ISDN

What is ISDN?

Integrated Services Digital Network (ISDN) is a set of communications standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. It was first defined in 1984 in the CCITT red book.

In Simple words

Integrated services refers to ISDN's ability to deliver at minimum two simultaneous connections, in any combination of data, voice, video, and fax, over a single line That means an ISDN line can take care of most people's complete communications needs at a much higher transmission rate, without forcing the purchase of multiple analog phone lines.

ISDN History• The early phone network consisted of a pure analog

system that connected telephone users directly by a mechanical interconnection of wires.

• This system was very inefficient, was very prone to breakdown and noise.

• Beginning in the 1960s, the telephone system gradually began converting its internal connections to a packet-based, digital switching system.

• A standards movement was started by the International Telephone and Telegraph Consultative Committee (CCITT), now known as the International Telecommunications Union (ITU). The ITU is a United Nations organization that coordinates and standardizes international telecommunications. Original recommendations of ISDN were in CCITT Recommendation I.120 (1984) which described some initial guidelines for implementing ISDN.

• Most recently, ISDN service has largely been displaced by broadband internet service, such as xDSL and Cable Modem service. These services are faster, less expensive, and easier to set up and maintain than ISDN. Still, ISDN has its place, as backup to dedicated lines, and in locations where broadband service is not yet available

Two Types Of ISDN Channel

Two Types Of ISDN Channel

1.Bearer channel or B channel

• The bearer channel (B) is a standard 64 kbit/s voice channel of 8 bits sampled at 8 kHz.

• B-Channels can also be used to carry data, since they are nothing more than digital channels.

• Each one of these channels is known as a DS0.• Most B channels can carry a 64 kbit/s signal.

2.Data Channel or D Channel

• D-channel, 16 kb/s or 64 kb/s• It carries control and signalling information• call signaling information:

who is calling type of call calling what number

There are several kinds of access interfaces to ISDN defined as Basic Rate Interface (BRI), Primary Rate Interface (PRI) and Broadband ISDN (B-ISDN).

1. Basic Rate Interface(2B+1D)

The entry level interface to ISDN is the Basic(s) Rate Interface (BRI), a 128 kbit/s service delivered over a pair of standard telephone copper wires. The 144 kbit/s rate is broken down into two 64 kbit/s bearer channels ('B' channels) and one 16 kbit/s signaling channel ('D' channel or delta channel).

The interface specifies the following network interfaces:

• The U interface is a two-wire interface between the exchange and a network terminating unit.

• The T interface is a serial interface between a computing device and a terminal adapter equivalent to a modem.

• The S interface is a four-wire bus that ISDN consumer devices plug into.

• The R interface defines the point between a non-ISDN device and a terminal adapter .

2.Primary Rate Interface(30B+1D)

• The primary Rate Interface (PRI) is a standardized telecommunications service level within the Integrated Services Digital Network (ISDN) specification for carrying multiple DS0 voice and data transmissions between a network and a user.

• PRI is the standard for providing telecommunication services to offices

• It is based on the T-carrier (T1) and the E-carrier (E1) line . The T1 line consists of 24 channels, while an E1 has 32.

• 2.048Mbps service

Services By ISDN

Software Architecture

• Layer 3 plus– Call Control Component– D channel Control– B channel Control

• Layer 3−L3 Call Control [Component (0x08) per

D channel]−L3 Global Call Control [Component

(0x09) per D channel]

− L3 D Channel Control [Component (0x0A) per D channel]

− L3 B Channel Control [Component (0x0B) per B channel]

• Layer 2 The Layer 2 (L2) module is the ITU-T Q.921 (LAPD) implementation. It performs flow control, sequence numbering (module 128), retry logic, and it also guarantees message delivery.

• Configuration The Configuration (CFG) module manages all configuration of parameters and options for the ISDN protocol. This task communicates with the Matrix Controller during configuration. It also verifies battery backed data and card level configuration.

• Management The Management (MGMT) module performs terminal endpoint identifier (TEI) management logic for Basic Rate Interface (BRI) access and it synchronizes Layers 2 and 3 correctly. It also acts as an alarm manager for the L2 protocol.

