w5 trunk administration and hierarchy

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SILVER CERTIFICATION COURSE DIGITAL SWITCHING SYSTEM

TRUNK ADMINISTRATION AND

HIERARCHY

Version 2 June 2014

Digital Switching Systems (DSS) Trunk &Routing Administration and Hierarchy

EETP / BSNL Silver Certification Course /Ver.02/June2014 Page1 of 13

For Restricted Circulation

TRUNK ADMINISTRATION AND HIERARCHY

INDEX

6.1 Objective ............................................................. 2

6.2 Introduction ........................................................ 2

6.3 Inter Exchange Traffic ...................................... 2

6.4 Trunk Group Management ............................... 3

6.5 Routing Management ......................................... 4

6.6 National Network ............................................... 5

6.7 Concept Of SDCA And LDCA ....................... 10

6.8 Summary ........................................................... 12

6.9 Self Assessment Questions ............................... 12




6 TRUNK ADMINISTRATION AND HIERARCHY

STRUCTURE

6.1 OBJECTIVE

6.2 INTRODUCTION

6.3 TRUNK GROUP MANAGEMENT

6.4 ROUTING MANAGEMENT

6.5 NATIONAL NETWORK

6.6 CONCEPT OF SDCA AND LDCA

6.7 SUMMARY

6.8 SELF ASSESSMENT QUESTIONS

6.1 OBJECTIVE

The objective of this lesson is to

Understand the activities followed by the exchange administration in the management of trunk and routes.

Understand the numbering plan and hierarchy in Network

6.2 INTRODUCTION

The connectivity with other exchanges in the network is maintained for efficient

working of the exchanges. Trunk group administration at an exchange involves

managing the corresponding data, by way of Creating, Modifying, Deleting and

Interrogating. Also the routing plan is to be followed for a proper routing of the

call may it be local, special service, national or international.

6.3 INTER EXCHANGE TRAFFIC

No telephone exchange can work in isolation in telecommunication network. To

provide communication between subscribers connected to different telephone

exchanges the exchanges are interconnected through junctions. Local exchanges

are either directly connected with each other or through tandem exchanges. All the

local exchanges are connected to Trunk automatic exchanges which connect

exchanges of different cities. TAXs are interconnected as per hierarchy.

Such interconnection of exchanges makes the overall network of

telecommunications.




6.4 TRUNK GROUP MANAGEMENT

a) Trunk Circuit:

A trunk circuit interconnects one "node" in network to the other for purposes of

putting through calls meant for terminating in one of the nodes for getting

transmitted via that node towards the final desired destination.

b) Trunk Group:

Trunk Group refers to a set of trunk circuits engineered as a unit, inter-connecting the

local exchange to a distant exchange. A Trunk group is a set of trunk circuits engineered as a unit, with common characteristics, like

Signalling,

Category,

hardware types,

traffic handling

type (I/C, O/G or BW) etc. directly connecting the "exchange in question" to another exchange. Trunk group

administration at an exchange involves managing the corresponding data, by way

of Creating, Modifying, Deleting and Interrogating.

During exchange commissioning, the trunk circuits are terminated at the DDF,

appropriate trunk cards are installed in the system and equipped through man-

machine commands.

The trunk group data defines the way trunks are associated as trunk groups and

their operational characteristics. The individual trunk circuits are identified by

their terminal equipment number.

All the trunks in a group are identical from the switching point of view. The

difference between them is in the operational status at any time, so that they may

be in normal in-service, out-of-service, blocked, etc.

6.4.1 Trunk group characteristics

(i)Trunk Group Status

Status of Trunk group depends on the direction of traffic flow.

Incoming (IC) - Trunk Group used for calls coming into the exchange in reference used by the other node(s) i.e. exchanges for putting through calls

meant for terminating on "local" subscribers of the exchange in reference

or for further transiting of these calls towards the desired destination of the

call. The "other" node has full control over these set of circuits in terms of

usage of any circuit for a particular call; the other node is the "master".

Outgoing (OG) - Trunk Group used by the exchange in reference for putting through calls to other exchanges. The exchange in reference is in

full control of allocating any circuit for putting through a particular call.

