Isdn&the c&c08 Switch

Course Description

Overview

The use of ISDN will allow subscribers in an exchange to connect to

existing telecommunication networks, as well as be able to transfer both

voice and data by a single telephone line. This Course mainly introduces

ISDN (Integrated Services Digital Network) in the C&C08 switch.

Course Objectives

On completion of this course, you will be able to

Identify the characteristics and advantages of ISDN

Identify the hardware structure of ISDN in the C&C08 switch

ISDN And The C&C08 SwitchOVSV610R003

Course OSB2A09Issue 1.0

OSB2A09-1

Section 1 Introduction To ISDN

1.1 Advantages Of ISDN

ISDN benefits the user in terms of cost saving and flexibility. The most

important advantage of ISDN is that voice and data are integrated on a

single telephone line meaning that the user does not have to buy multiple

services to meet multiple needs.

The typical business desk now has a telephone for a voice and a

data-terminal or computer. Two separate lines are needed to transmit

voice and data on the same time. Also a modem is needed to convert the

computer data to analog. However, with ISDN, both the voice phone

and the computer may be served by the existing phone line, and the

need for a second line and the need for a modem is eliminated.

1.2 ISDN Evolution

Here are three main features to characterize ISDN：

The evolution of ISDN is based on the existing telecommunication

networks （Integrated Digital Telephone Network ，IDN）

ISDN is a projected worldwide public telecommunication network

will provide end-to-end digital connectivity.

ISDN is intended to handle a variety of services both voice and non

voice via a set of standard user interfaces.

For three points above, here comes the more detailed explanation.

1. Based on the existing telecommunication network

ISDN And The C&C08 SwitchOVSV6.10R003


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It is not impossible that we build a new network for ISDN from

scratch. So we just make some modifications on the existing

network.

For the existing telecommunication networks, its evolution is based

on three technological developments:

Digital transmission was introduced on the trunks interconnecting

exchanges

The switching exchange is digital

The common channel signaling system (CCS7) has been adopted on

the trunks interconnecting exchanges

2. End-to-end digital connectivity

The term end-to-end digital connectivity refers to the fact that the

transmission from one user to the other is a completely digital

transmission. This also means:

The analog-to digital conversion occurs at the subscriber 's

premises, and not at the exchange.

A total digital path can then be made between two subscribers.

A path through the network can be made which is suitable for both

data and voice purpose.

So ISDN is one of the best solutions for digitizing subscriber loop.

LE L

EDigitalSubscriber

premiseSubscriberPremise（Analog）（Analog）

Fig 1-1 The Features of Existing Telephony Network



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LE L

EDigitalSubscriber

premiseSubscriberPremise（Digitized）（Digitized）

Fig 1-2 The Features of ISDN

3. Standard User-network interface

The user can access the network via a series of the unified

user-network interfaces to enjoy various services.

1.3 ISDN Network System

TE ISDNExchange

(TerminalEquipment) TEISDN

Exchange(Terminal

Equipment)CircuitSwitching

Packet Switching

CCS

Preivate LineUer—Network

(DSS1)Uer—Network

(DSS1)

TE ISDNExchange


Exchange(Terminal


Packet Switching

CCS


(DSS1)Uer—Network

(DSS1)

Uer—UserSignaling(UUS)

ISDNNetwork（ISUP）



Fig 1-3 ISDN Architecture

As figure 1-3 shown, ISDN is intended to handle a wide variety of

services and signaling.

There are totally three kinds of signaling in ISDN:

User-to-Network signaling: DSS1 （ ISDN Digital Subscriber

Signaling No.1 ） is used to transfer the control signals between

network and the user terminals.



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Network Signaling ： ISUP （ ISDN User Part ） is used on the

interoffice trunks.

User-to-user signaling: UUS（User-User Signaling）is used for the

end-to-end message between two user terminals and no dedicated

channel is required for UUS and just in virtue of DSS1 and ISUP.

Note

All signaling in ISDN adopt common channel signaling. There is

separate channel called D-channel for user-network signaling and

dedicated PCM time slot for interoffice signaling.

ISDN network owns multi-service as below:

Circuit-switched capability

Packet-switched capability

Private Network

Common channel signaling

1.4 ISDN User Access

ITU_T is responsible for most ISDN standards. To define the

requirements for ISDN user access, an understanding of the anticipated

configuration of user premises equipment and for ISDN user premises

equipment and of necessary standard interface is needed. The first step

is to group functions that may exist on the user's premises.



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TE1S

NT2T

NT1U

TAS

TE2R

Reference Point Functional Grouping

Fig 1-4 ISDN Subscriber—Network Interface reference Configuration

Functional groupings: Arrangement of physical equipment or

combination of equipment.

Reference points: Conceptual points used to separate groups of function.

1.4.1 Reference Points

The cross points between functional groupings are called reference

points. These reference points are designated with the letter R through U

(R-S-U).

1. U-interface

The U-interface is the 2-wire subscriber line and it separate a NT1

from the line termination (LT) equipment.

The main points of U-interface is to transfer digital signals on the

existing 2-wire subscriber loop, reducing the transmission loss as

its best ability. So multilevel scheme is a desirable solution.

The U-interface is a national standard. In China, 2B1Q code is

adopted. 2B1Q means there are four kinds of electricity level on the

loop, each stands for one combination of two bits.

The relationships is as below:



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Binary System Electricity Level

10 ＋3V

11 ＋1V

01 －1V

00 －3V

In this way, the transmission speed has been fallen into half and

eventually result in transmission loss.

For the equipment connected to the U-interface, there are two

status: active and inactive. The precondition for the user terminal to

work is that the U-interface is active. Inactive status is a low power

consuming, when the exchange detects that a U- interface has been

out of service for a period, it will make the U-interface inactive.

Next time, when the terminal wants to originate calls, the

exchange should activate U-interface first, which will take a few

seconds.

2. S、T -interface

The S-interface is 4 Wire interface for single subscriber termination

of TE1 equipment.

The T-interface is also 4 wire interface to terminate TE2 equipment.

The T-interface can be spilt into S-interface for multiply subscriber

termination.

Physically, the S- and T- interface are identical; both are 4-wire

connections with separate data flows in the send and receive

directions. The only difference between S- and T-interface is that T-

interface can be split into more interface, each of which can then

terminate an ISDN terminal.



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Sometimes when NT2 does not exist, S- and T- interface are

integrated as one entity so-called S/T interface.

