PRI,BRI,ISDN,Leaseline,MPLS,VPN,CDN,Telecom Solutions,Corporate services,Networking,

WWW.THECORPORATESERVICES.COM
C O R P O R A T E S E R V I C E S @ O U T L O O K . C O M
I N F O @ T H E C O R P O R A T E S E R V I C E S . C O M
Corporate Services
www.thecorporateservices.com
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Integrated Services Digital Network (ISDN)
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 Set of protocols that combines digital telephony
and data transport services. The whole idea is to
digitize the telephone network to permit the
transmission of audio, video and text over existing
telephone lines.
 The goal is to form a WAN that provides universal
end-to-end connectivity over digital media.

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 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
 Supplementary services – provide additional functionality
to the bearer services and tele services.
ISDN Services

ISDN Services
4

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Voice Communication over an
Analog Telephone Network

6
Voice and Data Communication
over an Analog Telephone Network

Analog and Digital Services
over the Telephone Network
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3 types of customers – the first one is the most prominent

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Integrated Digital Network (IDN)
 A combination of networks available for different purposes.
 Access to these networks is by digital pipes
 digital pipes – time-multiplexed channels sharing very-high-speed
paths.

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Integrated Services Digital Network
(ISDN)
ISDN incorporates all communication connections in a home or building
into a single interface With ISDN all customer services will become
digital rather than analog.

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Subscriber Access to the ISDN
 Subscriber loops – organized
into multiple channels of
different sizes
 B channel
 basic user channel
 Can carry any type of digital info
in Full-duplex mode
 Carries transmissions end-to-
end
 D channel
 Primary function is to carry
control signaling for the B
channel
 Acts like an operator between
the user and the network at the
network layer
Channel Data Rates
(Kbps)
Bearer (B) 64
Data (D) 16, 64
Hybrid (H) 384 (H0),
1536(H11),
1920(H12)
H Channels
- For high data rate applications
such as video, teleconferencing and
so on

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Two Types of Digital Subscriber Loops
 Basic rate interface (BRI)
 Primary rate interface (PRI)
 Each type is suited to a different level of customer needs
 Both include one D channel and some number of either B or H
channels

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Basic Rate Interface (BRI)
 Designed to meet the needs of residential and small-office customers
 The same twisted pair local loop that delivers analog transmission
 can be used to handle digital transmission

Primary Rate Interface (PRI)
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Other channel combinations:
– 3H0 + D
– 4H0 + D
– H12 + D
PRI was designed to be compatible with existing T-1 lines
In Europe, the PRI includes 30 B channels and 2 D channels
= capacity of 2.048 Mbps – the capacity of E-1 line

Functional Grouping
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Defines the function of
each type of equipment
NT – network termination
TE – terminal equipment
NT1
• Controls the physical & electrical termination of the ISDN at the user’s premises
• Connects the user’s internal system to the digital subscriber loop
• Organizes the data stream s from a connected subscriber into frames that can be sent over the digital pipe
• Translates the frames received from the network into a format usable by the subscriber’s devices.

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 NT2 ( ex. Digital PBX, LAN)
• Performs functions at the physical (multiplexing), data link (flow control),
network layers (packetizing) of the OSI model
• Provides intermediate signal processing between the data-generating devices
and an NT1
• Used primarily to interface between a multiuser system and an NT1 in a PRI.

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 TE1 – same thing as DTE
• Any device that supports the ISDN standards
• Ex. Digital telephones,integrated voice/data terminals
 TE2
• Any non-ISDN device
• Ex. Terminal workstation, regular telephone
• Can be used with the help of Terminal Adapter (TA)

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Reference Points
Label used to identify individual interfaces between two elements of an
ISDN installation
Defines the functions of the connections

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ISDN Layers

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Simplified Layers of ISDN
Mechanical and
electrical specs of
interfaces R, S, T, U
Encoding
Multiplexing
Power supply

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BRI Interfaces
 R interface
– not defined by ISDN, it can be any EIA standards or V or X series
 S interface
– ISO standard, ISO 8887, four-, six-, or eight-wire connections.
U interface
- Single-pair twisted-
pair cable in each
direction
- Two binary, one
quaternary (2B1Q)
encoding

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S Interface
Name TE NT
a Power source
3
Power sink 3
b Power source
3
Power sink 3
c Transmit Receive
d Receive Transmit
e Receive Transmit
f Transmit Receive
g Power sink 2 Power
source 2
h Power sink 2 Power
source 2

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2B/1Q Encoding
00 01 10 11
-3 -1 +3 +1

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BRI Frame
Over head

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BRI Topology
 Point-to-point
Multipoint
-limited distance to
ensure frame
synchronization
As many as 8 devices
can be connected to
NT1, two can access
the B-channels at 1
time
D channels use a
mechanism like CSMA

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PRI Interfaces
R and S – same
as those defined
for the BRI
T – identical to S
standard
- B8ZS Encoding
U – same for
both, different
rates

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PRI Frame

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LAPD Address Field
SAPI – Service Access Point Identifier
- identifies the type of upper-
layer service (network layer)
C/R – Command (0) / Response (1)
TEI – Terminal Equipment Identifier
000000 – call control for network
layer (signaling use of D-channel)
000001 – call control for upper layer
(ene-to-end signaling), not yet in use
010000 – packet communication (
data use of D channel)
111111 - management

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Network Layer Packet Format
Protocol discriminator – identifies the protocol in use, for Q.931 = 0000 1000
Call Reference – sequence number of the call
Message Type – identifies the purpose of the message
- call establishment
- call information
- call clearing
- call miscellaneous

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Call Reference Field

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Information Elements
 Carries specific details about the connection that are required for call
establishment:
 - addresses of the sender and receiver
 - routing information
 - type of network that is desired for the B-channel exchange
(X.25, ATM, Frame Relay)

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Information Element Types
ID – identify the information being sent
Length – length of the content in bytes

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Addressing in ISDN
Addressing – important information element type in ISDN
NC – national Code
Subaddress – identify the device connected to NT1

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Bit Rates for Different Applications

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B-ISDN Services
Broadband ISDN – based on a change from metal cable to fiber
optic cable at all levels of telecommunications
Interactive services – those that require two-way exchanges
between either 2 subscribers or between a subscriber & a service
provider
- conversational – real time exchanges such as telephone calls
- messaging – store & forward exchanges such as voice mail
- retrieval –retrieve info from a central office

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B-ISDN Services
Distributive services – unidirectional services sent from a provider to
subscribers, broadcast to the user
- without user control – user choice is limited to whether or not
to receive the service at all
- with user control – allow the user a choice of times during
which to receive them

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B-ISDN Accesses
155.520 Mbps – fill the needs of most residential and many
business subscribers
155.520/622.080 Mbps – fill the needs of businesses that require
the simultaneous receipt of multiple services and video
conferencing

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Thanks You
 www.thecorporateservices.com
 corporateservices@outlook.com
info@thecorporateservices.com

PRI,BRI,ISDN,Leaseline,MPLS,VPN,CDN,Telecom Solutions,Corporate services,Networking,

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