A computer network is interconnection of two or more computers connected to each other so that they can exchange information such as e-mail, messages or documents, or share resources such as disk storage or printer.
Features of computer network:
Network features:
Following are the features of network:
1. File Sharing
2. Printer Sharing
3. Application Services
4. E-Mail
5. Remote Access.
File sharing:
File sharing is the primary reason to have a network.
Before networking, computers become a popular way of sharing files, if you want to transfer a file from one computer to another; you would save the file to a floppy disk & walk it over to the other computer.
File sharing requires a shared directory or disk drive to which many users can access over the network.
When many users are accessing the same file on network, more than one person can make changes to a file at the same time.
Additionally, Network operating systems that perform file sharing also administer the security of these shared files.
Advantages:
1. Easily share information on network.
2. User needs regular access of word processing files, spreadsheets so they access easily.
Disadvantages:
1. Conflicting problem arises.
2. Less secure if permission not set proper.
Printer sharing:
Printer sharing enables you to reduce the number of printer s you need & also enables you to offer much higher quality printer.
Printer sharing can be done in several different ways on network.
The most common way is to use printer queues on server.
The printer queue holds print job until any currently running print jobs are
finished and then automatically send the waiting job to the printer.
Another way to share printer on network is that each workstation accesses the printer directly (Network Printer), but each must wait its turn.
network printer that use printer queue always have a print server that handles the job of sending each print job to the printer in turn
the print server function can be filed in a number of ways:-
- By a file server with a printer connected directly to it.
- By computer connected to the network with the printer connected to that computer.
Advantages:
1. Reduce number of printer.
2. Reduce cost.
Disadvantages:
1. Reduce server performance if printer connected to server.
2. Each user must wait its turn.
Application services:
Just as file sharing, applications can also be shared on network.
You can share copy of application & keeping it on the network server, from where it is also run.
When a workstation wants to run the program, it loads the file from the network into its own memory.
Keeping application centralized reduces the amount of disk space needed on each workstation. It is easier to administer the application.
Advantage:
1. Reduces the amount of disk space needed on each workstation.
2. Centralized administration, so more security and reliability.
3. Installation of software on each workstation without CD-ROM.
4. Installing application on workstation is much faster and more convenient.
5. Reduce cost.
Disadvantage:
1. It increases network traffic on network.
2. If server fail or crash, then workstation is useless on network.
3. Requires network license copy for application software or business software.
E-mail:
E-mail is extremely valuable and important feature for communication within organization or outside the people in word.
E-mail service can be used by user in two different ways:
a. File based
b. Client server.
File based e-mail system is consists of a set of files kept in a shared location on a server.
File based e-mail system requires gateway server for connecting or handling the e-mail interface between the two system using gateway software that is part of the file based e-mail system.
In a Client-server e-mail system, an e-mail server contains the message and handles all incoming and outgoing mail.
Client-server e-mail systems are more secure and powerful than File based e-mail system.
Advantage:
1. Helpful for communication within a company or outside a company.
2. Faster communication.
Disadvantage:
1. Network becomes unreliable due to viruses.
2. Require more security mechanism.
Remote access:
Another important service for most networks is remote access to the network users’ use this feature to access their files & e-mail.
When they are traveling or working from a remote location such as their homes.
Using this feature user can access their files and e-mail, when they are travelling or working on remote location.
Some of the methods to provide remote access feature can be implemented as follows :
1. Using modem
2. Using dial-up mechanism
3. Setting up VPN
Advantages:
1. User access their files and e-mails from remote location.
2. It enables user’s access to centralized application, stored private or shared files on LAN.
Disadvantages:
1. Require more security.
2. More hardware or complex hardware required.
Technologies:
1. Public Switched Telephone Network (PSTN).
2. Leased line.
3. Integrated Services Digital Network (ISDN).
4. Cable TV.
5. Digital Subscriber Line (DSL).