Chapter 9 - Network Organization Concepts Ivy Tech State College Northwest Region 01 CIS106 Microcomputer Operating Systems Gina Rue CIS Faculty

Chapter 9 - Chapter 9 - Network OrganizationNetwork OrganizationConceptsConcepts

Ivy Tech State College Northwest Region 01

CIS106 Microcomputer Operating Systems

Gina RueCIS Faculty

See Fig. p.199 2

Introduction - Introduction - Network Organization Network Organization ConceptsConcepts• Stand-alone computers linked together Stand-alone computers linked together

through communication systems to form through communication systems to form networks transmit & process data & networks transmit & process data & information among users in the systeminformation among users in the system

• Goal of networked systems are to provide a Goal of networked systems are to provide a way to share resources:way to share resources:– hardware: CPU, memory, printers, tape, and disk hardware: CPU, memory, printers, tape, and disk

drivesdrives

– software: programs & data filessoftware: programs & data files

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Introduction - Introduction - Network Organization Network Organization ConceptsConceptsOS Types for NetworkingOS Types for Networking

• OS built for the network is built on top of OS built for the network is built on top of the existing local computer OS is referred the existing local computer OS is referred to as a Network Operating Systemto as a Network Operating System

– users can access resources by:users can access resources by:

– logging on to a remote hostlogging on to a remote host

– transferring data from the remote computer transferring data from the remote computer to their ownto their own

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Introduction - Introduction - Network Organization Network Organization ConceptsConcepts• The Distributed OS provides good The Distributed OS provides good

control for distributed computing control for distributed computing systems & allows their resources to be systems & allows their resources to be accessed in a unified wayaccessed in a unified way– advantages: easy & reliable resource advantages: easy & reliable resource

sharing, improved computation sharing, improved computation performance, adequate load balancing, performance, adequate load balancing, dependable electronic communications dependable electronic communications among usersamong users

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Basic TerminologyBasic Terminology

• NetworkNetwork is a collection of processors is a collection of processors interconnected by a communication interconnected by a communication networknetwork

• In a distributed system each processor In a distributed system each processor classifies the other processors & their classifies the other processors & their resources as resources as remote remote & considers its & considers its own resources as own resources as locallocal

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Basic TerminologyBasic Terminology• Size, type, and identification of processors variesSize, type, and identification of processors varies

• Processors are referred to as Processors are referred to as sites, hosts, & nodes sites, hosts, & nodes – site is a specific location on the network containing one site is a specific location on the network containing one

or more computersor more computers

– host is a specific computer system found at a site host is a specific computer system found at a site whose services & resources can be used from remote whose services & resources can be used from remote locationslocations

– node refers to the name assigned to a computer node refers to the name assigned to a computer connected to the networkconnected to the network

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Basic TerminologyBasic Terminology

• Typically a host at one site is called Typically a host at one site is called the the server &server & has resources that a has resources that a host at another site, called the host at another site, called the clientclient wants to use wants to use

• Hosts can alternate between being Hosts can alternate between being clients or servers depending on the clients or servers depending on the requirementsrequirements

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Network TopologiesNetwork Topologies– Networks can be physically or logically connected Networks can be physically or logically connected

in a variety of topologiesin a variety of topologies

•Common arrangements are:Common arrangements are:– star, ring, bus, treestar, ring, bus, tree

– Each topology has tradeoffsEach topology has tradeoffs

•need for fast communication among all sitesneed for fast communication among all sites

•tolerance of failure at a site or communication tolerance of failure at a site or communication link link

•difficulty of connecting one site to a large difficulty of connecting one site to a large number of other sitesnumber of other sites

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Network TopologiesNetwork Topologies– Deciding which configuration to use, system Deciding which configuration to use, system

designers should consider 3 criteria:designers should consider 3 criteria:

