Wednesday, March 17, 2021

TOPOLOGIES OF COMMUNICATING MACHINES


TYPES OF NETWORK TOPOLOGY

NETWORK TOPOLOGY IS THE SCHEMATIC DESCRIPTION OF NETWORK ARRANGEMENT, CONNECTING VARIOUS NODES (SENDER AND RECEIVER) THROUGH LINES OF CONNECTION.

 

BUS TOPOLOGY


BUS TOPOLOGY IS A NETWORK TYPE IN WHICH EVERY COMPUTER AND NETWORK DEVICE IS CONNECTED TO A SINGLE CABLE.  WHEN IT HAS EXACTLY TWO END POINTS, THEN IT IS CALLED LINEAR BUS TOPOLOGY.

 

FEATURE OF BUS TOPOLOGY

1.       IT TRANSMITS DATA ONLY IN ONE DIRECTION

2.       EVERY DEVICE IS CONNECTED TO A SINGLE CABLE.

 

ADVANTAGES OF BUS TOPOLOGY

1.       IT IS COST EFFECTIVE CABLE REQUIRED IS LEAST COMPARED TO OTHER NETWORK TOPOLOGY.

2.       USED IN SMALL NETWORKS

3.       IT IS EASY TO UNDERSTAND

4.       EASY TO EXPAND JOINING TWO CABLES TOGETHER.

 

DISADVANTAGES OF BUS TOPOLOGY

1.       CABLE FAILS THEN WHOLE NETWORK FAILS.

2.       IF A NETWORK TRAFFIC IS HEAVY OR NODES ARE MORE THE PERFORMANCE OF THE NETWORK DECREASES.

3.       CABLE HAS LIMITED LENGTH

4.       IT IS SLOWER THAN RING TOPOLOGY.

 

 

RING TOPOLOGY


IT IS CALLED RING TOPOLOGY BECAUSE IT FORMS A RING AS EACH COMPUTER IS CONNECTED TO ANOTHER COMPUTER, WITH THE LAST ONE CONNECTED TO THE FIRST.  EXACTLY TWO NEIGHBOR FOR EACH DEVICE.

 

FEATURE OF RING TOPOLOGY

1.       A NUMBER OF REPEATERS ARE USED FOR RING TOPOLOGY WITH LARGE NUMBER OF NODES, BECAUSE OF SOMEONE WANTS TO SEND SOME DATA TO THE LAST NODE IN THE RING TOPOLOGY WITH 100 NODES THEN THE DATA WILL PASS THROUGH 99 NODES T EACH THE 100TH NODE.  HENCE TO PREVENT DATA LOSS REPEATERS ARE USED IN THE NETWORK.

2.       THE TRANSMISSION IS UNIDIRECTIONAL BUT IT CAN BE MADE BIDIRECTIONAL BY HAVING TWO CONNECTORS BETWEEN EACH NETWORK NODE.  IT IS CALLED DUAL RING TOPOLOGY.

3.       IN DUAL RING TOPOLOGY, TWO RING NETWORKS ARE FORMED AND DATA FLOW IS OPPOSITE DIRECTION IN THEM.  ALSO IF ONE RING FAILS THE SECOND RING ACTS AS BACKUP TO KEEP THE NETWORK UP.

4.       DATA IS TRANSFERRED IN SEQUENTIAL MANNER I.E. BIT BY BIT.  DATA TRANSMITTED HAS TO PASS THROUGH EACH NODE OF THE NETWORK TILL THE DESTINATION NODE.

 

ADVANTAGES OF RING TOPOLOGY

 

1.       TRANSMITTING NETWORK IS NOT AFFECTED BY HIGH TRAFFIC OR BY ADDING MORE NODES AS THE ONLY NODES HAVE TOKEN CAN TRANSMIT DATA.

