Network Basics

Chapter 9

Network DefinitionA network is a set of technologies that is used

to connect computersThe network allows communication and

collaboration between usersNetworking is a group of technologies working

together. These technologies include:1. Media is the wiring that connects the computers2. Hardware needs to be installed to connect the

media 3. Software needs to be written to handle

networks

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The Uses of a Network1. Simultaneous access to data

Network server is a central computer with large storage device and other resources that all users can share

Data files are sharedFile serversShared files stored on a server Access can be limited

Software can be sharedApplication servers Site licensesNetwork versions

Users can share data stored on Users can share data stored on central servercentral server

Network serverNetwork server

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The Uses of a Network2. Shared peripheral device

Printers and Faxes are commonly sharedReduces the cost per userDevices can be connected to the networkPrint servers control network printing

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The Uses of a Network3. Personal communication

– Email• Instantaneous communication

– Conferencing• Tele conferencing

1. Videoconferencing2. Audio-conferencing3. Data-conferencing

– Voice over IP• Phone communication

over network wires

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The Uses of a Network4. Easier data backup

Backup copies data to removable mediaServer data backed up in one step

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Assignment No. 2

a) What are the Network Operating Systems (NOS). Describe their roles?

b) Comparison of features of Linux and Windows operating systems

c) Write advantages and drawbacks of Internet in our life. (at least 5 each)

Due date: 05 February, 2009

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Common Network TypesLocal Area Network (LAN)

Contains printers, servers and computersSystems are close to each otherContained in one office or buildingOrganizations often have several LANS

Wide Area Networks (WAN)Two or more LANs connectedOver a large geographic areaTypically use public or leased lines

Phone linesSatellite

The Internet is a WAN

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Hybrid Network TypesMetropolitan Area Network (MAN)

Large network that connects different organizations

Shares regional resourcesA network provider sells timeTypically covers an area of between 5 and 50 km

diameter

Campus Area Networks (CAN)A LAN in one large geographic areaResources related to the same organizationEach department shares the LAN

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LAN, MAN, WAN

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Hybrid Network TypesHome Area Network (HAN)

Small scale networkConnects computers and entertainment

appliancesFound mainly in the home

Personal Area Network (PAN)Very small scale networkRange is less than 2 metersCell phones, PDAs, MP3 players

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How Networks Are StructuredServer based network

Node is any network deviceServers control what the node accessesUsers gain access by logging inServer is the most important computer

Client/Server networkNodes and servers share data rolesNodes are called clientsServers are used to control accessDatabase software

Access to data controlled by server

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How Networks Are StructuredPeer to peer networks (P2P)

All nodes are equalNodes access resources on other nodesEach node controls its own resourcesMost modern OS allow P2P NetworkDistributing computing is a form of P2PKazaa is a P2

Possible threats?

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Network TopologiesTopology

Logical layout of wires and equipmentChoice affects

Network performanceNetwork sizeNetwork collision detection

PacketsPieces of data transmitted over a network

• Packets are created by sending node• Data is reassembled by receiving node

Packet header• Sending and receiving address

Packet payload• Number and size of data• Actual data

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Network Topologies1. Bus topology

– Also called linear bus– One wire connects all nodes– Terminator ends the wires– Advantages

• Easy to setup• Small amount of wire

– Disadvantages• Slow• Easy to crash

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Network Topologies2. Star topology

– All nodes connect to a hub• Packets sent to hub• Hub sends packet to destination

– Advantages• Easy to setup• One cable can not crash network

– Disadvantages• One hub crashing downs entire network• Uses lots of cable

– Most common topology

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Network Topologies3. Ring topology

– Nodes connected in a circle– Tokens used to transmit data

• Nodes must wait for token to send

– Advantages• Time to send data is known• No data collisions

– Disadvantages• Slow• Lots of cable

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Network Topologies4. Mesh topology

All computers connected togetherInternet is a mesh networkAdvantage

Data will always be deliveredDisadvantages

Lots of cableHard to setup

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Network MediaLinks that connect nodes in a networkChoice can be made depending upon the

following factors:Speed of transmissionSize of networkSecurity

Can be broadly categorized as:Wire-Based MediaWireless Media

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Wire Based Media1. Twisted-pair

cablingMost common LAN

cableCalled Cat5 or

100BaseTFour pairs of copper

cable twistedMay be shielded

from interferenceSpeeds range from

1 Mbps to 1,000 Mbps

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Wire Based Media2. Coaxial cable

Similar to cable TV wireOne wire runs through cableShielded from interferenceSpeeds up to 10 MbpsNearly obsolete

3. Fiber-optic cableData is transmitted with light pulsesGlass strand instead of cableImmune to interferenceVery secureSpeeds up to 100 Gbps

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Wireless MediaData transmitted through the airLANs use radio wavesWANs use microwave signalsEasy to setupDifficult to secure

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Network HardwareNetwork interface cards

