Integrated Services Digital Integrated Services Digital Network (ISDN)Network (ISDN)

Prepared by:

(MADURAI KAMARAJ UNIVERSITY) Pawan Kumar Singh (B244033) Piyush Chandra (B244034)

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An overview of ISDN An overview of ISDN

ISDN was developed by ITU-T in 1970. It is a set of protocols that combines digital telephony and data transport services.

The goal of ISDN is to form a wide area network (WAN) that provides universal end to end connectivity over digital media.

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ISDN ServicesISDN Services

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Continue…Continue…

The purpose of the ISDN is to provide fully integrated digital services to users. These services fall into three categories:

Bearer Services Teleservices Supplementary Services

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Bearer Services:-

. Bearer Services provide to transfer information

(voice, data, and video) between the network

manipulating the content of that information.

. Bearer services belong to the first three layers of

OSI model and are well defined in the ISDN

standard. They can be provided using circuit –

switched, packet – switched, frame – switched or

cell – switched networks.

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Teleservices :-

. In teleservicing the network may change or process

the content of the data.

. These services correspond to layers 4-7 of the OSI

model.

. Teleservices include telephony, telefax, videotex,

telex and teleconferencing.

. The ISDN defines these services by name, they

have not yet become standards.04/12/23 6

Supplementary Services :-

Supplementary services are those services that

provide additional functionality to the bearer

services and teleservices.

Example:- reverse charging, call waiting, and

message handling.

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IDN

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ISDNISDN

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Types of channels . Bearer channels

. Data channels(Delta)

. Hybrid channels

Channel rates

Channel Data Rate(Kbps)Bearer (B) 64

Data (D) 16, 64 Hybrid (H) 384, 1536, 1920

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B Channels :- 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.

128 Kbps128 Kbps

B (64 Kbps)

B (64 Kbps)

Inverse Multiplexers

Inverse Multiplexing of B ChannelsInverse Multiplexing of B Channels

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D Channels :- A data channel (D channel) can be either 16 or 64

Kbps, depending on the needs of the user. The primary function of D channel is to carry

control signaling information for the B channels.

. Who is calling

. Type of call

. Calling what number Can also be used for packet switching or low speed

telemetry.

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H Channels :- Carry user information at higher bit rates 384 kb/s or

1536 kb/s or 1920 kb/s. These rates suit H channels 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. Uses include high speed data, fast facsimile, video,

high-quality audio.04/12/23 13

B Channel (64 kbps)

D Channel (16/64 kbps)

H Channel (384/1536 kbps)

Digital voice Signalling (using SS#7)

High-speed trunk

High-speed data (e.g. packet and circuit switched data)

Low- speed data, (e.g. packet, terminal, videotex)

Very high speed data

Other (e.g. fax, slow video)

Other (e.g. telemetry)

Other (e.g. fast fax. Video)

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Advantages of ISDNAdvantages of ISDN

ISDN also provides more bandwidth than a traditional 56 kbps dialup connection.

ISDN uses bearer channels, also called B channels, as clear data paths.

Each B channel provides 64 kbps of bandwidth. An ISDN connection with two B channels would provide a

total usable bandwidth of 128 kbps. Each ISDN B channel can make a separate serial connection

to any other site in the ISDN network. ISDN lines can be used in conjunction with PPP

encapsulation.

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Disadvantages of ISDNDisadvantages 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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User InterfaceUser Interface

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ISDN standards define two main channel types The bearer channel, or B channel, is defined as a

clear digital path of 64 kbps The second channel type is called a delta channel,

or D channel.

– There can either be 16 kbps for the Basic Rate Interface (BRI) or 64 kbps for the Primary Rate Interface (PRI).

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Basic

ISDN Channel StructuresISDN Channel Structures

B

B

D

Primary

BB..

DB

Basic Service:Management rate: 192 kbpsStandard throughput: 144 kbpsComposition: B + B + D channels, + Synch & framing

Primary Service:Rate: 1.544/2.048 MbpsComposition: 2.048 Mbps: 30 B at 64 kbps each 2 D at 64 kbps 1.544 Mbps: 23 B at 64 kbps each 1 D at 64 kbps

Information:Voice, Data

Signaling:Overhead ortelemetry, etc.

PCM voice channels

Signaling

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Basic Rate Interface (BRI)Basic Rate Interface (BRI)

• 2 B Channels• 1 D Channel

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BRIBRI

• Two B channels of 64 Kbps each, plus 1 D channel

of 16 kbps, equal 144 kbps. • In addition, the BRI services itself requires 48 kbps

of operating overhead. • BRI therefore requires a digital pipe of 192 kbps. • Conceptually, the BRI service is like a large pipe that

contains three smaller pipes, two for the B channel and one for the D channel.

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Primary Rate Interface (PRI)Primary Rate Interface (PRI)

• More sophisticated service compared to BRI• PRI service offers 23 B channels and 1 D channel

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PRIPRI

The usual primary rate interface(PRI) specifies a digital pipe with 23 B channels and one 64 kbps D channel.

In addition, the PRI service itself uses 8 kbps of overhead.

The PRI services is like a large pipe containing 24 smaller pipes. 23 for B channels and 1 for D channel.

