Introduction to

Computer Networks

Budditha Hettige

Computer Network ???

• A computer network is an interconnection of a

group of computers and the world of computers

Why Computer Networks?

• Resource Sharing

– Sharing a peripheral device (disk, printer, etc.)

among several users

• Communication

– Email, web, Skype, VOIP

• Security

– Restrict the user access

Network Classification

• By scale

• By connection method

• By functional relationship (Network

Architectures)

• By network topology

• By protocol

Source: http://www.slideshare.net/MukeshChinta/networks-classification

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Classification of a Computer network

by Scale

• Personal Area Network (PAN)

• Local Area Network (LAN)

• Campus Area Network (CAN)

• Metropolitan Area Network (MAN)

• Wide Area Network (WAN).

• Global Area Network(GAN)

PAN- personal area network

• Is a computer network used for communication

among computer devices (including telephones and

personal digital assistants) close to one person

• Typically a few meters

• Wireless Connections

– Bluetooth

– IR Remote sensers

LAN- local area network

• A local area network (LAN) is a computer network

covering a small geographic area, like a home,

office, or group of buildings

• Up to 1 KM

• Wireless/ wired

– Ethernet

– Wireless

MAN- Metropolitan Area Network

• A Metropolitan Area Network is a network that

connects two or more Local Area Networks

• Connections

– Optical fiber

– Telephone

WAN-Word Area Network

• A WAN is a data communications network that

covers a relatively broad geographic area

Classification of a Computer network

by Connection method

• Optical fiber

• Ethernet

• Wireless LAN

• Home PNA,

• Power line communication

Optical fiber

• A glass or plastic fiber designed to guide light along

its length

Ethernet

• family of frame-based computer networking

technologies for local area networks (LANs)

Wireless LAN

• linking of two or more computers without using wires

Classification of a Computer network

by functional relationship

• Active Networking

• Client-server networking

• Peer-to-peer (workgroup) architectures

Active Networking

• Active networking is a communication pattern that

allows packets flowing through a

telecommunications network to dynamically modify

the operation of the network

Client-server networking

• Client

• Server

• Nodes

Peer-to-peer Network

Client-Server & Peer-to-peer

Classification of a Computer network

by Network Topology

• Bus network topology

• Star network topology

• Ring network topology

• Mesh network topology

• Star-bus network topology

• Tree or Hierarchical topology

Bus network topology

Star Network

Ring Network

Mash Topology

Tree Network Topology

Hardware for Computer Networks

IP address

• Internet Protocol (IP) address

• IP addresses are usually expressed in four-octet,

dotted-decimal form—w.x.y.z

• octet ranges in value from 0 to 255

• Consist of

– network ID and a host ID

Address

• IP 192.168.1.2

• Subnet:

– 255.255.255.0

Name Sangeetha Silva

Address:

No 23, Panadura

IP Address classes

IP Address Class Used For

Class A 1 -126 Very large networks

Class B 128-191 Medium to large networks

Class C 192-223 Small networks

Class D 224-239 Multicasting

Class E 240-255 Reserved (experimental)

Private IPv4 network ranges

ANA-reserved private IPv4 network ranges

Start End No. of addresses

24-bit block (/8 prefix, 1 × A)

10.0.0.0 10.255.255.255 16777216

20-bit block (/12 prefix, 16 × B)

172.16.0.0 172.31.255.255 1048576

16-bit block (/16 prefix, 256 × C)

192.168.0.0 192.168.255.255 65536

IP Address

• IP addresses whose first octet is 127 (127.0.0.0)

represent the loopback address and are used for

troubleshooting purposes only, not for naming hosts

Terms in the Computer Network

Node

• Client

• Sever

– Mail Server

– File Server

– Web Server

– Proxy Server

– DHCP Server

– DNS Server

Web Server

Proxy Server

DHCP Server

DNS Server

Lab Activity

• Show Network Settings in your computer

– ipconfig

Lab Activity

• Show other computers that are available in the

network

– net view

Network Configuration

• Acknowledge to other computer using ping

command

– ping <ip address>

Example

• According to your PC configuration identify the following facts.

– IP Address

– Subnet mask

– Gateway

– DNS server

– Identify Other computers in your network

– Identify IP for the following URLs

• www.google.com

• www.ou.ac.lk

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