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Networks and the Networks and the InternetInternet

Unit EUnit E

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ObjectivesObjectives

Introduce NetworksIntroduce NetworksClassify NetworksClassify NetworksUnderstand Network TopologyUnderstand Network TopologyExplore Network Hardware Explore Network Hardware Explore Communications ChannelsExplore Communications ChannelsTransport DataTransport DataExplore LAN StandardsExplore LAN StandardsExplore WirelessExplore Wireless

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ObjectivesObjectives

Understand Internet connectionsUnderstand Internet connections

Introduce IP Addresses and Domain Introduce IP Addresses and Domain NamesNames

Connect to the Internet using Dial-upConnect to the Internet using Dial-up

Connect to the Internet using Connect to the Internet using BroadbandBroadband

Connect to the Internet using CableConnect to the Internet using Cable

Connect to the Internet without WiresConnect to the Internet without Wires

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Communications NetworkCommunications Network

The combination of hardware, The combination of hardware, software and connecting links that software and connecting links that transport datatransport data

Data is encoded, sent to its Data is encoded, sent to its destination then decodeddestination then decoded

Source Transmitter Receiver Destination

EncodedData

CommunicationsChannel

Signal

DecodedData

Noise

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Shared ResourcesShared Resources

Networks share hardware, Networks share hardware, software, and datasoftware, and data

Sharing reduces costsSharing reduces costs– Peripheral devices, site licensesPeripheral devices, site licenses

Provides access to InternetProvides access to Internet

Share dataShare data– Groupware, e-mail, IM, online Groupware, e-mail, IM, online

conferencingconferencing

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Shared Resources (cont.)Shared Resources (cont.)

Networks are vulnerableNetworks are vulnerable– Unauthorized accessUnauthorized access– Malicious codeMalicious code

• Viruses, Trojan horses, wormsViruses, Trojan horses, worms

Networks are becoming more Networks are becoming more standardizedstandardized

Most benefits outweigh risksMost benefits outweigh risks– Computers can be protectedComputers can be protected

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Network Classifications by Network Classifications by Geographic CoverageGeographic Coverage

PAN: PAN: Personal Area Network Personal Area Network (PDAs)(PDAs)WAN:WAN: Wide Area Network Wide Area Network (Internet is one)(Internet is one)MAN:MAN: Metropolitan Area Network Metropolitan Area Network (50 miles)(50 miles)LAN:LAN: Local Area Network (single Local Area Network (single building)building)

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Network Classifications by Network Classifications by Organizational StructureOrganizational Structure

Client/Server: Client/Server: – One or more computers configured as One or more computers configured as

servers and other computers configures servers and other computers configures as clientsas clients

– Server is central repository for dataServer is central repository for data

Peer-to-Peer (P2):Peer-to-Peer (P2): – Treats every computer as an equalTreats every computer as an equal– Workstations transfer data to each other Workstations transfer data to each other

without going through serverwithout going through server– File-sharing networksFile-sharing networks

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Network Classifications by Network Classifications by Organizational StructureOrganizational Structure

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Network Software LicensesNetwork Software Licenses

Single-userSingle-user

Multiple-userMultiple-user– Priced per userPriced per user

Concurrent-userConcurrent-user– Certain number of copies at a timeCertain number of copies at a time

SiteSite– Any and all computers at a locationAny and all computers at a location

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Network ClassificationsNetwork Classifications

CATEGORYCATEGORY DESCRIPTIONDESCRIPTION EXAMPLESEXAMPLESGeographical Geographical Area where network devices Area where network devices

are locatedare locatedPAN, LAN, WAN, PAN, LAN, WAN, MANMAN

OrganizationalOrganizational Hierarchy of devicesHierarchy of devices Client/Server, P2PClient/Server, P2P

PhysicalPhysical Layout and relationship Layout and relationship between devicesbetween devices

Star, bus, ring, mesh, Star, bus, ring, mesh, treetree

NetworkNetwork Technologies for cables and Technologies for cables and signals that carry datasignals that carry data

Twisted-pair, coaxial, Twisted-pair, coaxial, or fiber-optic cable; or fiber-optic cable; RF; microwaves; RF; microwaves; Infrared; power or Infrared; power or phone linephone line

BandwidthBandwidth Capacity of networkCapacity of network Broadband, Broadband, narrowbandnarrowband