1. R-interface

The R-interface is a 2-wire interface that connects non-ISDN

equipment (TE2 equipment) to the TA. There are many types of

interface for the R-interface ( for example, an RS-232C or a 2-wire

telephone cable). Therefor, the physical limitations on the

R-interface varies.

Note:

It is important to know that the reference points are conceptual terms

and do not necessarily indicate a physical interface. However, the term

interface is commonly used in conjunction with the reference points.

1.4.2 Functional Groupings

1. NT1（Network Termination 1 ）

is the physical line termination at the subscriber's premised. The

NT1 interface s with subscriber line and contains echo cancelers

and provides a 4-wires interface to the TEE.

The NT1 is considered part of the network, not CPE (customer

Premise Equipment).

The NT1 can be remotely powered by the switch over the interface.

As a result, the switch can place the NT1 in a low power state

when the interface is not being used.



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NT2 is a intelligent devices, meaning that it does more than just

provide a physical interface. NT2 functions may include switching

functions, concentration functions and some level 2 and level 3

protocol processing functions. The ISPBX and LAN router are

examples of NT2 devices.

3. TE1（Terminal Equipment Type 1 ）

TEE refers to devices that support the standard ISDN interface. This

means the devices uses 4 wires. TEE is the standard ISDN terminal,

such as ISDN phone set， ISDN PC，G4 Fax ，Video telephone

and so on.

4. TE2（Terminal Equipment 2 ）

TE2 is non-ISDN equipment, meaning it can not be directly

connected to the NT1. It requires a TA.

5. TA（Terminal Adapter ）

The TA provides the option of using existing non-ISDN equipment

in an ISDN environment. TA mainly acts as a velocity adapter and

protocol conversion with S interface on the one end and various

non-ISDN interfaces on the other end.

Some TA has built-in AT command set.( AT command set is a kind

of general format for MODEM configuration via PC) and can

convert AT command to D-channel signaling directly. So with the

help of TA, a PC can transfer data as well as setup phone call.



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1.4.3 MPA (MultiPoint Adapter)

Fig 1-6 A Typical Structure of MPA

AS port can be split to make accessible for more than one terminals.

This is done with an MPA( multipoint Adapter) built in the NT1. The

MPA performs concentration functions, allowing up to eight terminals

to be connected to a single subscriber line. This capability is known as

passive bus. Passive bus is only supported on the U-interface circuit.

1.5 DSS1( Digital Subscriber Signaling One)

DSS1 adopts three-layer hierarchy: physical layer, data link layer and

connection management layer.

Fig 1-7 Digital Subscriber Signaling System



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1.5.1 Layer 1: Physical Layer

Layer 1( the physical layer) uses the D- channel either the BRA or

2B+D, or the PRA, which is either 23B+D or 30B+D. The D-channel

speed is 16 kbps for BRA, and 64 kbps for PRA.

1.5.2 Layer 2: Data Link Layer

Data link layer support the following functions：

Assembling as well as synchronization, transparent transmission

frames

Acts as a data multiplexed link of one D-channel

Keep the sequence of the frames between sending and receiving

sides.

Detect the transmission error, format error and manipulation error on

the data link

To correct transmission error by repeat sending

Inform the management entity when the error can not be corrected

Flow control

manage the activation of the physical layer

1.5.3 Layer 3: Connection Management Layer

The layer 3 messages are used to manage ISDN connections on the

B-channels, the main functions are：

Process the layer 3 message, communicate with the call control and

source management entity of the switch to complete call processing

together.

Communicate the neighboring layer with original Language.



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Source management（such as channel, call reference value etc.）；

Provide the subscriber with the basic service and supplementary

services.

Prompt

The calling control procedure is made of the layer 3 message

communication of both parties. The detailed information about the layer

3 message will be discussed in the appendix.

1.6 Channel and Interface

1.6.1 Channel Type

1. B-Channel（Bearer Channel）

A B-channel is a 64 kbps channel in two directions and can be used

for the following purposes:

Circuit-switched voice (like a normal telephone set)

Circuit-switched data (for example, connection to a computer or

terminal)

The type of information carried on a B-channel is known as the bear

service.

The following bearer services are valid:

Speech

3.1 kHz audio ( data switched in the voice band, i.e., modem and

facsimile data)

64kbit/s unrestricted circuit-switched data



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2. D-Channel（Demand Channel）

The D-channel is a 16-kb/s channel can carry data in two directions.

Its main purpose is to transport the signaling and control information

between the subscriber equipment and the exchange. This signaling

and control information are in the packet form.

For analog subscribers, signals such as on-hook, off-hook an direct

current are transferred via subscriber line. These signals are now

coded and conform to a special protocol for the D-channel and are

transferred via C-channel.

Totally, two types of D-channel are available as below:

D16：16kbit/s （2B+D）


1.6.2 User Interface

All these terms are limited to the narrow band ISDN.

1. BRA/BRI（Basic Rate Interface/Access ）

The BRA is a digital stream of 144kb/s, which flows over two wires

between the subscriber equipment and the exchange. These two

wires are called a-and b- wires. The stream is divided into three

distinct channels : two B-channels of 64kb/s and one D-channel of

16 kb/s. Therefore, the term 2B+D is used to characterize the BRA.

The term DSL (digital subscriber line) is another term used to

describe the BRA.

Although the BRA has to provide more functions than analog line,

the physical line remains the same. It is very expensive to change all

the subscriber cable. Therefore the same two wires are used, but

they transfer digital signals instead of analog signals.



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In the case of multiple ISDN terminals under one interface, you can

distinguish each other by telephone number + sub address. The sub

address is registered on the corresponding terminals, but the

supplementary service should be entitled to the user..

2B+D用户线

N1=6600000N2=6600001

U口NT1

S/T口

SUB1=1

SUB1=2

SUB1=3

SUB1=4

N1=6600000

SUB1=1

SUB1=2

SUB1=3

SUB1=4

N2=6600001

Fig 1-8 ISDN Subscriber Number and Sub-address

2. PRI /PRA（Primary Rate Interface / Access ）

The BRA is used for the individual subscribers. There is another

configuration of the B- and D- channel that can be used for ISPBX

or for access server ( a equipment for Internet service provider). This

configuration is called the PRA.

The PRA consists of 32 64-kb/s channels divided into 30

B-channels, 1 D-channel, and 1 control channel. The B-channel is

used for data and voice. The D-channel is used for signaling

information associated with the B-channels. The Control channel is

used for frame alignment for PRA.

