Computer Communication & Networks

Introduction to Networking

Made by:Sidra !

What is a Network?

A network consists of 2 or more computers connected together, and they can communicate and share resources

Why Networking?

• Sharing information — i.e. data communication

• Do you prefer these?

• Or this?

• Sharing hardware or software

• Centralize administration and support

• E.g. print document

• E.g. Internet-based, so everyone can access the same administrative or support application from their PCs

How many kinds of Networks?

• Depending on one’s perspective, we can classify networks in different ways

• Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless

• Based on network size: LAN and WAN (and MAN)• Based on management method: Peer-to-peer and

Client/Server• Based on topology (connectivity): Bus, Star, Ring …

• Local Area Network (LAN)• Small network, short distance

• A room, a floor, a building• Limited by no. of computers and distance covered• Usually one kind of technology throughout the LAN• Serve a department within an organization

• Examples: • Network inside the Student Computer Room• Network inside your home

LAN - Local Area Network

• A network that uses long-range telecommunication links to connect 2 or more LANs/computers housed in different places far apart.

• Towns, states, countries• Examples:

• Network of our Campus• Internet

WANCampus

Your home

USA

WAN – Wide Area Network

MAN - Metropolitan Area Network

Larger than a LAN and smaller than a WAN- example: campus-wide network- multi-access network

Technologies: coaxial cable microwave

Peer to Peer Network• Peer-to-peer network is also called workgroup

• No hierarchy among computers all are equal

• No administrator responsible for the network

Peer-to-peer

Network Management Method

• Advantages of peer-to-peer networks:• Low cost• Simple to configure• User has full accessibility of the computer

• Disadvantages of peer-to-peer networks:

• May have duplication in resources• Difficult to uphold security policy• Difficult to handle uneven loading

• Where peer-to-peer network is appropriate:

• 10 or less users• No specialized services required• Security is not an issue• Only limited growth in the foreseeable future

Network Management Method

Clients and Servers

• Network Clients (Workstation)• Computers that request network resources or services

• Network Servers• Computers that manage and provide network resources and

services to clients• Usually have more processing power, memory and hard disk

space than clients• Run Network Operating System that can manage not only

data, but also users, groups, security, and applications on the network

• Servers often have a more stringent requirement on its performance and reliability

Network Management Method

• Advantages of client/server networks• Facilitate resource sharing – centrally administrate and

control• Facilitate system backup and improve fault tolerance• Enhance security – only administrator can have access

to Server• Support more users – difficult to achieve with peer-to-

peer networks• Disadvantages of client/server networks

• High cost for Servers• Need expert to configure the network• Introduce a single point of failure to the system

Network Management Method

• Bus Topology• Simple and low-cost• A single cable called a trunk (backbone, segment)• Only one computer can send messages at a time• Passive topology - computer only listen for, not

regenerate data

Topology ― 3 basic types

Topology ― 3 basic types

Advantages of a bus topology: uses less cable compared to other physical topologies

like star works well for small networks does not need a central device, such as a hub, switch, or

router Disadvantages of a bus topology:

slower access to the network and less bandwidth due to the sharing of the same cable by all devices

challenging to identify and isolate problems break at any point in the bus cable can disable the

entire bus network

Star Topology• Each computer has a cable connected to a single

point• More cabling, hence higher cost• All signals transmission through the hub; if down,

entire network down• Depending on the intelligence of hub, two or more

computers may send message at the same time

Topology ― 3 basic types

Hub

Topology ― 3 basic types

Advantages of a Star Topology: upgradeable, flexible, and reliable easy to design and install diagnosing problems relatively easy allows for more throughput than any other topology

Disadvantages of a Star Topology: requires a lot of cable to connect computers . expensive to build because of the additional cost of

cables and devices

• Ring Topology• Every computer serves as

a repeater to boost signals• Typical way to send data:

• Token passing• only the computer who

gets the token can send data

• Disadvantages• Difficult to add computers• More expensive• If one computer fails, whole network fails

TT

T

data

T

data

T

data

T data

T data

T data

T Ack

T Ack

T Ack

TAck

T

Topology ― 3 basic types

Network Devices: Repeaters A repeater receives the

signal, regenerates it, and passes it on.

Repeaters are used mainly at the edges of networks to extend the wire so more workstations can be added.

Network Devices: Hubs

Using a hub changes the network topology from a linear bus, where each device plugs directly into the wire, to a star.

Hubs come in three basic types: Passive Active Intelligent

Network Devices: Bridges

Bridges operate at the data link layer of the OSI model.

The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network.

When a bridge sees a frame on the network, it looks at the destination MAC address and compares it.

Network Devices: Switches

Switches learn certain information about the data packets that they receive from computers on the network.

They use this information to build forwarding tables to determine the destination of data sent by one computer to another on the network.

They help segment a network and reduce network traffic congestion.

Network Devices: Routers Routers operate at the

Network layer of the OSI model.

They are slower than bridges and switches but make "smart" decisions on how to route packets.

Routers are capable of segmenting the network.