Communications Communications protocolsprotocols

Standards for orderly & safe Standards for orderly & safe data transferdata transfer

TCP/IP, SPX/IPX, TCP/IP, SPX/IPX, NetBEUI/NetBIOS, NetBEUI/NetBIOS, AppleTalkAppleTalk

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Network TopologyNetwork Topology

Physical arrangement of devices, Physical arrangement of devices, cables, and wirescables, and wires5 common topologies named for 5 common topologies named for their shapestheir shapes– StarStar (central connection point) (central connection point)– RingRing (connects devices in a circle) (connects devices in a circle)– BusBus (common backbone) (common backbone)– MeshMesh (each device connected to others) (each device connected to others)– TreeTree (blend of star and bus) (blend of star and bus)

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Network TopologyNetwork Topology

Star Bus Ring

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Network Topology (cont.)Network Topology (cont.)

Each connection point on a Each connection point on a network is a Node:network is a Node:– ServerServer– WorkstationWorkstation– Network peripheralNetwork peripheral– Network deviceNetwork device

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Interconnecting NetworksInterconnecting Networks

Two similar networks can be Two similar networks can be connected by a bridgeconnected by a bridge– Transfers data without regard to formatTransfers data without regard to format

GatewayGateway– A device or software used to join dissimilar A device or software used to join dissimilar

networks by making data compatiblenetworks by making data compatible

RouterRouter– Electronic device that connects 2 or more Electronic device that connects 2 or more

networksnetworks

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Network Hardware OverviewNetwork Hardware Overview

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Network HardwareNetwork Hardware

Server (also called host computer)Server (also called host computer)– Distribute resources to network usersDistribute resources to network users– Contains network management software Contains network management software

and filesand files

Workstation (also called client)Workstation (also called client)– PC on a LANPC on a LAN– Client is software that lets it talk to serverClient is software that lets it talk to server

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Network HardwareNetwork Hardware

Network Interface Card (NIC) Network Interface Card (NIC) – Example: Ethernet cardExample: Ethernet card

Connection DevicesConnection Devices– Modem:Modem: converts PC digital signals converts PC digital signals– Hub:Hub: connects nodes on a LAN connects nodes on a LAN– Router:Router: decides best way to route data decides best way to route data

on networkon network– Gateway:Gateway: entrance to another network entrance to another network– Repeater:Repeater: amplifies and regenerates amplifies and regenerates

signalssignals

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Network AddressesNetwork Addresses

Physical address: Physical address: – Every node has oneEvery node has one– Built into circuitry of Built into circuitry of

network devicenetwork device

Logical address:Logical address:– Used if physical address Used if physical address

is incompatible with is incompatible with particular networkparticular network

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Wired Communication Wired Communication ChannelsChannels

Twisted-pair cables (phones) Twisted-pair cables (phones) – STP: shielded twisted pairSTP: shielded twisted pair– UTP: unshielded twisted pair for small UTP: unshielded twisted pair for small

networksnetworks

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Wired Communication Wired Communication ChannelsChannels

Coaxial cable (television)Coaxial cable (television)– High capacityHigh capacity

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Wired Communication Wired Communication ChannelsChannels

Fiber-optic cable Fiber-optic cable – Pulses of light in thin glass tubesPulses of light in thin glass tubes– Essential to Internet backboneEssential to Internet backbone

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Wireless Communication Wireless Communication ChannelsChannels

RF: radio frequency signalsRF: radio frequency signals– Send and receive by a transceiver with Send and receive by a transceiver with

antennaantenna

MicrowavesMicrowaves– More capacity than radio wavesMore capacity than radio waves– Need clear path between transmitter Need clear path between transmitter

and receiverand receiver– Cannot penetrate metal objectsCannot penetrate metal objects

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Wireless Communication Wireless Communication ChannelsChannels

SatellitesSatellites– Signal relayed from ground station Signal relayed from ground station

to satelliteto satellite– Transponder on satellite receives, Transponder on satellite receives,

amplifies and retransmits signal amplifies and retransmits signal back to earthback to earth

– Key technology for Internet Key technology for Internet backbonebackbone

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Wireless Communication Wireless Communication ChannelsChannels

Infrared lightInfrared light– Short distance with clear line of siteShort distance with clear line of site– Example: connect notebook with printerExample: connect notebook with printer

Laser lightLaser light– Larger distance with clear line of siteLarger distance with clear line of site– Example: between buildings in futureExample: between buildings in future

