Computer networking and telecommunication Notes:


Definition: Communication means the exchange of idea, views, opinion, understanding, feelings, emotions, facts or information between two or more persons by any sources or medium.


Definition: Telecommunication is the exchange of information over significant distances by electronic means.
Mobile phones, land lines, VOIP, etc. are examples of telecommunication.

Data communication:

Definition: Data communication is the movement of encoded information from one point to another by means of the electrical or optical transmission system.
Basic elements of data communication:
Following are the basic elements of data communication:
a) Source / Sender.
b) Data communication device.
c) Communication medium.
d) Sink / Receiver
e) Communication protocol, etc.

Mode of data transmission:

Definition: A data transmission mode refers to how the data travels from sender to receiver.
There are three types of Mode of data transmission:
i. Simplex Duplex.
ii. Half Duplex.
iii. Full duplex, etc.

Simple duplex:

Definition: The mode of data transmission in which data transmitted in one way only is called simplex duplex.
Example: Television, Radio, and Newspaper, etc.

Half duplex:

Definition: The mode of data transmission in which data transmitted in both direction but not at the same time is called half-duplex mode.
Example: Fax transfer and Willkie talkie, etc.

Full duplex:

Definition: The mode of data transmission in which data transmitted in both direction at the same time.
Example: Telephone signal and Computer transmission, etc.

Analog and Digital Signals:

Analog signal: The data transmission in which analog signals are transmitted in continuous form and can be represented in sine waves is known as an analog signal.
Example: T.V transmission is an example of an Analog signal.

Digital signal: The data transmission in which data flow is in the form of bits (0,1) is known as the digital signal.
Example: Pen drive to hard drive, RAM to a microprocessor, etc.

Transmission media (Communication media):

Definition: Transmission media are the physical channels through which data is transmitted between transmission media.
Types of Transmission media:
i. Guided/Bounded/Wired communication media.
ii. Unguided/Unbounded/ Wireless communication media, etc.

Guided/Wired communication media:

Definition: The transmission media which use wire to transfer data and information from source to destination are called guided communication media.
For Example Twisted pair cable, Coaxial cable and Fiber optic cable, etc.

Twisted pair cable:

It has two types:
a) Shielded Twisted pair cable (STP)
b) Unshielded Twisted pair cable (UTP), etc.

Shielded Twisted pair cable (STP): The data carrying capacity from 16Mbps to 500Mbps, and more expensive than UTP.
Unshielded Twisted pair cable (STP): The data carrying capacity is up to 100Mbps, and less expansive than STP.

Coaxial Cable:

Following are the properties of coaxial cable:
a) Data transfer rate is up to 150Mbps.
b) Wider bandwidth, more difficult to install, and more costly than twisted pair.
c) Less susceptible to noise.
d) A quarter inch or more diameter, therefore less flexible than twisted pair.
e) It consists of wire surrounded by an insulating layer, a shielding layer, and outer jacket, etc.

Following are the uses of coaxial cable:
a) Data communication.
b) Voice communication.
c) Video communication, etc.

Types of Coaxial cable:
a) Thinnet.
b) Thicknet, etc.

Thinnet: It is a variant of Ethernet technology uses a thin type of coaxial cable.
Thicknet: It is an Ethernet technology uses a thick type of coaxial cable.

Fiber Optic cable:

Following are the properties of fiber optic cable:
a) Low error rate, very high noise immunity to electrical and magnetic noise.
b) Reduced size and weight, but easy to break.
c) Broadband width.
d) High data rate over 2Gbps.
e) Uses Voice communication, Data communication, and Video communication, etc.

Unguided/Wireless communication media:

Definition: Unguided communication media transmits the information through the air in much the same way as radio stations broadcast their programming.
Example: Bluetooth, Wi-Fi, Satellite, etc.


Following are the properties of Microwave:
a) Parabolic antennas are mounted on a tower to send beams.
b) Lack of security.
c) High initial equipment cost.
d) Possible interference from the environment.
e) Relatively high-speed data rates up to 25Mbps.
f) Uses Voice communication, etc.


Following are the properties of Satellite:
a) The line of sight required between satellite and earth stations.
b) Geosynchronous orbit (22,300).
c) Low security.
d) Easy of adding stations.
e) Data rates up to 50Mbps, etc.

Wireless Media:

Following are the types of wireless media:
a) Infrared
b) Bluetooth
c) Wi-Fi (Wireless Fidelity),etc.


Definition: Infrared (IR) is the type of electromagnetic wave of large wavelength and small frequencies than visible light.
Its frequencies are low.


Definition: The wireless radio frequency technology that allows various devices to communicate with each other is known as Bluetooth.
It is low cost, low power device.

Wi-Fi (Wireless Fidelity):

Definition: The popular networking technology that used radio wave to provide high-speed internet and the network connection is known as Wi-Fi.
It is the product of LAN. Its full form is Wireless Fidelity.