Both way (BW) - Combination of incoming & outgoing. Both the nodes have the choice to initiate an outgoing call from their end to the other end.




As such it may so happen that at an instant both may choose same circuit

for putting through a call from their end to other end resulting in what is

termed as 'collision'.

(ii) Line Signalling

Line signals are essentially signals which deal with supervision

of a circuit e.g., seizure of circuits and disconnection of

communication onthat circuit.

(iii) Register Signalling

Register signals accomplish the transmission of information

pertaining to dialling and the nature and status of the trunks /

subscriber lines.

These signals are exchanged between register devices of the two

(ormore) involved exchanges during call set up phase.

6.5 ROUTING MANAGEMENT

Routing administration relates to managing the data which is used in translation

and routing. This data is used in completing a call by interpreting information

received from the calling subscriber as a function of the latter's routing category,

numbering plans, priority and the received digits.

The routing data defines the destination of the call, the outgoing trunk groups to

be used to complete an outgoing call and how it is to be metered.

A route is identified by its route code, which designates the destination for an

outgoing call. It is the sequence of digits to be received which is sufficient for

analyzing the destination for routing the call.

The route code can be any sequence of digits with the restriction that it cannot be

a subset or superset of any other existing Route Code. For example, if 243 is a

route code, then there should not be any other routes with 24 or 2439 as route

codes.

The purpose of the translation function in an exchange is to check and translate

the digits received into data handled by the call processing. The structure and the

size of the dialing received depends on:

The type of service requested

The parent exchange of the caller (public exchange, public or private centrex)

The network in which the calling party or/and the called party is /are (regional, national, international network) connected

6.5.1 Special Route

Normally, when a 'route' is defined in an exchange, it is assumed that a call made

to that route shall be ultimately going "out" of the exchange in question since the

route code is much different than exchange code

However, there are cases when we may wish that though a certain sequence of

digits do "look" as if calls to these should not terminate in the exchange under

reference (because the sequence of digits do not match with exchange code), calls

are infact required to terminate within the exchange. Examples of such calls are




complaints service in Indian network which is given route code 198, or lines

men's service (163) etc. Such "routes" are called special routes

These routes may have following characteristics:

Terminate on a Time Announcement Equipment

Posses on Alternate Directory Number (which may be a principal directory number of a hunt group or an individual directory number).

Fig1. PSTN

6.6 NATIONAL NETWORK

A national network can be seen to consist of a hierarchy of interconnected

networks, as follows:

A subscribers premises network. For example, this may consist of extension lines

connected to a private automatic branch exchange (PABX) for telephony or a

LAN for data.

The subscribers distribution network, which is sometimes called the access

network or local-loop plant. This connects subscribers telephones or PABXs to a

local exchange.

The junction network, which interconnects a group of local exchanges and

connects them to the level2 TAX .

The core or level 1 TAX network, which interconnects level 2 TAXes throughout

the Country

Public Switched Telephone Network

Three major components of PSTN:

Local loops

Trunks

Switching Offices

Local CO

408-527-xxxx

22,000 in US

1-10 Km

Tandem

(class 4)

Mostly fiber or microwave




Fig2. National Telecommunication Network

6.6.1 Numbering Plans

Subscriber numbers: The geographical area of a nation is divided into several

numbering areas and the subscriber number identify the subscriber line within a

particular numbering area.

a) SN= EC+LN

TAX Network

International

Gateway Exchange

Satellite

Links Submarin

e Cables

Subscriber Lines

Local Exchanges

Local network

Network

Internationa

l Network

Tandem Exchanges

Level II TAX

Exchanges

Level1TAX

Exchanges




Where SN : Subscriber Number

EC : Exchange Code

LN : Line Number

b) Within a country a subscriber is identified by a national number consisting of an area code

NN=AC+EC+LN

Where NN : National Number

AC : Access Code

EC : Exchange Code

LN : Line Number

c) International numbers consists of country code followed by national number

IN=CC+NN=CC+AC+SN=CC+AC+EC+LN

Where CC : Country Code

When subscriber calls another subscriber located in the same numbering area SN is dialed.