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BandwidthsBandwidths

The transmission capacity of a The transmission capacity of a communications channel measured communications channel measured in bps (bits per second)in bps (bits per second)Low-bandwidth carries less data than Low-bandwidth carries less data than high bandwidthhigh bandwidth– TelephoneTelephone– NarrowbandNarrowband

High-bandwidthHigh-bandwidth– Coaxial cableCoaxial cable– DSL linesDSL lines– Called broadbandCalled broadband

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Transporting Data Transporting Data Depends On:Depends On:

Network Topology:Network Topology: configurationconfiguration

Packet Switching Packet Switching Technology:Technology: determines how determines how data is broken updata is broken up

Protocols:Protocols: rules for rules for successful and accurate successful and accurate data transmissiondata transmission

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Packet Switching TechnologyPacket Switching Technology

Packet is a parcel of data on network Packet is a parcel of data on network or a file broken into small, equal size or a file broken into small, equal size piecespiecesContainsContains– Sender addressSender address– Destination addressDestination address– Sequence numberSequence number– DataData

Packet switching: packets sent Packet switching: packets sent independently of each otherindependently of each other

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Circuit SwitchingCircuit Switching

Establishes a dedicated, private Establishes a dedicated, private link between phone lines during link between phone lines during a calla call

Inefficient because it reserves a Inefficient because it reserves a circuit even if data is not being circuit even if data is not being transmittedtransmitted

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Communications ProtocolCommunications Protocol

Allows two devices to negotiate Allows two devices to negotiate and agree on how data will be and agree on how data will be transmittedtransmitted

TCP/IP TCP/IP – Transport Control Protocol/Internet Transport Control Protocol/Internet

ProtocolProtocol– Most commonMost common– TCP: breaks data into packetsTCP: breaks data into packets– IP: addresses packetsIP: addresses packets

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Controlling Direction Controlling Direction of Data Flowof Data Flow

Simplex:Simplex: one direction (TV) one direction (TV)

Half duplex:Half duplex: can send and can send and receive data, but not at same receive data, but not at same time (CB radio)time (CB radio)

Full Duplex:Full Duplex: can send and can send and receive data at same time on receive data at same time on same channel (Telephone)same channel (Telephone)

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Protocol CharacteristicsProtocol Characteristics

Handshaking:Handshaking: negotiating negotiating transmission speedtransmission speed

Synchronous Protocol:Synchronous Protocol: sender and sender and receiver synchronize signal with a receiver synchronize signal with a fixed clock ratefixed clock rate

Asynchronous Protocol:Asynchronous Protocol: requires a requires a start and stop bit (most common)start and stop bit (most common)

Parity bits:Parity bits: used for error checking used for error checking

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Communications ProtocolsCommunications Protocols

PROTOCOLPROTOCOL MAIN USEMAIN USE

TCP/IPTCP/IP InternetInternet

NetBIOS/NETBEUINetBIOS/NETBEUI Microsoft Microsoft networksnetworks

AppleTalkAppleTalk Macintosh Macintosh networksnetworks

IPX/SPXIPX/SPX Novell networksNovell networks

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LAN StandardsLAN Standards

Institute of Electrical and Institute of Electrical and Electronics Engineers (IEEE)Electronics Engineers (IEEE)IEEE designation numbers IEEE designation numbers identify compatible network identify compatible network technologiestechnologies– ARCnet: old, simple, inexpensiveARCnet: old, simple, inexpensive– Token Ring: ring topologyToken Ring: ring topology– FDDI: fiber-optic cablesFDDI: fiber-optic cables– Ethernet: simultaneous broadcast of Ethernet: simultaneous broadcast of

data packetsdata packets

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EthernetEthernet

Packets accepted only by device Packets accepted only by device to which it is addressedto which it is addressedCSMA/CD protocolCSMA/CD protocolRefers to a family of LAN Refers to a family of LAN technologiestechnologies– Various transmission ratesVarious transmission rates– Fiber-optic and twisted-pair cablesFiber-optic and twisted-pair cables– Bus or star topologyBus or star topology

Connect many workstationsConnect many workstations

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EthernetEthernet

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Home Ethernet EquipmentHome Ethernet Equipment

Ethernet card in each Ethernet card in each workstation and peripheral workstation and peripheral devicedevice

Link between network nodes Link between network nodes such as cablesuch as cable

Central connection point (hub)Central connection point (hub)