Since the PRA is a 2-MB/s PCM carrier, it connects to the exchange

at the digital trunk interface ( DTF board).



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1.7 ISDN Service

ISDN service contains basic service and supplementary service

1.7.1 ISDN Basic Service

The ISDN approach is to provide an end user with full support of the

seven layer of OSI Model, although ISDN confines itself to defining the

operation at layer 1, 2, 3 of this model.

In doing so, ISDN is divided into two kinds of the services: Bearer

Service and Teleservice.

So, in the view point of theory, the bearer service is responsible for

providing the layer of the lower 3 layers of seven-layer standard, the

teleservice ( for example, telephone, Teletex, videotex message

handling) is responsible for providing through all 7 layers of the model

and generally making use of the underlying low-layer capability of the

bearer services.

Practically, you can understand these two services in this way: bearer

service is provided by the network (including NT1, NT2 and the

exchange), while teleservice is offered by the Customer Premises

(including TEE, TA, TE2 ) , as fig 1-8 illustrated。

ISDNExchange

ISDNExchange

TeleService Teleservice

Basic Service

Beare Service

Fig 1-8 The illustration of ISDN Basic Service



OSB2A09-15

1. Bear Service

Bear service indicates the exchange transmission capability. ITU

defines the bearer service based on the following aspects.

Message Transfer mode ( circuit switch or packet switch)

Message Transfer speed (64kbit/s, 2 × 64kbit/s, 384kbit/s,

1920kbit/s)

Message Transfer capability (unrestricted digital information,

speech, 3.1KHz audio, 7 kHz audio)

Message Transfer structure ( 8KHz structured, non-structured)

Correspondingly, there are following bearer services for various

application:

64kbit/s, 8KHz, unrestricted services for 64Kbit/s speech, data,

image transmission.

64kbit/s, 8KHz speech only for speech.

64kbit/s、8KHz、3.1KHz audio only for speech or modem audio or

non-G4 fax.

64kbit/s, 8KHz structure, 7KHz audio is for high quality audio.

2×64kbit/s, 8KHz structure，unrestricted digital service is used to

transfer speech, data, image.

2. Tele Service

The tele service provided by the terminals and the network both.

Normally, the tele service capability are determined by the user

terminals since all the network services are available to the

subscribers.



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The typical tele services include:

1) Telephony：the speech occupies 3.1KHz bandwidth of B-channel.

2) Teletex

3) Telefax G4.

4) Videotex.

5) Telephony 7KHz

6) PC_Communication

Prompt

Assumed that the bear service is a train, Teleservice is like the goods the

train loading. The user can select desirable carriage based on his

requirements.

1.7.2 ISDN Supplementary Service

There are many supplementary services that can be added to a digital

subscriber line. Some service have been available before ISDN was

added. These services are still available with ISDN. The following are

the supplementary services available with ISDN.

Direct Dialing In

Multiple User Number

Calling Line Identification Presentation

Calling Line Identification Restriction

Connected Line Identification Presentation

Connected Line Identification Restriction



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Sub-address

Call Forwarding Unconditional

Call Forwarding Busy

Call Forwarding No Reply

Call Waiting

Call Hold

Terminal Portability

Conference Call

Three-party Call

Then we only depict those supplementary services frequently used

service.

1. MSN（Multiple Subscriber Number ）

MSN ( Multiple Subscriber Number) allows you to assign multiple

ISDN numbers to a single BRA interface. This can be used if a

subscriber uses more than one (up to 8 ) terminals to connect on the

BRA Each terminals connected may have a separate subscriber

number.

After data setting on the switch, the multiple subscriber number

must be registered on the terminal respectively.

2. SUB（Sub-Addressing）

With MSN, the terminal connoted to the same U-interface can be

distinguished one from another. But it occupies public number

resource. When we introduce sub-addressing, it is also set on the

terminals. Therefore, the address of each terminal can identified by



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number + sub-address. The network only analyze the number and the

sub-address is left for the terminals.

3. Calling Line Identification

There are three types of calling line identification available:

CLIP (calling line identification presentation)：This service allows

the called party to see the number of the calling person in the

interval of ringing.

CLIR ( calling line identification restriction )：This service allows

the calling party to restrict the presentation of the calling party's

number.

CLIRO (calling line identification Restriction override): This service

is used to override restricted numbers using the CLIR service.

4. Connected Line Identification

COLP（Connected Line Identification Provision） : This service

allows the calling party to number of the connected party.

COLR (Connected line identification restriction) ： This service

allowed the connected party to restrict presentation of their number

when being called.

COLRO ( connected line identification restriction override): This

service is used to override restricted numbers using the COLR

service.

5. UUS（User-to-User Signaling）

UUS (user-to-user signaling) allows a user to send information to

another user during the setup and clearing phased of the call via D

channel. This information is called UUI ( user-to-user information )

.The UUI is embedded within call control message during call setup



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and in information messages during the call. This service allows the

transmission of 32 octets per message.

6. TP（Terminal Portability）

TP allows a user to suspend an active call and

Move a terminal from one socket to another and resume the call

within the same BRA

Replace a terminal by another compatible terminal and resume the

call in the same socket

Move from one terminal to another compatible terminal and resume

the call within the same BRA

Question

What is the difference between ISDN supplementary service and

telephony supplementary services?

1.8 ISDN Applications

With the rapid development of Internet, ISDN gets a larger stage to

show its ability. Here lists some typical applications of ISDN.

1.8.1 Access Internet Via ISDN

1. Subscriber： Access Internet with 128 kbps speed

Two B channels of BRA can provide total 128 kbps and it is almost as

much as twice of the capability of the current high speed MODEM.

（56Kbps）



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PC NT1DSL

ISDN Adapter Router

Router

DSL

PRA

ISDN Exchange

ISP

Internet

Fig 1-9 Access Internet

2. Network

ISDN exchange can access ISP (Internet service provider) via

PRA/BRA interface. On the side of ISP, it is an Access Server.

1.8.2 Home Office

High speed data transmission of ISDN turns working at home into a

fact. When you and your colleagues discuss the issue on the phone, you

can exchange files of data at the same time. All these completion's is just

on one subscriber line.

