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Computer Networks

Part -2


Types of Networks by Components


According to the role played by network computers in the network operation. On the basis of this, there can be two types of computer networks:

Peer to peer networks

Client/Server Networks

Difference between Client-Server and Peer-to-Peer Network:





In Client-Server Network, Clients and
server are differentiated, Specific
server and clients are present.

In Peer-to-Peer Network, Clients and
server are not differentiated.


Client-Server Network focuses on
information sharing.

While Peer-to-Peer Network focuses on


In Client-Server Network, Centralized
server is used to store the data.

While in Peer-to-Peer Network, Each peer
has its own data.


In Client-Server Network, Server
respond the services which is request
by Client.

While in Peer-to-Peer Network, Each and
every node can do both request and
respond for the services.


Client-Server Network are costlier than
Peer-to-Peer Network.

While Peer-to-Peer Network are less
costlier than Client-Server Network.


Client-Server Network are more stable
than Peer-to-Peer Network.

While Peer-to-Peer Network are less
stable if number of peer is increase.

Wire and Wireless Networks

Wired Network

As we know “wired” is the term refers to any physical medium consisting of cables.

The most commonly used cables in wired networks are one of the following three types.

1. Twisted pair cables

2. Coaxial Cable

3. Fiber optic Cable

Wireless Network

“Wireless” is the term refers to medium made of electromagnetic waves or infrared waves. All the wireless devices will have antenna or sensors. Typical wireless devices include cellular mobile, wireless sensors, TV remote, satellite disc receiver, laptops with WLAN card etc.

Examples are Wi-Fi, Bluetooth , infra red, Wimax, etc.

Wired Network

1.Twisted Pair Cables

Twisted Pair or Ethernet cable is most common type of media which consists four insulated pairs of wires twisted around each other. Twisting helps to reduce crosstalk and Electro Magnetic Interference (EMI) effects. It is available in Shielded Twisted Pairs (STP) or Unshielded Twisted Pair (UTP) types. In STP, pairs are covered by an extra insulation to further reduce the signal interference.


  • It is low-cost, low-weight and flexible cables.
  • It is easy to install and maintain and requires RJ-45 Connector.


  • Suitable for short distance (up to 100 mt.). For long distance Repeater is required.
  • It supports low bandwidth and offers up to 100 Mbps speed.

2.Coaxial cable

This types of cable consists a solid insulated wire surrounded by wire mesh, each separated by some kind of foil or insulator. The inner core carries the signal and mesh provides the ground. Co-axial C ab1le or Coax, is most common in Cable TV transmission.

It comes in two types- Thinnet (185 mt), Thicknet(500 mt) A connector known as BNC connector is used to connect network devices.


  • It offers high bandwidth and carry data for a long distance (185-500 m)
  • Suitable for Broadband transmission (cable TV) and can be used in shared cable network.


  • It is less flexible and expensive compared to Twisted Pair cable.
  • Not compatible with modern cables like UTP and STP

3.Fiber Optic

Optical Fiber consists of thin glass or glass like material and carry light. Signal are modulated and transmitted in the form of light pulses from source using Light Emitting Diode (LED) or LASER beam.

The Fiber cable consists Core (Glass or Plastic) covered by Cladding, which reflects light back to the core. A Protective cover including Buffer Jacket is used for extra protection.

Two types of transmission i.e. Single mode (LESER) and Multimode (LED) is possible.


  • It is free from EMI since no Electrical signal are carried.
  • Offers secure and high speed transmission up to a long distance.


  • Expensive and quite fragile (breakable).
  • Complicated Installation procedure and difficult to join two broken fiber.
  • Not suitable for domestic purposes due to high maintenance cost.  

Wireless Transmission Medium

1. Infrared Waves

  • Infrared Wave Network allows devices to communicate within a short-range (approx. 5 meters) using wireless signals.
  • The infrared transmission technology used in computers is similar to that used in modern Remote Operated Electronic product like TV, Cordless phones and Toys etc.
  • Infrared Communication is affected by various factors like angle, distance, electromagnetic noise and heat etc.
  • The biggest drawback with Infrared communication is its short range and angle problems which makes it unsuitable for modern day mobility needs.

Features of Infrared Transmission

  • Line of sight transmission.
  • No Government License.
  • Do not cross solid objects.
  • Applicable for short-range.

2. Radio Wave

  • Radio communication uses Radio frequencies like Medium Wave, Short Wave, VHF and UHF (3KHz-3 GHz).
  • Signal are modulated on a high speed Radio wave carrier frequency using Amplitude Modulation (AM), Frequency Modulation(FM) or Phase Modulation(PM) etc.
  • Generally, it is used to make Broadcast Network like AM/FM Radio network within a city.