Protocols and Frame StructureProtocols in ISDN are based on the ISDN-PRM (ISDN-Protocol Reference Model) which is constructed following the principles of the ISO/OSI-RM (International Standardization Organization/Open Systems Interconnection Reference Model). The ISDN-PRM consists of two different planes: the user and the control plane (see figure 3).

Basic Access Reference Model

PTT

Equipment at

Phone Company

Switch

U InterfaceTermination Point

T InterfaceTermination Point

S InterfaceTermination Point

Standard PSTN Equipmenthas an R InterfaceTermination Point

U T S

R

TE2TA

TE1 TE1

NT1 NT2

ISDN Equipment thatcan connect directlyto an ISDN Line

Terminal Adapter usedto connect TE2 devices

to an ISDN line

Equipment thatcannot connect to an ISDN line

Network Termination

used to convert U

into T interface

Network Termination

used to convert T

into S interface

Function Groups & Reference Points

• TE1 Terminal Equipment 1, End user equipment such as ISDN telephones or data terminals compliant with ISDN call set up procedures and capable of interfacing directly to the S-bus.

• TE2 Terminal Equipment 2, End user equipment for non ISDN environments (typically uses an RS232 interface)

• NT1 Network Termination 1, Handles physical layer interface functions such as line termination (eg NTE 8).

• NT2 Network Termination 2, Handles physical layer plus layer 2 and 3 functions such as multiplexing, switching and concentration (e.g. an ISPBX).

• LT Line Termination, Handles termination of 2 wire pair at the exchange, operating 2B1Q or 4B3T line coding.

• TA Terminal Adaptor, Equipment that supports ISDN call set up and provides an interface for connecting to non ISDN equipment.

ISDN ProtocolsProtocols beginning with

Used For

E Standards(E.164 describes international addressing)

I Concepts, Terminology(I.300 series describes network aspects)

Q Signalling, Call setup(operation of switching and signalling)

ISDN VERSIONSUSA:

5ESS/DMS100/NI-1/NI-2Europe: NET3France: VN2/VN3/NET33Germany: 1TR6/NET3JapanAustralia

Advantages (ISDN)

• It is an integrated system.• It is widely available as a new wide area

networking alternative.• It provides better quality and high digital data

rates than PSTN systems.• Some of the principles of ISDN:-

Support of voice and non voice applications. Support for switched and non switched applications. Reliance on 64-kbps connections. Intelligence in the network. Layered protocol architecture.

Variety of configurations.

Limitations• ISDN is more expensive to install than a

standard telephone.• ISDN is more expensive to rent per month

than a standard telephone line.• An engineer has to fit the system in your

home.• Not all exchanges have ISDN enabled.• If all you require is a telephone service,

then the standard analogue service is fine.• It costs money to convert your telephone

line back should you decide to revert to an analogue service.

• Although ISDN offers a faster connection to the internet, on some web sites you may not notice a difference in speed of response.

• The reason for this is that for many web servers the bottleneck is not the speed of connection but rather the number of people accessing the same web site at the same time.

Future of ISDN

• ISDN is intended to be a worldwide public telecommunications network.

• The impact of ISDN on users and vendors is significant.

• Some of the points that brings forth its future are as follows:-

National ISDN.Applications.Broadband ISDN.The real world.

APPLICATIONS• Bharat Sanchar Nigam Limited - The

State owns the largest communication service provider. It offers both ISDN BRI and PRI services across the country.

• France Telecom offers ISDN services under their product name Numeris (2 B+D), of which a professional Duo and home version is available.

• In the United Kingdom, British Telecom (BT) provides ISDN2e (BRI) as well as ISDN30 (PRI). Until April 2006, they also offered services named Home Highway and Business Highway.

ConclusionISDN is a great WAN technology, if you can get it. However, if you have the option of DSL or cable modem, those are faster, cheaper technologies. You would still use ISDN if you required voice, video, data, and special application services, which are not provided by DSL and cable modems.

References• www.wikipedia.com• articles.techrepublic.com.• Forouzan• Webopedia.com• Bsnl.co.in

Thank You

Presented ByRahul Kumar GuptaChirag GhelaniNikita GautamVinaya Godbole