1

CHAPTER 1

INTRODUCTION

This training was research based training in this training we had covered some topics which are

related to communication services.

Exchange- It is a place where switching between two subscribers is done through either manually

or electronically. In addition to switching, signaling and controlling are also done at exchange.

It consists of the following functional blocks: Main Distribution Frame, Card Frame, Mother

Board, Power supply panel with protective devices.

Main functional areas in Telephone Exchange:

Controlling function

Signaling Function

Switching Function

Optical fiber- Optical Fiber is new medium, in which information (voice, Data or Video) is

transmitted through a glass or plastic fiber, in the form of light, following the transmission

sequence give below:

1. Information is encoded into Electrical Signals.

2. Electrical Signals are converted into light Signals.

3. Light Travels down the Fiber

4. A Detector Changes the Light Signals into Electrical Signals.

5. Electrical Signals are decoded into Information.

Basics of Networking- The physical network consists of all internal switching nodes, their

interconnecting links and the links leading to externally connected devices. The external devices

themselves, computers and terminals collectively referred to as Data Terminal Equipment

(DTE), are then considered as attached to, rather than forming part of, the physical network.

2

A wider view of the network may be that of the network including the physical network attached

with all DTE along with all the services available on it, including those available on the attached

DTE. At times, these services are also referred to as ‗networking services‘.

Railnet- Railnet is the name of the Corporate Wide Information System (CWIS) of Indian

Railways. It is aimed to provide computer connectivity between Railway Board, Zonal Railways,

Production units, RDSO, Centralized Training Institutes.

3

CHAPTER 2

COMPANY/ORGANIZATION OVERVIEW

The first railway on Indian sub-continent ran over a stretch of 21 miles from Bombay to Thane.

The idea of a railway to connect Bombay with Thane, Kalyan and with the Thal and Bhore Ghats

inclines first occurred to Mr. George Clark, the Chief Engineer of the Bombay Government,

during a visit to Bhandup in 1843. The formal inauguration ceremony was performed on 16th

April 1853, when 14 railway carriages carrying about 400 guests left Bori Bunder at 3.30 pm

"amidst the loud applause of a vast multitude and to the salute of 21 guns." The first passenger

train steamed out of Howrah station destined for Hooghly, a distance of 24 miles, on 15th

August, 1854.

INDIAN RAILWAYS, the premier transport organization of the country is the largest rail

network in Asia and the world‘s second largest under one management.

Indian railways run around 11,000 trains everyday

7566 -

locomotives

37,840 -

Coaching

vehicles

222,147 - Freight

wagons 6853 - Stations

300 - Yards

2300 -

Good

sheds

700 - Repair shops 1.54 million - Work force

INDIAN RAILWAY LOGO

4

Type Public sector

Industry Railways

Founded 16 Th

April 1853

Headquarters New Delhi, India

Area served India (also limited service to Nepal, Bangladesh and

Pakistan)

Key people Suresh Prabhakar Prabhu (Minister of railways)

Services Passenger railways, freight services, parcel carrier, catering

and

Tourism services, parking lot operation and other related

Services.

Net income ₹157.8 billion (US$2.5 billion)(2015)

Owner Government of India

No. of employees 1.307 million (2013)

Divisions 17 railway zones

Website www.indianrailways.gov.in

Honors and Awards

Darjeeling Himalayan Railways attained the World Heritage Status from UNESCO.

Fairy Queen, the oldest functioning steam engine in the world, which finds a place in the

Guinness Book of World Records, got Heritage Award at the International Tourist

Bureau, Berlin in March, 2000.

5

On operational front, Delhi Main station entered the Guinness Book for having the

world‘s largest route relay interlocking system.

CHAPTER 3

TECHNOLOGY USED IN TRAINING

It was a study based training which only covered the basics of the telecom and Railnet without

going too deep into the implementation details.

During training we also studied about basics of networking.

The Internet is a computer network made up of thousands of networks worldwide. No one knows

exactly how many computers are connected to the Internet. It is certain, however, that this

number is in the millions and is increasing at a rapid rate. No one is in charge of the Internet.

There are organizations which develop technical aspects of this network and set standards for

creating applications on it, but no governing body is in control. The Internet backbone, through

which Internet traffic flows, is owned by private companies.

All computers on the Internet communicate with one another using the Transmission Control

Protocol/Internet Protocol suite, abbreviated to TCP/IP. Computers on the Internet use

client/server architecture. This means that the remote server machine provides files and services

to the user's local client machine. Software can be installed on a client computer to take

advantage of the latest access technology. An Internet user has access to a wide variety of

services: electronic mail, file transfer, vast information resources, interest group membership,

interactive collaboration, multimedia displays, real-time broadcasting, shopping opportunities,

breaking news, and much more. The Internet consists primarily of a variety of access protocols.

Many of these protocols feature programs that allow users to search for and retrieve material

made available by the protocol.

A computer network may be defined in various ways. One approach is to consider the network to

be simply the ‘physical network‘. The physical network consists of all internal switching nodes,

their interconnecting links and the links leading to externally connected devices. The external

6

devices themselves, computers and terminals collectively referred to as Data Terminal

Equipment (DTE), are then considered as attached to, rather than forming part of, the physical

network. A wider view of the network may be that of the network including the physical network

attached with all DTE along with all the services available on it, including those available on the

attached DTE. At times, these services are also referred to as ‗networking services‘. A common

misconception is that a ‗computer network‘ is a network in which he DTEs are computers. Well,

it is half true. A computer network may consist of DTE that are not computer. But today, almost

all the DTEs, if not a computer, are based on or controlled by a computer. In this sense the

misconception seems to be correct. The network services may be built into the nodes of the

network or may be provided by a DTE attached to the network.

7

CHAPTER 4

TELECOM

4.1 Telephone Exchange:

It is a place where switching between two subscribers is done through either manually or

electronically. In addition to switching, signaling and controlling are also done at exchange.

It consists of the following functional blocks:

1. Main Distribution Frame.

2. Card Frame.

3. Mother board.

4. Power supply panel with protective devices.

4.1.1 Main distribution frame: In a Telephone exchange different subscribers from

different places are terminated on a frame called ―Main Distribution Frame‖

(MDF) in the exchange and from there they are extended to subscriber‘s line

cards/Trunk cards kept in the exchange rack. Protective devices are located in the

MDF.

Purpose of MDF:

There are three purposes of MDF,

1. It is the place where both external and internal cables are terminated. The cross

connection between the two cables conductors is done on the MDF and this is done by

means of jumper wires (Red & White).

2. It carries all the protective devices used in the exchange. They are Fuses, Heat coils &

Lightning protectors.

3. The MDF is the most suitable place for testing purposes.

Protection of MDF: In MDF primary protection is provided. Primary protectors are Gas

Discharge Tube (GDT) or Carbon blocks or Integrated Protection Modules (IPM). The primary

8

protectors limit the very high energy transients. The secondary protectors are incorporated on

Telecom line card itself, which limit the voltage and current to acceptable levels. Here are other

types of over voltage protectors such as ―Metal Oxide Varistors (MOV) and Thyristor Surge

protection devices (TSPD) preferred choice for Telecom protection applications.