Networking connecting devices:

Definition: The devices used to connect two or more network from a single network is known as networking connecting devices.
Some examples of networking connecting devices:
a) Modem
b) NIC
c) Switch/Hub
d) Router
e) Gateway
d) Repeater, etc.


Definition: Modem is an electronic device used to convert digital signal to analog and vice versa.
The full form of Modem is Modulator and Demodulator. The modulator converts a digital signal into analog and demodulator converts an analog signal into digital.

NIC (Network Interface Card):

Definition: The network interface card (NIC) provides the physical connection between the network and the computer workstation.
It stands for Network interface card.


Definition: A switch is a device that provides a central connection point for the cable from workstations, servers, and peripherals.


Definition: A router is a multiport network connectivity device that directs data between nodes on the network.
It is similar to the super intelligent bridge.
Following are the function of the router:
a) Direct signal traffic efficiently.
b) Router message between any two protocols.
c) Router message between different topologies.
d) Router message across fiber optic, coaxial, and twisted-pair cabling, etc.


Definition: A gateway is a node or device that serves as an entrance to another network.
It is used to connect the user to the internet. It also acts as the firewall in the network.


Definition: The device which boosts weak signals into strength passing along the cable is known as a repeater.

Network software:

Definition: Network software is an extremely broad term for a range of software aimed at the design and implementation of modern networks.
Some example of network operating software is Windows NT, Linux, Novell NetWare, etc.

Communication protocol:

Definition: A protocol is a set of rules that govern the transmission of data over a communication network.
Following are the types of protocols:
a) TCP/IP (Transmission control protocol/ Internet protocol).
b) SMTP (Simple mail transfer protocol).
c) POP (Post office protocol).
d) FTP (File transfer protocol)
e) HTTP ( Hypertext transfer protocol).
f) Telnet Protocol (Tele Type network protocol), etc.

Protocols with uses:
a) TCP/IP (Transmission control protocol/ Internet protocol): It is used for the reliable transmission of data over a network.
b) SMTP (Simple mail transfer protocol): It is used for sending email between servers.
c) POP (Post office protocol): It is used to retrieve e-mail from mail servers.
d) FTP (File transfer protocol): It is used for file transfer (Uploading and downloading).
e) HTTP (Hypertext transfer protocol): It is used for transmitting and displaying information in the form of web pages on the browser.
f) Telnet Protocol (Tele Type network protocol): It is used to remote logins to the computer via the internet, etc.

Computer Network:

Definition: The interconnection of two or more than two computers by wire or wireless to share data, information, hardware, and software with other users is called computer network.
SNA (System Network Architecture) was the first computer network developed by IBM to establish the link between its computer and it was limited to the company only.

Following are the advantages of a computer network:
a) It can share copies of the single file among many users at the same time.
b) It can share the application of the entire network, which reduces the cost of purchasing multiple software.
c) It can share computers resources link printer, scanner, fax machine, modem, etc.
d) Faster and cheaper communication possible.
e) Data backup and recovery is possible, etc.

Following are the disadvantages of a computer network:
a) A virus can spread each mostly through the computer network.
b) Cybercrime is originated from the computer network.
c) It is expensive to set up.
d) Lots of chances of the technical problem in a computer network.
e) Specially skilled manpower is required to operate and maintain a computer network, etc.

The terminology used in a computer network:

Following are the terms used in a computer network:

Definition: A network node is a connection point that can receive, create, store or send data along distributed network routers.

Definition: A server is central, and usually the largest, and most powerful computer in a network which stores data and provides to workstations.
Following are the types of servers:
a) Application server.
b) Database server.
c) Printer server.
d) File server.
e) Web server, etc.

Definition: A client is a computer that retrieves information from or uses resources provided by the server or the main computer.

Definition: A workstation is a computer intended for individual use that is faster and more capable than a personal computer.

Host computer:
Definition: The main or controlling computer connected to other computer or terminals to which it provides data or computing services via a network is known as the Host computer.

Definition: The amount of data that can be carried from one point to another in a given time period (usually a second) is known as bandwidth.
Bandwidth usually expressed in bits per second (bps), megabits per second (Mbps), etc.

Types of a computer network:
Computer network is generally classified into two types according to the architecture and geographical area. They are:
On the basis of architecture:
i. Peer to peer network:
ii. Client-server network, etc.
On the basis of geographical area:
i. LAN (Local area network).
ii. MAN (Metropolitan area network).
iii. WAN (Wide area network), etc.

On the basis of architecture:

Peer to peer network:

Definition: The architecture network which can take both a client and server role is known as peer to peer.
It has no server.
Advantages of Peer-To-Peer Network:
a) Easy to install.
b) Inexpensive.
c) No central administrator who set the network policies.
d) No extra investment in server hardware or software required.
e) Doesn’t required a dedicated workstation.
f) Easy to troubleshoot, etc.

Disadvantages of Peer-To-Peer Network:
a) Less security.
b) Not suitable for more than 10 users.
c) Useful for the only a small organization.
d) Difficult to later time expand.
e) Each machine must be backed up individually to protect all shared data, etc.