•Basic costBasic cost– expense required to link the various sites in the expense required to link the various sites in the

systemsystem

•Communication costCommunication cost– time required to send a message from one site to time required to send a message from one site to

anotheranother

•ReliabilityReliability– assurance that many sites can still communicate assurance that many sites can still communicate

with each other even if a link or site in the system with each other even if a link or site in the system failsfails

See Fig. 9.1 p.201 10

Network TopologiesNetwork Topologies– StarStar

• sometimes called a “hub” or “centralized” approach sometimes called a “hub” or “centralized” approach to interconnect devicesto interconnect devices

• data must pass through a central controller when data must pass through a central controller when going from sender to receivergoing from sender to receiver

• permits easy routing, central station knows the path permits easy routing, central station knows the path to all other sitesto all other sites

• central points makes access to the network easy to central points makes access to the network easy to control and priority status control and priority status

• central site must be extremely reliable & able to central site must be extremely reliable & able to handle heavy network traffichandle heavy network traffic

See Fig. 9.2 p.202 11

Network TopologiesNetwork Topologies– RingRing

• all sites are connected in a closed loopall sites are connected in a closed loop

• data is transmitted in packets also contain source data is transmitted in packets also contain source & destination address fields& destination address fields

• a data packet is passed in one direction from node a data packet is passed in one direction from node to node to a local buffer on the destination nodeto node to a local buffer on the destination node

• a packet will continue to move through the ring & a packet will continue to move through the ring & returns to the source then removed from the ring returns to the source then removed from the ring

• several variations with more flexibility but at a several variations with more flexibility but at a costcost

See Fig. 9.5 p.206 12

Network TopologiesNetwork Topologies– BusBus

• all sites are connected to a single communication all sites are connected to a single communication line running the length of the networkline running the length of the network

• physically connects the devices by cables that physically connects the devices by cables that run between themrun between them

• only one node can send a message successfully only one node can send a message successfully at one timeat one time

• data may pass directly from one device to data may pass directly from one device to another or may be routed to an end point another or may be routed to an end point controller controller

See Fig. 9.6 p.206 13

Network TopologiesNetwork Topologies

– TreeTree• a collection of bussesa collection of busses

• communication line is branching cable with no communication line is branching cable with no closed loopsclosed loops

• tree layout begins at the “head end” one or tree layout begins at the “head end” one or more cables startmore cables start

• each cable may have branches that may each cable may have branches that may additional branches additional branches

• bridges are used to translate different protocolsbridges are used to translate different protocols

See Fig. 9.7 & 9.8 p.207 14

Network TopologiesNetwork Topologies

– HybridHybrid• combination of any of the four combination of any of the four

topologiestopologies

• ObjectivesObjectives– select among the strong points of select among the strong points of

each topologyeach topology– combine topologies to meet the that combine topologies to meet the that

system’s communication system’s communication requirements most cost effectivelyrequirements most cost effectively

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Network TypesNetwork Types

Often used to group networks Often used to group networks according to the physical according to the physical distances they coverdistances they cover

– Local Area Network (LAN)Local Area Network (LAN)

– Metropolitan Area Network (MAN)Metropolitan Area Network (MAN)

– Wide Area Network (WAN)Wide Area Network (WAN)

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Network TypesNetwork Types Local Area Network (LAN)Local Area Network (LAN)– configuration found in a single office building, configuration found in a single office building,

warehouse, campus, labwarehouse, campus, lab• generally owned, used, & operated by a single generally owned, used, & operated by a single

organizationorganization

• LAN can be a component of a larger networkLAN can be a component of a larger network– BridgeBridge is a device & software that connects is a device & software that connects

two or more LANs that use the same two or more LANs that use the same protocolsprotocols

– GatewayGateway is a more complex device & software is a more complex device & software used to connect two or more LANs that use used to connect two or more LANs that use different protocolsdifferent protocols

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Network TypesNetwork Types Local Area Network (LAN)Local Area Network (LAN)– operates at speeds from one MB per second to one operates at speeds from one MB per second to one