4.1.2 Card frame: It contains different slots in which the nominated cards are to be

inserted. It is different in different types of exchanges.

4.1.3 Mother board: It connectivity between different cards. It is a PCB with 1, 2, 3

layers.

4.1.4 Power supply panel: It provides power supply to different cards in the exchange

at different low D.C. voltages. It also includes protective devices like fuses etc.

4.2 Main functional areas in Telephone Exchange:

4.2.1 Switching Function:

The switching functions are carried out through the switching network, which provides a

temporary path for simultaneous, bi-directional speech between,

1. Two subscribers connected to the same exchange. This is called as ―Local switching‖

2. Two subscribers connected to different exchanges. This is known as ―Trunk switching‖.

3. Pairs of trunks towards different exchanges. This is known as ―Transit switching‖.

4.2.2 Signaling function:

The signaling function enables the various equipment in a network to communicate with each

other in order to establish and supervise the calls. It is of two types:

1. Subscriber line signaling: It enables the exchange to identify calling subscribers line, extend

dial tone, receive the dialed digits, extend the ringing voltage to the called subscriber, extend the

ring back tone to the calling subscriber to indicate the called subscriber is being is being

connected. In the event the called subscriber is busy, engage tone is sent to the calling subscriber.

2. Inter exchange signaling: It enables a call to be set up, supervised and cleared between

exchanges.

9

4.2.3 Controlling function:

The controlling function performs the task of processing the signaling information and

controlling the operation of the switching network. The control functions may be:

1. Wired logic control: In this pre wiring is done between different speech path devices

and common control. Any changes are required in facilities of subscribers or

introduction of new services require wiring changes.

2. Stored Program Control (SPC): In this system the establishment and supervision of

the connections in the exchange is under the control of ―Microprocessor‖, which is

suitably programmed.

4.3 Types of switching

The following are the different types of switching used in different are as:

1. Message switching: It is the type switching used to send the message from town‘ A‘ to

‗B‘via circuits A and C and one between C and B. The operator at ‗A‘ sent the message

to C, where it was written down by the receiving operator. This operator recognized the

address of the message as being at B and then retransmitted the message over the circuit

to B. This manual process is shown in the Fig. 4.1.

Fig. 4.1 Message Switching

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2. Circuit switching: In circuit switching the circuit of calling subscriber‘s telephone to

that of called subscriber‘s telephone on demand and to maintain this connection for the

duration of the call. The disadvantage of circuit switching is, if the required outgoing

circuit from a switch is already engaged on another call, the new call offered to it cannot

be connected. The call cannot stored, as in message switching.

3. Manual switching: In manual switching the interconnection between calling and called

Subscribers are done by man (operator) through multiple jack fields.

4. Electronic switching: In this electronic devices are used as switching devices in

switching network. In SPC systems digital computer to be used as a central control and

perform different functions with same hardware by executing different programs.

Electronic switching systems may be classified as:

i) Space – division (SD) systems: Each connection is made over a different path in

space which exists for the duration of the connection.

ii) Time-division (TD) systems: Each connection is made over the same path in space,

but at different of time.

The distinction between SD and TD in between the control arrangements of an exchange as well

as to its switching network. For example, if an exchange uses individual registers, this is space

division. In time a central processor, handling each call in turn, performs division the register

function.

i) Digital switching: When signals are transmitted through the switch in digital form,

then it is called ―Digital switching‖. These signals may represent speech samples or

data. The digital signals of several speech samples are time multiplexed on a common

media, while transmitted through the switching system. However, it has become

synonymous with digital switching.

ii) Time and Space switching: Generally a digital switching system serves several time

division multiplexed (PCM) signals. These PCM signals are conveyed on PCM

highways (the common path over which many

11

Channels can pass with separation achieved by time division). Switching of calls, in this

environment, placing digital signals from one time-slot of one PCM multiplex in the same or

Different time-slot of another PCM multiplex. The interconnection of time slots, i.e., switching

of digital signals, can be achieved using two different modes of operation. These modes are

- Space switching

- Time switching

5. Packet switching: For transmitting the data by a data network, packet switching is used. Long

messages are split into a number of short ones, called packets, which are transmitted separately,

as shown in the Fig.4.2. Thus the single packet from the VDU operator is sent between pockets

of the large computer file, instead of waiting until its transmission is complete and the delay is

minimized.

Fig.4.2 Packet Switching

The format of a typical pocket is shown above. Since each pocket is handled as a complete

message, its data must be preceded by a header, which contains the destination address of the

message. It is possible for pockets sometimes to arrive at their destination in a different order

from that in which they are sent. Each header is therefore contains a sequence number, to enable

12

pockets to be reassembled in the correct order at the receiving terminal. Other bits are added to

the header for controlling purposes, e.g. to indicate whether a pocket contains a message or is

being sent to control the network. The pocket ends with bits added for error detection and

correction. The data network and its terminals handle the pockets by procedures known as

―Protocols‖. Pocket switching was first developed for the use in private data network. It is

widely used in local-area networks (LAN‘s), in wide-area networks (WAN‘s).

4.4 Types of signaling

4.4.1 Subscriber line Signaling: Signaling concerned with calling subscriber line / Called

subscriber line, basically subscriber loop signaling comes under this category. Different signals

are explained below.

1. Call report signal:

i) When the subscriber line is idle, the line impedance is high.

ii) The impedance falls as soon as the subscriber lifts the handset, resulting in increase of line

current.

iii) This increase is detected as a new call signal by the exchange

iv)The exchange connects appropriate equipment / module to the line to receive the address

information (subscriber is going to dial)

v) The exchange notifies its readiness to receive the ‗to be dialed number information‘, by

extending the dial tone to the subscriber

vi) Address signal

vii) After receipt of dial tone, subscriber dials the number (decadic/tone)

viii) This causes sending of address digits (called subscriber‘s number) in sequence to the

exchange.

2. End of selection signal:

(i) Establishment of connection by the exchange as per dialed number can be successful / Un-

successful .The exchange sends one of the following signals to calling subscriber

i) Ring-back tone if the called line is free

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ii) Busy tone if called line is engaged or otherwise inaccessible

iii) Recorded announcement to give reasons for the call failure other than ‘line-busy‘

3. Answer-back signal:

i) On hearing the ringing, the subscriber lifts the handset.

ii) A battery reversal signal is transmitted on the line of the calling subscriber.

iii) This signal is used to operate special equipment attached to calling subscriber (e.g. short

circuiting the transmitter of CCB till the coin is inserted)

4. Release signal:

i) When the calling subscriber goes on hook, i.e. releases the call, the line impedance goes high.

ii) This is detected by the exchange which releases al equipment / modules involved in the call.

5. Permanent line or permanent glow (PG):

i) A PG signal is sent to the calling subscriber if the subscriber fails to release call even after the

called subscriber has gone on-hook and the call is released after a time delay.

ii) The PG signal is also sent if the subscriber takes too long to dial.

