CHAPTER-8 TELECOMMUNICATIONS AND NETWORKS. IS THE COMMUNICATION AND TRANSMISSION OF DIGITALLY CODED...

CHAPTER-8CHAPTER-8

TELECOMMUNICATIONS TELECOMMUNICATIONS

AND NETWORKSAND NETWORKS

IS THE COMMUNICATION AND TRANSMISSION OF DIGITALLY CODED INFORMATION OR DATA FROM ONE

LOCATION TO ANOTHER

TELECOMMUNICATIONSTELECOMMUNICATIONS

HARDWARE – INCLUDES COMPUTER AND INPUT AND OUTPUT DEVICES FOR SENDING AND RECEIVING OUTPUT.

COMMUNICATION CHANNELS – INCLUDES LINKS THROUGH WHICH DATA ARE TRANSMITTED FROM ONE DEVICE IN A NETWORK TO ANOTHER.

COMPONENTS OF A COMPONENTS OF A TELECOMMUNICATION SYSTEMTELECOMMUNICATION SYSTEM

COMMUNICATION PROCESSORS – PROVIDE SUPPORT FUNCTIONS FOR DATA TRANSMISSION AND RECEPTION.

COMMUNICATION SOFTWARE – CONTROLS THE COMMUNICATION PROCESSES AND FUNCTIONS.

COMPONENTS OF A COMPONENTS OF A TELECOMMUNICATION SYSTEMTELECOMMUNICATION SYSTEM

FUNCTIONS OF FUNCTIONS OF TELECOMMUNICATION SYSTEMSTELECOMMUNICATION SYSTEMS

1. TRANSMIT INFORMATION2. ESTABLISH THE INTERFACE BETWEEN THE

SENDER AND THE RECEIVER3. ROUTE MESSAGES ALONG THE MOST

EFFICIENT PATHS4. PROCESS THE INFORMATION TO ENSURE

THAT THE RIGHT MESSAGE GETS TO THE RIGHT RECEIVER

FUNCTIONS OF FUNCTIONS OF TELECOMMUNICATION SYSTEMSTELECOMMUNICATION SYSTEMS

5. EDIT THE DATA TO CHECK FOR ERRORS AND REARRANGE THE FORMAT IF NECESSARY

6. CONVERT MESSAGES FROM ANOTHER SPEED INTO THE SPEED OF A COMMUNICATIONS LINE OR FROM ONE FORMAT TO ANOTHER

7. CONTROL THE FLOW OF INFORMATION BY ROUTING MESSAGES, AND MAINTAINING THE NETWORK

8. SECURE THE INFORMATION AT ALL TIMES

SET OF RULES AND PROCEDURES FOR TRANSFERRING INFORMATION ACROSS

THE NETWORK

COMMUNICATION PROTOCOLSCOMMUNICATION PROTOCOLS

IDENTIFY EACH DEVICE IN THE COMMUNICATION PATH

SECURE THE ATTENTION OF THE OTHER DEVICE

VERIFY CORRECT RECEIPT OF THE TRANSMITTED MESSAGE

VERIFY THAT A MESSAGE REQUIRES RETRANSMISSION BECAUSE ITCANNOT BE CORRECTLY INTERPRETED

PERFORM RECOVERY WHEN ERRORS OCCUR

SOME FUNCTIONS OF PROTOCOLSSOME FUNCTIONS OF PROTOCOLS

ANALOG SIGNALS—ARE CONTINUOUS WAVES THAT “CARRY” INFORMATION BY ALTERING THE CHARACTERISTICS OF THE WAVES. VOICE COMMUNICATION IS HANDLED BY ANALOG SIGNALS.

DIGITAL SIGNALS – ARE DISCRETE ON-OFF PULSES THAT CONVEY INFORMATION IN TERMS OF 1S AND 0S. COMPUTERS COMMUNICATE WITH DIGITAL SIGNALS.

ELECTRONIC SIGNALSELECTRONIC SIGNALS

BANDWIDTH: REFERS TO THE RANGE OF FREQUENCIES AVAILABLE IN ANY COMMUNICATION CHANNEL. THE GREATER THE BANDWIDTH THE GREATER THE CHANNEL CAPACITY.

BAUD RATE: REFERS TO THE AMOUNT OF DATA THAT CAN BE TRANSMITTED THROUGH A COMMUNICATIONS CHANNEL. BAUD RATE IS MEASURED IN BITS PER SECOND (BPS).

TRANSMISSION SPEEDTRANSMISSION SPEED

1. TWISTED WIRE—MOST PREVALENT FORM OF COMMUNICATION WIRING, USED FOR MOST BUSINESS TELEPHONE WIRING, CONSISTS OF STRANDS OF COPPER WIRE TWISTED IN PAIRS.