GB per secondGB per second

– bandwidths are available to support high-speed bandwidths are available to support high-speed transmission for graphics, video, digital, & voice transmission for graphics, video, digital, & voice

– transmission medium varies from one topology to transmission medium varies from one topology to another - cable, wire, fiber-opticanother - cable, wire, fiber-optic

– transmission medium considerations are cost, data transmission medium considerations are cost, data rate, reliability, number of devices, distance, & rate, reliability, number of devices, distance, & technical limitationstechnical limitations

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Network TypesNetwork Types

Metropolitan Area Networks (MAN)Metropolitan Area Networks (MAN)– defines configurations spanning an area larger defines configurations spanning an area larger

than a LAN, ranging from several blocks to an than a LAN, ranging from several blocks to an entire city, not exceeding 100 kilometersentire city, not exceeding 100 kilometers

– may be owned & operated by a single or many may be owned & operated by a single or many individuals & organizations or by public utilities individuals & organizations or by public utilities providing means for connecting LANSproviding means for connecting LANS• typically configured as a ring for one direction typically configured as a ring for one direction

transmission or dual ring transmitting in two transmission or dual ring transmitting in two directionsdirections

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Network TypesNetwork Types Wide Area Network (WAN)Wide Area Network (WAN)– configuration that interconnects communication configuration that interconnects communication

facilities in different parts of the country or world, or facilities in different parts of the country or world, or operates as part of a public utilityoperates as part of a public utility

– use communication lines of “common carriers” such as use communication lines of “common carriers” such as telephone companiestelephone companies• use broad range of media, satellites, microwaves & high-use broad range of media, satellites, microwaves & high-

speed transmissionspeed transmission

• generally slower than LANsgenerally slower than LANs

• Internet is the most widely recognized WANInternet is the most widely recognized WAN

• ARPnet, TelenetARPnet, Telenet

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Software Designing IssuesSoftware Designing Issues

Network designers must address four Network designers must address four issues: issues:

– How do sites use addresses at other sites?How do sites use addresses at other sites?

– How are messages routed & how are they sent?How are messages routed & how are they sent?

– How do processes communicate with each other?How do processes communicate with each other?

– How are conflicting demands for resources How are conflicting demands for resources resolved?resolved?

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Software Designing IssuesSoftware Designing IssuesAddressing Conventions Addressing Conventions

– sites need to be uniquely identified by using names, sites need to be uniquely identified by using names,

addresses & routesaddresses & routes• local name refers a name each unit is known by on its local name refers a name each unit is known by on its

own systemown system

• global name refers to a name each unit is known by global name refers to a name each unit is known by outside its own systemoutside its own system

– Domain Name Service (DNS) protocol a general Domain Name Service (DNS) protocol a general purpose distributed data query service that resolves purpose distributed data query service that resolves Internet addressesInternet addresses

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Routing Strategies Routing Strategies

– allows data to get from one point on the network to anotherallows data to get from one point on the network to another• requires each destination be uniquely identifiedrequires each destination be uniquely identified

• forwards data between networksforwards data between networks

– each router records a table of addresses of the networks each router records a table of addresses of the networks that are connectedthat are connected• variety of message formats variety of message formats

• two most common routing protocols, routing information two most common routing protocols, routing information protocol & open shortest path firstprotocol & open shortest path first

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Software Designing IssuesSoftware Designing IssuesRouting Strategies Routing Strategies

– Routing Information Protocol (RIP)Routing Information Protocol (RIP)

• chooses the best path for data transfer with the smallest number of chooses the best path for data transfer with the smallest number of “hops”“hops”

• distance vector algorithm is easy to implement but may not choose distance vector algorithm is easy to implement but may not choose the most reliable paththe most reliable path

