules about where information is stored,and no one regulates the quality of information available on the Internet.Even though the lack of central control can make it hard for beginners to find their way through the Inernet’s resources,decentralization offers some advantages.The Internet is open to innovation and rapid growth because different organizations and individuals are free to test new pronducts and services and make them quickly available to a global to audience.One such service is World Wide Web,an Internet service that makes finding information and moving aroud the Internet easy.Other services on the Internet include:
FTP,short for File Transfer Protocal,which provides an efficient means of file transfer.
Telnet,which lets you connect to other computers and use their services,such as a public library’s card catalog.
Gopher,which organizes a server’s resources via easy-to-use menus.
E-mail,or electronic mail,which allows the electronic transfer of messages between people who have Internet access.
Some Web sites incorporate these services into their Web pages.When this is the case,the Internet Explorer suite accesses the services without requiring any action on your part.
The domain name service(DNS)
The Domain Name System(DNS)was created to centralize the task of making changes to the network name to address assignments and to automate the task of performing the translation functions.In the early days of the Internet,a central location(SRI NIC at Stanford Research Institute in Melo Park,California)was responsible for maintaining a HOSTS file that contained the name fo every host on the Internet along with its address.Administrators had to communicate changes to SRI NIC,and these changes were incorporated into the file periodically.Of course,this meant that the file then had to be distributed to every single host so that it could hava the updated version.
DNS uses a hierarchical distributed architecture that is spread across many computers throughout the Internet.A root server holds information about top level domains(such as.COM,.EDU,and.GOV),and each domin throughout the Internet has a domain name server that is responsible for the computer names and addresses used in that domain.Client computers query DNS servers when they need to get the address for a hostname.If the local DNS knows the address,it return it to the client computer.If it does not,it sends the query up the chain of DNS servers until a DNS server is found that can resolve the name ,provided that it is indeed a valid name.The topmost entry in the DNS hierarchy is called the root domain and its represented by the period character(.).Underneath this root domain are the top-level directories that fall into two groups: geographical and organizational.Geographical domains are used to specify specific countries.For example,.au for Australia and .uk for the United Kingdom.Under each of the geographical domains,you can find organizational domains.Organizational domains you might be familiar with include the following:
Com Used for commercial organizations
Edu Used for educational institutions.
Gov Used for U.S.Government entities.
<< 上一页 [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] ... 下一页 >>