6. Ring signal:

i) On receipt of call to a line which is free, the exchange sends ‗Ring signal‘.

ii) Ring signals is 25 Hz or 50Hz signal with suitable interruptions

iii) Ring-back tone is fed to calling subscriber line.

7. Answer signal:

i) When the called subscriber lifts the handset on receipt of ring, the line impedance goes low.

ii) This is detected by exchange, which cuts off ringing tone on called subscriber and ring-back

tone on calling subscriber.

8. Release signal:

14

i) After completion of conversation if the called subscriber goes on-hook (before the calling

subscriber), the high line impedance of called subscriber line is detected by the exchange.

ii) The exchange sends PG to the calling line and releases the call after a time delay if the calling

subscriber is still holding

9. Register re-call signal:

i) Using DTMF dialing, another number can be dialed while holding on to the call in progress in

order to set up a call to a third subscriber.

ii) The signal to recall the dialing phase during the talking phase is called ‗Register recall signal‘.

iii) It is achieved through interruptions on the calling subscriber‗s loop for a duration less than

the release signal.

4.4.3 Inter Exchange signaling: It is the signaling between interconnected exchanges.

Classification based on type of transmission:

i) Pulsed Signaling - Signal information transmitted as pulses.

ii) Continuous Signaling - Presence of a signal is characterized by transition from one condition

to another

iii) Compelled Signaling - Similar to pulsed signaling, but transmission of signaling information

continues till ack. is received from other end.

Classification based on Trunk Circuit Configuration:

1. Loop Signaling:

i) Trunk connection between exchanges comprises of dc loop similar to exchange subscriber

loop

ii) DC related condition like high/low ohmic loop, normal/reverse polarity on a lead,

earth/battery on a lead are detected and interpreted by the system. Hence, also known as dc

signaling

iii) Signaling and speech are carried on the same pair of limbs which form the loop.

15

2. E&M Signaling:

i) In E&M Signaling, an additional pair of line is utilized per trunk

ii) One wire is dedicated to the forward signals (M-wire for transmit or mouth) which

corresponds to receive or R-lead of the destination exchange.

iii) The other wire is dedicated to the backward signals (E-wire for receive or ear) which

corresponds to the transmit or send wire or S-lead of the destination exchange.

3. Single Frequency Tone Signaling:

i) Exchanges far apart cannot be connected by loop or E&M leads. Hence, Single Frequency

Tone is used to transmit signaling states.

ii) Tone can be In-band (2400 Hz or 2600 Hz) or Out-of band (3825 Hz)

iii) In case of in-band signaling, it shall be ensured that simulated tone of 2400 Hz or 2600 Hz

does not switch-off the circuit.

4.4.4 Classification based on duration of Signaling Operation:

1. Line Signaling:

i) Signaling operative throughout the call. Examples: Loop signaling, E&M signaling, Single

Frequency Tone signaling.

2. Register signaling:

i) signaling is operative only during relatively short phase of setting up of call

ii) Trunk register holds the address information

iii) Register information is interchanged between exchanges during the phase between the receipt

of trunk seizure signal and switching of exchange to speech phase.

iv) Register signals can be transmitted ‗In-band‘ or ‗Out-of-band‘

v) In ‗out-of-band‘ method, only Single Frequency Tone is used and fewer combinations of

signals are possible

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vi) In ‗In-band‘ method, which is easy as no interference can take place in ‗Register signaling‘, 2

out of 6 frequencies are used. For reliability, ‗Compelled Sequence‘ is used. This is known as

‗CSMF‘ or ‗R2‘ signaling.

4.4.5 Classification based on Setting up signaling over multiple hops:

1. End-to-end signaling:

Signaling is between ends of a connection as the call progresses. On A-B-C Exchange

connection, it first between A-B, then B-C and finally A-C.

2. Link-by-link signaling:

Signaling is confined to individual links i.e. A-B and B-C and not A-C.

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CHAPTER 5

OPTICAL FIBER CABLE

5.1 What is optical fiber?

Optical Fiber is new medium, in which information (voice, Data or Video) is transmitted through

a glass or plastic fiber, in the form of light, following the transmission sequence give below:

1. Information is encoded into Electrical Signals.

2. Electrical Signals are converted into light Signals.

3. Light Travels down the Fiber

4. A Detector Changes the Light Signals into Electrical Signals.

5. Electrical Signals are decoded into Information.

5.2 Geometry of Fiber:

Consist of two concentric layers of high-purity silica glass- the core and the cladding, which are

enclosed by a protective sheath. Core and cladding have different refractive indices, with the

core having a refractive index, n1, which is slightly higher than that of the cladding, n2. It is this

difference in refractive indices that enables the fiber to guide the light and allows total internal

reflection to occur. As a minimum there is also a further layer known as the secondary cladding

that does not participate in the propagation but gives the fiber a minimum level of protection, this

second layer is referred to as a coating. The light stays confined to the core because the cladding

has a lower refractive index—a measure of its ability to bend light.

Fiber sizes are usually expressed by first giving the core size followed by the cladding size. Thus

50/125 means a core diameter of 50 micrometer and a cladding diameter of 125 micrometer.

18

5.3 Fiber Types

The refractive Index profile describes the relation between the indices of the core and cladding.

Two main relationships exist:

1. Step Index-The step index fiber has a core with uniform index throughout.

2. Graded Index- The graded index has a non-uniform core. The Index is highest at the

center and gradually decreases until it matches with that of the cladding.

By this classification there are three types of fiber:

1. Multimode Step Index fiber (Step Index fiber)

2. Multimode graded Index fiber (Graded Index fiber)

3. Single- Mode Step Index fiber (Single Mode Fiber)

Step-Index Multimode Fiber:

Some of the light rays that make up the digital pulse may travel a direct route, whereas others

zigzag as they bounce off the cladding. These alternative pathways cause the different groupings

of light rays, referred to as modes, to arrive separately at a receiving point. The pulse, an

aggregate of different modes, begins to spread out, losing its well-defined shape. The need to

leave spacing between pulses to prevent overlapping limits bandwidth that is, the amount of

information that can be sent. Consequently, this type of fiber is best suited for transmission over

short distances, in an endoscope, for instance.

Graded-Index Multimode Fiber:

It contains a core in which the refractive index diminishes gradually from the center axis out

toward the cladding. The higher refractive index at the center makes the light rays moving down

the axis advance more slowly than those near the cladding. Also, rather than zigzagging off the

cladding, light in the core curves helically because of the graded index, reducing its travel

distance. The shortened path and the higher speed allow light at the periphery to arrive at a

receiver at about the same time as the slow but straight rays in the core axis. The result: a digital

pulse suffers less dispersion.

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Single-Mode Fiber:

It has a narrow core (eight microns or less), and the index of refraction between the core and the

cladding changes less than it does for multimode fibers. Light thus travels parallel to the axis,

creating little pulse dispersion. Telephone and cable television networks install millions of

kilometers of this fiber every year.

