Chapter 16 WAN Technologies

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WAN Technologies

Chapter 16



Chapter 16 2

Chapter Objectives – I

Differentiate between the types of network switchingExplain the Public Switched Telephone SystemDiscuss the Mobile Telephone SystemExplain point-to-point WANsDescribe the X.25 protocol



Chapter 16 3

Chapter Objectives – II

Explain Frame RelayExplain ATMExplain the ISDN protocol and BISDNExplain the FDDI protocol

Explain satellite communication



Chapter 16 4

Recall – I

Router is an Internetworking device used to link twodifferent networksTwo types of NAT are:

Static NATDynamic NAT

Proxy server is a computer that allows networkusers to make an indirect network connection todifferent network services



Chapter 16 5

Recall – II

Types of proxies are:Transparent proxiesReverse proxies

Anonymous proxies

Zones of Internet explorer:Internet zoneLocal Intranet zone

Trusted Sites zoneRestricted Sites zone



Chapter 16 6

Recall – III

Applications of Internet:World Wide WebElectronic mail

File Transfer ProtocolTELNET



Chapter 16 7

Types of Switching

Switching

Circuit Switching Message Switching Packet Switching

Switching is a process of moving the data through aseries of intermediate steps rather than moving fromthe start point directly to the end point.



Chapter 16 8

Circuit Switching

Direct physical connection established between senderand receiver before data transmission

Allows a fixed rate of transmissionMajor drawbacks are:

Unused transmission is wastedUnused bandwidth cannot be used by any othertransmission



Chapter 16 9

Message Switching

No direct physical connection established betweensender and receiverMessage routed through the intermediate nodesThis technology is also known as store and forward

method



Chapter 16 10

Packet SwitchingMessage to be transmitted broken into units calledpacketsPacket contains addressing informationPackets are carried on virtual circuits. Virtual circuitsare temporary connections over which the sendingand receiving stations communicate



Chapter 16 11

Connectionless Services

Before transmitting the packets, actual connectionnot established between the sender and the receiverEach packet considered as an independent unit

Each packet treated as a complete messagePackets follow different routes to reach destination



Chapter 16 12

Connection-oriented Services

Before transmitting packets, communication linkestablishedPackets follow same route to reach destination

For transmission, uses Switched Virtual Circuit(SVC) or Permanent Virtual Circuit (PVC)



Chapter 16 13

Public Switched Telephone Network

Telephone system that uses copper wires to carryanalog voice data is called Public SwitchedTelephone Network (PSTN)Telephone services carried by the PSTN are oftencalled as Plain Old Telephone Service (POTS).Services offered by POTS are follows:

Bi-directional

Ringing signals and dial-toneOperator services



Chapter 16 14

Structure of Telephone System – I

Telephone system consists of following majorcomponents:

Local loops – Analog twisted pairs going into housesand businessesSwitching offices – Place where the calls moved fromone trunk to anotherTrunks – Switching offices connected using digitalfiber optics called trunks



Chapter 16 15

Structure of Telephone System – II

Typical circuit route for a medium-distance call:



Chapter 16 16

Point to Point WANs

Two remote devices connected using a lineavailable from a public networkPublic network can be a telephone network

Services basically provided at the physical layerUsers responsible for the data link layer protocols



Chapter 16 17

Physical Layer

To accomplish point-to-point connection betweentwo devices at the physical layer, use the followingservices:

Modem technology

Digital Subscriber Line (DSL)Cable modemT-lineE1 LinesSONET



Chapter 16 18

Data Link Layer

Concerned with data transferProtocol needed for reliable connection

A protocol is needed at this layer to have a reliablepoint-to-point connection. For reliability, uses Point-to-Point Protocol (PPP)For establishing, maintaining and terminating thelink, uses Link Control Protocol (LCP)

For providing flexibility to PPP, uses NetworkControl Protocol (NCP)



Chapter 16 19

X.25 Protocol

Connection-oriented packet-switching protocolDefines the way in which the connections betweenthe user devices and the network devices areestablished and maintained.Used in the packet-switched networks (PSNs) suchas the telephone companies.



Chapter 16 20

X.25 DevicesX.25 network devices are:

Data terminal equipment (DTE)Data circuit-terminating equipment (DCE)Packet-switching exchange (PSE)



Chapter 16 21

X.25 Virtual Circuits

X.25 virtual circuits are:Switched Virtual Circuits (SVCs)Permanent Virtual Circuits (PVCs)



Chapter 16 22

Frame Relay

High performance WAN protocol, faster than X.25Operates at the physical and data link layer of theOSI reference modelDoes not involve error correction and network flowcontrol operationsFrame relay virtual circuits are:

Switched Virtual Circuits (SVCs)

Permanent Virtual Circuits (PVCs)



Chapter 16 23

Frame Relay Devices

The devices attached to the Frame Relay WAN fortransmission of data packets are, Data terminalequipment (DTE) and Data circuit-terminatingequipment (DCE).



Chapter 16 24

Case Study – I

The head office of the MoneyMaker bank in Mumbaiis integrated with all its branches using the FDDItechnology. All the transactions are carried out usingthis network. Due to congestion in the network thebank is losing critical data which has become amajor area of concern for the bank.



