lecture 7 & 8 isdn

IT-5302-3

Internet Architecture and ProtocolsPunjab University College of Information Technology,

University of the Punjab, Pakistan.

Internet Architecture and Protocols,University of Education

Lahore

Lecture - ISDN

Internet Architecture and Protocols, University of Education Lahore

Internet Architecture and Protocols,University of Education Lahore

Lecture – Objectives• Introduction to Integrated Services Digital Network• ISDN Channels

– B, D– ISDN services

– BRI– PRI

• ISDN Advantages• ISDN Applications• ISDN Architecture• ISDN devices and how they operate

– TE1, TE2 ,TA,NT1 and NT2 devices• ISDN Reference Points• ISDN Layer Specifications


ISDN

• ISDN stands for Integrated Services Digital Network. ISDN is an international standard for sending voice, video and data over digital lines. It is a standard developed by CCITT/ITU (Consultative Committee for International Telephone and Telegraph/International Telecommunications Union)


ISDN

• ISDN uses a standard phone line (a copper wire pair) in a home or office and converts it from a single analog circuit into multiple high speed digital circuits capable of transmitting

• audio,

• still images,

• motion video,

• and text data simultaneously.


ISDN Channels -The B-Channel

• Bearer channel or B-channel. – B channels are used to transport data. B channels are

called bearer channels because they bear or carry the data. B channels operate at speeds of up to 64 kbps, although the speed might be lower depending on the service provider.


The D (Delta) Channel

• The D-channel is used for control signaling (call setup) and may also carry some data.

• D channels carries the signaling information for setting up and clearing down calls.

• ISDN signals new data calls using the D channel. When a router creates a B channel call to another device using a BRI or PRI, it sends the phone number it wants to connect to inside a message sent across the D channel.

• The phone company’s switch receives the message and sets up the circuit. Signaling a new call over the D channel is effectively the same thing as picking up the phone and dialing a number to create a voice call.


D (Delta) - Channel

• D - Channel– D-channels can be different sizes, depending on how many

B-channels they are controlling.

• For a BRI, the D-channel is a 16Kbps pipe

• For a PRI, the D-channel is a 64Kbps Pipe.


ISDN Services

• There are two types of services associated with ISDN:– BRI (Basic Rate Interface)– PRI (Primary Rate Interface)


BRI Service

• Basic Rate Interface (BRI) service offers:

– 2 B channels

• 64kbps, Carry user data

– 1 D channel

• 16kbps, Carry control and signaling info

--Thus BRI uses two B and one D Channel (2B+D)

• The B channels are dial able, and the D channel can be always on. Many users combine both B channels for a 128 Kbps data channel.

• Existing one or two pair of twisted pair cable is used to provide full duplex digital communication.


BRI Service• Used for residential and small office use• Existing two-wire local loops supports BRI• A BRI will allow users to access both voice and data services

simultaneously.• Depending on your hardware, you can connect up to eight

distinct devices to your BRI. • This allows you to build a network of devices, both phone,

data, and video, and use any three of them at the same time. • NOTE:

– While some people will promote the BRI as being a 144Kbps data channel (64 + 64 + 16 = 144), remember that only the 128Kbps B-channel bandwidth (64 +64 = 128) is commonly available to the user. The 16Kbps data channel is reserved for signaling in most circumstances.


PRI Services

• PRI ISDN is used by larger businesses• Primary Rate Interface (PRI) service offers:

– 23 B channels • 64kbps• Carry user data

– 1 D channel 64kbps• Carry control and signaling info • It can also support user data if required• Signaling protocols comprises of OSI layer 1 to layer 3

– (23B+D) used in North America and Japan. • Supports total bit rate of 1.544Mbps.