5.4 Buffers

5.4.1 Loose buffer:

More than one fiber can be inserted in a single plastic tube. The diameter of the tube is several

times than fiber diameter (after primary coating). This arrangement protects fiber from

mechanical forces. It also eliminates micro bending of fiber. Its loose tube is usually filled with

jelly for protection from moisture and at curve fiber moves frictionless from one end to another.

5.4.2 Tight buffer:

In this case plastic coating is directly applied over the primary coating. This arrangement

provides better crush and impact resistance but it may produce micro bends due to stresses. Such

types are also affected due to temperature variations, plastic expansion & contraction which are

different from glass. These are mainly used as indoor cables such as jumper cords, pigtail &

patch cords.

5.5 Attenuation:

Attenuation in optical fiber is caused by intrinsic factors, primarily scattering and absorption, and

by extrinsic factors, including stress from the manufacturing process, the environment, and

physical bending. Attenuation is measured in decibels (dB). A dB represents the comparison

between the transmitted and received power in a system.

20

5.5.1 Intrinsic Attenuation

It is loss due to inherent or within the fiber. Intrinsic attenuation may occur as

1. Absorption - Natural Impurities in the glass absorb light energy.

2. Scattering - Light rays travelling in the core reflect from small imperfections into a

new pathway that may be lost through the cladding. The most common form of

scattering, Rayleigh scattering, is caused by small variations in the density of glass as

it cools. These variations are smaller than the wavelengths used and therefore act as

scattering objects.

5.5.2 Extrinsic Attenuation

It is loss due to external sources. Extrinsic attenuation may occur as –

1. Macro bending - The fiber is sharply bent so that the light travelling down the fiber

cannot make the turn & is lost in the cladding.

2. Micro bending - Micro bending or small bends in the fiber caused by crushing

contraction etc. These bends may not be visible with the naked eye.

5.6 Splicing

Splices are permanent connection between two fibers. The technique is called as splicing. There

are two types of fiber splicing –

1. Mechanical splicing- Mechanical splicing doesn‘t physically fuse two optical fibers together,

rather two fibers are held butt-to-butt inside a sleeve with some mechanical mechanism. You will

get worse insertion loss and back reflection in mechanical splices than in fusion splices

2. Fusion splicing- Two fibers are literally welded (fused) together by an electric arc. Fusion

splicing is the most widely used method of splicing as it provides for the lowest insertion loss

and virtually no back reflection.

5.6.1 Splice Losses

Splice losses can be divided into two categories:

21

1. Extrinsic- Includes factors which are induced by the splicing methods and procedures. Splice

process factors include lateral and angular misalignment (separation and transverse offset

between the fibers cores, axial tilt), fiber end quality, contamination and core deformation.

2. Intrinsic splice loss factors- Intrinsic parameters include variations in fiber diameter (both core

and cladding), index profile, Numerical aperture, Mode Field Diameter (MFD) and non-

circularity of the fiber cores.

5.6.2 FIBER OPTIC CABLE SPLICING PROCEDURE (HOW TO SPLICE FIBER

OPTIC CABLE)

1. Strip fiber cable jacket. Strip back about 1 meters of fiber cable jacket to expose the fiber

loose tubes or tight buffered fibers. Use cable rip cord to cut through the fiber jacket. Then

carefully peel back the jacket and expose the insides. Cut off the excess jacket. Clean off all

cable gel with cable gel remover. Separate the fiber loose tubes and buffers by carefully cutting

away any yarn or sheath. Leave enough of the strength member to properly secure the cable in

the splice enclose.

2. Strip fiber tubes. For a loose tube fiber cable, strip away about 0.9 meters of fiber tube using a

buffer tube stripper and expose the individual fibers.

3. Clean cable gel. Carefully clean all fibers in the loose tube of any filling gel with cable gel

remover.

4. Secure cable tubes. Secure the end of the loose tube to the splice tray and lay out cleaned and

separated fibers on the table. Strip and clean the other cable tube‘s fiber that is to be spliced, and

secure to the splice tray.

5. Strip first splicing fiber. Hold the first splicing fiber and remove the 250um fiber coating to

expose 5cm of 125um bare fiber cladding with fiber coating stripper tool. For tight buffered

fibers, remove 5cm of 900um tight buffer first with a buffer stripping tool, and then remove the

5cm of 250um coating.

22

6. Place the fusion splice protection sleeve. Put a fusion splice protection sleeve onto the fiber

being spliced.

7. Clean the bare fiber. Carefully clean the stripped bare fiber with lint-free wipes soaked in

isopropyl alcohol. After cleaning, prevent the fiber from touching anything.

8. Fiber cleaving. With a high precision fiber cleaver, cleave the fiber to a specified length

according to your fusion splicer‘s manual.

9. Prepare second fiber being spliced. Strip, clean and cleave the other fiber to be spliced.

10. Fusion splicing. Place both fibers in the fusion splicer and do the fusion splice according to

its manual.

11. Heat shrinks the fusion splice protection sleeve. Slide the fusion splice protection sleeve on

the joint and put it into the heat shrink oven, and press the heat button.

12. Place splice into splice tray. Carefully place the finished splice into the splice tray and loop

excess fiber around its guides. Ensure that the fiber‘s minimum bending radius is not

compromised.

13. Perform OTDR test. Perform a OTDR test of the splice and redo the splice if necessary.

14. Close the splice tray. After all fibers have been spliced, carefully close the splice tray and

place it into the splice enclosure.

15. Bidirectional OTDR test (or power meter test). Test the splices with an OTDR or power

meter from both directions.

16. Mount the splice enclosure. Close and mount the splice enclosure if all splices meet the

specifications.

5.7 FIBER OPTIC CONNECTORS

Fiber optic connector facilitates re-makeable (disconnection or reconnection) connection. The

connectors are used in following applications.

23

1. Flexibility is required in routing an optical signal

2. To couple the signal from sources to receivers

3. Reconfiguration is wherever required

4. Termination of cable is required

5.7.1 Different types of connectors

1. FC connector

FC connector has a 2.5mm ferrule (made of ceramic (zirconia) or stainless alloy). It is

specifically designed for telecommunication applications and provides non-optical disconnect

performance. Designed with a threaded coupling for durable connections. It has been the most

popular single mode connectors for many years. Simplex only, screw-on mechanism. Available

in single mode and multimode.

Fig.5.1 FC Connector

2. SC Connectors

SC was developed by NTT of Japan. It is widely used in single mode applications for its 2.5mm

pre-radiused zirconia or stainless alloy ferrule. It features a snap-in (push-pull connection design

for quick patching of cables into rack or wall mounts. Two simplex SC connectors can be

clipped together by a reusable duplex holding clip to create a duplex SC connector. Simplex and

duplex, snap-in mechanism in single mode and multimode SC connectors available.

24

Fig.5.2 SC connector and adaptor - simplex

3. LC connector

Externally LC connectors resemble a standard RJ45 telephone jack. Internally they resemble a

miniature version of the SC connector. LC connectors use a 1.25mm ceramic (zirconia) ferrule

instead of the 2.5mm ferrule. LC connectors are licensed by Lucent and incorporate a push-and-

latch design providing pull-proof stability in system rack mounts. Simplex and duplex

connectors available in market. Highly useful for single mode applications.

