Computer Networks – an Computer Networks – an overviewoverview

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Computer NetworksComputer Networks Advantages of a networkAdvantages of a network Client/server and peer-to-peer Client/server and peer-to-peer

networksnetworks Classifications of client/server Classifications of client/server

networksnetworks Client/server network componentsClient/server network components Types of serversTypes of servers Network topologiesNetwork topologies

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Topics Topics

Types of transmission mediaTypes of transmission media Network softwareNetwork software Network adaptersNetwork adapters Moving data in a client/server Moving data in a client/server

networknetwork

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Networking AdvantagesNetworking Advantages

Networks:Networks:• Increase productivityIncrease productivity• Enable the sharing of resourcesEnable the sharing of resources• Facilitate Internet connectivityFacilitate Internet connectivity

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Client/Server NetworksClient/Server Networks

Server based network:Server based network:• ClientsClients• ServersServers

Data flows efficientlyData flows efficiently Servers respond to Servers respond to

requests from clientsrequests from clients Servers perform Servers perform

specific tasksspecific tasks Scalable networkScalable network

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Classifications of Client/Server Classifications of Client/Server NetworksNetworks LAN:LAN:

• Local area networkLocal area network• Computers linked together over a small Computers linked together over a small

geographic regiongeographic region WAN:WAN:

• Wide area networkWide area network• Computers linked together over large diverse Computers linked together over large diverse

geographic locationsgeographic locations MAN:MAN:

• Metropolitan area networkMetropolitan area network• Computers linked together within a city or countyComputers linked together within a city or county

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Classifications of Client/Server Classifications of Client/Server NetworksNetworks

PAN:PAN:• Personal area networkPersonal area network• Wireless devices connected in close Wireless devices connected in close

proximity to each otherproximity to each other Intranet:Intranet:

• Private corporate networkPrivate corporate network

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Constructing Client/Server Constructing Client/Server NetworksNetworks

Servers Network topologies Transmission media Network operating system (NOS) Network adapters Network navigation devices

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Servers Servers

Number and type of servers depend Number and type of servers depend on network size and workloadon network size and workload

Dedicated server:Dedicated server:• Perform one specific functionPerform one specific function

Authentication server:Authentication server:• Keeps track of network logins and Keeps track of network logins and

services availableservices available File server:File server:

• Store and manage filesStore and manage files

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Dedicated ServersDedicated Servers Print server:Print server:

• Manages client-requested printing jobsManages client-requested printing jobs• Creates print queue (prioritizes print jobs)Creates print queue (prioritizes print jobs)

Applications server:Applications server:• Acts as a storage area for application softwareActs as a storage area for application software

Database server:Database server:• Provides clients with access to database Provides clients with access to database

informationinformation E-mail server:E-mail server:

• Process and deliver in-coming and outgoing e-Process and deliver in-coming and outgoing e-mailmail

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Dedicated ServersDedicated Servers

Communications server:Communications server:• Handles communications between Handles communications between

networks including the Internetnetworks including the Internet Web server:Web server:

• Hosts a Web site available through the Hosts a Web site available through the InternetInternet

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Network TopologiesNetwork Topologies

The physical layout of computers, The physical layout of computers, transmission media, and other transmission media, and other componentscomponents

Types of network topologies include:Types of network topologies include:• Bus topology• Ring topology• Star topology

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Bus TopologyBus Topology All nodes are connected All nodes are connected

in sequence on a single in sequence on a single cablecable

Used most often on Used most often on peer-to-peer networkspeer-to-peer networks

Networked computers Networked computers communicate with each communicate with each otherother

One computer transmits One computer transmits data at a time:data at a time:• Access methods avoid Access methods avoid

data collisionsdata collisions• Data is transmitted in Data is transmitted in

“packets”“packets”

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Ring TopologyRing Topology Nodes are laid out Nodes are laid out

in a ringin a ring Token (data Token (data

packet) flows in packet) flows in one direction from one direction from device to devicedevice to device

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Star TopologyStar Topology

Nodes connect to a Nodes connect to a central communications central communications device (hub/switch)device (hub/switch)

A node sends a signal A node sends a signal to the hub which to the hub which retransmits it to the retransmits it to the other nodesother nodes

A node accepts the A node accepts the signal addressed to itsignal addressed to it

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Avoiding Data Collisions on a Avoiding Data Collisions on a Star NetworkStar Network

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Transmission MediaTransmission Media

The routes data takes to flow The routes data takes to flow between devices on a network:between devices on a network:

Wired Wired Wireless: Wireless:

• Wireless Fidelity (Wi-Fi)Wireless Fidelity (Wi-Fi)• Uses radio wavesUses radio waves• 802.11 standard802.11 standard

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Choosing a CableChoosing a Cable

Maximum run lengthMaximum run length Bandwidth Bandwidth Bend radiusBend radius Cable costCable cost Installation costsInstallation costs Susceptibility to interferenceSusceptibility to interference Signal transmission methodsSignal transmission methods

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Twisted Pair CableTwisted Pair Cable Pairs of copper wire twisted around each otherPairs of copper wire twisted around each other Twists make the wires less susceptible to Twists make the wires less susceptible to

interferenceinterference Shielded twisted pair (STP)Shielded twisted pair (STP)

• Layer of foil shieldingLayer of foil shielding Unshielded twisted pair (UTP)Unshielded twisted pair (UTP)

• Cat 5ECat 5E Bandwidth 1GbpsBandwidth 1Gbps

• Cat 6Cat 6 Bandwidth 200 MbpsBandwidth 200 Mbps

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Coaxial CableCoaxial Cable

Four components:Four components:• Copper coreCopper core• Nonconductive insulating materialNonconductive insulating material• Braided metalBraided metal• Plastic coverPlastic cover

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Fiber-Optic CableFiber-Optic Cable

Components include:Components include:• Glass or plastic fibersGlass or plastic fibers• CladdingCladding• Outer jacketOuter jacket

Uses light impulses to transmit dataUses light impulses to transmit data Immune to interferenceImmune to interference

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Network Operating Systems Network Operating Systems (NOS)(NOS)

Provide the protocol that controls the Provide the protocol that controls the communication between devices on communication between devices on the networkthe network

Major network operating systems:Major network operating systems:• Windows Server XXWindows Server XX• UNIXUNIX• Novell NetWareNovell NetWare

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Network AdaptersNetwork Adapters

Devices that enable computers to Devices that enable computers to communicate on a networkcommunicate on a network

Network interface cards (NICs):Network interface cards (NICs):• Generate network transmission signalsGenerate network transmission signals• Create data packetsCreate data packets• Act as information gatekeepersAct as information gatekeepers• Ethernet compliantEthernet compliant• Wireless NICsWireless NICs

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Network Navigation DevicesNetwork Navigation Devices

Media Access Control (MAC) address:Media Access Control (MAC) address:• Six 2-digit numbers (01:40:87:44:79:A5)Six 2-digit numbers (01:40:87:44:79:A5)• Physical address of network adapterPhysical address of network adapter• Internal network identificationInternal network identification

Repeaters and Hubs:Repeaters and Hubs:• Amplify signals and retransmit themAmplify signals and retransmit them

Switches and Bridges:Switches and Bridges:• Send data on a specific route through the networkSend data on a specific route through the network• Bridges send data between collision domainsBridges send data between collision domains

Routers:Routers:• Send information between two networksSend information between two networks