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Network class i f icat ions

Computer Networks are classified according tothe distance between individual computers

that are attached to the network.

The classification includes the following:

1. Local Area Network (LAN)

2. Wide Area Network (WAN)

3. Metropolitan Network (MAN)

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Local Area Network (LAN)

is a network that

connects computers

and devices in a limited

geographical area suchas a house, school

laboratory or an office

building

Each computer or

device on the network

is called a node

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Wide Area Network (WAN)

is a network that coversa large geographic areasuch as a city, countryor the world

Uses communicationschannels such astelephone lines, cables,and radio waves inconnecting computers

The Internet is theworlds largest WAN

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Metropolitan Network (MAN)

is a network that spansa whole metropolitanarea.

It is referred to as a highspeed-network thatcovers a city

MANs use similartechnology to LANs butcover a much widergeographic region

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Types of LANs (Network Architecture)

There are two (2) main types of network

architectures. These include:

1. Client/Server

2. Peer to Peer

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Client/Server

Client

-is the requesting

computer machine

Server

-is the supplying

computer machine

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Client/Server

Client

-requests services

-rely on the server

for resources suchas files, processingpower and storage

Server

-provides theservices

-controls access tothe hardware andsoftware on thenetwork and

provides acentralized storagearea for data

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Peer-to-peer Network

(P2P)

- Simple and inexpensive thatconnects less than 10 computers

using twisted pair or coaxial

cables

- Each computer is called a peer

- Peers act as clients and server

- Each computer can share thehardware located on any other

computer

- Each computer has equal

responsibilities and capabilities

- The Network Operating System

(NOS) must be installed on eachcomputer.

- Ideal for small businesses and

home offices

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Internet Peer-to Peer

-is a different kind of peer-to-peer network exists on

the Internet that allows

users to share files on their

hard disks, essentially

creating global peer-to-peer networks

-sharing of music,

documents, books,

software and video/moviefiles

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Network Topo log ies

Network Topology is the configuration or

physical arrangement of the devices or nodes.

The layout of the computers and devices on a

network.

The 3 main topologies are:

1. Ring

2. Star

3. Bus

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Network Components

o are networking hardware are needed to

perform data-processing and communications

within the network.

o These includes:

computers

communication devices (modem, hub, switch)

interface cards (LAN cards)

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Modem

Short formodulator/demodulator

Converts digital signal toanalog and vice versa

converts digital signals toanalog signals and viceversa.

Computer information isstored digitally whereasinformation transmittedover telephone lines istransmitted in the form ofanalog waves

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Modem

Characteristics/terms thatinvolves MODEM

Bps (bits per second) how

fast the device can transmit

and receive data (baud rate).

The fastest ones are about57600bps.

Voice/data many support a

switch to change between

voice and data modes.

Auto-answer enables your

computer to receive calls in

your absence.

Voice/data many support a

switch to change between

voice and data modes.

Auto-answer enables your

computer to receive calls in

your absence.

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16 Copyright 2003 by PrenticeHall

Types of Modems

External modem separate from computer

Internal modem inserted into computer

Standard on most computers today

PC Card modem slides into slot on laptop

Roughly credit card size

Cable connects modem to standard phonejack

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Modem Data Speeds

Measured in bits per second (bps)

Early modems transmitted at 300 bps

Fastest current modems transmit at 56,000 bps

Federal Communications Commission (FCC)restrictions prohibit actual speeds faster than53,000 bps

Actual speed depends on line conditions andother variables

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23Copyright 2003 by Prentice Hall

Coordinating Sender and Receiver

Sending data to remote location only works if

receiving device is ready to accept it

Two approaches to keeping devices in step:

Asynchronous transmission

Synchronous transmission

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Simplex, Half-Duplex, and Full-Duplex

Transmission

Simplex transmission sends data in one directiononly

Example: television broadcasting

Half-duplex transmission sends data in bothdirections, but only one way at a time

Example: bank teller sends data about a deposit; after datareceived, a confirmation returns

Full-duplex transmission allows transmission in bothdirections at same time

Example: a conversation

Typically used for high-speed data communication

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Multiplexer

Combines data streams from slow-speeddevices into single data stream

Transmits over high-speed circuit (ex T1)

Multiplexer on receiving end needed to restoreto component data streams

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Basic Network Design

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NIC

Most modern computershave these devices built

into the motherboard, but

in some computers you

have to add an extra

expansion card (small

circuit board)

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Network Cable

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Hub

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Switch

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Router

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Proxy Server

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Bridge

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Client/Server Network

Server computer controls network

Often has several hard drives, fastest printer

Client computer requests services from server

Thin client has little or no storage

Processing approaches

Client/server

File server

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Firewall

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Software: Network Operating SystemsThe similarities and differences between a single-user operating system and a

network operating system

Similarities

Controls/manages the computerhardware (e.g. memory)

Provides a user interface

Allows more than one program torun at the same time.

Schedules jobs and configuresdevices

Manages programs

Provides file management andother utilities

Starts the computer

Differences A network operating system (NOS) is an

operating system that organizes andcoordinates how multiple users accessand share resources on a network. Asingle user operating system allows onlyone user to run one or more programsat a time.

An NOS has more security controlfeatures. It also controls a network,establish internet connection andallows more than one computers to talkto each other.

An NOS allows for the management offiles on other computers.

NOS typically resides on a server.

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44Copyright 2003 by Prentice Hall

Types of Communications Media

Wire pairs

Coaxial cables wired transmission media (guided)

Fiber optics

Microwave transmission wireless transmission

Satellite transmission media (unguided)

Wireless Transmission

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Wire Pairs Physical characteristics

Requires two conductors

Twisted around each other to reduce electrical interference

Plastic sheath

Shielded twisted pair

Metallic protective sheath

Reduces noise

Increases speed

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Coaxial Cable

Higher bandwidth

Less susceptible to noise

Used in cable TV systems

Physical characteristics Center conductor wire

Surrounded by a layer of insulation

Surrounded by a braided outer conductor

Encased in a protective sheath

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Fiber Optics

Physical characterizes

Glass or plastic fibers

Very thin (thinner than human hair)

Material is light

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Microwave Transmission

Uses line-of-sight transmission of datasignals Sending microwave must see receiver

Requires relay stations approximately

every 30 miles Waves are straight, earth is curved

Offers high speed and cost-effectiveness Easy to implement

Weather can cause interference

Physical characteristics Data signals sent through atmosphere

Signals cannot bend of follow curvature of earth

Relay stations required

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Satellite Transmission

Documents

Module 4 - A