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Functional GroupingFunctional Grouping The devices that enable users to access the services of the BRI or PRI are described by their functional duties and collected in func- tional groupings. Functional grouping is a model that can be implemented using devices or equipment chosen by the subscriber.

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Network Termination 1(NT1) :- A network termination 1(NT1) device controls the

physical and electrical termination of the ISDN at

the user’s premises and connects the user’s internal

system to the digital subscriber loop. These functions are comparable to those define for

the OSI physical layer. An NT1 organizes the data streams from a connected

subscriber into frames that can be sent over the digital

pipe, and translate the frames received from the

network.04/12/23 25

Network Termination 2(NT2) :- A network termination 2(NT2) device performs at the

physical, data link and network layers of the OSI model(layers 1, 2, 3).

An NT2 provides multiplexing (layer 1), flow control (layer 2), and packetizing (layer 3).

NT2 can be implemented by a veriety of equipment

types. For example, a private branch exchange

(digital PBX).

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Terminal Equipment 1(TE1) :- Terminal equipment 1(TE1) is any device that

supports the ISDN standards. Example of TE1 are digital telephones, integrated

voice/data terminals, and digital facsimiles. Terminal Equipment 2(TE2) :- TE2 equipment is any non ISDN device, such as a

terminal, workstation, host computer, or regular

telephone. Terminal Adapter(TA) :- TA converts information received in non-ISDN Format

from a TE2 into a format capable of being carried by the

ISDN .

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Reference PointsReference Points

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Interfaces and Devices (1)Interfaces and Devices (1)

Interfaces– S/T (4w)– U (2w)

Devices– NT1– TE1 - ISDN devices– TE2 - analog devices (need TA)– TA - Terminal Adapter (rate adaptation (V.110, V.120)

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Interfaces and Devices (2)Interfaces and Devices (2)

TE1

TE2 TA

NT12W4W

ISDN devices

Analog devices:phone, Fax III,...

Rate adaptation

S/T interface U interface

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ISDN Access Servers (1)ISDN Access Servers (1)

Digital modems (accepting analog and ISDN calls)– software busy-out feature

56 kbit/s technologies Rate adaptation (V.110, V.120,..) Compression (Stack,..) Synchronous PPP (with CHAP/PAP

authentication)

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ISDN LayersISDN Layers

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Simplified Layers of ISDNSimplified Layers of ISDN

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ISDN and OSI modelISDN and OSI model

Layer1 - Physical Layer2 - Data Link Layer3 – Network

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ISDN Access Servers (2)ISDN Access Servers (2)

PPP Multilink BACP (Bandwidth Allocation Control

Protocol) Controlling the number of B-channels per

user D-channel based callback CLIP - Caller Line Identification

Presentation

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56 k Technology56 k TechnologyAccess server

Modem

Telephone switch

Telephone switch

Telephone switch ?

Access server

Modem

Modem

Digital lineAnalog line

<= 33,6 kbps

<= 56 kbpsISDN, E1,..

<= 33,6 kbps

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56 k Prerequisites56 k Prerequisites

Only one analogue/digital conversion– less noise and faster digital lines

Digital Access Server Same technology in Access Server and in

dial-up modem – 56K Flex from Lucent Technologies and Rockwell– X2 from U.S. Robotics, Texas Instruments and Cirrus

Logic– V.90 - ITU-T standard (to be confirmed in 9/98)

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56 k Considerations56 k Considerations

56 k not reached in reality– 45 kbps practical maximum

Cost for upgrading equipment to ITU-T standard

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Using ISDN for Using ISDN for IP Data Networks (1)IP Data Networks (1)

Characteristics– Speed

– Fast call setup

– Bandwidth on Demand

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Using ISDN for Using ISDN for IP Data Networks (2)IP Data Networks (2)

Modes of Usage– Dial Up (LAN or host)

– Bandwidth on Demand

– Backup lines

– Permanent connections

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ISDN AdaptersISDN Adapters

Internal/external Active/passive (for internal) Integrated NT Plug for telephone line Integrated modem Synchronous PPP (with CHAP/PAP

authentication)

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ISDN Adapters 2ISDN Adapters 2

PPP Multilink Rate adaption (V.110, V.120,..) CAPI Compression (Stac,…)

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ISDN RoutersISDN Routers

Integrated NT Plug for telephone line Integrated modem Synchronous PPP (with CHAP/PAP

authentication) PPP Multilink Compression (Stac,…) Tariff management

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ISDN ArchitectureISDN Architecture

Terminalequipment

(TE)

NetworkTermination

(NT)

Subscribersite orserviceprovider

User-networksignaling

User-networksignaling

Subscriberinterface to

ISDN

Digitalsubscriberloop toC. O.

Subscriberpremises

>64kbpsnon-switchedcapabilities

>64kbpsswitched

capabilities

64kbpsckt non-switched

capabilities

>64kbpsckt switchedcapabilities

ISDNswitch

ISDNswitch

Packet switchedcapabilities

Frame modecapabilities

Common-channel signaling

capabilities

Network

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National ISDN variationsNational ISDN variations

USA: 5ESS/DMS100/NI-1/NI-2 Europe: NET3 France: VN2/VN3/NET33 Germany: 1TR6/NET3 Japan Australia

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Thanks

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