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Computer Networking and Telecommunication
Introduction to Telecommunication
The word “tele” means large distance and “communication” means sharing of ideas, views, and information with other individuals or machines. So telecommunication is the art of communicating at a distance. In the past, people used pigeons to send and receive messages for long distances. later on, the invention of the Telegraph and Telephone made a remarkable change in the field of telecommunication. The three main media of telecommunication are telephone, radio, and television.
After the development of microcomputers in the 1980s, people started using computer and telephone (Internet) lines to send or receive data from one place to another. The use of the computer to send and receive data from one location to another is known as Data Communication. Nowadays people in Nepal also use computer and telephone media to transmit data, get the information of the examination result, to get account information in bank, reserve the air tickets, rooms in the hotel, railway reservation and so on.
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| Fig. Networking |
Basic Elements of a Communication System
The five basic elements of any communication system are:
- A sender (source), which creates the message to be transferred.
- A medium, which carries the message.
- A Receiver (sink) receives the messages.
- Data – instruction or information to be carried out from one place to other.
- Protocols – rules for the safe transfer of data.
For example: when you speak to your friend on the telephone, you are the sender. The telephone line through which your voice is transmitted is the medium and your friend is the receiver. This is a simple example of voice communication. Data communication is also the same. In data communication, the sender and the receiver are normally computers. The transmission media are the telephone lines, microwave links, satellite links, and wired connections. In data communication, data can be text, picture, or sound. For the transmission of data from one point to another point, computers are interconnected through transmission media. Some examples of data communication are reservation of hotels, trains, and planes, etc.
Data Transmission Modes
The different modes of transmitting data from one place to another are:
- Simplex
- Half-duplex
- Full duplex or Duplex
Simplex
When the transmission of data takes place in only one direction, we call it a simplex mode of data transmission. Devices connected to this mode can either send or receive data at one time. for example radio, television and newspapers.
Half-duplex
When data travels in both directions, but only one direction at a time we call it a half-duplex mode of transmission. Thus, a half-duplex mode can alternatively send or receive data. This is the most common type of transmission for voice communication as only one person is supposed to speak at a time. For example Walkie-talkie.
Full duplex
When data travels in both directions simultaneously, we call it a full-duplex mode of transmission or simply duplex. It improves the efficiency as the data can travel in both directions at a time. For example Telephone and Mobile.
Common terms used in communication media
a. BITS
BITS stands for Binary digits. It is the smallest unit of measurement of data in the computer system. It is either 0 or 1.
b. Bandwidth
It is the amount of data that can travel through a given transmission medium. It is the range of frequency that is available for the transmission of data. It is measured in kbps (Kilo Bits Per Second) or bps (Bits Per Second). Like in a narrow road, less flow of traffic is required and in a wide road, the flow of traffic is more, similarly, less bandwidth means less amount of data and more bandwidth means more data can pass through the communication medium.
Computer Network
When two or more than two computers are connected with each other, either with the help of a cable or without a cable, the computers are in-network. Computers in networks can share the resources like data, applications, software, hardware, and so on.
Services provided by a network
Network services are the things that a network can do. The major services provided by the network are:
a. File services
It includes the transfer of files and storage, migration of data from one place to another, file update, and others.
b. Print Services
It includes sharing printing devices like printers. A printer that is used for sharing in a network acts as a print server.
c. Message Services
It includes sharing the messages like e-mail, manages integrated email and voice mail, instant messaging (IM).
d. Application services
It includes sharing the application programs. The server holds the application and they are accessed by the users in the network.
e. Database Services
It includes distributing data. The main server holds the data and distributes it to a number of users that can access the database and modify the data. It also provides print facilities for the data.
Advantages of computer network
- Hardware Sharing
- Software sharing
- Sharing Remote Database
- Communication
- Cost-Effective
Disadvantages of computer network
- Virus transfer
- Less secure
- Less reliable
Networking Components
Stand-alone PC can use the resources that are available in a single PC or computer. But networked PCs can access the resources of the network and its capabilities. The most essential components of a simple network are:
- Server
- Workstation
- Network Interface Card(NIC)
- Communication Channel or Transmission media
Server
The main computer in the network, which allows sharing its resources like sharing of hardware and software, is known as a server. The operating software used in a server is different from a standalone computer. The software used by a server is Network Operating System (NOS) like Novell NETWARE, Linux, Unix, Windows NT, Advanced 2000 servers, and so on. There are two types of servers. They are:
i. Non-dedicated server
The server which provides services to the workstation and can be used as a workstation is known as a non-dedicated server. Windows NT, Advances 2000 servers are examples of non-dedicated servers.
ii. Dedicated server
The computer which are reserves for server’s job only and helps workstations to access data, software, and hardware resources are dedicated servers. These computers cannot be used as workstations. They are powerful computers capable of handling the huge workloads demanded by the workstations. For example, the Novell NETWARE server is a dedicated server OS. In a large network, where there are hundreds of workstations sharing resources, a single computer is not sufficient to function as a server. So, there may be several servers that allow workstations to share specific resources. Other servers in the network may be a File server, print server, Modem server, and so on.
File server
A file server is a server exclusively used for serving files related requests like storing files, deciding about their privileges, and regulating the amount of space allowed for each user.
Print server
The print server takes care of the printing requirements of a number of workstations. In a LAN with a large number of workstations, several users can request printing in intervals of just a few minutes. The print server actually stores the files to be printed on this memory and then executes these requests on a First In First Out (FIFO) basis.
MODEM server
A modem server allows network users to use a MODEM to transmit long-distance messages through the internet.
Workstation
Workstations are the computers that are attached to a network and use the resources of the network. A computer in a network is also called a node.
Network Interface Card (NIC)
NIC is a hardware device that acts as an interface between the networking cable and the computer. Each NIC that is attached to a computer having a unique number to identify it, called node address. Thus a node address of the NIC is attached to the computer. NICs are the major factors in determining the speed and performance of a network. It is a good idea to use the fastest network card available for the workstations we are using.
