ISDN (Integrated Services Digital Network) is a set of communication protocols that allows digital transmission of voice, video, and data over existing telephone lines. It was developed to digitize and integrate telephone networks to allow transmission of different data types. ISDN provides bearer, tele, and supplementary services through basic rate interface (BRI) with 2 B channels of 64 kbps each and 1 D channel of 16 kbps, or primary rate interface (PRI) with 23 B channels of 64 kbps and 1 D channel of 64 kbps. While ISDN provided faster speeds than analog networks, it has been surpassed by newer technologies like DSL and cable that provide even higher speeds at lower costs.

1. COMPUTER NETWORKS
Presented By
Rahul Kumar Karn
Presented to
Siddheshwari Dutt Mishra
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2. Contents
 ISDN INTRODUCTION
 ISDN SERVICES
 ISDN CHANNELS
 ISDN USER INTERFACE
 FUNCTIONAL GROUPING
 ISDN REFERENCE POINT
 ISDN ADVANTAGE
 ISDN DISADVANTAGE
 REFERENCES
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3. ISDN INTRODUCTION
 ISDN Full Form
I – INTEGRATED
S – SERVICE
D – DIGITAL
N - NETWORK
 ISDN was Developed by International
Telecommunications Union (ITU-T) in
1976.
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4. Continued
 The main purpose is to digitize the
telephone network to permit the
transmission of audio, video, and text
data over existing telephone lines.
 Definition
 ISDN is a set of protocols that combines
digital telephony and data transport
services.
 The goal is to form a WAN that provides
universal End-to-End connectivity over
Digital Media.
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5. ISDN Services
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6. ISDN Services
 Bearer services – provide the means to
transfer information (voice, data,
video) between users without the
network manipulating the content of
that information. Belongs to the first
3 layers of the OSI model.
 Teleservices – the network my change
or process the contents of the data.
 correspond to layers 4-7 of the OSI model
 rely on the facilities of bearer services
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7. Continued
 Supplementary services – provide
additional functionality to the bearer
services and tele-services
 Ex. : reverse charging, call waiting, and
message handling
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8. Continued
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9. Types of ISDN Channels
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10. Barrier(B) Channel
 A Bearer Channel (B Channel) is
defined at a rate of 64 kbps.
 It is the basic user channel and can
carry any type of digital information in
full duplex mode as long as the
required transmission rate does not
exceed 64 kbps.
 It can be used to carry digital data,
digital voice and any other low data
rate information.
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11. Continued
 Several transmission can be accommo-
dated at once if the signals are
multiplexed first.
 Four kind of connections can be set up
over a B channel:
 Circuit Switched
 Packet switched
 Frame mode
 Semi-permanent
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12. Data(D) Channel
 A data channel (D channel) carry
control signal for bearer channels.
 This channel does not carry data and
can be either 16 or 64 kbps, depending
upon the user's need.
 If we are using in-band signalling, the
same cable carries data as well as
control signals.
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13. Continued
 If we are using out-of-band signaling
(as in ISDN), then two different
cables carry data and control
information.
 Can also be used for packet switching
or low speed telemetry.
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14. Hybrid(H) Channel
 A Hybrid channel (H-channel) is
provided for user information at
higher bit rates.
 There are three types of H-Channels
depending on the data rates:
 H0 with data rate of384 kbps
 H11 with data rate of 1536 kbps
 H12 with data rate of 1920 kbps
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15. Continued
 Hybrid channels are used for high
data rate applications such as video,
teleconferencing and so on.
 Can be used as a high-speed trunk.
 Can also be subdivided as per user’s
own TDM scheme.
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16. User Interface of ISDN
User Interface
BRI
Basic Rate
Interface
PRI
Primary Rate
Interface
B-ISDN
Broadband-
ISDN
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17. Basic Rate Interface
 Basic Rate Interface specifies a
digital pipe, consisting of two 64 Kbps
B channels and one 16 Kbps D channel
for a total of 144 Kbps (2B+D).
 In addition, the BRI service itself
requires 48 Kbps operating overhead.
BRI therefore requires a digital pipe
of 192 Kbps.
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18. Continued
 Conceptually, the BRI service is like a
large pipe that contains three smaller
pipes, two for the B channels and one
for the D channel. The remainder of the
space inside the large pipe carries the
overhead bits required for its operation
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19. Continued
 Each B channel can be used for
separate applications Such as Internet
and Voice.
 Allows individual B channels to be
aggregated together into a Multilink
channel.
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20. Primary Rate Interface
 The usual Primary Rate Interface (PRI)
specifies a digital pipe with 23 B
channels and one 64 Kbps D channel for
signalling purpose.
 Primary Rate Interface service consists
of a D channel and either 23 B Or 30 B
channels (depending on the country you
are in) .
 In addition, the PRI service itself uses
8 kbps of overhead.
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21. Continued
 Twenty three B channels of 64 Kbps
each, plus one D channel of 64 Kbps
equals 1.536 Mbps.
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22. Continued
 Each B channel to be used for
separate applications including voice,
data and Internet.
 Multiple B channels can be Multilinked
together.
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23. Continued
 ISDN Primary Rate Interface service
provides digital access via a T1 line.
 ISDN PRI service is used primarily by
large organizations with intensive
communications needs.
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24. Broadband-ISDN
 Narrowband ISDN has been designed
to operate over the current
communications infrastructure, which
is heavily dependent on the copper
cable. BISDN however, relies mainly on
the evolution of fiber optics. According
to CCITT BISDN is best described as
'a service requiring transmission
channels capable of supporting rates
greater than the primary rate.
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25. Functional Grouping
 Terminal Adapter (TA)
 Converter device that converts standard
electrical signals into the form used by
ISDN - allows non-ISDN devices to
operate on an ISDN network.
 Exchange Termination (ET)
 This is the local phone company's logical
connection from your telephones to "the
phone network".
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26. Continued
 Terminal Equipment type 1
 Compatible with the ISDN network.
 Ex.- Digital telephones, integrated
voice/data terminals, personal computers,
fax machine or videoconferencing machine.
 Terminal Equipment type 2
 Not compatible with the ISDN network.
 Ex.- Analog telephone or modem, requires
a TA, Terminal workstation
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27. Continued
 Network Termination type 1
 This is the end of the line for the local
phone company, and the beginning of your
house's phone network.
 Network Termination type 2
 In most homes, this won't exist. If you
were a big company with your own private
telephone system, then this would be the
guts of that telephone system.
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28. Continued
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 Line Termination (LT)
 This is the physical connection to the
phone company.
Defines the functions
of the connections