DIFFERENT TYPES OF DIFFERENT TYPES OF COMMUNICATION MEDIA COMMUNICATION MEDIA

(CHANNELS)(CHANNELS)

ADVANTAGES:• LOW COST • EASY TO WORK WITH

DISADVANTAGES: • RELATIVELY SLOW • SUBJECT TO INTERFERENCE FROM OTHER ELECTRICAL SOURCES

2. COAXIAL CABLE—USED FOR CABLE TELEVISION, CONSISTS OF INSULATED COPPER WIRE.



ADVANTAGES:• FASTER THAN TWISTED WIRE• LESS SUSCEPTIBLE TO ELECTROMAGNETIC INTERFERENCE

DISADVANTAGES: • RELATIVELY EXPENSIVE• SOMEWHAT DIFFICULT TO WORK WITH

3. FIBER OPTIC—CONSISTS OF CLEAR GLASS FIBER AND TRANSMITS INFORMATION IN THE FORM OF LIGHT WAVES, INSTEAD OF ELECTRIC CURRENT.



ADVANTAGES:• CONSIDERABLY FAST • SMALLER AND LIGHTER THAN COAXIAL CABLES

DISADVANTAGES: • EXPENSIVE• HARD TO INSTALL AND DIFFICULT TO WORK WITH

4.A. MICROWAVE—ARE WIDELY USED FOR HIGH-VOLUME, LONG DISTANCE, POINT-TO-POINT COMMUNICATION. THEY TRANSMIT HIGH FREQUENCY RADIO SIGNALS IN THE ATMOSPHERE. MICROWAVE SIGNALS FOLLOW A STRAIGHT LINE BETWEEN RELY STATIONS 30 MILES APART (DO NOT BEND WITH EARTH’S CURVATURE). THIS LIMITATION MAKES MICROWAVE SYSTEMS MORE EXPENSIVE.



4. WIRELESS COMMUNICATIONS

4.B. SATELLITES—TRANSMIT DATA USING ORBITING SATELLITES. SATELLITES SERVE AS RELY STATIONS FOR TRANSMITTING MICROWAVE SIGNALS OVER VERY LONG DISTANCES. SATELLITES ARE EFFICIENT WAY OF TRANSMITTING LARGE AMOUNT OF DATA OVER A VERY LONG DISTANCE.




4.C. PAGING SYSTEM—NOTIFIES THE USER BY BEEPING AND DISPLAYING A SHORT MESSAGE ON THE SCREEN WHEN MESSAGES ARE RECEIVED. IT IS A USEFUL SYSTEM WHEN MOBILE COMPUTING POWER IS REQUIRED.




4.D. CELLULAR PHONES—TRANSMITS VOICE, USING RADIO WAVES TO COMMUNICATE WITH RADIO ANTENNAS PLACED WITHIN ADJACENT GEOGRAPHIC AREAS CALLED CELLS.

FRONT-END PROCESSOR—A SMALL COMPUTER WHICH MANAGES THE COMMUNICATION PROCESSES FOR THE HOST COMPUTER IN A NETWORK.

CONCENTRATOR—A COMPUTER THAT COLLECTS AND TEMPORARILY STORES MESSAGES FROM TERMINALS FOR BATCH TRANSMISSION TO THE HOST COMPUTER.

COMMUNICATION PROCESSORSCOMMUNICATION PROCESSORS

CONTROLLER—A SPECIAL COMPUTER THAT SUPERVISES COMMUNICATION TRAFFIC BETWEEN THE CPU AND PERIPHERAL DEVICES.

MULTIPLEXER—IS AN ELECTRONIC DEVICE THAT ALLOWS A SINGLE COMMUNICATIONS CHANNEL TO CARRY DATA TRANSMISSIONS SIMULTANEOUSLY FROM MANY SOURCES.


MODEM—TELEPHONE SYSTEMS PROCESS ANALOG SIGNALS. THESE SYSTEMS CANNOT PROCESS DIGITAL SIGNALS, THEREFORE DIGITAL SIGNALS NEED TO BE CONVERTED INTO ANALOG SIGNAL. THE CONVERSION FROM DIGITAL TO ANALOG IS CALLED MODULATION AND THE REVERSE IS DEMODULATION. THE DEVICE THAT HANDLES THESE TWO PROCESSES IS CALLED A MODEM.