Network adapterConnects node to the mediaUnique Machine Access Code (MAC)

Network linking devicesConnect nodes in the networkCable runs from node to deviceCrossover cable connects two computers

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Network HardwareHubs

Center of a star networkAll nodes receive transmitted packetsSlow and insecure

SwitchesReplacement for hubsOnly intended node receives transmissionFast and secure

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Network HardwareBridge

Connects two or more LANs togetherPackets sent to remote LAN cross

Other packets do not crossSegments the network on MAC addresses

RouterConnects two or more LANs togetherPackets sent to remote LAN crossNetwork is segmented by IP addressConnect internal networks to the InternetNeed configured before installation

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Network HardwareGateway

Connects two dissimilar networksMost gateways contained in other devices

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Network CablingCabling specifications

Bandwidth measures cable speedTypically measured in Mbps

Maximum cable lengthConnector describes the type of plug

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Network CablingEthernet

Very popular cabling technology10 Base T, 10Base2, 10Base5Maximum bandwidth 10 MbpsMaximum distances100 to 500 meters

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Network CablingFast Ethernet

Newer version of EthernetBandwidth is 100 MbpsUses Cat5 or greater cable

Sometimes called 100Base TRequires a switch

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Network CablingGigabit Ethernet

High bandwidth version of Ethernet1 to 10 GbpsCat 5 or fiber optic cableVideo applications

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Network CablingToken ring

Uses shielded twisted pair cablingBandwidth between 10 and 25 MbpsUses a multiple access unit (MAU)Popular in manufacturing and finance

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Network ProtocolsLanguage of the network

Rules of communicationError resolutionDefines collision and collision recoverySize of packetNaming rules for computers

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Network ProtocolsTCP/IP

Transmission Control Protocol/Internet Protocol

Most popular protocolMachines assigned a name of 4 numbers

IP address209.8.166.179 is the White House’s web site

Dynamic Host Configuration ProtocolSimplifies assignment of IP addresses

Required for Internet access

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Network ProtocolsIPX/SPX

Internet Packet Exchange/Sequenced Packet Exchange

Older protocolAssociated with Novell NetwareReplaced by TCP/IP

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Network ProtocolsNetBEUI

Network BIOS Extended User InterfaceUsed by Windows to name computersTransmission details handled by TCP/IP

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Network ProtocolsToken ring

Popular in manufacturing and financeNodes communicate when they have the

token

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Modem CommunicationsPlain Old Telephone System (POTS)

Standard phone lineAlso known as Public Switched Telephone

Network (PSTN)Two-way voice communicationUses analog transmission techniquesData communication is slow

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Modem CommunicationsModems

Modulator/DemodulatorModulator converts digital to analog

Speed measured in bits per second (bps)Current fastest speed is 56 KbpsQuality of phone lines dictates speed

V.92 is the current modem standardSeveral modem types

InternalExternalVoiceFax

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Modem CommunicationsModem uses

Connection to the InternetFile transfer

UploadingDownloading

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Digital Data ConnectionsDigital phone lines

Local telephone companies are upgradingService will faster and more reliableNew phones will be neededModems will need to be upgraded

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Digital Data ConnectionsBroadband connection

Any data connection faster than 56 KbpsCommon in businessBecoming popular in home installations

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Digital Data ConnectionsISDN lines

Integrated Services Digital NetworkBasic rate uses three channels

Two data channels each support 64 KbpsError correction channel

Primary rate uses 24 data channels

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ISDN Connection

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Digital Data ConnectionsT lines

High-capacity voice/data linesUsed to control phone and dataSeveral variantsT1 transmits at 1.544 MbpsT3 transmits at 44.736 Mbps

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Digital Data ConnectionsDSL technologies

Digital Subscriber LinePopular with home usersSpeeds range from 100 Kbps to 30 MbpsAsymmetrical DSL (ADSL)

Upload speed slower than download speedSymmetrical DSL (SDSL)Requires a DSL modem

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Digital Data ConnectionsCable modem connections

Popular with home and office usersSpeeds between 1 and 3 MbpsRequires a cable modem

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Digital Data ConnectionsATM

Asynchronous Transfer ModeEfficient transfer of video and soundRequires a special NIC and hardware

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Wireless NetworksBenefits

No cable to pullMobile devices access network resourcesMobility and flexibility for office workers

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Wireless NetworksWireless 802.11

Also called Wi-FiIEEE standard

Institute of Electronic and Electrical EngineersSeveral versions

802.11b connects up to 11Mbps802.11g connects up to 56Mbps

Use the same type of devices

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Wireless NetworksWireless Access Point

Center of a wireless networkWAP combined cover a larger areaRange is 50 to 150 metersExtension points can extend range

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Wireless NetworksWireless Adapters

Used by devices to connectIncludes signal strength software

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ProjectAbstract Submission (next week)

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End of Chapter

Chapter 9