PC

G3Fax

TAPhone NT1

ISDN-PC

ISDNPhone

G4Fax

DSL

DSL

DSL

PRA

Home ISDN Exchange

Company Phone

ISDN PC

ISDN Phone

G4Fax

Router Server

PC

PC

NT1

PC

PC

Server

CompanyLAN

CompanyLAN

Fig 1-10 Illustration of SOHO



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Section 2 ISDN & The C&C08 Switch

As Figure 2-1 shown, the C&C08 switch provides three types of

interfaces for N-ISDN environment, i.e. , 2B+D, 30B+D and ISUP.

30B+DPRA

BNET

ISUP

DSL

LAPN7

LPRANOD

MPU

HW HW

HW

HW

HW

2B+D

No7 Trunk

Inner BusNOD

Fig 2-1 C&C08 ISDN Structure

2.1 BRA（2B+D ）

In the C&C08 switch, the BRA port is provided by the DSL（Digital

Subscriber Line board). There are totally eight BRA ports for one DSL

board and all of them are introduced from the upper position of the slot

via the same wires as the analog.

The first and second layer message of DSS1 is processed by DSL board

and the third layer is due to MPU.

As we have discussed, the DSL board is compatible with ASL board.

The exchange can power the NT1 via DSL board.



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2.2 PRA Interface（30B+D）

PRA interface is provided by DTF board. There are two PRA interfaces

for one DTF board. It is used to connect router, access server, and

ISDN-PABX.

DSS1 of PRA interfaces are carried in TS16, the LPRA board will

afford data link layer function.

LPRA board positioned in MFC slot and each board supports 8 links,

which has semi-permanent connection with DSS1 signaling TS on PRA

board via BNET board.

2.3 ISUP

In the case of using ISUP as the inter office signaling, DTF board

should be configures as ISUP and LAPN7 board is indispensable.。



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Section 3 BRA Data Setting

ISDN user data includes BRA and PRA, in this section, only BRA user

data setting is covered.

3.1 Hardware Configuration

We 'd better describe the boards associated with ISDN via online setting.

DSL board positioned in subscriber frame is used for BRA interface

and its board number is unified with that of the ASL board.

Suppose the slot is used for a ASL board, now replace ASL with

DSL, so you should use the commands as below:

CMD：ORMV BRD：MN=1，FN=5，S=4；

CMD: OADD BRD：MN=1，FN=5，S=4，BT=DSL，BN=2，

NT=NOD，NN=9，SNN=0，HGN=0，VSB=TRUE；

PRA board for 30B+D port locates on the Digital Trunk Frame, it is

a DTF board with board type of PRA. LPRA board locates at MFC

slot.

Since the PRA data setting is beyond the scope of this course, so the

detailed information is not included.

For the ISUP, the DTF board ( set as ISUP) and LPN7 board are

indispensable. The more information about this part can be found on

the course about trunk data.

3.2 BRA User Data Setting

The whole procedure of BRA user data setting is as below：

1. Add or verify the number segment ；



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2. Add or verify the ISDN index ;

3. ADD the ISDN user data。

3.2.1 Number Resource

The ISDN subscriber can share the number segment with the analog or

get a dedicated number segment.

Commands involved:

Append a new number segmentADD DNSEG

List all the number segmentLST DNSEG

DescriptionCommand

Before allocating number to DSL user, make sure whether the number

segment exists with command LST DNSEG, if it is, just turn to next

step. Otherwise define it with ADD DNSEG.

E.g. Append a new number segment 8880000~8880909 with the starting

number index as 1000.

CMD ： ADD DNSEG ： P=0 ， BEG=K ’ 8880000 ， END=K ’

8880909，NDX=1000；

3.2.2 ISDN Data

It may be convenient to group users by calling attribute, transmission

speed or other administrative purposes. To allow same administrative

information to be assigned to individual users. There are ISDN data you

use. Normally, same attributes is assigned to all BRA subscriber if no

other regulations.

The commands involved are listed as below:

Append a new ISDN data ADD ISDNDAT

List ISDN Data LST ISDNDAT

descriptionCommand



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Modify ISDN DataMOD ISDNDAT

Remove ISDN Data RMV ISDNDAT

Before input a new ISDN data, you should verify the existing record

with command LST ISDNDAT, if the record exists, just deeply it

directly otherwise add a new record with the command ADD

ISDNDAT.

CMD:ADD ISDNDAT：ID=0，CMF=TRUE，PMF=BS，BCN=2，

CWN=5；

【ISDN Index/ID】

ISDN index is the record ID and is referenced by the BRA

subscriber data.

【Circuit Accessing / CMF】【Packed Accessing / PMF】

These two parameters have not been put into use by now.

【Called Number Change Index /DCX】

This field is only used by ISDN PBX functions to complete the

DDI (direct dialing in) service.

【Maximum B channels / BCN】

The maximum B channels can be used by one call, for a BRA

user, it can not be more than 2.

【Call waiting number / CWN】

The maximum call waiting numbers the network can

accommodate for a BRA subscriber.



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【Call Max Times / CMT】

Though the maximum B- channel for a BRA user is 2, but the

network can accept the call setup or call in progress far more

than that. The default number is 10.

【CF Noticing Caller /CLN】

When CF service has been activated, whether to notify the caller

or not.

【CF Noticing Mode/CFA】

There are totally three options for CF noticing mode, they are

service enjoyed party receive the CF announcement tone,

Subscriber receives the CF service activation notification,

subscriber provide the number to the forward destination

subscriber. All this option are only applicable to the case of CF

service.

E.g. The call subscriber A made to subscriber B was diverted to

subscriber C.

A：The caller；

B：The service enjoyed party；

C：The diverted party;

Option 1： Service enjoyed party receive the CF announcement

tone（only B involved）, when set, the B will receive the such

message as the caller number and the service type( if B applies

CLIP ), otherwise, no information will be presented to B.

Option 2: Subscriber receives the CF service activation

notification (only subscriber A involved), when this option is

ticked, then after the call has been diverted to C, A will get such



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message as " the CF service has been activated", otherwise no

notification will be sent to A.

Option 3: Subscriber provide the number to the forward

destination subscriber (only B, C involved). When this option is

ticked for B, then C can know where the call is diverted from

with B's telephone number, otherwise B 's number can not be

sent to C.

【Transmission Capability/TA】【Transmission Speed/TS】

If no other regulations, you are supposed to use the default

value, i.e. All.

3.2.3 ADD ISDN User Data

We use ADD DSL to set a ISDN subscriber data.

Remove a subscriber（ISDN also involved）RMV ST

Modify a 2B+D subscriberMOD DSL

Append Digital Subscriber in batch ADB DSL

Append a MSN to a 2B+D portADD MSN

Append a 2B+D subscriberADD DSL

List the subscriber attributeLST ST

DescriptionCommand

E.g Put the equipment number 20 or SM 1# in service and the

telephone number is 8880010.