STAR—HAS A CENTRAL HOST COMPUTER THAT CONNECTS TO SMALLER COMPUTERS OR TERMINALS. ANY COMMUNICATION BETWEEN DIFFERENT POINTS IN THE NETWORK MUST PASS THROUGH THE HOST COMPUTER. THEREFORE, IF THE CENTRAL COMPUTER IS NOT FUNCTIONING THEN THE COMMUNICATION BETWEEN OTHER COMPUTERS IN THE NETWORK WILL BE DISRUPTED.

CLASSIFICATION OF NETWORKS CLASSIFICATION OF NETWORKS BY THEIR SHAPE OR TOPOLOGYBY THEIR SHAPE OR TOPOLOGY

BUS—COMPUTERS ARE ARRANGED IN A SINGLE LENGTH OF TWISTED WIRE, COAXIAL CABLE, OR FIBER OPTIC CABLE THAT CAN BE EXTENDED AT THE ENDS. LOSING A COMPUTER IN THIS TYPE OF NETWORK WILL NOT CAUSE THE NETWORK TO FAIL. THE CHANNEL IN THIS TYPE OF NETWORK CAN PROCESS ONE MESSAGE AT A TIME THEREFORE A LARGE VOLUME OF MESSAGES WILL POORLY AFFECT THE PERFORMANCE OF THE NETWORK.


RING—COMPUTERS ARE ARRANGED ALONG THE TRANSMISSION PATH (A CLOSED LOOP) SUCH THAT A SIGNAL PASSES THROUGH ONE COMPUTER TO ANOTHER AND THE FLOW OF DATA IS ALWAYS IN ONE DIRECTION.

THIS TYPE OF NETWORK WILL STILL WORK EVEN IF ONE OF ITS COMPONENTS FAIL.


PRIVATE BRANCH EXCHANGE (PBX)—IS A SPECIAL-PURPOSE COMPUTER THAT CONTROLS TELEPHONE SWITCHING AT A COMPANY SITE. PBXS CAN CARRY BOTH VOICE AND DATA AND PROVIDE FUNCTIONS SUCH AS CALL WAITING, CALL FORWARDING, VOICE MAIL, CALL TRANSFER, AND REDIAL CALLS. PBX CAN SWITCH DIGITAL INFORMATION AMONG COMPUTERS AND OFFICE DEVICES.

CLASSIFICATION OF NETWORKS CLASSIFICATION OF NETWORKS BY THEIRBY THEIR

GEOGRAPHICAL SCOPEGEOGRAPHICAL SCOPE

(PBX)—PBX IS LIMITED TO A SMALL GEOGRAPHIC AREA. THEY ARE LIMITED TO PHONE LINES AND ARE NOT SUITABLE FOR PROCESSING LARGE VOLUMES OF DATA.



LOCAL AREA NETWORK (LAN)— CONNECTS TWO OR MORE COMMUNICATING DEVICES WITHIN A SHORT DISTANCE (E.G. 2000 FEET). LANS ARE USUALLY INTERORGANIZATIONAL, PRIVATELY OWNED, INTERNALLY ADMINISTERED. LANS CAN GIVE USERS FAST AND EFFICIENT ACCESS TO A COMMON COLLECTION OF INFORMATION AND PROVIDE POOLING OF RESOURCES SUCH AS PRINTERS AND FACSIMILE MACHINES.

CLASSIFICATION OF NETWORKS BY CLASSIFICATION OF NETWORKS BY THEIRTHEIR


THE NETWORK GATEWAY CONNECTS THE LAN TO PUBLIC NETWORKS, OR OTHER ORGANIZATION NETWORKS.

“GATEWAY” IS A COMMUNICATION PROCESSOR FOR CONNECTING DISSIMILAR NETWORKS WHILE A “BRIDGE” CONNECTS TWO NETWORKS OF THE SAME TYPE. A “ROUTER” ROUTES MESSAGES THROUGH SEVERAL CONNECTED LANS OR TO A WAN.



LANS MAY BE IN THE FORM OF CLIENT/SERVER NETWORK ARCHITECTURE OR A PEER-TO-PEER NETWORK ARCHITECTURE. UNLIKE CLIENT/SERVER NETWORKS, WHERE NETWORK INFORMATION IS STORED ON THE SERVER AND MADE AVAILABLE TO DIFFERENT CLIENTS, THE INFORMATION STORED ACROSS PEER-TO-PEER NETWORKS IS DECENTRALIZED AND EACH COMPUTER ACTS AS A CLIENT AND A SERVER. IN A PEER-TO-PEER NETWORK EACH COMPUTER HAS TRANSPARENT ACCESS TO ALL FILES ON ALL OTHER COMPUTERS.