– (30B+D) used in Australia and other countries• Supports total interface rate of 2.048 Mbps


BRI and PRI B and D Channels

Type of Interface

Number of Bearer (B) Channels

Number of Signaling (D) Channels

Descriptive Term

BRI 2 1 (16kbps) 2B+D

PRI (T1) 23 1 (64kbps) 23B+D

PRI (E1) 30 1 (64kbps) 30B+D


ISDN BRI and PRI Services

Service B Channels

D Channel

Bandwidth

BRI 2 x 64 kbps 1 x 16 kbps 144 kbps

T1 PRI 23 x 64 kbps 1 x 64 kbps 1.544 Mbps

E1 PRI 30 x 64 kbps 1 x 64 kbps +1 Synchronization channel

2.048 Mbps


Advantages of ISDN

• Speed• Data can be sent faster than ordinary lines.• There is an upper limit to the amount of information that an

analog telephone line can hold.• Currently, it is about 56 kb/s bi-directionally. Commonly

available modems have a maximum speed of 56 kb/s, but are limited by the quality of the analog connection and routinely go about 45-50 kb/s.


Advantages of ISDN

• Multiple Devices– Previously, it was necessary to have a separate phone line

for each device you wished to use simultaneously. For example, one line each was required for a telephone, fax, computer, and live video conference system.

– Up to eight different devices can be operated simultaneously over a single ISDN line.


Advantages of ISDN

• Cost effective:Simultaneous audio, video, and data services over a single pair of copper wires reduces infrastructure and maintenance costs for service and subscribers


Advantages of ISDN

• Bandwidth Utilization: ISDN is as easy to use as analog but offers much more. For example, we can utilize the two 64 kbps B channels as individual voice and data lines at the same time. we can use one channel to talk while you're using the second to send data files. Or, with ISDN's BONDING capability, we can aggregate both lines into a single high-speed 128 kbps link for dependable transmission

• ISDN’s dynamic bandwidth allocation feature accommodates the bandwidth-intensive applications.


Advantages of ISDN

• Better Quality:

• Digital transmissions produce clearer and quieter voice telephone service and more reliable and accurate connectivity than analog technology


Advantages of ISDN

• Faster Connection Time:Protocols such as IP and IPX are better supported by ISDN connections across WANs due to faster connect times (between 1 and 4 seconds) than analog service (between 10 and 40 seconds).

• Compatibility:ISDN is compatible with other WAN services like X.25, Frame Relay and higher speed services like Asynchronous Transfer Mode (ATM).


Advantages of ISDN

• Signaling• Instead of your phone company sending a ring voltage signal

to ring the bell in your phone, it sends a digital packet on a separate channel. This does not disturb established connections and call set-up time is very fast. An ISDN call usually takes less than 2 seconds.


Sample ISDN Configuration Illustrates Relationships Between Devices and Ref. Points


Network Termination 1 (NT1)

• NT1 includes functions associated with the physical and electrical termination of the ISDN on the user’s premises

• These correspond to OSI layer 1• It may be controlled by the service provider• It provides a physical connector interface for user device

attachment• Also perform line maintenance functions• It supports multiple channels, using synchronous TDM


Functional Devices

• Network Terminator 1– The Network Terminator 1 (NT1) is the device that

communicates directly with the Central Office switch. The NT1 receives a "U" interface connection from the phone company, and puts out a "T" interface connection for the NT2, which is often in the same piece of physical hardware.

– The NT1 handles the physical layer responsibilities of the connection, including physical and electrical termination, line monitoring and diagnostics, and multiplexing of D- and B-channels.


Network Termination 2 (NT2)

• NT2 is an intelligent device that can perform switching and concentration functions

• It includes functionality up to layer 3 of OSI model• Examples

– Digital PBX– A LAN

• The concentration function– Multiple devices attached to a digital PBX, or a LAN

may transmit data across an ISDN• Note

– NT2 Device is used where we have to provide switching facility.


Network Terminator 2

– The Network Terminator 2 (NT2) sits between an NT1 device and any terminal equipment or adapters.

– An NT2 accepts a "T" interface from the NT1, and provides an "S" interface

– In most small installations, the NT1 and NT2 functions reside in the same piece of hardware.


Network Terminator 2

– In larger installations, including all PRI installations, a separate NT2 may be used.

– ISDN Network routers and digital PBX's are examples of common NT2 devices.

– The NT2 handles data-link and network layer responsibilities in ISDN installations with many devices, including routing and contention monitoring.

lecture 7 & 8 isdn

Economy & Finance

data channel

bchannel bearer channel

d delta channel

bchannel bandwidth

d pri e1

d pri t1

synchronization channel

data services