CMD: ADD DSL：MN=1，DS=10，D=K’ 8880010，P=0，

ISDN=0，RSC=0，UTP=NRM；

【Device/DS】

For ISDN user, only even port on the DSL board can be used. So we

just do data setting for the even equipment number.



OSB2A09-28

【ISDN Feature /ISA】

Network Detection: it indicates whether the network will detect the

caller number.

Point to multipoint configuration: Each S-interface can be equipped

with up to 8 terminals. This option will make the network assume

that more than one terminals has been configured to this user.

Multiply Subscriber Number (MSN): a typical supplementary for

ISDN and in the case of more than one subscriber number has been

assigned to a subscriber.

Remote Power Supply: whether the exchange( from DSL board)

will power the NT1.

Check local power supply of NT1: This option is reserved and does

not make any sense by now.

3.3 Implement Supplementary Service

3.3.1 MSN (Multiple Subscriber Number)

MSN allows you to assign multiple ISDN numbers to a signal interface

and each terminal connected may have a separate subscriber number.

To apply MSN service is actually add a new subscriber number on the

corresponding user port

The added number has the same property as a normal number and it can

be modified with command MOD DSL.

There are two commands involved :

Remove a MSNRMV MSN

Append a MSNADD MSN

DescriptionCommand



OSB2A09-29

When a subscriber applies MSN service, first you should make sure that

the MSN option in the ISDN feature has been ticked. Then Add the new

number to the user,

E.g. Add a new number 8880001 to the user with the number 8880000.

CMD: ADD MSN：OD=K’8880000，ND=K’8880001；

OD indicates the existing number of the port and ND indicates the new

one.

3.3.2 Other Supplementary Services


subscriber line. Some services have been available before ISDN was

added. These services are still available with ISDN. No matter what kind

of supplementary service it is, the general procedure of data setting is as

below:

1. Authorization

All the supplementary service should be granted to the user after data

setting on the subscriber data.

2. Operation

You should operate on the terminal to register according to your

requirements.



OSB2A09-30

Section 4 ISDN Maintenance

4.1 Circuit Status

In ISDN maintenance, equipment status query includes: equipment

status, circuit status and port signaling trace.

For circuit status query, the commands below are involved, and all of

them are applicable to ASL circuit, DSL circuit as well as Trunk

circuit.

DSP N1C：Display the circuit status

In order to convince yourself whether the circuit is in service or has

been properly blocked maintenance personnel can verify the status of the

circuits with command DAP N1S.

BLK N1C：Block the circuit

UBL N1C：Unblock the circuit

RST N1C：Reset the circuit

If you fail to unblock a circuit or the circuit is out of service for some

reason, you can reset the circuit.

In real world, reset operation is more frequent used. Since in addition

to initialization the circuit itself, it also cause reallocation of the

resource.

Note

For DSL circuit, only those with even channel number can be identified.

Any attempt to odd ones get such response as "circuit uninstall"

ISDN Data SettingVersion6.10R003

Course SW1127Issue 1.0

27-SW1127-31

4.2 Call Trace

4.2.1 Dynamic Connecting Trace

Similar with Analog subscriber, the connection of digital subscribers

can also be observed with command ACT CALLTRAC.

The only different is the parameter DID ( Device type), DSL or PRA

is the option for ISDN subscriber.

ACT CALLTRAC：Run the call connection trace.

STP TRAC：Stop all the trace operation on the current WS.

4.2.2 Port Signaling Trace

Perform dynamic trace for the message packets of DSL, PRA, port

signaling. Observe the connection process, signaling connection, help

to locate connection failure.

ACT ISDNTRC：Start a port trace

STP TRAC：Stop all the trace operation running on current WS.

The port signaling trace form defines the signaling message and source

and destination.

U：The caller or the called

C：The called CCB (Call processing block)

N：Network DSS1 processing module

U：the caller；C：the called；N：network ；I：DSL board

Highlight a message then press "Enter", the detailed explanation will be

displayed on the screen.



27-SW1127-32

4.3 ISDN Maintenance

ISDN maintenance is a complicated job, so the following preparation is

essential to daily maintenance.

1. Familiarize some ISDN fundamentals.

2. Some quality terminals for testing purpose and it is vital for the

troubleshooting.

3. Familiarize BAM and its testing subsystem, it really helps a lot. The

detailed information about testing ISDN subscriber is covered in course

Testing Subsystem.

4. Prepare some dedicated testing instruments to resolve some hot

potatoes (such as line error code analyzer ) . Those commonly used

meters include multimeter, IBT-5, COBRA, SUNSET ISDN

TESTER, prove to be very helpful in your daily maintenance.

5. Set up user file, including the transmission distance, user terminals

type and the loop resistance etc. And it will save you a lot trouble when

fault occurs.

6. Try you best to learn as much as possible the C&C08, in most of

cases, experience will help you solve the problems.



27-SW1127-33

Appendix DSS1 Layer 3 Messages

1.1 Message Type

The DSS1 layer 3 messages are used to manage ISDN connections on

the B channels and Table 1-1 lists some more significant messages and

a short explanation about their functions.

Table 2-1

Responded by the network to show the

suspend request has been accepted.

SUSPEND

ACKNOWLEDGE

Sent by the user to request to temporarily

suspend the call.

SUSPEND

Sent by the network or by the called to indicate that the call establishment has been initiated.

SETUP ACKNOWLEDGE

Sent by the caller or by the network to the

called to indicate a call establishment

SETUP

Sent by the subscriber or network to inform

each other the call progress

PROGRESS

To indicate the call has been accepted by the network.

CONNECT ACKNOWLEDGE

To indicate that the called party has accepted the call.

CONNECT

To indicate that the call is being processed andalso indicate that the network has all theinformation it needs to process the call.

CALL PROCEEDING

Sent by the called or by the network to informthe caller that the called is alerting.

ALERTINGFunction Messages



27-SW1127-34

Sent by the user or the network to report on

the conditions of the call or other

administrative matter.

STATUS

To indicate the information related with

calls, such as subscriber has been

suspended, and calls has been diverted.

NOTIFY

Sent by the subscriber or the network

carrying information of call setup and call in

progress such as the called address.

INFORMATION

Used for the control message of

supplementary service between user and

network.

