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Communications and Networks

Reading: Chapter 9

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Why are networks so useful?

They fa

cilit

ate

com

mu...

They a

llow

for s

harin

g ..

Both

of the

abo

ve

33% 33%33%1. They facilitate

communications2. They allow for

sharing of resources3. Both of the above

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NetworkNetwork

Uses of communications technologies Internet Global Positioning System (GPS) Short Message Service (SMS)

Network Interconnected group of computers and devices connected

via communications devices and media Facilitates sharing of resources and supports communications Requires

Sending & receiving devices Communications devices Communications channel or path Network OS (NOS)

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Networks – Communications Devices

Communications Device Hardware capable of sending/receiving data Convert signals so that they are suitable for

the communications channel May convert between analog and digital

Common types Dial-up modems ISDN and DSL modems Cable modems Network interface cards Wireless access points Routers

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Networks – Communications Devices

Networks – Communications Devices

Dial-up Modem Modulate/demodulate External modem

Connects to serial or RS-232 port Internal modem

Card inserted to expansion slot/PC Slot

ISDN and DSL ModemsDo not modulate/demodulateExternalSends and receives data over a digital telephone line

ISDN lineDSL line

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Networks – Communications Devices

Cable modem Cable television network Faster than dial-up access or ISDN line Splitter runs separate cables to TV’s and cable modem External

USB port or Ethernet NIC via a cable

Network Interface Card (NIC) Coordinates transmission/receipt of data to/from the

device Card installed in an expansion slot of a PC, printer, PC

slot Wireless transmission includes antenna Works with a particular network technology

Ethernet or token ring

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Networks – Communications Devices

Hub Provides a central

point of connectivity for cables in a network

May include a router Router

Connects multiple computers and routers together

Transmits packets to correct destination

May include built-in firewall

Wireless access point Allows computers

and devices to communicate wirelessly

Allows data transfer to a wired network

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Communications devices include ______.

route

rshubs

modem

sNIC

s

All of t

he a

bove

20% 20% 20%20%20%

1. routers2. hubs3. modems4. NICs5. All of the above

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Networks – Communications Channels

Channel Communications path between two devices Transmission rate

Speed at which data flows through the channel Bandwidth of the channel

Bits per second (bps), Hertz (cycles per second) Transmission media

Materials or techniques capable of carrying one or more signals

Baseband media – carry one signal at a time Broadband media – carry multiple signals concurrently

Physical transmission media Twisted pair, Coaxial, Fiber Optic

Wireless transmission media Infrared, Radio Frequency, Infrared, Microwave

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Networks –Physical Transmission Media

Twisted-pair cable Used for network cabling and

telephone systems One or more twisted-pair wires

bundled together Each pair has two insulated

copper wires twisted togetherCoaxial cable (coax)

Used for network cabling and cable TVSingle copper wire surrounded by 3 layers

Insulating materialWoven/braided metalPlastic outer coating

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Networks –Physical Transmission Media

Fiber optic cable Light used to send signals Thin glass or plastic

strands Surrounded by insulating

glass cladding and a protective coating

Carries many signals High speed Less noise Smaller size Expensive, difficult to

install and modify

glass cladding

optical fiber core

Protective coating

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Networks –Physical Transmission Media

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All of the following except ______ are examples of physical media.

coax

ial c

able

twis

ted p

air

mic

rowav

e ca

ble

fiber

optic

cab

le

25% 25%25%25%

1. coaxial cable2. twisted pair3. microwave cable4. fiber optic cable

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Networks –Wireless Transmission Media

Radio Frequency Antenna, transmitter,

receiver Bluetooth (2.45 GHz) 802.11b & g (2.4 GHz) Cellular Radio Waves

Cell phones, mobile devices

High frequency radio waves

824 to 849 MHz

MicrowavesHigh-speed signal transmissionSignals sent between microwave stations

Fixed-point wirelessRequires line-of-sight

Communications SatellitesSatellite receives microwave signal and amplifiesRetransmits over wide-area, to a number of land-based stations

Infrared SignalsIR light waves with line-of-sight transmission

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Networks –Wireless Transmission Media

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All of the following except ______ are examples of wireless media.

mic

rowav

es

sate

llite

s

radio

freq

uency

wav

es

fiber

optic

wav

es

25% 25%25%25%

1. microwaves2. satellites3. radio frequency

waves4. fiber optic waves

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Networks

Classified according to Geography – Geographic Distribution

LAN MAN WAN

Architecture Topology Protocol/Communications Technology

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Networks –Geographic Distribution

Networks –Geographic Distribution

Local Area Network (LAN) Connects computers in a

limited geographical area

Each computer and device is a node

Metropolitan Area Network (MAN)

High-speed network that connects LANs in a metropolitan area

Managed by a consortium of users or a single network provider

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Networks –Geographic Distribution

Wide Area Network (WAN)Connects computers and devices in a large geographical area

Connected via many types of mediaOne large network or two or more interconnected LANs, MANs

OthersCANHANTAN

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A ______ is a network that encompasses a limited geographic area.