29. ISDN Reference Points
 U - Two wire cable that connects the
customer’s equipment to the tele-
communications provider.
 R - Point between non-ISDN
equipment (TE2) and the TA.
 S - Four-wire cable from TE1 or TA to
the NT1 or NT2.
 T - Point between NT1 and NT2.
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30. Continued
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31. ISDN Layers
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32. Simplified Layers of ISDN
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Mechanical and
electrical specs of
interfaces R, S, T, U
Encoding
Multiplexing
Power supply

33. Advantage of ISDN
 Speed
 BRI ISDN, using a channel aggregation
protocol such as BONDING or Multilink-
PPP, supports an uncompressed data
transfer speed of 128 kb/s, plus bandwidth
for overhead and signalling. PRI transfers
at an even higher speed of up to 1920 kb/s.
 Multiple Devices
 ISDN allows multiple devices to share a
single line. It is possible to combine many
different digital data sources and have the
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34. Continued
information routed to the proper destination.
 Signaling/Fast Call Setup
 Instead of the phone company sending a
ring voltage signal to ring the bell in your
phone ("In-Band signal"), it sends a digital
packet on a separate channel ("Out-of-
Band signal").
 The Out-of-Band signal does not disturb
established connections, no bandwidth is
taken from the data channels, and call
setup time is very fast.
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35. Disadvantage of ISDN
 BRI is slower than DSL and cable.
 More expensive than DSL and cable.
 Bottom line: ISDN, in its current
form, is no longer a “first-choice”
technology
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36. REFERENCES
 https://en.wikipedia.org/wiki/Integrated_
Services_Digital_Network
 http://ecomputernotes.com/
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