FACILITY

Sent by subscriber or network to indicate

that the message sender has released the

channel and calling reference.

RELEASE

COMPLETE


that the message sending equipment has

been cut off and is also about to release the


RELEASE

FunctionMessage

2.2 Signaling Procedure

Fig 2-1 illustrates a signaling procedure of a call setup, the detailed

information for message refers table 2-1.



27-SW1127-35

Subscriber Exchange

SETUP

SETUP ACK

INFORMATION

INFORMATION

CALL PROCEEDING

ALERTING

CONNECT

CONNECT ACK

COMMUNICATING

DISCONNECT

RELEASE

RELEASE COMPLETE

· · ·

Fig 2-5 The procedure of DSS 1



27-SW1127-36

Summary

1. The ITU-T defined a series of recommendations for both the ISDN

equipment (known as functional groupings) and the ISDN interface

(known as reference points) 。

2. BRA and PRA

Some important aspects should keep in mind, such as the channel

structure and bit rate.

3. ISDN hardware structure in C&C08 switch

Familiarize yourself with the related boards.

4. Identify the procedure of BRA user data setting

Keep in mind only the equipment with the even number can be used.

And the BRA users with the same calling and transmission attributes

are grouped into the same ISDN index,



OSB2A09-37

Exercises

1. Analog-to- digital conversion equipment is not necessary in the

switching offices in ISDN？( True or False)

2. Which of the following interfaces is used to connected non-ISDN

terminals? (Circle one)

A. U-interface

B. T-interface

C. R-interface

D. S-interface

3. The NT1 convert the 2-wire subscriber line into a 4-wire interface.

(true or false)

4. The existing a- and b-wires have to replaced by a digital wire when a

subscriber becomes an ISDN subscriber? (True or false)

5. Which board type should the DTF board respectively be configured

for PRA and for ISUP data setting?

6. ISDN Caller line identification presentation service serves whom,

the caller or the called?

7. Which kind boards should be equipped to provide BRA, PRA, and

ISUP ?



OSB2A09-38

Keys To The Exercises

1. True

2. C

3. True

4. False

5. DSL、DTF、LPRA、LPN7 should be equipped.

6. PRA board type for the PRA port and ISUP board type for ISUP interface.

7. The caller



OSB2A09-39

Table of Contents

313.3.2 Other Supplementary Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303.3.1 MSN (Multiple Subscriber Number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303.3 Implement Supplementary Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293.2.3 ADD ISDN User Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263.2.2 ISDN Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263.2.1 Number Resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .253.2 BRA User Data Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .253.1 Hardware Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Section 3 BRA Data Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

242.3 ISUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242.2 PRA Interface（30B+D） . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232.1 BRA（2B+D ） . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Section 2 ISDN & The C&C08 Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

211.8.2 Home Office . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211.8.1 Access Internet Via ISDN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211.8 ISDN Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171.7.2 ISDN Supplementary Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151.7.1 ISDN Basic Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151.7 ISDN Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131.6.2 User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121.6.1 Channel Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121.6 Channel and Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111.5.3 Layer 3: Connection Management Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111.5.2 Layer 2: Data Link Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111.5.1 Layer 1: Physical Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101.5 DSS1( Digital Subscriber Signaling One) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101.4.3 MPA (MultiPoint Adapter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

81.4.2 Functional Groupings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61.4.1 Reference Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51.4 ISDN User Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41.3 ISDN Network System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21.2 ISDN Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21.1 Advantages Of ISDN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Section 1 Introduction To ISDN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1Course Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Course Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



i

40Keys To The Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

39Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

38Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

362.2 Signaling Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .351.1 Message Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 Appendix DSS1 Layer 3 Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

344.3 ISDN Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .334.2.2 Port Signaling Trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .334.2.1 Dynamic Connecting Trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .334.2 Call Trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .324.1 Circuit Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32Section 4 ISDN Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



ii

Course OSB2A09

ISDN And The C&C08 Switch

Course Description

Overview

The use of ISDN will allow subscribers in an exchange to connect to

existing telecommunication networks, as well as be able to transfer both

voice and data by a single telephone line. This Course mainly introduces

ISDN (Integrated Services Digital Network) in the C&C08 switch.

Course Objectives

On completion of this course, you will be able to

Identify the characteristics and advantages of ISDN

Identify the hardware structure of ISDN in the C&C08 switch



OSB2A09-1

Section 1 Introduction To ISDN

1.1 Advantages Of ISDN

ISDN benefits the user in terms of cost saving and flexibility. The most

important advantage of ISDN is that voice and data are integrated on a

single telephone line meaning that the user does not have to buy multiple

services to meet multiple needs.

The typical business desk now has a telephone for a voice and a

data-terminal or computer. Two separate lines are needed to transmit

voice and data on the same time. Also a modem is needed to convert the

computer data to analog. However, with ISDN, both the voice phone

and the computer may be served by the existing phone line, and the

need for a second line and the need for a modem is eliminated.

1.2 ISDN Evolution

Here are three main features to characterize ISDN：

The evolution of ISDN is based on the existing telecommunication

networks （Integrated Digital Telephone Network ，IDN）

ISDN is a projected worldwide public telecommunication network

will provide end-to-end digital connectivity.

ISDN is intended to handle a variety of services both voice and non

voice via a set of standard user interfaces.

For three points above, here comes the more detailed explanation.

1. Based on the existing telecommunication network



OSB2A09-2

It is not impossible that we build a new network for ISDN from

scratch. So we just make some modifications on the existing

network.

For the existing telecommunication networks, its evolution is based

on three technological developments:

Digital transmission was introduced on the trunks interconnecting

exchanges

The switching exchange is digital

The common channel signaling system (CCS7) has been adopted on

the trunks interconnecting exchanges

2. End-to-end digital connectivity

The term end-to-end digital connectivity refers to the fact that the

transmission from one user to the other is a completely digital

transmission. This also means:

The analog-to digital conversion occurs at the subscriber 's

premises, and not at the exchange.

A total digital path can then be made between two subscribers.

A path through the network can be made which is suitable for both

data and voice purpose.

So ISDN is one of the best solutions for digitizing subscriber loop.

LE L

EDigitalSubscriber

premiseSubscriberPremise（Analog）（Analog）

Fig 1-1 The Features of Existing Telephony Network



OSB2A09-3

LE L

EDigitalSubscriber

premiseSubscriberPremise（Digitized）（Digitized）

Fig 1-2 The Features of ISDN

3. Standard User-network interface

The user can access the network via a series of the unified

user-network interfaces to enjoy various services.