Fig.5.3 LC connector and adaptor

4. FDDI Connector

FDDI connector utilizes two 2.5mm ferrules. The ferrules are sheltered from damage because of

the fix shroud that has been constructed in the FDDI connector. FDDI connector is a duplex

multimode connector designed by ANSI and is utilized in FDDI networks. FDDI connectors are

generally used to connect to the equipment from a wall outlet, but the rest of the network will

have ST or SC connectors.

25

Fig.5.4 FDDI connector

26

CHAPTER 6

NETWORKING BASICS

6.1 Introduction to Networking

The physical network consists of all internal switching nodes, their interconnecting links and the

Links leading to externally connected devices. The external devices themselves, computers and

terminals collectively referred to as Data Terminal Equipment (DTE), are then considered as

attached to, rather than forming part of, the physical network.

A wider view of the network may be that of the network including the physical network attached

with all DTE along with all the services available on it, including those available on the attached

DTE. At times, these services are also referred to as ‗networking services‘.

6.2 Advantages of a Network

When we connect computers in a network we have the advantage of:

1. High Reliability- When many computers use a server of the network, the reliability of works

go up. All will be able to store their data on the server and a backup of only the server make data

secure from crashes viruses etc.

2. Lesser Maintenance- When a network has been established, many maintenance can be done

through the network by running appropriate services like DHCP etc. on the net.

3. Cost Effectiveness - A network of PCs cost considerably less than a mainframe and has

equivalent performance.

4. Alternate Communication Media-A network gives us an alternate means of communication.

6.3 Components of a Network

A network consists of the following hardware components:

27

1. Servers - A server is one of the main constituent of the network. In a small network it has a lot

of responsibilities.

2. Clients/Workstations - These are the PCs that use the network functionality through the server.

3. NICs- Network interface cards are the hardware that every computer should have to enable

networking on them.

4. Shared Resources- A network is used to share resources like printers etc.

6.4 Categories of Networks

The computer networks are mostly divided into three categories. They have different

characteristics that are enumerated below.

6.4.1 LAN (Local Area Network)

Its main characteristics are:

• Spans only a few kilometers.

• Used to share files, printers etc.

• Normally have only one type of transmission media.

• Bus, ring and star are the most preferred topologies.

6.4.2 MAN (Metropolitan Area Network)

Its main characteristics are:

• Normally spans a city.

• Normally is privately owned by a company.

• It connects LANs.

6.4.3 WAN (Wide Area Network)

Its main characteristics are:

• Provides long distance communication.

• Span is unlimited.

• May utilize many different types of transmission media.

28

• AWAN owned privately is called an Enterprise network.

6.5 Network Topology

Topology of a network signifies the method of connecting devices that are to participate in

networking. Some of the topologies are discussed below.

6.5.1 MESH

Fig.6.1 Mesh

Characteristics

• Every device is connected to every other device with a dedicated link.

• N (n − 1)/2 physical channels to link n devices are required.

• Hence, every device must have (n − 1) I/O ports.

Advantages

• No traffic problems i.e. congestions, as a dedicated link is available for every communication

path.

• Robust. Even if one of the link is down, the network is not.

Disadvantages

• Large amount of cabling.

• Each device must have (n−1) I/O ports, making it difficult to expand. Usually, this topology is

implemented in a limited way for the backbone of a network connecting routers.

29

6.5.2 STAR

Fig.6.2 Star

Characteristics

• Each device is connected to a central controller.

• Only n links are required for n devices.

• Only one IO port is required in each device.

Advantages

• Less expensive as less cable is required.

• Robust. If a link fails only that device connected to it is affected.

• Easy to add more devices to the network.

6.5.3 TREE

Fig.6.3 Tree

Characteristics

This topology makes available the opportunity to span the network for large distances. The

central hub is usually an active hub.

30

All the three topologies that were discussed above are point-to-point topologies.

6.5.4 BUS

Fig.6.4 Bus

This is a multipoint topology.

Advantages

• Installation is easy.

• Cabling requirement is the least.

Disadvantages

• Difficult to reconfigure.

• Difficult to analyze/localize fault.

• Not robust. A link failure brings the whole network to a grinding halt.

6.5.5 RING

Fig.6.5 Ring

31

Characteristics

• It has dedicated point-to-point links with two adjacent devices.

• Each device should have two IO ports.

• Signal passes in only one direction. Each device thus has a transmit link and a receive link.

Advantages

• Easily reconfigurable.

• Fault isolation is easy.

Disadvantages

• To add a device, the network has to be stopped.

• Unidirectional signals mean that there might be a dedicated link between two devices and yet

no communication between them. A typical situation is depicted below.

A break between B and C means A can‘t communicate with C even though a dedicated link is

available between A and C.

6.5.6 HYBRID

It is also possible to have a hybrid network in which various topologies may be connected. The

Internet is an example of such a network.

32

Fig.6.6 Hybrid

33

CHAPTER 7

OSI MODEL

7.1 What is OSI Model?

The OSI (Open System Architecture) specifies a model for designing and understanding a

network architecture that is flexible robust and interoperable. The OSI model specifies that the

networks architecture can be viewed as consisting of seven layers. These layers define a specific

type of task and thus group them. Each layer provides services to the layer above and takes

services from the layer below. The layer taking services need not bother about the way the lower

layer functions but can assume that it is taking/communicating to its equivalent on the

destination/remote device.

The seven layers defined by OSI model are:

1. Physical layer

2. Data Link Layer

3. Network Layer

4. Transport Layer

5. Session Layer

6. Presentation Layer

7. Application Layer

7.2 Description of 7 Layers

7.2.1 Physical Layer

This layer looks after the following

1. Line Configuration- It answers how two devices are linked together? Whether link is

shared or not? Whether line is available or not?

2. Data Transmission mode- It is here that the data transmission mode is defined. Should it

be one way, two ways or alternate?

3. Topology- In this category, the topology of the network/LAN is decided. Should it be

star, mesh, bus, hybrid etc.?

34

4. Signals- Here, the type of signals to be used for transmitting information is defined.

Digital or analog?

5. Encoding- How are bits encoded for transmission?

7.2.2 Data Link layer

Node-to-Node Delivery- The node to node delivery of data is done by this layer.

1. Addressing- Headers and trailers are added to the information data here to include the

address of the most recent and the next node.

2. Access Control When two or more devices are connected to the same link, the data link

layer protocols determine which device has control over the line at any given time.

3. Flow Control- To avoid overwhelming the receiver, this layer regulates the amount of

data that can be transmitted at one time. It adds identifying number to enable the

receiving node to control the ordering of the data frame.

4. Error handling- Data Link layer protocols provide for data recovery, usually by having

the entire frame retransmitted.

5. Synchronization- The synchronization between the receivers is handled by this layer. It

adds headers as well as trailers to indicate the start and end of a frame.