2.       CHEAP TO INSTALL AND EXPAND

 

DISADVANTAGES OF RING TOPOLOGY

 

1.       TROUBLESHOOTING IS DIFFICULT IN RING TOPOLOGY.

2.       ADDING OR DELETING THE COMPUTERS DISTURB THE NETWORKING ACTIVITIES.

3.       FAILURE OF ONE COMPUTER DISTURBS THE WHILE NETWORK.

 

 

STAR TOPOLOGY


IN THIS TYPE OF TOPOLOGY ALL THE COMPUTERS ARE CONNECTED TO A SINGLE HUB THROUGH A CABLE. THIS HUB IS THE CENTRAL NODE AND ALL OTHER NODES ARE CONNECTED TO A CENTRAL NODE.

 

FEATURES OF STAR TOPOLOGY

 

1.       EVERY NODE HAS ITS OWN DEDICATED CONNECTION TO THE HUB.

2.       HUB ACTS AS A REPEATER FOR DATA FLOW.

3.       CAN BE USED WITH TWISTED PAIR, OPTICAL FIBER OR COAXIAL CABLE.

 

ADVANTAGES OF STAR TOPOLOGY

 

1.       FAST PERFORMANCE WITH FEW NODES AND  LOW NETWORK TRAFFIC.

2.       HUB CAN BE UPGRADED EASILY.

3.       EASY TO TROUBLESHOOT.

4.       EASY TO SETUP AND MODIFY.

5.       ONLY THAT NODE IS AFFECTED WHICH HAS FAILED, REST OF THE NODES CAN WORK SMOOTHLY.

 

DISADVANTAGES OF STAR TOPOLOGY

 

1.       COST OF INSTALLATION IS HIGH

2.       EXPENSIVE TO USE

3.       IF THE HUB FAILS THEN WHOLE NETWORK IS STOPPED BECAUSE ALL THE NODES UPON THE HUB.

4.       PERFORMANCE IS BASED ON THE HUB I.E. IT DEPENDS ON ITS CAPACITY.

 

 

MESH TOPOLOGY


 

IT IS POINT TO POINT CONNECTION TO OTHER NODES OR DEVICES.  ALL THE NETWORK NODES ARE CONNECTED TO EACH OTHER.  MESH HAS  (n(n-1))/2 PHYSICAL CHANNELS TO LINK N DEVICES.  THERE ARE TWO TECHNIQUES TO TRANSMIT DATA OVER THE MESH TOPOLOGY.

 

THEY ARE

1.       ROUTING

2.       FLOODING

 

MESH TOPOLOGY ROUTING

 

IN ROUTING, THE NODES HAVE A ROUTING LOGIC, AS PER THE NETWORK REQUIREMENTS.  THE ROUTING LOGIC TO DIRECT THE DATA TO REACH THE DESTINATION USING THE SHORTEST DISTANCE.  OR ROUTING LOGIC WHICH HAS INFORMATION ABOUT THE BROKEN LINKS, AND IT AVOIDS THOSE LINKS., AND IT AVOIDS THOSE NODES.

WE CAN HAVE ROUTING LOGIC, TO RECONFIGURE THE FAILED NODES.

 

MESH TOPOLOGY FLOODING

 

IN FLOODING, THE SAME DATA IS TRANSMITTED TO ALL NETWORK NODES, HENCE NO ROUTING LOGIC IS REQUIRED.   THE NETWORK IS ROBUST AND IT IS VERY UNLIKELY TO LOOSE THE DATA. BUT IT LEADS UNWANTED LOAD OVER THE NETWORK.

 

TYPES OF MESH TOPOLOGY

 

PARTIAL MESH TOPOLOGY

IN THIS TOPOLOGY SOME OF HE SYSTEMS ARE CONNECTED IN SOME FASHION AS ESH TOPOLOGY BUT SOME DEVICES ARE ONLY ONNECTED TO TWO OR THREE DEVICES.

 

FULL MESH TOPOLOGY

EACH AND EVERY NODES ARE CONNECTED TO EACH OTHER.