1.3 ISDN Network System

TE ISDNExchange


Exchange(Terminal


Packet Switching

CCS


(DSS1)Uer—Network

(DSS1)

TE ISDNExchange


Exchange(Terminal


Packet Switching

CCS


(DSS1)Uer—Network

(DSS1)





Fig 1-3 ISDN Architecture

As figure 1-3 shown, ISDN is intended to handle a wide variety of

services and signaling.

There are totally three kinds of signaling in ISDN:

User-to-Network signaling: DSS1 （ ISDN Digital Subscriber

Signaling No.1 ） is used to transfer the control signals between

network and the user terminals.



OSB2A09-4

Network Signaling ： ISUP （ ISDN User Part ） is used on the

interoffice trunks.

User-to-user signaling: UUS（User-User Signaling）is used for the

end-to-end message between two user terminals and no dedicated

channel is required for UUS and just in virtue of DSS1 and ISUP.

Note

All signaling in ISDN adopt common channel signaling. There is

separate channel called D-channel for user-network signaling and

dedicated PCM time slot for interoffice signaling.

ISDN network owns multi-service as below:

Circuit-switched capability

Packet-switched capability

Private Network

Common channel signaling

1.4 ISDN User Access

ITU_T is responsible for most ISDN standards. To define the

requirements for ISDN user access, an understanding of the anticipated

configuration of user premises equipment and for ISDN user premises

equipment and of necessary standard interface is needed. The first step

is to group functions that may exist on the user's premises.



OSB2A09-5

TE1S

NT2T

NT1U

TAS

TE2R

Reference Point Functional Grouping

Fig 1-4 ISDN Subscriber—Network Interface reference Configuration

Functional groupings: Arrangement of physical equipment or

combination of equipment.

Reference points: Conceptual points used to separate groups of function.

1.4.1 Reference Points

The cross points between functional groupings are called reference

points. These reference points are designated with the letter R through U

(R-S-U).

1. U-interface

The U-interface is the 2-wire subscriber line and it separate a NT1

from the line termination (LT) equipment.

The main points of U-interface is to transfer digital signals on the

existing 2-wire subscriber loop, reducing the transmission loss as

its best ability. So multilevel scheme is a desirable solution.

The U-interface is a national standard. In China, 2B1Q code is

adopted. 2B1Q means there are four kinds of electricity level on the

loop, each stands for one combination of two bits.

The relationships is as below:



OSB2A09-6

Binary System Electricity Level

10 ＋3V

11 ＋1V

01 －1V

00 －3V

In this way, the transmission speed has been fallen into half and

eventually result in transmission loss.

For the equipment connected to the U-interface, there are two

status: active and inactive. The precondition for the user terminal to

work is that the U-interface is active. Inactive status is a low power

consuming, when the exchange detects that a U- interface has been

out of service for a period, it will make the U-interface inactive.

Next time, when the terminal wants to originate calls, the

exchange should activate U-interface first, which will take a few

seconds.

2. S、T -interface

The S-interface is 4 Wire interface for single subscriber termination

of TE1 equipment.

The T-interface is also 4 wire interface to terminate TE2 equipment.

The T-interface can be spilt into S-interface for multiply subscriber

termination.

Physically, the S- and T- interface are identical; both are 4-wire

connections with separate data flows in the send and receive

directions. The only difference between S- and T-interface is that T-

interface can be split into more interface, each of which can then

terminate an ISDN terminal.



OSB2A09-7

Sometimes when NT2 does not exist, S- and T- interface are

integrated as one entity so-called S/T interface.

1. R-interface

The R-interface is a 2-wire interface that connects non-ISDN

equipment (TE2 equipment) to the TA. There are many types of

interface for the R-interface ( for example, an RS-232C or a 2-wire

telephone cable). Therefor, the physical limitations on the

R-interface varies.

Note:

It is important to know that the reference points are conceptual terms

and do not necessarily indicate a physical interface. However, the term

interface is commonly used in conjunction with the reference points.

1.4.2 Functional Groupings


is the physical line termination at the subscriber's premised. The

NT1 interface s with subscriber line and contains echo cancelers

and provides a 4-wires interface to the TEE.

The NT1 is considered part of the network, not CPE (customer

Premise Equipment).

The NT1 can be remotely powered by the switch over the interface.

As a result, the switch can place the NT1 in a low power state

when the interface is not being used.



OSB2A09-8


NT2 is a intelligent devices, meaning that it does more than just

provide a physical interface. NT2 functions may include switching

functions, concentration functions and some level 2 and level 3

protocol processing functions. The ISPBX and LAN router are

examples of NT2 devices.

3. TE1（Terminal Equipment Type 1 ）

TEE refers to devices that support the standard ISDN interface. This

means the devices uses 4 wires. TEE is the standard ISDN terminal,

such as ISDN phone set， ISDN PC，G4 Fax ，Video telephone

and so on.

4. TE2（Terminal Equipment 2 ）

TE2 is non-ISDN equipment, meaning it can not be directly

connected to the NT1. It requires a TA.

5. TA（Terminal Adapter ）

The TA provides the option of using existing non-ISDN equipment

in an ISDN environment. TA mainly acts as a velocity adapter and

protocol conversion with S interface on the one end and various

non-ISDN interfaces on the other end.

Some TA has built-in AT command set.( AT command set is a kind

of general format for MODEM configuration via PC) and can

convert AT command to D-channel signaling directly. So with the

help of TA, a PC can transfer data as well as setup phone call.



OSB2A09-9

1.4.3 MPA (MultiPoint Adapter)

Fig 1-6 A Typical Structure of MPA

AS port can be split to make accessible for more than one terminals.

This is done with an MPA( multipoint Adapter) built in the NT1. The

MPA performs concentration functions, allowing up to eight terminals

to be connected to a single subscriber line. This capability is known as

passive bus. Passive bus is only supported on the U-interface circuit.

1.5 DSS1( Digital Subscriber Signaling One)

DSS1 adopts three-layer hierarchy: physical layer, data link layer and

connection management layer.

Fig 1-7 Digital Subscriber Signaling System



OSB2A09-10

1.5.1 Layer 1: Physical Layer

Layer 1( the physical layer) uses the D- channel either the BRA or

2B+D, or the PRA, which is either 23B+D or 30B+D. The D-channel

speed is 16 kbps for BRA, and 64 kbps for PRA.