If the subscriber is in the same country but in different area then NN is dialed.

If the party lives in another country then IN is dialed.

Until 1960 the transmission was only analog, Today the network is mostly digital

except for subscriber lines. T1 and E1 are the two standards for first order

transmission systems (E1 is a European Standard, T1 is a American Standard).

Telecommunication networks that employ Common Channel Signaling (CCS)

require in addition to network of trunks and exchanges a signaling network. This

network consists of signaling points inter connected by signaling links.

Telecommunication networks are evolving into intelligent networks that offer in

addition to exchange based services a number of services whose logic and data

reside in centralized information sources that can be queried by exchanges.

6.6.2 DIALLING SCHEMES

Type of dialing

There are two types of dialing schemes

The open schemes, where the number may have a variable length. In this case it is necessary to record the minimum and maximum length of the

possible dialling in the exchange

The close schemes, where the number has a set length a) DIALLING MADE BY SUBSCRIBERS

Regional or local dialling

A subscribers dialling area is the area that the subscriber may reach when dialling

minimal length numbers. Such a number is referred to as a regional number (or

local if the called party is on the same switch as the calling party).

It generally consists of the two following parts




The regional code, defining the switch

A subscribers number in this code

Fig3. Call within SDCA

National dialing

The national dialling is used to call from one dialling area to another .It generally

consists of a prefix which indicates to the switch that the dialling that follows is of

national type an area code or national code a regional number.

Fig4. Call Between Two LDCA

LOCAL

EXCHANGE

LOCAL

EXCHANGE

LOCAL

EXCHANGE

LOCAL EXCHANGE

/ TANDOM

LOCAL

EXCHANGE

LDCC LDCC

SDCC SDCC




International dialling :

For an international automatic call between two subscriber lines, the number to be

dialled generally takes the shape access prefix to the international country code

national number of the subscriber which generally does not include the prefix used

within the destination country for the national dialing

Fig5. International Call

Supplementary services dialing

To use these services the multi-frequency telephone, generally makes use of the

special characters * and #. The rotary sets use prefixes, followed by other digits

LOCAL

EXCHANGE LOCAL

EXCHANGE

LDCC LDCC

SDCC SDCC

International

Gateway International

Gateway


EETP / BSNL Silver Certification Course /Ver.02/June2014 Page10 of

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6.7 CONCEPT OF SDCA AND LDCA

Indian Telecom Network is divided into number of LDCAs (Long Distant

Charging area). Each LDCA consists of one or more SDCAs(Short Distant

Charging area), which are also known as local areas. Each SDCA has one or

more number of exchanges. Each LDCA has a Long Distance Charging Centre

(LDCC), which is a Trunk Automatic Exchange (TAX).Each SDCA has a Short

Distance Charging Centre (SDCC).

Normally each SDCC is an integrated local cum- tandem or a transit switch. In

certain cases SDCC itself may also be LDCC. Each SDCA normally covers one

or more taluka or other administrative areas. Normally the N(S)N is of 10 digits

including 2 to 4-digit National Destination Code (SDCA Code) and 8 to 6-digit

subscriber number. This excludes the access code 0. Most of the SDCAs have

4-digit trunk code, leaving 6 digits for subscriber number.

6.7.1 Numbering Plan Area (NPA)

Numbers in an NPA are not duplicated and are called subscriber numbers.To

make a call from one subscriber to another subscriber in the same NPA, only the

subscriber number needs to be dialed.

NPA relates to specific geographic or administrative area as far as possible. At

present the NPA is same as SDCA. For calls outside the SDCA, 0+N(S)N need

to be dialled. All such adjacent areas shall have to be accessible by dialling N(S)N

with 0 prefix or through carrier selection

6.7.2 Objective of Numbering Plan

The new National Numbering Plan will be able to meet the challenges of multi

operator, multi-service environment and will be flexible enough to allow for

scalability for next 30 years without any change in its basic structure.