 

FEATURES OF MESH TOPOLOGY

 

1.       FULLY CONNECTED

2.       ROBUST

3.       NOT FLEXIBLE

 

 

ADVANTAGES OF MESH TOPOLOGY

 

1.       EACH CONNECTION CAN CARRY ITS OWN DATA LOAD.

2.       IT IS ROBUST

3.       FAULT IS DIAGNOSED EASILY

4.       PROVIDES SECURITY AND PRIVACY

 

DISADVANTAGES OF MESH TOPOLOGY

 

1.       INSTALLATION AND CONFIGURATION IS DIFFICULT

2.       CABLING COST IS MORE

3.       BULK WIRING IS REQUIRE

 

TREE TOPOLOGY


 

IT HAS ROOT NODE AND ALL OTHER NODES ARE CONNECTED TO IT FORMING HIERARCHY  IT IS ALSO CALLED HIERARCHICAL TOPOLOGY.  IT SHOULD AT LEAST THREE LEVELS TO THE HIERARCHY.

 

FEATURES OF TREE TOPOLOGY

 

1.       IDEAL IF WORKSTATION ARE ARRANGED IN GROUP

2.       USED IN WIDE AREA NETWORK.

 

 

ADVANTAGES OF TREE TOPOLOGY

 

1.       EXTENSION OF BUS AND STAR TOPOLOGY

2.       EXPANSION OF NODES IS POSSIBLE AND EASY

3.       EASILY MANAGED AND MAINTAINED

4.       ERROR DETECTION IS EASILY DONE

 

DISADVANTAGES OF TREE TOPOLOGY

 

1.       HEAVILY CABLED

2.       COSTLY

3.       IF MORE NODES ADDED MAINTENANCE IS DIFFICULT

4.       CONTROL HUB FAILS NETWORK FAILS

 

 


Saturday, March 6, 2021

MONITORS IN SUMMARY

 

MONITORS

MONITOR IS A PRIMARY OUTPUT DEVICE.  IT DISPLAYS ALL CURRENT PROCESS APPLICATION AND DATA I.E. RUNNING INSIDE A COMPUTER SYSTEM.  A STANDARD MONITOR USES AN ANALOG , VGA INTERFACE WHICH PLUGS INTO TP15 PIN VGA CONNECTOR TO THE MOTHERBOARD.

 

 THERE ARE TWO TYPES OF MONITOR TECHNOLOGY AVAILABLE TO THE MARKET.

HERE ARE THOSE

 

CATHODE RAY TUBE (CRT)

THIS MONITOR IS FADING IN POPULARITY BUT STILL IN WIDESPREAD USE WITH OLDER COMPUTER SYSTEMS. IT IS ANALOG STANDARD MONITOR. A CRT USES A PICTURE TUBE THAT WAS USED IN OLDER TUBE BASED TV SETS.


 

THE NARROW END OF PICTURE TUBE CONTAINS AN ELECTRON GUN.  IT EMITS 3 ELECTRON BEAMS.  ONE EACH FOR RED, GREEEN, BLUE LIGHT.  THE FRONT END OF THE PICTURE TUBE IS COATED WITH PHOSPHOROUS. 

 

WHEN THE ELECTRON HITS PHOSPHOROUS COATING IT STARTS TO GLOW.  JUST BEFORE THE PHOSPHOROUS COATING A METAL PLATE CALLED SHADOW MASK IS USED TO DIVIDE THE IMAGE CREATED BY THE ELECTRON GUN INTO RED, GREEN AND BLUE PIXELS ON STRIPS THAT FORM THE IMAGE. 

 

SHADOW MASK USES ON OF THREE TECHNOLOGIES.  A PHOSPHOUR TRIAD, AN APERTURE GRILL, A SLOTTED MASK.  CRT MONITORS ARE BULKY TAKES MORE DISK SPACE,   CONSUMES MORE POWER AND EMITS MORE HEAT.  CRT MONITOR WAS AVAILABLE FROM 15 INCH TO 19 INCH SIZE.  IT USES VGA CONNECTOR TO ATTACH WITH A CPU

 

LCD AND LED SCREENS

 

THE MOST POPULAR MONITOR IN TODAY MARKET IS LED MONITOR SUPPRESED LCD MONITORS.  BECAUSE IT GIVES BETTER COLOUIR QUALITY, WIDE VIEWING ANGLE AND CONSUMES LESS POWER.  


 

IT USES LIQUID CRYSTAL CELLS TO POLARIZE THE LIGHT.   LCD MONITORS USES FLUOROSCENT LAMP AND LED MONITORS USES LED LAMPS FOR BAKCLIGHTING .  THIS DISPLAY USES AN ARRAY OF TRANSISTORS TO CONTROL EACH CELL.