WIDE AREA NETWORK (WAN)— REFERS TO A NETWORK WHICH COVERS WIDE GEOGRAPHIC AREAS. WANS MAY COMBINE SWITCHED AND DEDICATED LINES, MICROWAVE, AND SATELLITE COMMUNICATIONS.



VALUE-ADDED NETWORK (VAN)— IS A TYPE OF WAN. VANS ARE PRIVATE, MULTIPATH, THIRD-PARTY MANAGED NETWORKS. THEY ARE COST EFFICIENT IN TERMS OF SERVICE AND MANAGEMENT OF THE NETWORK, BECAUSE THEY ARE USED BY MULTIPLE ORGANIZATIONS. VANS OFFER SEVERAL VALUABLE SERVICES; CUSTOMERS DO NOT HAVE TO INVEST IN NETWORK HARDWARE AND SOFTWARE OR PERFORM THEIR OWN ERROR CHECKING, EDITING, ROUTING, AND PROTOCOL CONVERSION.



PACKET SWITCHING — NETWORK HARDWARE AND SOFTWARE BREAK DATA INTO PACKETS (SMALL FIXED BUNDLES OF FIXED DATA).

EACH PACKET HAS AN ADDRESS. EACH NODE ON THE NETWORK LOOKS AT THE

ADDRESS AND DETERMINES THE BEST PATH FOR SENDING IT TO ITS FINAL DESTINATION.

NETWORK HARDWARE AND SOFTWARE REASSEMBLE THE PACKETS ON THE RECEIVING END.

PACKETS ALSO CONTAIN INFORMATION FOR CHECKING TRANSMISSION ERRORS.

NETWORK SERVICESNETWORK SERVICES

FRAME RELAY — IS SIMILAR TO PACKET SWITCHING BUT IS FASTER AND CHEAPER. DATA ARE DIVIDED INTO FRAMES. IT DOES NOT CHECK FOR TRANSMISSION ERROR, THEREFORE IT IS MORE SUITABLE FOR RELIABLE LINES.


ASYNCHRONOUS TRANSFER MODE (ATM)—DIVIDES DATA INTO UNIFORM CELLS OF FIXED LENGTH. ATM CAN CARRY VOICE, VIDEO, AND DATA TRAFFIC WITHOUT SACRIFICING MUCH EFFICIENCY. ATM CAN BE USED FOR CONNECTING LAN AND WAN

TOGETHER.


INTEGRATED SERVICES DIGITAL NETWORK (ISDN)—INTERNATIONAL STANDARD FOR TRANSMITTING VOICE, DATA, VIDEO THROUGH THE USE OF TELEPHONE LINES.

ELECTRONIC MAIL VOICE MAIL FACSIMILE MACHINES DIGITAL INFORMATION SERVICES AND DISTANCE

LEARNING TELECONFERENCING DATA CONFERENCING VIDEO CONFERENCING GROUPWARE ELECTRONIC DATA INTERCHANGE (EDI)

PRINCIPAL TELECOMMUNICATION PRINCIPAL TELECOMMUNICATION APPLICATIONS FOR ELECTRONIC APPLICATIONS FOR ELECTRONIC

COMMERCE AND ELECTRONIC COMMERCE AND ELECTRONIC BUSINESSBUSINESS

THE PLAN SHOULD BE STRATEGIC AND MOVE THE FIRM TOWARDS ACHIEVING ITS OBJECTIVES. THERE ARE THREE STEPS TO IMPLEMENTING A STRATEGIC TELECOMMUNICATIONS PLAN:

AUDIT THE CURRENT COMMUNICATIONS OF THE FIRM

IDENTIFY THE LONG-RANGE PLANS OF THE FIRM AND DETERMINE HOW TELECOMMUNICATIONS CONTRIBUTE TO THE LONG TERM STRATEGIES

IDENTIFY THE CRITICAL AREAS WHERE TELECOMMUNICATION CAN MAKE A SIGNIFICANT DIFFERENCE

TELECOMMUNICATIONS PLANTELECOMMUNICATIONS PLAN

DISTANCE RANGE OF SERVICES SECURITY MULTIPLE ACCESS UTILIZATION COST INSTALLATION CONNECTIVITY

FACTORS THAT SHOULD BE FACTORS THAT SHOULD BE CONSIDERED WHEN CHOOSING CONSIDERED WHEN CHOOSING

TELECOMMUNICATIONS SYSTEMSTELECOMMUNICATIONS SYSTEMS

CHAPTER-8 TELECOMMUNICATIONS AND NETWORKS. IS THE COMMUNICATION AND TRANSMISSION OF DIGITALLY CODED...

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