– Open Shortest Path First (OSPF)Open Shortest Path First (OSPF)• if an intermediate hop is malfunctioning it is eliminated from if an intermediate hop is malfunctioning it is eliminated from

consideration until it is restoredconsideration until it is restored

• topological database data structure is maintained by OSPF & topological database data structure is maintained by OSPF & updated when failure occursupdated when failure occurs

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Software Designing IssuesSoftware Designing IssuesConnection Models Connection Models

– not concerned with data content, but with moving data not concerned with data content, but with moving data

from one point to anotherfrom one point to another

– network designed to minimize costsnetwork designed to minimize costs

– provides full connectivity among attached devicesprovides full connectivity among attached devices

– data entering the network at one point is routed to its data entering the network at one point is routed to its destination by switching from node to node, whether bydestination by switching from node to node, whether by• circuit switchingcircuit switching

• packet switchingpacket switching

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– Circuit Switching Circuit Switching

• communication model where a dedicated communication path communication model where a dedicated communication path is established between 2 hostsis established between 2 hosts

• the path is a connected sequence of linksthe path is a connected sequence of links

• connection between points only exists until one is connection between points only exists until one is disconnecteddisconnected

• telephone system a good exampletelephone system a good example

• once connection is complete, transparent to usersonce connection is complete, transparent to users

• information transmitted at a fixed rateinformation transmitted at a fixed rate

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– Packet Switching Packet Switching

• store-and-forward techniquestore-and-forward technique

• message is divided into multiple equal-sized units called packets message is divided into multiple equal-sized units called packets

• packets reaching a destination are reassembledpackets reaching a destination are reassembled

• effective for long-distance transmissioneffective for long-distance transmission

• flexible to different transmission ratesflexible to different transmission rates

• no guarantee data will arrive in physical sequential orderno guarantee data will arrive in physical sequential order

• allows users to set priorities to their messagesallows users to set priorities to their messages

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Connection Models Connection Models

– Packet Switching, two methods of selecting a pathPacket Switching, two methods of selecting a path•datagramsdatagrams

– destination & sequence number of the packet is destination & sequence number of the packet is added, a route is selected as it is accepted into the added, a route is selected as it is accepted into the networknetwork

•virtual circuitvirtual circuit– destination & packet sequence number are not added destination & packet sequence number are not added

because complete path from sender to receiver is because complete path from sender to receiver is established before transmission startsestablished before transmission starts

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Conflict Resolution Conflict Resolution

– Because networks consist of devices Because networks consist of devices sharing a common transmission sharing a common transmission capability, a method to control access capability, a method to control access is necessary to facilitate equal & fair is necessary to facilitate equal & fair access to this common resourceaccess to this common resource

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Software Designing IssuesSoftware Designing IssuesConflict Resolution Conflict Resolution

– Access Control Techniques Access Control Techniques • Round RobinRound Robin

– Allows each node to use the communication medium for a Allows each node to use the communication medium for a certain amount of timecertain amount of time

• ReservationReservation– Access time on the medium is divided into slots & nodes can Access time on the medium is divided into slots & nodes can

reserve future timereserve future time

• ContentionContention– no attempt is made to determine whose turn it is to transmit no attempt is made to determine whose turn it is to transmit

so nodes compete for access to the mediumso nodes compete for access to the medium

See Fig. 9.9 p.216 30

Software Designing IssuesSoftware Designing IssuesConflict Resolution Conflict Resolution

– Medium Access Control Procedures Medium Access Control Procedures •Carrier Sense Multiple Access (CSMA)Carrier Sense Multiple Access (CSMA)

– contention-based protocolcontention-based protocol– a node on the network will listen to, or test, the a node on the network will listen to, or test, the

communication medium before sending a messagecommunication medium before sending a message– prevents collision with another node currently transmittingprevents collision with another node currently transmitting

•Carrier Sense Multiple Access with Collision Detection Carrier Sense Multiple Access with Collision Detection (CSMA/CD)(CSMA/CD)

– Ethernet most widely knownEthernet most widely known– reduces the number of collisionsreduces the number of collisions