7.2.3 Network Layer

Source to Destination Delivery- This layer is responsible for source to destination delivery of a

packet across multiple network links. It uses the data link layers functionality for node-to-node

delivery for having a source-to-destination delivery possible.

1. Logical Addressing- To achieve source to destination delivery, it defines the logical

addressing of communicating devices.

2. Routing- This layer is responsible for routing of packets efficiently.

3. Address Transformation- As this layer defines a logical address, the responsibility of

converting the physical address to logical one and vice-versa lies on its shoulder.

4. Multiplexing – It is also responsible for using a single link to carry data of many devices.

35

7.2.4 Transport Layer

End to End Message Delivery- This layer is responsible for end to end delivery of the whole

message. This layer ensures that the whole message arrives intact and in order, overseeing both

error control and flow control.

1. Service Point (port) Addressing- It is this layer that guarantees message delivery to the

appropriate application on a computer. We generally use many windows of IE to browse

the internet. This layer ensures that the messages/information goes to the correct window.

2. Segmentation and Reassembly- This layer, in its task to ensure end to end message

delivery, uses the functionality provided by the network layer. But the network layer

works with only a packet. And hence, it segments the message into packets to use the

network layer. It is also responsible for reassembly of these packets into messages at the

destination.

3. Connection Control It also decides whether or not to send all the packets by a single

route.

7.2.5 Session Layer

Session Management -The main function of this layer is to manage session. It acts like a network

dialog controller establishing, maintaining and synchronizing the interaction between

communication devices. It also validates before establishing a connection.

1. Graceful Close- It is responsible for acquiring network resources for communication and

then gracefully releasing control of the network resources, called closing network

connection in the jargons.

7.2.6 Presentation Layer

Translation- This layer ensures interoperability among communicating devices. Functions at this

layer make it possible for two computers to communicate even if their internal representation of

data differs. It changes the format of a message from that used by the sender into one mutually

acceptable for transmission.

36

1. Encryption and Compression- This layer is also responsible for encrypting data as well as

compressing it, if required.

2. Security- This layer is responsible for the famous login and password validation.

7.2.7 Application Layer

This layer enables the user (computer or human) to use the network. It provides user interfaces

and support for services like E-Mail, ftp, telnet etc. It also provides the user with a network

virtual terminal. It provides file access, transfer, and management over a network as well.

7.3 Data Transfer in OSI Model:

The data is generated by the user of the network. It is passed to the Application layer. This layer

prefixes the data with its header and passes it to the next layer i.e. the Presentation layer. For the

presentation layer, the original data with the application layer header is the data to be

transmitted. It does not know about the header that the Application layer adds to it.

Application AH Data

Application

Presentation PH Data

Presentation

Session SH Data

Session

Transport TH Data

Transport

Network NH Data

Network

Data Link DH Data DT

Data Link

Physical Bits

Physical

Fig.7.1 The data transmission process

DATA

RECEIVER SENDER

37

7.4 TCP/IP Networking

The Internet uses a protocol suite called TCP/IP. TCP/IP reference model has only four layers.

1. Host to Network Layer-The TCP/IP reference model does not speak about this layer.

Different vendors may use different technologies to achieve the functionality of this

layer.

2. Network/Internet Layer-This layer permits hosts to inject packets into any network and

have them travel independently to the destination. They may even arrive in different

order than they were sent, in which case it is the job of higher layers to rearrange them, if

in-order delivery is required. Internet layer officially defines a packet format and protocol

(IP). This layer then has the main function of packet routing and congestion control.

3. Transport Layer- It defines two end to end delivery protocol viz. TCP and UDP.

TCP (Transmission control protocol)

TCP is a reliable connection oriented protocol that allows a byte stream originating on one

machine to be delivered without error on any other machine in the Internet. It fragments the

incoming byte stream into discrete messages and passes each one to the Internet Layer. At the

destination, the receiving TCP/IP process reassembles the received messages into the output

stream. TCP also handles the flow control to make sure a fast sender cannot swamp a slow

receiver with more messages than it can handle.

UDP (User datagram protocol)

UPD is an unreliable connection less protocol for application that do not wants TCP‘s

sequencing or flow control and wish to provide their own. There is no guarantee about the packet

delivery to the destination. It is most analogous to the post office of today. We drop a letter and

then the post office does its best to see that it reaches the destination. Similarly UDP makes the

best effort to deliver a packet.

38

4. Application Layer-This layer is on top of Transport layer and takes its services. It

contains all high level protocols as telnet, ftp, Mail services etc. It is responsible for

encryption/decryption, user validation etc. In all, it is an embodiment of the three upper

layers of OSI model.

7.5 ETHERNET

Ethernet is a family of computer networking technologies for local area networks (LANs)

and metropolitan area networks (MANs).

Addressing: Each device on the Ethernet network has its own network interface card (NIC). The

NIC is provided with a six bytes address that is unique to it. No two NIC in the world will have

the same address. While purchasing NIC, the Ethernet standard should be mentioned. We mostly

use the 10BaseT or 100BaseT Ethernet. Nowadays, NICs supporting 10/100BaseT6. These are

available in the market and hence are the right choice. It ensures that no communication

disruption occurs because of old NICs, yet delivering maximum performance of the new

hardware.

10/100BaseT

The 10/100BaseT standard is the most prevalent today. It is a star topology LAN. It uses UTP7

cable. It supports a data rate of 10/100MBPS and has a maximum cable length (hub to device) of

100m. Devices are linked into the hub by four pair RJ45 cable terminating at each end in male

type connector. The hub fans out any transmitted frame to all of its connected devices. Logic in

the NIC assures that the only station to open and read a given frame is the device to which that

frame is addressed. For 10BaseT Ethernet CAT3 (category 3) and for 100BaseT CAT5

(category5) UTP cable may be used. Today, it is advisable to go for Cat5 cable only.

7.6 IP ADDRESSING

The IP address consists of four bytes (32 bits), defining three fields: class type, nested and

hosted. These four bytes are represented by the dotted decimal representation. Thus an IP address

like 00001010 00000000 00000000 00000001 is represented as 10.0.0.1.

39

To accommodate a vast number of addresses required for global interconnectivity, the class type

field varies in length. There are currently five different classes. Currently class A and B are full.

Addresses are only available in class C. Class D is reserved for multicast addresses. Multicast

allows copies of a datagram to be passed to a select group of host rather that to an individual

host. Class E addresses are reserved for future use. The distribution for the network ID bits and

host ID bits for different classes of network are shown below.

Class A

XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX

Nested Hosted

Class B

XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX

Nested Hosted

Class C

XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX

Hosted

Nested

7.7 BUILDING A LAN NETWORK

LAN is slowly becoming quintessential in our day-to-day working. The demand to reap in the

benefits of networking/LAN is increasing from all quarters. In such a scenario, it becomes

40

essential to plan and design a LAN with careful consideration and deliberation. The most

common demand of a LAN is to share resources. Sharing of files with proper security is one of

the major demands. At times, sharing of printers is also sought after. Looking into all these, the

best bill fits a Windows NT/2000 network having one server and many clients. Here we will see

how we proceed to make a Windows NT/2000 network, in cooperating file sharing with security

and sharing of printers. The clients will run one of the Windows families of operating system

from Microsoft.

