The Birth of Domain Names

In the 1980's, a major change occurred as a result of the increase in scale of the Internet and its associated management issues. To make it easy for people to use the network, hosts were assigned names, so that it was not necessary to remember the numeric addresses. Originally, there were a fairly limited number of hosts, so it was feasible to maintain a single table of all the hosts and their names and addresses. The shift to having a large number of independently managed networks or so called Local Area Networks (LANs) meant that having a single ta­ble of hosts was no longer feasible, and the Domain Name System (DNS) was established. A domain name is the letters or words that vis­itors must type in to come to your website. The DNS permitted the conversion of a numeric host address (i.e, 215.72.87.66) to a simpler, easier to remember name address (e.g. www.prospekt.org).

The Birth of the Web Browser

In October of 1994, Mosaic Communications Corporation (renamed "Netscape Communications" on 11 November 1994) introduced the first public version of their browser, "Mosaic NetScape." A browser is a software program, which reads the computer language (Hyper Text Markup Language - HTML) used to code information on the Web and allows you to view documents on the Web. This was one of the first web browsers to be freely distributed across the Internet.

How does email work?

Let's say you're sending mail to (user name@domain name). When you've finished composing your email, your mailer (email software) performs a gethostbyname system call to look up the IP address of the remote host (aol.com). The IP address (INTERNET PROTOCOL ad­dress) is an assigned number, which identifies a host in an Internet. It has three parts: network number, optional subnet number, and host number.

Your system queries an Internet name server to find the address of aol.com.

Your mailer opens a virtual circuit over the Internet to "joy's" mailer. It communicates with the remote mailer by using the Simple Mail Transfer Protocol (SMTP).

If all goes well, the mail is usually delivered within a few seconds, even if the recipient's machine is on the other side of the world.

If the remote site is down, your mailer will keep trying every hour or so, usually for a couple of days.

If the site still can't be reached, the mail will be returned to you as "undeliverable message."

People and organizations without fulltime Internet connections may also use the Post Office Protocol (POP).

TASKS

I. Answer the questions:

1. When and how did Internet get started?

2. What is the TCP/IP protocol?

3. Who provides physical connections that allow the access to the Internet?

4. How is the host address expressed in DNS?

5. What is a browser?

6. What is a domain name?

7. What is the IP address?

Дата добавления: 2015-09-06