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Transport Protocol StandardsTransport Protocol Standards

In the early 1980s network usage grew In the early 1980s network usage grew & the need to integrate dissimilar & the need to integrate dissimilar network devices & their complexitynetwork devices & their complexity•To allow multi-vendor interoperability, To allow multi-vendor interoperability,

two standards were developedtwo standards were developed– International Organization for International Organization for

Standardization (ISO)Standardization (ISO)– Transmission Control Protocol/Internet Transmission Control Protocol/Internet

Protocol (TCP/IP) Protocol (TCP/IP)

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International Organization Standardization International Organization Standardization (ISO)(ISO)

– makes technical recommendations about data makes technical recommendations about data communication interfacescommunication interfaces

– Open System Interconnect (OSI) reference model is Open System Interconnect (OSI) reference model is the frame work for defining the services that a the frame work for defining the services that a network should provide to its usersnetwork should provide to its users

– 7 layers are used to group localized functions so 7 layers are used to group localized functions so redesigning layers & protocol to take advantage of redesigning layers & protocol to take advantage of changing serviceschanging services

See Fig. 9.10 p.218 33


ISO-OSI reference modelISO-OSI reference modelLayer 1 - Physical LayerLayer 1 - Physical Layer

Layer 2 - Data Link LayerLayer 2 - Data Link Layer

Layer 3 - Network LayerLayer 3 - Network Layer

Layer 4 - Transport LayerLayer 4 - Transport Layer

Layer 5 - Session LayerLayer 5 - Session Layer

Layer 6 - Presentation LayerLayer 6 - Presentation Layer

Layer 7 - Application LayerLayer 7 - Application Layer

See Fig. 9.11 p.221 34


Transmission Control Protocol/Internet Protocol Transmission Control Protocol/Internet Protocol (TCP/IP)(TCP/IP)

– oldest & most widely used protocol developed by U.S. Dept. of oldest & most widely used protocol developed by U.S. Dept. of Defense’s ARPAnetDefense’s ARPAnet

– provides efficient & error-free transmission between different provides efficient & error-free transmission between different systemssystems

– file-transfer protocol (FTP) allows large files to be sent across file-transfer protocol (FTP) allows large files to be sent across unreliable networks error-freeunreliable networks error-free

– Three main components:Three main components:• processes, hosts, networksprocesses, hosts, networks

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Transmission Control Transmission Control Protocol/Internet Protocol Protocol/Internet Protocol (TCP/IP)(TCP/IP)

Layer 1 - Network Access Layer 1 - Network Access

Layer 2 - InternetLayer 2 - Internet

Layer 3 - Host-HostLayer 3 - Host-Host

Layer 4 - Process/ApplicationLayer 4 - Process/Application

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SummarySummary

• Network operating systems (NOS) include Network operating systems (NOS) include functions of the four managersfunctions of the four managers– memorymemory

– processorprocessor

– devicedevice

– filefile

• NOS need to coordinate all functions among NOS need to coordinate all functions among network hardware & software, no matter where network hardware & software, no matter where they are physically locatedthey are physically located

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SummarySummary

• NOS success must meet reliability NOS success must meet reliability requirements of its owner, NOS must requirements of its owner, NOS must detect:detect:– node failurenode failure

– changing routing instructions to avoid that changing routing instructions to avoid that nodenode

– make sure lost messages are make sure lost messages are retransmitted until successfully receivedretransmitted until successfully received

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SummarySummary

• Introduced basic network Introduced basic network organization concepts:organization concepts:– common terminologycommon terminology

– network topologiesnetwork topologies

– types of networkstypes of networks

– software design issuessoftware design issues

– transport protocol standardstransport protocol standards

Documents

Chapter 9 - Network Organization Concepts Ivy Tech State College Northwest Region 01 CIS106 Microcomputer Operating Systems Gina Rue CIS Faculty