7.7.1 Nodes/Clients

The first step in planning a LAN is to understand and analyze the nodes3 requirements. You

must analyze how many nodes/clients will be there on the LAN. Identification Nodes/clients of

physical location of these nodes is also important. It gives an idea of the cable requirement and

also an idea of where to place the hub/switch/router.

7.7.2 LAN Architecture

Depending upon the number of nodes, LAN architecture should be chosen. If there are only two

nodes, then they may be directly connected using a cross cable. If there are more clients then a

tree structure is advisable.

7.7.3 HUB, SWITCH OR ROUTER

Hub- A network hub is a device for connecting multiple twisted pair or fiber optic Ethernet

devices together and thus making them act as a single network segment. Hubs work at the

physical layer of OSI model.

Hubs do not manage any of the traffic that comes together them and any packet entering any port

is broadcast out on every other port. Since every packet is being sent through every other port,

packet collisions result-which greatly impedes the smooth flow of traffic.

Switch- A switch is a device that divides a network into separate collision domains while

retaining the broadcast domain. It divides a network into segments having a reduced number of

41

nodes that are competing for access to the transmission medium. Switches are bridges with

multiple ports.

Ethernet switches increases network performance by decreasing the amount of extraneous traffic

on individual network segments attached to the switch. They also filter a bit a router does.

Routers- Routers were devised I order to separate networks logically. For instance, a TCP/IP

router can segment the network based on IP subnets. Filtering at this level will take longer time

than that of a bridge or switch which only looks at the MAC address. Most routers can filter

packets at a protocol level, is to act as a firewall. This is essentially a barrier, which prevents

unwanted packets either entering or leaving the networking.

7.7.4 STRUCTURED CABLING

Once the architecture and the physical location of the clients have been decided, cabling

considerations are to be made. First, let us see what structured wiring scheme looks like. The

wiring shown in Figure is from the hub to the node. Here a jack-panel has been utilized to patch

all the ports of the hub to itself via a 3 ft. patch cord. The patch cords are multiple stranded and

hence are flexible. A Cat 5 single stranded cable is used to connect the jack panel to the info-

outlet box. We again use a 7 ft. patch cord to connect the client to the information outlet box.

For best results, it is advisable that none of the Cat 5 cable is more than 90m in length and

between two computers in a LAN there may not be more than two hub/switch.

So, the main things that you will have to plan during the LAN wiring stage are

• The location of the hubs.

• The locations of the info-outlet boxes.

This planning should consider the total length of the cable that will be used and optimization can

be done at this stage. The limits of about 100m of the Cat 5 cable should also be kept in mind.

The Structured cabling scheme:

42

Fig.7.2 cabling scheme

Straight & Cross Cable

A UTP cable has 8 cores out of which only 4 cores decide whether a cable is straight and or

crosses.

A cross cable is used to connect similar devices. For example, in a two node LAN, the two

clients can be directly connected, without the need of a hub/switch, through a cross cable.

Similarly, the cable that connects two hubs must be a cross cable. Here, I would like to mention a

special feature in most of the hubs in the market today. Almost all these hubs come with a

special switch controlling one of the ports, mostly port No. 1. The switch is capable of

converting the controlled port to an uplink port. This simply means that the switch is capable of

internally crossing the connection. Hence, if an uplink port is used for connecting similar hubs, a

straight cable should be used. Mostly, the similar devices that we need to connect are hubs. And

they come with an uplink port. One end of the cable goes in the uplink port of the device; the

other end can be any normal port of the other device. Hence, a cross cable is normally not

required.

The straight cable connection

6 6

5 5

4 4

3 3

2 2

43

1 1

The cross cable connection

6 6

5 5

4 4

3 3

2 2

1 1

44

CHAPTER-8

APPLICATION

RAILNET Railnet is the name of the Corporate Wide Information System (CWIS) of Indian Railways. It is

aimed to provide computer connectivity between Railway Board, Zonal Railways, Production

units, RDSO, Centralized Training Institutes.

8.1 Railnet General Arrangement

Fig.8.1 Railnet General Arrangement

The general arrangement of the equipment‘s used in Railnet is shown in the diagram above. The

WAN link (or the Railnet link) terminates at the router. The router in turn is connected to the

switch. All the computers including the server are connected to the switch. Additional

45

hubs/switches may be connected to this switch so as to extend the Railnet LAN further. Railnet

users can exchange emails on the Internet. Commercial Dept. is extensively using Railnet for

their ―Complaint Center.‖ Railways have launched their web pages and they keep up to date

information in these web pages. A Railnet authorized user can browse the Internet through

Railnet. A Railnet user can share resources with a co-user on Railnet. Railnet has used the

private IP address of 10.0.0.0/8. The IP addressing scheme is uniform and consistent. The

following table shows the network addresses of some of the major Railnet servers.

Railnet Center Network Address

Railway Board 10.1.0.0/16

Northern Railway 10.2.0.0/16

Western Railway 10.3.0.0/16

Eastern Railway 10.4.0.0/16

Southern Railway 10.5.0.0/16

South Central Railway 10.51.0.0/16

IRISET 10.195.0.0/16

The Major Railnet equipment‘s also has been given fixed numbers and the configuration of the

whole of Railnet depends on proper addressing. The following table shows the IP addresses of

the major equipment‘s.

Railnet Equipment IP Address

Router 10.X.2.1/16

Railnet Server 10.X.2.19/16

46

8.2 Railway connectivity –Jodhpur Division

Fig 8.2 Connectivity of Jodhpur Division

8.3 E-MAIL ADDRESSING

With the coming of Railnet, we have registered the Internet domain name ―railnet.gov.in‖ and it

is being used for Railnet mails. The table below gives the generic email addresses for some of

the places of Railnet.

Place Email address

SCR user@scr.railnet.gov.in

Railway Board user@rb.railnet.gov.in

IRISET user@iriset.railnet.gov.in

47

8.3.1 Understanding the World Wide Web

The World Wide Web is a system of Internet servers that supports hypertext to access several

Internet protocols on a single interface. The World Wide Web is often abbreviated as the Web or

WWW. The World Wide Web was developed in 1989 by Tim Berners-Lee of the European

Particle Physics Lab (CERN) in Switzerland. The initial purpose of the Web was to use

networked hypertext to facilitate communication among its members, who were located in

several countries. Word was soon spread beyond CERN, and a rapid growth in the number of

both developers and users ensued. In addition to hypertext, the Web began to incorporate

graphics, video, and sound. The use of the Web has now reached global proportions. Almost

every protocol type available on the Internet is accessible on the Web.

1. Internet protocols are sets of rules that allow for inter machine communication on the

Internet. The following major protocols are accessible on the Web:

2. E-mail (Simple Mail Transport Protocol or SMTP)

Distributes electronic messages and files to one or more electronic mailboxes.