Client-Server Network:

Definition: An arrangement of a computer to resources sharing and communicate with each other through a central device (Server) to all workstation (clients) is called client-server network.
Advantages of Client-server network:
a) It covers a large geographical area.
b) High speed.
c) High data security.
d) Centralize network management.
e) Data backup and recovery is possible, etc.

Disadvantages of Client-server network:
a) Expensive.
b) Difficult to troubleshoot and maintain.
c) Sever failure leads to the whole network failure.
d) Difficult to install and required technical manpower, etc.

On the basis of geographical area:

LAN (Local Area Network):

Definition: A LAN is a system of the interlinked personal computer in a localized area, typically less than 1km across.
Ethernet which was developed by Xerox Corporation is the famous example of LAN.
Advantages of LAN:
a) It provides a cheaper and reliable communication medium.
c) Easy to add the new computer to the network.
d) Failure of one computer in the computer doesn’t affect the functioning of the other computer, etc.

Disadvantages of LAN:
a) Installation cost is high.
b) User authority and identification is poor.
c) Occupies limited geographical area, etc.

MAN (Metropolitan Area Network):

Definition: A network which is designed to extend over an entire city is known as MAN.
It extends around 100km or less. Example of MAN is Cable television network, microwave links in the bank, etc.
Advantages of MAN:
a) Nodes are located in the wider area (generally connected the cities).
b) It enables you to connect many fast LANs together.
c) It offers a centralized managed of data.
d) It provides high security, etc.

Disadvantages of MAN:
a) The data rate is slow as compared to LAN.
b) The error rate is high as compared to LAN.
c) It offers centralized management of data.
d) Expansive.
e) Difficult to maintenance, etc.

WAN (Wide area network):

Definition: A network that connects LAN over a potentially large geographic distance is known as WAN.
It is extended worldwide. Some examples of WAN are the Internet.
computer -network-systems
Advantages of WAN:
a) It covers a large geographical area.
b) It connects different types of the network together.
c) WAN has made life and communication very easy.
d) It can support a large number of hosts.
e) It is owned by multiple organizations, etc.

Disadvantages of WAN:
a) Lower data transfer rate.
b) Set-up cost is higher.
c) Difficult to maintenance, etc.

Network Topologies:

Definition: Topology refers to the way in which a network is laid out physically.
Following things should be considered before selecting topology:
a) The cost of physical interconnections.
b) The time delay during the communication.
c) Reliability and possibility of failure.
d) Network controlling strategy or protocol, etc.

Bus/Linear Topology:

Definition: A Bus topology uses one long cable (backbone) to which network devices are directly attached by using short drop cable.
Advantages of Bus topology:
a) Easy to install and cheap.
b) Easy to add new nodes.
c) Less cable required.
d) It doesn’t affect the network if one computer goes down, etc.

Disadvantages of Bus topology:
a) It covers a small geographical area.
b) If the backbone goes down then the whole network goes down.
c) The possibility of data collision.
d) Difficult to identify the fault, etc.

Ring topology:

Definition: Ring topology consists of several computers joined together to form a circle.
It is also called Loop topology.
Advantages of Ring topology:
a) All computers are given equal access to the network.
b) It is easy to install.
c) Short cable connection which causes an increase in the network reliability.
d) Fewer chances of data collision because data travel in one direction, etc.

Disadvantages of Ring topology:
a) The failure of one station will cause the system to break down as the link will be broken.
b) Adding and removing nodes disturbs the entire network.
c) Difficult to the configuration, etc.

Star topology:

Definition: The topology which is connected with hub and star-like structure is known as a star topology.
Advantages of Star topology:
a) Easy to install and configuration.
b) Easy to find out the fault.
c) Easy to modify and expansion.
d) High data transmission is possible.
e) Single computer failure doesn’t affect the entire network, etc.

Disadvantages of Star topology:
a) Difficult to expand.
b) Require more cable than most topologies.
c) More expansive.
d) If the central controller (Hub) fails the whole network goes down, etc.

Tree topology:

Definition: The nodes are connected to each other in such a way that forms like a tree structure is known as Tree Topology.
Advantages of Tree topology:
a) Easy to extend because it is divided into many sub-units.
b) Easy to add new nodes to branches.
c) Support by  hardware and software vendors.
d) It supports various types of cable, etc.

Disadvantages of Tree topology:
a) It is expensive.
b) Less reliable.
c) If the main root or hub fails to operate, then the entire network will go down.
d) More difficult to configure and wire than other topologies, etc.

Mesh Topology:

Definition: The topology in which each computer has a dedicated point to point the link to other computer is called Mesh Topology.
The advantageA of Mesh Topology:
a) It provides alternative routes between nodes.
b) Point-to-point link makes fault isolation easy.
c) Fastest data transmission.
d) Failure in one of the computer doesn’t affect the entire network.
e) More reliable, etc.

Disadvantages of Mesh Topology:
a) Difficult to install/setup.
b) It is expensive difficult to expand.
c) It requires large cabling, etc.