  • It covers a larger span of coverage and offers mobility.
  • Propagates in Omni direction (surrounding) and can penetrate solid walls/buildings easily.


  • Expensive and in-secure communication.
  • It is susceptible to whether effects.

3. Microwave

Microwaves are high energy radio waves that are used for line of sight communication between a pair of communication devices equipped with Parabolic antenna, aligned with each other.


  • Suitable for high speed and long distance (upto 100 km.) communication.
  • No need for lying cable and ability to communicate over oceans.


  • Implementation and maintenance cost is high.
  • Insecure communication and propagation of waves is susceptible to whether effects like Rain and thunder etc.
  • Only Line-of-sight transmission is possible.  

4. Satellite

  • Satellite communication uses Microwave (1.5 GHz -20GHz)as media. Satellites like the Geo-stationary or Polar satellites are used to establish communication links among various earth based stations having Antenna.
  • Services like DTH, VSAT, GPS and Satellite phones etc. are offered by the satellite.
  • Satellite works like a Trans-Receiver Antenna in the space, which receives, regenerates and redirects signals.


  • It covers a larger geographical area of the earth.
  • Offers secure, uninterrupted and high quality transmission.


  • Very expensive and high operating cost.
  • Slower than Microwave transmission.
  • Requires legal permissions.

5. Bluetooth

  • Bluetooth is a wireless technology for creating personal networks operating within a range of 10 meters.
  • It uses 2.4 GHz unlicensed band.
  • Bluetooth is used to establish a PAN across handheld devices like a cell phone and Bluetooth enabled Computer.
  • Bluetooth is a communications protocol standard primarily designed for low power consumption, with a short range.

6.Wi-Fi (Wireless Fidelity)

  • Communication is similar to Bluetooth in operation but covers a large range of coverage (50 -200mts.).
  • It offers network connectivity with mobility (Any place) within its range.
  • Mostly it is used in home, office buildings, college or university campus, Cyber Café and hotels to provide Internet connectivity.

7. WiMAX (Worldwide Interoperability for Microwave Access)

  • is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide multiple physical layer (PHY) and Media Access Control (MAC) options.
  • WiMax developed to provide wireless broadband access to buildings, either in competition to existing wired networks or alone in currently unserved rural or thinly populated areas.
  • It can also be used to connect WLAN hotspots to the Internet. WiMAX is also intended to provide broadband connectivity to mobile devices.

Network Protocols

Protocol refers to the set of rules applicable for a network. The protocol defines standardised format for the data packet to be transmitted through the network.


Commonly used protocols:


HTTP (HyperText Transfer Protocol)

HTTP is an application layer protocol. It is widely used protocol. This protocol is used by the world wide web. HTTP defines how messages are formatted and transmitted and what actions web servers and browsers should take in response to various commands. It is a request/response standard between a client (end-user) and a server (website).


TCP/IP (Transmission Control Protocol/Internet Protocol)

TCP/IP is the communication protocol for the Internet. It defines the rules, computers must follow to communicate with each other over the Internet. The TCP/IP is a protocol used in E-mail transmission. The TCP/IP is a protocol, which is responsible for finding path for the destination. It also splits the message into several datagrams, if it does not fit in one datagram. Therefore, these datagrams are sent through different alternate paths towards the destination.

The TCP makes sure that the datagram arrives at the destination correctly. While IP is responsible for moving packet of data from source to destination. It handles the address part of each packet so that it reaches to the right destination.


PPP (Point-to-Point Protocol)

It is a data link layer protocol, which encapsulates other network layer protocols for transmission on synchronous and asynchronous communication lines. The PPP is used with dial-up Internet connections including ISDN. It is a layered protocol, which is used for transmitting the IP data packets over usual telephone lines



FTP (File Transfer Protocol)

It is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is based on client/server principle. It establishes two connections between the hosts. One connection is used for data transfer, which is opened and closed for each file transfer and the other for control information, which remains connected during the entire interactive FTP session.


Remote Login (Telnet)

Telnet is a protocol used for creating a connection with a remote computer. Once your telnet client establishes a connection to the remote host, telnet client becomes a virtual terminal, allowing you to communicate with the remote host from your computer. It establishes a connection either with command line client or with a programmatic interface. Telnet provides an error free connection, which is always faster than the latest conventional modems. Post


Office Protocol (POP)

POP is an application-layer Internet standard protocol, used by local E-mail clients to retrieve E-mail from a remote server over a TCP/IP connection.

