INTERNET AND ITS SERVICES

                                       THE INTERNET

DEFINITION:

The Internet is a network of computers, which links many different types of computers all over the world. It is a network of networks sharing a common mechanism for addressing (identifying) computers, and a common set of communication protocols for communications between two computers on the network.

BRIEF HISTORY:

The internet has its root in the ARPANET system of the Advanced Research Project Agency of the U.S. Department of Defense. ARPANET was the first Wan and had only four sites in 1969. The Internet evolved from basic ideas of ARPANET for interconnecting computers. Initially, research organizations and universities used it to share and exchange information. In 1989, the U.S. Government lifted restrictions on the Internet, and allowed its usage for commercial purpose as well. Since then, the Internet has grown rapidly to become the world’s largest network. It now interconnects more than 30,000 networks, allowing more than 10 million computers, and more than 50 million computer users in more than 150 countries around the world to communicate with each other. The Internet continues to grow at a rapid pace.

ITS BASIC SERVICES:

     The Internet provides the following four types of basic services to its users.
(1.)  ELECTRONIC MAIL:

Electronic mail service (known as e-mail in short) enables an internet user to send a mail (message) to another internet user in any part of the world in a near-real-time manner. An e-mail message takes a few seconds to several minutes to reach its destination, because it travels from one network to another, until it reaches its destination.

E-mail service has many similarities with postal mail service. All internet users have an e-mail address, just as all of us have a postal address. Each Internet user has a logical mailbox, just as each one of us has a mailbox in our house. When sending a mail to another user, a sender specifies the e-mail address of the receiver, just as we write postal address of the receiver of a post in postal mail system. E-mail service delivers an already sent mail into its receiver’s mailbox. The receiver extracts the mail from his/her mailbox and reads it at his/her own convenient time, just as in a postal mail system. After reading the message, the receiver can save it , delete it, forward it to someone else, or respond to it by sending another message back.

Message in e-mail service can contain not only text documents but also image, audio, and video data. Only restriction is that the data must be in computer-readable format.

With E-mail service, the Internet has proved to be rapid and productive communication tool for millions of users. As compared to paper mail, telephone, and fax many prefer e-mail because of its following advantages:

     (1.)  It is faster than paper mail.

     (2.)  Unlike telephone, the persons communicating need not be available at the same time.
     (3.)  Unlike fax documents, the receiver of an e-mail document can store it in computer, and can edit it easily using editing programs.

    (2.)  FILE TRANSFER PROTOCOL (FTP):

FPT service enables an internet user to move a file from one computer to another on the Internet. A file may contain any type of digital information- text document, image, network, movie, sound, software etc. Downloading is the process of moving a file from a remote computer to one’s own computer, and uploading is the process of moving a file from one’s computer to a remote computer.

In FTP service, a file transfer takes place in following manner:

      (1.)  A user executes the ftp command on his/her local computer, specifying address of the remote computer as a parameter.

      (2.)  An FTP process running on user’s computer (called FTP client process) establishes a connection with an FTP process running on remote computer (called FTP server process).

      (3.)  The system then asks the user to enter his/her login name and the password on the remote computer to ensure that the user processes permission to access the remote computer.

      (4.)  After successful login, the user downloads or uploads the desired file(s) by using get (for downloading) and put (for uploading) commands. The user can also list directories, or move between directories of the remote computer, before deciding which file(s) to transfer.

Notice that a user needs access rights for a remote computer to transfer files to/from it. With this restriction, it is almost impossible to provide access rights to the large number of users on the Internet to a computer that contains shareable information. The concept of anonymous FTP site solves this problem. An anonymous FTP site is a computer allowing a user to log in with a username of anonymous and a password that is user’s e-mail address. The user can then download files that have been stored for sharing on this site (computer). Such sites are called publicly accessible sites because any user on the internet can access them.

    (3.)  TELNET.

Telnet service enables an Internet user to log in to another computer on the Internet form his/her local computer. That is, a user can execute the telnet command on his/her local computer to start a login session on a remote computer. This action is also called “remote login”.

To start remote login session, a user types telnet command and address of the remote computer on his/her local computer. The remote computer then authenticates the user by asking him/her to enter a login name (user ID) and a password. If the user specifies a correct login name and password, the remote computer logs in the user, and telnet command then enters input mode. From now onwards (until the telnet session is active), anything that the user types on the local computer is sent to the remote computer for processing.

Some common uses of telnet service are.

     (1.)  For using computing power of a remote computer. For example, when a user’s local computer is an ordinary personal computer while the remote computer is a powerful supercomputer, and the user needs to process a job on supercomputer.

     (2.)  For using some software on a remote computer, which is not available on user’s local computer.

     (3.)  For accessing information from a database or archive on a remote computer. An information archive of interest to a user, such as public database or library resources, may be available on the remote computer.

     (4.)  For logging in to one’s own computer from another computer. For example, if a user is attending a conference in another city, he/she can use a computer on the Internet in that city to telnet to his/her own computer in his/her office and access information stored on it.

(4.)USENET NEWS:

Usenet service enables a group of Internet users to exchange their views/ideas/information on some common topic of interest with all members belonging to the group. Several such groups exist on the Internet and are called newsgroups. For example, a newsgroup named comp.security.misc consists of users having interest in computer security issues.

A newsgroup is like a large notice board accessible to all members belonging to the group. A member, who wants to exchange his/her views/ideas/information with other members, creates a special formatted message and submits it to the usenet software running on his/her own computer. The software posts the message on the virtual notice board. Any member belonging to the same newsgroup can read (see) the posted message, just as anyone having access to a notice board can read a notice posted on it.

There are two types of newsgroups-moderated and non-moderated. In a moderated newsgroup, only selected members have right to post (write) a message directly on a virtual notice board, whereas in a non-moderated newsgroup, any member can post a message on it directly. In a moderated newsgroup, when an ordinary member creates a new message, he/she first sends it to one of the members having right to post a message on the notice board-directly. The authorized member then checks the message to decide its appropriateness for posting. He /she does necessary editing (if any) to improve the message’s quality, and then post it on the notice board. The message now becomes readable to (can be seen by) other members.

Main idea of a moderated newsgroup is to ensure quality of posted message. As no one moderates quality of message in a non-moderated newsgroup, anyone can post anything. However, members of such newsgroups should be careful in posting a message, because other members may react angrily by sending a flaming message in response to an ill-mannered message. To address this issue, the concept of netiquette (network etiquette) has evolved, which deals with rules of framing messages that will not hurt others.