 

VARIATION ARE THE COLOUR BIT, RESPONSE TIME  AND THE REFRESH RATE.   THIS MONITORS COMES WITH TWO TYPES OF TRANSISTOR TECHNOLOGY 1) PASSIVE MATRIX 2) ACTIVE MATRIX

 

PASSIVE MATRIX

 


A PASSIVE MATRIX DISPLAY DOESNOT HAVE A DEDICATED TRANSISTOR FOR EACH PIXEL OR SUB PIXEL,  BUT INSTEAD A MATRIX OF CONDUCTIVE TRACES.  IN SIMPLIFIED TERMS FOR A SINGLE PIXEL WHEN THE DISPLAY  IS INSTRUCTED TO CHANGE THE CRYSTAL LINE ALIGNMENT FOR A PARTICULAR PIXEL.

 

IT SENDS A SIGNAL ACROSS THE X AND Y COORDINATE TRACES THAT INTERSECT AT THAT PIXEL, THUS TURNING IT ON.  A 1366 X 768 RESOLUTION MONITOR CONTAINS 1366  TRANSISTOR AT THAT HORIZONTAL EDGE AND 768 TRANSISTORS AT THE VERTICAL EDGE.

 

THE VIEWING ANGLE IS A MOST UNCONSIDERABLE ISSUE OF A PASSIVE MATRIX DISPLAY.  THE PICTURE QUALITY IS MUDDY BECAUSE THE CONDUCTIVE TRACES SOMETIMES EFFECTS THE NEIGHBOURING IXELS OF A TARGET PIXEL

 

THE ONE ADVANTAGE OF PASSIVE MATRIX IS IT ONSUMES LESS POWER COMPARING TO ACTIVE MATRIX DISPLAY.

 

DUAL SCAN DISPLAY

 


A DUAL SCAN IS A VARIATION OF THE PASSIVE METRIC DISPLAY.  THE CLASSIC PASSIVE MATRIX SCREEN IS SPLIT IN HALF TO IMPLEMENT A DUAL SCAN DISPLAY.  EACH HALF OF THE DISPLAY IS REFRESHED SEPERATELY LEADING TO INCREASED QUALITY.

 

ALTHOUGH DUAL SCAN IMPROVES THE QUALTY OF REFRESH RATE BUT IT CANNOT RIVAL THE QUALITY PRODUCED BY ACTIVE MATRIX.

 

ACTIVE MATRIX

 

THIS SCREEN IS MADE OF SEVERAL INDEPENDENT LCD OR LED PIXELS.  A TRANSISTOR AT EACH PIXEL LOCATION, WHEN SWITCHED AMONG VARIOUS LEVELS.  ACTIVATES TWO OPPOSING ELECTRODES THAT ALIGH THE PIXELS CRYSTALS AND ALTER THE PASSAGE OF LIGHT AT THAT LOCATION TWO PRODUCE MILLIONS OF COLOUR SHADES.  THIS TYPE OF DISPLAY IS VERY CRISP AND EASY TO LOOK FROM ANY ANGLE.

 

IT DOESN’T REQUIRE AN SCAN REFRESHING TO MAINTAIN AN IMAGE, BECAUSE REANSISTORS CONDUCT CURRENT ONLY IN ONE DIRECTION AND THE PIXELS ACT LIKE A CAPACITOR BY HOLDING ITS CHARGE UNTIL IT IS REFRESHED

 

HIGHER REFRESH RATES ESULTS IN BETTER VIDEO OR GAING PERFORMANCE NOT FOR STILL IMAGE.   THE MAJOR DISADVANTAGE OF ACTIVE MATRIX SCREEN THAT IT REQUIRES MORE POWER TO OPERATE ALL TRANSISTOR.   EVEN IF THE BACKLIGHT IS TURNED OF THE SCREEN CAN STLL CONSUME POWER AT AN ALARMING RATE. 

 

ANOTHER PROBLEM WITH ACTIVE MATRIX IS LIGHT BLEED.

 

THANKS FOR READING.  I HOPE YOU LIKED IT.

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