Chapter 16 25

Problem

Data loss due to congestion in FDDI networktechnology.



Chapter 16 26

Suggested Solution

All the branches should be integrated using theFrame Relay technology. Frame Relay provides acongestion control mechanism.



Chapter 16 27

Asynchronous Transfer Mode (ATM)

Cell-switching and multiplexing technology whichcombines the benefits of both circuit switching andpacket switching

Transmits data, voice and video signalssimultaneously over the same communication linesBefore transmission, this information is convertedinto fixed size cells



Chapter 16 28

ATM Devices

ATM network consists of two devices: ATM Switch ATM endpoint



Chapter 16 29

ATM Services

ATM Services

Permanent

VirtualCircuits(PVC)

Switched

VirtualCircuits

(SVC)

ConnectionlessService



Chapter 16 30

ATM Reference Model

Reference model comprises of the following: ATM layers ATM planes



Chapter 16 31

Integrated Services Digital Network(ISDN)Involves digital telephony and data-transportservices offered by the regional telephone carriersPermits transmission of voice, data, text, graphics,

music and video over existing telephone linesConsists of following devices:

TerminalsTerminal Adapters

Network Termination Devices



Chapter 16 32

ISDN Devices



Chapter 16 33

ISDN Services

The information transmitted over the ISDN networktravels through the three logical digital communicationchannels:

B-Channel - Carries user service information thatincludes digital data, video and voice. It is the basicuser channelD-Channel - Carries signals and data between theuser and the network.H-Channel - Performs the same functions as that ofthe B-Channels and operates at data rate of 64 Kbps.



Chapter 16 34

Broadband ISDN (BISDN)

Extension of ISDNUsed for technologies such as video conferencingand file transfer

Provides two types of services as follows:Interactive ServicesDistributive Services



Chapter 16 35

Case Study – II

All the branches of MoneyMaker bank have to senddaily transaction details to the Mumbai branch. Thesize of this file is very large. The bank uses a regulartelephone line and a standard modem to send thisfile.



Chapter 16 36

Problem

Slow data transmission



Chapter 16 37

Suggested Solution

Setup an ISDN. Certain things are required to setup an ISDN service which includes, a ISDNmodem or router, Service Profile Identifiers

(SPIDs) from the telephone company, the nameof the switch or the network type the phonecompany uses, and account information from theISDN service provider.



Chapter 16 38

Fiber Distributed Data Interface

Based on ring topology and token passingTwo optical fibers used as follows:

Multimode optical fiber

Single-mode optical fiberTwo types of copper cables used as follows:

Category 5 Unshielded Twisted Pair copper wiringIBM Type 1 Shielded Twisted Pair copper wiring



Chapter 16 39

Satellite Communication

Two parts of satellite communication are:Uplink – Transmitter consisting of a ground-basedpart Transponder – The satellite-based part reflectingsignals towards receivers

Advantages: Satellites can cover large areas of earth

It is commercially attractiveIt is preferred instead of cables as maintenanceof cables is expensive and difficult



Chapter 16 40

Polling

Communication technique which determines when aterminal is ready to send dataRound robin sequence is used by the computer tocontinuously interrogate its connected terminals

Communication system comprises of the following: A Master stationNumber of slave stations each communicating withthe master station

A two-way transmission line connecting the masterstation and the slave stations



Chapter 16 41

ALOHA

A simple communications scheme in which eachtransmitter or source in a network sends datawhenever there is a frame to send is called as

ALOHANext frame sent only if the first frame reaches thedestination successfullyIf the frame fails to reach the receiver, it is sentagainTypes of ALOHA:

Pure alohaSlotted aloha



Chapter 16 42

Summary - I

WAN covers a large geographical area and consistsof two or more local area networks (LANs)Circuit switching, message switching and packet

switching are types of switching technologies usedby WANLeased lines are the permanent point-to-point linksused for data communication

Circuit switching networks establish a direct physicalconnection between a sender and a receiver beforecommunication occurs



Chapter 16 43

Summary – II

In message switching, each switch stores the wholemessage and forwards it to the next switchPacket switching network transmits messages in theform of packets

The telephone system that uses copper wires tocarry analog voice data is called Public SwitchedTelephone Network (PSTN)Multiplexing is the technique that allows thesimultaneous transmission of multiple signals acrossa single data link



Chapter 16 44

Summary – III

X.25 is a connection-oriented packet-switchingprotocol which was earlier used by the InternetFrame relay is a high performance WAN protocolwhich operates at the physical and data link layersand uses fiber optic cable and ISDN for digital datatransmission

ATM transmits data, voice and video signalssimultaneously over the same communication lines

ISDN digitizes the telephone network, to transmit theinformation over the existing telephone wires



Summary – IV

BISDN which an extension to ISDN used for highspeed data transfer application such as videoconferencing and the ATM technology fortransmitting informationFDDI is based on ring topology and token passingPolling is a communication technique whichdetermines when a terminal is ready to send data

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Chapter 16 WAN Technologies

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