URLs and Domain Names

WEBBITS explains the Internet:
URLs and Domain Names
URLs, or Uniform Resource Locators, are the addresses on the Internet where you can access services such as the World Wide Web, FTP, Gopher, WAIS, UseNet and Telnet. There are three parts to a URL, namely:

the protocol
the domain name (the host address), and
the directory path and filename

For example, in the following URL:

http://www.netscape.com/home/welcome.html

*http*	*is the protocol*
*netscape.com*	*is the domain name, and*
*/home/welcome.html*	*is the path and filename*

Protocols
A protocol defines the Internet service. A common set of protocols that make the Internet work is TCP/IP (Transmission Control Protocol and Internet Protocol

Examples of protocols that WWW browsers can use to find documents are :

*http:*	*used by the World Wide Web*
*ftp:*	*starts an ftp session*
*gopher:*	*starts a Gopher session*
*file///c\|*	*gets a file from your local disk. The word file is followed by ///c\| insted of the colon which has a different meaning in a URL*
*wais:*	*accesses a WAIS server*
*news:*	*reads UseNet newsgroups*
*telnet:*	*starts a Telnet session*
*mail to:*	*open up E-mail, and Listserv*
*nntp:*	*Usenet*

The protocol name is always followed by a colon (except for the special case, file///c|). In a Web address, the two slashes after the colon indicate that what follows is a valid Internet host address or symbolic location. The single forward slashes within a Web address indicate a directory path for a file that you want to access from the computer at that Web address.

Domain Names

The domain name consists of the name of the host server and the type of server (the domain identifier).

A domain name contains subnames separated by periods, as:
computername.clustername.organizationtype.country

Not all of the subnames need be present in the name. For example, in the URL: http://www.cs.dawsoncollege.qc.ca

cs is the computername,

dawsoncollege is the clustername,

qc is a subname used to represent Quebec, and

ca is the country code for Canada

In the Domain Name, only the following domain identifiers are available as organization types:

*.arpa*	*An ARPAnet-Internet identification*
*.com*	*Commercial company*
*.edu*	*Educational institution*
*.gov*	*any governmental body*
*.mil*	*Military*
*.net*	*An Internet access provider*
*.org*	*Anything else not in the above categories*

Any address outside of the USA must have a country designator, for example:

uk for United Kingdom

ca for Canada

fr for France

au for Australia

us for United States

These country codes are often used without one of the standard domain identifiers, e.g. aei.ca

Subdomain names can be used to represent states in the US, e.g. "ga" or "ny".

Some examples of domain names are:

*aircanada.ca*	*Air Canada*
*health.state.ny.us*	*New York State Department of Health*
*microsoft.com*	*Microsoft*
*nsf.gov*	*National Science Foundation*
*acm.org*	*Association for Computing Machinery*
*washington.edu*	*University of Washington*

All domain names must be registered with the InterNIC (Network Infomation Centre).

A large corporation may have many machines (hosts) within its network. For example, Dawson College has a host machine managed by the college for general administration purposes, and a host machine managed by the Computer Science department for student and faculty use. It has two different URLs:

http://www.dawsoncollege.qc.ca

http://www.cs.dawsoncollege.qc.ca

The "cs" in the name is a generally accepted name for a host computer for a Computer Science department within an educational institution.

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