The other main objectives of the plan are

i) To plan in conformity with relevant and applicable ITU standards to the extent

possible.

ii) To meet the challenges of the changing telecom environment.

iii) To reserve numbering capacity to meet the undefined future needs.

iv) To support effective competition by fair access to numbering resources.

v) To meet subscriber needs for a meaningful and user-friendly

6.7.3 Salient features of the National Numbering Plan

It is a SDCA based linked numbering scheme. N(S)N is 10-digit for both the

basic as well as cellular mobile services. The Subscriber Number (SN) for basic

services will be of 6, 7 or 8 digits depending upon the length of SDCA code. Basic

to cellular mobile service calls shall use prefix 0 only if Point of Interconnect

(POI) is not available in the same Long Distance Charging Area (LDCA) from

where the call is originated.



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Numbering

Certain three digit spare codes like 555, 666 and 888 are not to be used as SDCA

codes. These are reserved for future services First digit of the telephone exchange

codes can have any value between 2 to 6. Digit 2 has been allocated as the

first digit for BSNL/ MTNL numbers. For the private BSOs, digit 3 or 5 are

allotted. First digit in subscriber number should not be 0, 1, 7, 8 and 9.

Salient features of the National Numbering Plan

Basic services shall be accessed by cellular mobile using 0.

All the service providers shall use 100, 101 and 102 for Police, Fire and Ambulance services respectively.

107X has been defined for emergency information services like earthquake, floods, air and train accident etc.

Certain level 1 codes are earmarked for all service providers to offer various subscriber related services, as per their choice, within their

network

6.7.4 NATIONAL NUMBERING SCHEME

Level 0:

Sub level 00 - INTERNATIONAL PREFIX:

The prefix 00 shall be used for International dialling. It will be followed by

country code and the N(S)N of the country to which that call is attempted. The

format is as per ITU Recommendation

Prefix Country Code + National(Significant)Number ie. 00 CC N(S)N

Sub level 0 - NATIONAL PREFIX:

The prefix 0 shall be used for national long distance calls (cellular mobile as

well as basic services), intra service area (Circle) long distance calls of basic

services, cellular mobile to basic services calls and calls from basic services to

cellular mobile (depending upon point of interconnect).

The format shall be as under:

(i) For basic services (PSTN) long distance calls:

Prefix National Destination Code Subscriber Number

0 + 2/ 3/ 4-digit trunk (SDCA) code + 8/ 7/ 6-digit subscriber number

respectively.

(ii) For basic services to cellular mobile calls if Point of Interconnect is not available in the same LDCA from where the call is originated:

Prefix PLMN Access Code + MSC Code + Subscriber Number

0 + 2-digit ( e.g. 98, 94 etc. ) + 3-digit + 5-digit

(iii) For cellular mobile to cellular mobile calls outside the service area from where the call is originated:



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Prefix PLMN Access Code + MSC Code + Subscriber Number

0+ 2-digit ( e.g. 98, 94 etc ) + 3-digit + 5-digit

(iv) For cellular mobile to basic services calls:

Prefix National Destination Code + Subscriber Number

6.8 SUMMARY

This unit gives detailed information about trunk and route related data which

need to be provisioned in the exchange database by means of man machine

commands. The Concept of SDCA and LDCA is also given . An overview of the

National Numbering Plan is also given

6.9 SELF ASSESSMENT QUESTIONS

1. Trunk group administration at an exchange does not involves modification(T/F)

2. The trunk group data defines the way trunks are associated as .. groups and their operational characteristics. (trunk , subscriber)

3. The trunks .at any time, may be normal ,in-service, out-of-service, blocked(database /operational status)

4. A is identified by its route code(route/circuit) 5. A subscribers premises network.may consist of extension lines connected

to a private automatic branch exchange (PABX)(T/F)

6. In Subscriber numbers SN= +LN( Country code / Exchange code)

7. A group of local exchanges are connected to the level TAX .(1,2,3)

8. Within a country a subscriber is identified by a national number consisting of a country code( T/F)

9. International numbers consists of country code followed by ..(subscriber/national number)

10. The two types of dialling schemes can be . and .

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