POP3 (Post Office Protocol version 3) is the most recent version of a standard protocol for receiving E-mail. POP3 is a client/server protocol in which E-mail is received and held for you by your Internet server  


Simple Mail Transfer Protocol (SMTP)

SMTP is the protocol used for sending E-mail over the Internet. Your E-mail client uses SMTP to send a message to the mail server and the mail server uses SMTP to relay that message to the correct receiving mail server. Basically, SMTP is a set of commands that authenticate and direct the transfer of electronic mail. When  configuring the settings for your E-mail program, you usually need to set the SMTP server to your local Internet Service Provider’s
SMTP settings.


Voice over Internet Protocol (VoIP)

VoIP is a technology that enables voice communications over the Internet through the compression of voice into data packets that can be efficiently transmitted over data networks and then converted back into voice at the other end. It required broadband connection


IP Address (Internet Protocol Address)

The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another on the Internet. Each computer (known as a host) on the Internet has atleast one IP address that uniquely identifies it from all other computers on the Internet. The format of an IP address is a 32 bits numeric address written as four numbers separated by periods (.). Each number can be in range 0 to 255. e.g.



Web Services

Web services are built on many technologies, which work in conjunction with emerging standards to ensure the manageability and standards, which extend the World Wide Web infrastructure to provide the means for software to connect to other software applications.

World Wide Web (WWW)

The World Wide Web (WWW) is an Internet service, which allows a particularly configured server computer to distribute documents across the Internet in a standard way. This web standard allows programs on many different computer platforms to properly format and display the information server. These programs are called web browsers. The WWW is a collection of millions of files stored on thousands of computers all over the world. The flow of information is controlled by a protocol. The protocol used in this exchange is called HyperText Transfer Protocol (HTTP).

HyperText Markup Language (HTML)

HyperText Markup Language (HTML) is the main markup language for creating web pages and other information that can be displayed in a web browser.

eXtensible Markup Language (XML)

XML is a markup language that defines a set of rules for encoding documents in a format, that is both human-readable and machine-readable. It is defined in the XML 1.0 specification produced by the W3C and several other related specifications. The design goals of XML emphasise simplicity, generality and usability over the Internet

Domain Name

A domain name is a unique name that identifies a particular website and represents the name of the server, where the web pages store. Domain names are formed by the rules and procedures of the Domain Name System (DNS).

Uniform Resource Locator (URL)

A uniform resource locator, abbreviated URL, also known as web address, is a specific character string that constitutes a reference to a resource. In most web browsers, the URL of a web page is displayed on top inside an address bar.

URL consists of three parts

(i) Network protocol

(ii) Host name or address

(iii) File or resource location.

These parts are separated by special characters as follows Protocol://host/location An example of a typical URL would be “”

Web Page

The backbone of the World Wide Web is made up of files or documents called pages or web pages, that contain information and links to resources both text and multimedia. It is created using HTML. The web is a collection of large number of computer  documents and web pages that stored on computers around the world which are connected to one another using hyperlink.

A web page can be of two types

Static Web Page

A web page which displays same kind of information whenever a user visits, it is known as a static web page.
A static web page generally has .htm or .html as extension.

Dynamic Web Page

An interactive web page is a dynamic web page.
A dynamic web page uses scripting languages to display changing content on the web page. Such a page generally has .php, .asp or .jsp as extension.


A group of related web pages that follow the same theme and are connected together with hyperlinks is called a website. A website displays related information on a specific topic. Each website is accessed by its own address known as URL (Uniform Resource Locator). The main or first page of a website is known as home page.

Web Browser

A web browser (commonly referred to as a browser) is a software application for retrieving, presenting and traversing information resources on the World Wide Web

Web Server

The term web server can refer to either the hardware (the computer) or the software (the computer application) that helps to deliver web content, accessible through the Internet. The most common use of web server is to host websites, but there are other uses such as gaming, data storage or running enterprise applications.

Web Hosting

A web hosting service is a type of Internet hosting service that allows individuals and organisations to make their website accessible via the World Wide Web. A web host is the business of providing server space, web services and file maintenance for websites controlled by individuals or companies that do not have their own web servers. Many ISPs (Internet Service Providers), such as America Online will allow subscribers a small amount of server space to host a personal web page.

Web hosting can be of four types as follows

  1. Free Hosting
  2. Virtual or Shared Hosting
  3. Dedicated Hosting
  4. Co-location Hosting
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