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Wireless StandardsWireless Standards

Wi-Fi (Wireless Fidelity)Wi-Fi (Wireless Fidelity)– Set of wireless networking technologiesSet of wireless networking technologies– Defined by IEEE 802.11 standardsDefined by IEEE 802.11 standards– Compatible with EthernetCompatible with Ethernet

Popular because of absence of Popular because of absence of cablescables

Desirable for notebook and tablet Desirable for notebook and tablet computerscomputers

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Wi-Fi DisadvantagesWi-Fi Disadvantages

Speed Speed – Radio wavesRadio waves

DistanceDistance– 25-150 feet25-150 feet

SecuritySecurity– War driving/LAN-jackingWar driving/LAN-jacking– Wired Equivalent Privacy: encryptionWired Equivalent Privacy: encryption

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Wi-Fi (cont.)Wi-Fi (cont.)

Wi-Fi cards requiredWi-Fi cards required– Include transceiver and antennaInclude transceiver and antenna– Can be added to notebooks, PCs, and TabletsCan be added to notebooks, PCs, and Tablets– Wireless access point is same as hub or router Wireless access point is same as hub or router

in Ethernetin Ethernet

Bluetooth makes short-range Bluetooth makes short-range wireless connections between wireless connections between devices such as a mouse, keyboard, devices such as a mouse, keyboard, printer printer

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Internet ConnectionsInternet Connections

The Internet isn’t owned or The Internet isn’t owned or operated by corporations or operated by corporations or governmentsgovernments

Traffic exceeds 100 trillion bytes Traffic exceeds 100 trillion bytes (terabytes) each week(terabytes) each week

Backbone provides high-speed Backbone provides high-speed routes for data trafficroutes for data traffic

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Internet ConnectionsInternet Connections

Users connect to Internet Service Users connect to Internet Service Provider (ISP) or through LANProvider (ISP) or through LAN

ISP provides e-mail and access ISP provides e-mail and access to Webto Web

Networks use TCP/IP as Networks use TCP/IP as standard standard

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Internet ConnectionsInternet Connections

Ping software: Packet Internet GroperPing software: Packet Internet Groper– Checks internet pathways to be sure they are Checks internet pathways to be sure they are

openopen

Traceroute software: traces data pathsTraceroute software: traces data paths

HTTPHTTPHTTPHTTP

FTPFTPFTPFTP

POPPOPPOPPOP

SMTPSMTPSMTPSMTP

IMAPIMAPIMAPIMAPTELNETTELNETTELNETTELNET

SSLSSLSSLSSL

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IP AddressesIP Addresses

ISP gives unique IP address to ISP gives unique IP address to subscribersubscriberSeries of numbers in 4 partsSeries of numbers in 4 parts– 204.127.129.001204.127.129.001

Static IP address: permanent, usually Static IP address: permanent, usually serversserversDynamic IP address: temporary, for Dynamic IP address: temporary, for one sessionone sessionLook at your Internet configuration Look at your Internet configuration settings to find your IP addresssettings to find your IP address

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Domain NamesDomain Names

Translates directly into IP addressTranslates directly into IP address

Examples: course.com, rutgers.eduExamples: course.com, rutgers.edu

Top-level domain: indicated by Top-level domain: indicated by extensionextension

ICANN handles domain name ICANN handles domain name registration and controlregistration and control

infoinfoinfoinfo

netnetnetnet

eduedueduedu

comcomcomcom intintintintgovgovgovgov

milmilmilmil orgorgorgorg

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Dial-up Internet ConnectionsDial-up Internet Connections

Plain old telephone Plain old telephone service (POTS)service (POTS)Dial-up connection Dial-up connection via modemvia modemCircuit switching Circuit switching technology gives technology gives continuous private continuous private linklink

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Dial-up Internet ConnectionsDial-up Internet Connections

Modem: Modulate/demodulate; Modem: Modulate/demodulate; digital to analogdigital to analog– Speed: 56 KbpsSpeed: 56 Kbps– Upstream actually 33 KbpsUpstream actually 33 Kbps– Downstream actually 44 KbpsDownstream actually 44 Kbps

VIOP (Voice Over IP): can talk VIOP (Voice Over IP): can talk on computer at same time as on computer at same time as running other programs on-linerunning other programs on-line

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Broadband Internet Broadband Internet ConnectionsConnections

