Introduction to Networking

computers connected together, and they can communicate and share resources

(e.g. information).

this?

so everyone can access the same administrative or support application

from their PCs

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 …

radio, microwave, infrared, sound, sonar
We will concentrate on guided media

here:
Twisted-Pair cables:
Unshielded Twisted-Pair (UTP) cables
Shielded Twisted-Pair (STP) cables
Coaxial cables
Fiber-optic cables

Transmission Media

from, e.g., motors, will affect the closer wire more than

the further one, thereby causing errors

Twisted-Pair Cables

mechanical protection)
A sample UTP cable with 5 unshielded twisted pairs

of wires

there is a metal foil or braided-metal-mesh cover that encases

each pair of insulated wires

higher freq (100KHz–500MHz) than UTP cables
Outer metallic wrapping serves both

as a shield against noise and as the second conductor that completes the circuit

and is the fastest possible speed in the Universe
Light slows

down in denser media, e.g. glass
Refraction occurs at interface, with light bending away from the normal when it enters a less dense medium




Beyond the critical angle  total internal reflection

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 CF502
Network inside your home

to connect 2 or more LANs/computers housed in different places

far apart.
Towns, states, countries
Examples:
Network of our Campus
Internet

WAN

Student Computer Centre

Your home

USA

may raise performance and security problems
Fiber-optic cable
Cable company
Coaxial
Cable
TV
PC
Cable Drop

 all are equal
No administrator responsible for the network


Peer-to-peer

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

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

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

together?

Bus Topology Ring Topology





Star Topology

segment)
Only one computer can send messages at a time
Passive topology

- computer only listen for, not regenerate data

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
Bus Topology
BNC T-Connector
Coaxial cable
Network Card

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

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