1.5.2 Layer 2: Data Link Layer

Data link layer support the following functions：

Assembling as well as synchronization, transparent transmission

frames

Acts as a data multiplexed link of one D-channel

Keep the sequence of the frames between sending and receiving

sides.

Detect the transmission error, format error and manipulation error on

the data link

To correct transmission error by repeat sending

Inform the management entity when the error can not be corrected

Flow control

manage the activation of the physical layer

1.5.3 Layer 3: Connection Management Layer

The layer 3 messages are used to manage ISDN connections on the

B-channels, the main functions are：

Process the layer 3 message, communicate with the call control and

source management entity of the switch to complete call processing

together.

Communicate the neighboring layer with original Language.



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Source management（such as channel, call reference value etc.）；

Provide the subscriber with the basic service and supplementary

services.

Prompt

The calling control procedure is made of the layer 3 message

communication of both parties. The detailed information about the layer

3 message will be discussed in the appendix.

1.6 Channel and Interface

1.6.1 Channel Type

1. B-Channel（Bearer Channel）

A B-channel is a 64 kbps channel in two directions and can be used

for the following purposes:

Circuit-switched voice (like a normal telephone set)

Circuit-switched data (for example, connection to a computer or

terminal)

The type of information carried on a B-channel is known as the bear

service.

The following bearer services are valid:

Speech

3.1 kHz audio ( data switched in the voice band, i.e., modem and

facsimile data)

64kbit/s unrestricted circuit-switched data



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2. D-Channel（Demand Channel）

The D-channel is a 16-kb/s channel can carry data in two directions.

Its main purpose is to transport the signaling and control information

between the subscriber equipment and the exchange. This signaling

and control information are in the packet form.

For analog subscribers, signals such as on-hook, off-hook an direct

current are transferred via subscriber line. These signals are now

coded and conform to a special protocol for the D-channel and are

transferred via C-channel.

Totally, two types of D-channel are available as below:



1.6.2 User Interface

All these terms are limited to the narrow band ISDN.

1. BRA/BRI（Basic Rate Interface/Access ）

The BRA is a digital stream of 144kb/s, which flows over two wires

between the subscriber equipment and the exchange. These two

wires are called a-and b- wires. The stream is divided into three

distinct channels : two B-channels of 64kb/s and one D-channel of

16 kb/s. Therefore, the term 2B+D is used to characterize the BRA.

The term DSL (digital subscriber line) is another term used to

describe the BRA.

Although the BRA has to provide more functions than analog line,

the physical line remains the same. It is very expensive to change all

the subscriber cable. Therefore the same two wires are used, but

they transfer digital signals instead of analog signals.



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In the case of multiple ISDN terminals under one interface, you can

distinguish each other by telephone number + sub address. The sub

address is registered on the corresponding terminals, but the

supplementary service should be entitled to the user..

2B+D用户线

N1=6600000N2=6600001

U口NT1

S/T口

SUB1=1

SUB1=2

SUB1=3

SUB1=4

N1=6600000

SUB1=1

SUB1=2

SUB1=3

SUB1=4

N2=6600001

Fig 1-8 ISDN Subscriber Number and Sub-address

2. PRI /PRA（Primary Rate Interface / Access ）

The BRA is used for the individual subscribers. There is another

configuration of the B- and D- channel that can be used for ISPBX

or for access server ( a equipment for Internet service provider). This

configuration is called the PRA.

The PRA consists of 32 64-kb/s channels divided into 30

B-channels, 1 D-channel, and 1 control channel. The B-channel is

used for data and voice. The D-channel is used for signaling

information associated with the B-channels. The Control channel is

used for frame alignment for PRA.

Since the PRA is a 2-MB/s PCM carrier, it connects to the exchange

at the digital trunk interface ( DTF board).



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1.7 ISDN Service

ISDN service contains basic service and supplementary service

1.7.1 ISDN Basic Service

The ISDN approach is to provide an end user with full support of the

seven layer of OSI Model, although ISDN confines itself to defining the

operation at layer 1, 2, 3 of this model.

In doing so, ISDN is divided into two kinds of the services: Bearer

Service and Teleservice.

So, in the view point of theory, the bearer service is responsible for

providing the layer of the lower 3 layers of seven-layer standard, the

teleservice ( for example, telephone, Teletex, videotex message

handling) is responsible for providing through all 7 layers of the model

and generally making use of the underlying low-layer capability of the

bearer services.

Practically, you can understand these two services in this way: bearer

service is provided by the network (including NT1, NT2 and the

exchange), while teleservice is offered by the Customer Premises

(including TEE, TA, TE2 ) , as fig 1-8 illustrated。

ISDNExchange

ISDNExchange

TeleService Teleservice

Basic Service

Beare Service

Fig 1-8 The illustration of ISDN Basic Service



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1. Bear Service

Bear service indicates the exchange transmission capability. ITU

defines the bearer service based on the following aspects.

Message Transfer mode ( circuit switch or packet switch)

Message Transfer speed (64kbit/s, 2 × 64kbit/s, 384kbit/s,

1920kbit/s)

Message Transfer capability (unrestricted digital information,

speech, 3.1KHz audio, 7 kHz audio)

Message Transfer structure ( 8KHz structured, non-structured)

Correspondingly, there are following bearer services for various

application:

64kbit/s, 8KHz, unrestricted services for 64Kbit/s speech, data,

image transmission.

64kbit/s, 8KHz speech only for speech.

64kbit/s、8KHz、3.1KHz audio only for speech or modem audio or

non-G4 fax.

64kbit/s, 8KHz structure, 7KHz audio is for high quality audio.

2×64kbit/s, 8KHz structure，unrestricted digital service is used to

transfer speech, data, image.

2. Tele Service

The tele service provided by the terminals and the network both.

Normally, the tele service capability are determined by the user

terminals since all the network services are available to the

subscribers.



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The typical tele services include:

1) Telephony：the speech occupies 3.1KHz bandwidth of B-channel.

2) Teletex

3) Telefax G4.

4) Videotex.

5) Telephony 7KHz

6) PC_Communication

Prompt

Assumed that the bear service is a train, Teleservice is like the goods the

train loading. The user can select desirable carriage based on his

requirements.

1.7.2 ISDN Supplementary Service


subscriber line. Some service have been available before ISDN was

added. These services are still available with ISDN. The following are

the supplementary services available with ISDN.

Direct Dialing In

Multiple User Number

Calling Line Identification Presentation

Calling Line Identification Restriction

Connected Line Identification Presentation

Connected Line Identification Restriction



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