3. Telnet (Telnet Protocol)

Facilitates login to a computer host to execute commands.

4. FTP (File Transfer Protocol)

Transfers text or binary files between an FTP server and client

5. Usenet (Network News Transfer Protocol or NNTP)

Distributes Usenet news articles derived from topical discussions on newsgroups

6. HTTP (Hypertext Transfer Protocol)

Transmits hypertext over networks. This is the protocol of the WWW.

Many other protocols are available on the Web. To name just one example, the Voice over

Internet Protocol (VoIP) allows users to place a telephone call over the Web. The World Wide

Web provides a single interface for accessing all these protocols. This creates a convenient and

user-friendly environment. It is no longer necessary to be conversant in these protocols within

separate, command-level environments. The Web gathers together these protocols into a single

48

system. Because of this feature, and because of the Web's ability to work with multimedia and

advanced programming languages, the World Wide Web is the fastest-growing component of the

Internet.

8.3.2 Retrieving Documents on the Web: The URL

URL stands for Uniform Resource Locater. The URL specifies the Internet address of a file

stored on a host computer connected to the Internet. Every file on the Internet, no matter what its

access protocol, has a unique URL. Web software programs use the URL to retrieve the file from

the host computer and the directory in which it resides. This file is then displayed on the monitor

connected to the user's local machine. URLs are translated into numeric addresses using the

Internet Domain Name System (DNS). The numeric address is actually the "real" URL. Since

numeric strings are difficult for humans to use, alphanumeric addresses are employed by end

users. Once the translation is made, the Web server can send the requested page to the user's

Web browser.

8.3.3 Anatomy of a URL

This is the format of the URL:

Protocol://host/path/filename

For example, this is a URL on the home page of the courses of IRISET is

http://www.iriset.ac.in/courses/index.html

This URL is typical of addresses hosted in domains in the United States.

Structure of this URL:

1. Protocol: http

2. Host computer name: www

3. Third-level domain name: iriset

4. Second-level domain nam

49

CHAPTER-9

FUTURE WORK

The topics covered in the training can be further studied and explored in a more practical scenario.

Tele-computing has several implications. The first is that it should be tailored to the person at

work or at home. The goal is to serve employees and residential users. This means it is end-user-

driven. Technology must not be cumbersome. It must be very easy to use. Further, it must be

reliable. Once people count on these PC-based devices for all their information needs, the devices

and supporting networks cannot ever fail. Our PCs will become video telephones, using flat panel

displays that can be hung on any wall. PCs will also become more portable and wearable. They

will be small but have big displays and make loud sounds. The most important PCs will be

wearable and part of our garments, just as many cell phones are worn on the hip today.

Telecommunications and Telephony: All telephony will migrate to IP networks (for instance, the

Internet). The voice telephone network as we know it is history. It is being transformed into a

high-speed IP delivery system between distribution networks. Distribution networks will cover

the last mile to the home or office using telephone wire, coaxial cable, radio frequency channels,

or power wiring. Each of these will compete vigorously for the around $200 per month each

household will spend on communications. New services will cater to consumer and business

needs. Those that master these technologies have the dollars of investment behind them, and meet

present and future needs will become the Microsoft like companies of tomorrow. Those that do

not master these technologies will be absorbed like Digital Equipment Corporation.

Residential Telecommunications: Residential services will depend on high-speed Internet access.

High-speed today is 100 Kbps to 900 Kbps. This will increase in the future to 1 Mbps to 10

Mbps for each household. This will be driven by the entertainment industry selling video over

the Internet. At first, downloading a movie over several hours will be acceptable. But soon, only

a few seconds will be tolerated. Several residential communications technologies, including

cable modems, telephone company DSLs, radio frequency channels, and electric power

distribution channels, will compete for consumer communications spending. Prices will drop

50

because these services can be delivered effectively with few employees. The services must be

highly reliable. Those that provide high reliability, high-speed, and low cost will dominate the

market in the geographical areas they serve.

This means that people will no longer be bound to cities for high-paying jobs, provided high-

speed communications are universally available in rural and other areas. This should radically

change the way we work and manage workers.

Telecommunications and Business: Video telephony is anywhere and everywhere. We already

wear cell phones. Some have push to talk (intercom-like) features and the ability to surf the

Balanced Tele-computing Web. GPS tracking/locating and more is on the way. The net result is

that businesses will need to reinvent themselves on two fronts, how they deal with employees

and how they deal with customers. In dealing with employees, working hours and locations will

become more fluid and less definable. Access to key data and public information must be

provided securely to any working location. Network and PC operation can have no glitches. The

cost of a single outage may not be the cost of

lost time, but rather the loss of that million-dollar sale. In dealing with customers, there are new

opportunities to track and identify customers. These abilities must weight against the invasion of

customer privacy they produce or bring about. There are also opportunities to provide new

products and services that are highly cost-effective. These services will rely heavily on electronic

delivery, but will not be able to split themselves from other physical advertising and delivery

mechanisms. Mouse clicks and mortar will beat mouse clicks every time. This means that the

company that has the facilities and electronic presence (mouse clicks and mortar) will beat the

electronic company (mouse clicks) every time.

51

CHAPTER 10

CONCLUSION

The training at north western railway has helped me to learn about different technologies used in

the railway department. We got some hands on experience on how the communication set up is

established with different equipment‘s, the way of propagation and finally the end user.

We also gained some basic knowledge in the field of computer networking and the whole network

spread out and some theoretical information about Railnet.

The communication and networking is the backbone of Indian railway. To give a total transparent

system with continuous Cargo visibility and an upto date business environment to the Customers

with instant access to information regarding their consignments in transit for just in time

inventory. FOIS in an online real-time system based on current state of art technology and

efficient communication system. It has a management tool to optimize utilization of assets and

resources by improving the distribution of Rakes/wagons, scheduling and outing traffic. It

provides continuous cargo visibility and enables the freight customers to have instant access to

information regarding the current status of their consignment in transit for just in time inventory.

Networks are categorized in three different categories as

LAN (Local Area Network): Local Area Networks (LANs) are networks that connect computers

and resources together in a building or buildings close together. The computers share resources

such as hard-drives, printers, data, CPU power, fax/modem, applications, etc... They usually

have distributed processing - means that there is many desktop computers distributed

around the network and that there is no central processor machine (mainframe).

MAN (Metropolitan Area Network): Metropolitan Area Networks (MANs) are networks that

connect LANs together within a city. From The Big Picture, we see that telecommunication

services provide the connection (storm clouds) between networks. A local telecommunication

service provides the external connection for joining networks across cities.

WAN (Wide Area Network): Wide Area Networks (WAN) are a communication system linking

LANs between cities, countries and continents. The main difference between a MAN and a

WAN is that the WAN uses Long Distance Carriers rather than Local Exchange carriers

52

REFERENCE

www.wikipedia.com

www8.hp.com/in/en/networking.com

www.extremenetworks.com

www.indianrailways.gov.in/railwayboard/view_section.jsp?id=0,1.com