High-speed digital High-speed digital communications links for voice communications links for voice and dataand dataDSL: Digital Subscriber Line DSL: Digital Subscriber Line (always-on)(always-on)– Uses standard copper phone cablesUses standard copper phone cables– Fastest and most affordable to Fastest and most affordable to

individualsindividuals– Variations are ADSL, SDSL, HDSL Variations are ADSL, SDSL, HDSL

AND DSL liteAND DSL lite– DSL modems give 1.5 Mbps DSL modems give 1.5 Mbps

downstreamdownstream

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Broadband Internet Broadband Internet ConnectionsConnections

ISDN: Integrated Services Digital ISDN: Integrated Services Digital NetworkNetwork– 64 or 128 Kbps64 or 128 Kbps– Mostly used for business LANsMostly used for business LANs– Need ISDN terminal adapterNeed ISDN terminal adapter

–1.544 Mbps1.544 Mbps

–24 channels24 channels

–Used by business Used by business and ISPs on and ISPs on dedicated leased dedicated leased lineslines

T1T1–43 Mbps43 Mbps

–672 channels672 channels

–Also called DS3 Also called DS3 (Digital Service-3)(Digital Service-3)

T3T3

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Security When Always-OnSecurity When Always-On

Same IP address when Same IP address when on – hackers can useon – hackers can use

High-speed access High-speed access desirable for hackersdesirable for hackers

Turn machine off oftenTurn machine off often

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Cable Internet ConnectionsCable Internet Connections

You need You need – Ethernet card Ethernet card – Cable modem: usual ISP Cable modem: usual ISP

providesprovides– Splitter to connect both Splitter to connect both

modem and TB if necessarymodem and TB if necessary

Could slow down as Could slow down as more neighbors use more neighbors use serviceservice

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Cable SecurityCable Security

DOCSIS-compliant cable DOCSIS-compliant cable modemsmodems– Security technology filters packets to Security technology filters packets to

certain portscertain ports– Secures your computer from your Secures your computer from your

neighborsneighbors– Doesn’t close up all security holes Doesn’t close up all security holes

associated with always-on connectionsassociated with always-on connections

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Wireless Internet ConnectionsWireless Internet Connections

DSS: Direct Satellite ServiceDSS: Direct Satellite Service– Some allow only downstreamingSome allow only downstreaming

Two-way Satellite ServiceTwo-way Satellite Service– Downstream 500 Kbps vs. 40-60 Kbps Downstream 500 Kbps vs. 40-60 Kbps

upstreamupstream

Cellular telephone infrastructure Cellular telephone infrastructure is slowest at 14.4 Kbpsis slowest at 14.4 Kbps

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Wireless Internet ConnectionsWireless Internet Connections

Mobile Internet ConnectionsMobile Internet Connections

Public Wi-FiPublic Wi-Fi– Range of coverage: hotspotRange of coverage: hotspot

WWAN (wireless WAN)WWAN (wireless WAN)– Cell phone networksCell phone networks– Cell-ready modem or subscriptionCell-ready modem or subscription

WAP (wireless access protocol)WAP (wireless access protocol)

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TechTalk: Installing a LANTechTalk: Installing a LAN

Install Ethernet NICInstall Ethernet NIC– On motherboard or with PC card; both have On motherboard or with PC card; both have

port for network cableport for network cable

Attach cable to NIC port and hub portAttach cable to NIC port and hub portTurn on PCsTurn on PCsWindows should automatically detect Windows should automatically detect and establish connectionand establish connectionCan activate file sharing and drive Can activate file sharing and drive mapping by using Windows Network mapping by using Windows Network NeighborhoodNeighborhood

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Context: EducationContext: Education

CBT (computer-based training)CBT (computer-based training)CAL (computer-aided learning)CAL (computer-aided learning)CAI (computer-aided instruction)CAI (computer-aided instruction)SimulationsSimulations99% of American public schools 99% of American public schools have computershave computers– Not all students have daily access Not all students have daily access

thoughthough

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Context: EducationContext: Education

Some colleges require incoming Some colleges require incoming students to have a computerstudents to have a computer

DE/DL (Distance DE/DL (Distance Education/Learning)Education/Learning)

Life-long learningLife-long learning

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Issue: Free Wi-Fi?Issue: Free Wi-Fi?

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Networks and the Networks and the InternetInternet

EndEnd