MAN

WAN

LANPAN

25% 25%25%25%

1. MAN2. WAN3. LAN4. PAN

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Networks

Classified according to Geography

Architecture – Broad outline of the network

Peer-to-Peer Client/Server

Topology Protocol/Communications Technology

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Network Architectures –Client/Server and Peer-to-

Peer

Peer-to-Peer Share peripheral devices Up to 10 “peer” computers

NOS & applications software, storage

Internet Peer-to-Peer (P2P) Users connect directly to each

other’s hard disk Popular, inexpensive

client client client

serverprinter

Client/Server Server controls resources

More storage space, power Serves as a repository

Dedicated servers Client relies on the server for

access to resources

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Networks

Can be classified according to Geography Architecture

Topology – Physical arrangement of devices connected to the network

Bus Ring Star

Networks often use a combination of topologies

Protocol/Communications Technology

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Network Topologies –Bus and Ring Networks

Bus Network Single central cable connects computers and devices Transmits in both directions If a device fails, network continues to function

Reliable Popular, inexpensive Ring Network

Cable forms a closed ring Transmits in only one direction If one device fails, all those after

the device cannot function Spans larger distance than bus

network LANs and WANs

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Network Topologies –Star and Other Networks

Star Network Devices connect to a

central computer Hub

If one device fails, only that device is affected

Hub fails

Other Topologies Mesh

Redundant interconnections between nodes Tree

Star networks connected together via a bus

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With ______ topology, the devices on the network are connected together in a closed loop.

BusRin

gSta

rtre

e

25% 25%25%25%

1. bus2. ring3. star4. tree

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Networks

Can be classified according to Geography Architecture Topology

Protocol/Communications Technology – Standards that govern how data/instructions flow over the network

Ethernet Token Ring TCP/IP WAP Others

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Networks –Network Communications

Technologies

Networks –Network Communications

Technologies Communications Protocol

Set of rules and procedures for exchanging information among computers

Ethernet Token ring TCP/IP WAP Others

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Network Communications Technologies –

Ethernet

Network Communications Technologies –

Ethernet

Ethernet Widely used LAN standard Developed by Xerox, DEC, Intel - 1976

Fast Ethernet (100Base-T) - 100 Mbps Gigabit Ethernet - 1000 Mbps 10-Gigabit Ethernet – 10 Gbps

Bus or star topology PCs in the network to contend for

access Collision

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Network Communications Technologies –

Token Ring

Network Communications Technologies –

Token Ring

Token Ring Ring or star topology LAN standard Passes a signal called a token

Special bit pattern Only device with token can transmit Device catches the token, attaches message ,

sends it to travel around the network to receiving device

Receiving device catches token, strips off the message, resends token

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Network Communications Technologies –

TCP/IP

Network Communications Technologies –

TCP/IP TCP/IP

Used to connect hosts on the Internet Includes several protocols

Transmission Control Protocol and Internet Protocol Data broken up into small packets

Origin information Destination information Sequence information Data/information/instructions

Packet switching Break up message into packets, route packets,

destination reassembles the message Routers direct packets individually along fastest path

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Network Communications Technologies –

WAP

Wireless Application Protocol (WAP) Access Internet via mobile devices 2.0 Specification

Open Mobile Alliance (OMA) Web sites provide wireless content

to display on microbrowsers WML – XML application designed for

small screens

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Network Communications Technologies –

802.11, Bluetooth, IrDA

IEEE 802.11 (802.11b, g – “WiFi”) Family of standards used with wireless LANs

Used for public Internet access points

Bluetooth Devices contain special chip Short-range radio waves transmit between Bluetooth

devices Short distance

IrDA IrDA devices contain IrDA ports Infrared light waves Line-of-sight transmission

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With TCP/IP is used to send data over the Internet, the data is divided into small pieces or ______.

bundle

s

packe

ts

toke

nshubs

25% 25%25%25%

1. bundles2. packets3. tokens4. hubs

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Networks –Intranets

Networks –Intranets

Intranet Internal network in an organization used to share

information Uses Internet technologies (TCP/IP, Web server, Web

pages) Enterprise network Connects to the Internet

Extranet - Allows outside user access Firewall

Designed to prevent unauthorized access to a private network

Firewall blocks messages that do not meet security criteria Uses hardware, software, combination of both All messages entering or leaving the intranet must pass

through the firewall

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Networks – Home Area Networks

(HAN) Network within a home

Connects digital devicesHomePLC – electrical lines; cables connect card/USB/parallel port to wall outletPhoneline – telephone lines; cables connect NIC/PC card to telephone jack

Network card that plugs into PCI slot and wall outlet for home power-line network

Howstuffworks.com

HomeRF, 802.11b – radio waves; NIC connects to transceiver with antenna or to wireless access pointEthernet – twisted pair cables; Ethernet NIC cards and cables to connect devices

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Do you have a home area network?

Yes No

50%50%1. Yes2. No

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Networks Summary Uses of Communications Technology Networks

Communications Devices Communications Channels

Physical and Wireless Transmission Media Geographic

LAN, MAN, WAN Architectures

Peer-to-Peer, Client/Server Topologies

Bus, Ring, Star Protocols

Ethernet, Token Ring, TCP/IP, WAP, 802.11, others Intranets and Firewalls Home Networks