national chung cheng university public switched telephone

National Chung Cheng UniversityDept. Computer Science & Information Engineering

Public Switched Telephone Networks and

Intelligent Networks

Chiang, Wei-Kuo (江為國)

Assistant Professor Department of CSIE National Chung Cheng University Office : EA 311 Phone : 05-2720411~33126 Email : [email protected]

URL : http://www.cs.ccu.edu.tw/~wkchiang/

National Chung Cheng University


Mobile Communication Networks PSTN and IN 2

Outline

PSTN (Public Switch Telephony Network)

Digital Signaling Systems

SS7 Architecture

SS7 Protocol Suite

IN (Intelligent Networks)

What is IN ?

IN Call Model

Bellcore AIN Call Model

ITU-T IN Call Model

Evolution of ITU-T IN Capability Sets



Class 5

End Office Switch

The Telephone Network (1/2)

Circuit Switched Network

Intelligent

Peripheral

Signal

Transfer

Point

Service

Control

Point

Class 4

Tandem Switch

Service

Data

Point

+

Transport Layer

Control Layer

SS7 Signaling

ISUP Messages

INAP/TCAP Messages



備忘稿

傳統電信網路中電話建立的過程為：語音(Voice)部份是經由局用交

換機(CO Switches)之間的Trunk介面傳輸；信令(Signaling)部份

則是透過SS7網路傳遞。如果只是一般的通話，負責通話控制(Call

Control)的SS7 ISUP信令，僅會透過SS7網路的信號轉運點

(Signal Transfer Point；STP)，在發話端交換機(Originating

Switch)與受話端交換機(Terminating Switch)之間傳送；然而，

當通話需要智慧型網路服務(IN Services)時，則要發送SS7 TCAP

信令，經由SS7網路轉送至提供該服務的服務控制點(Service

Control Point；SCP)，要求提供該項服務；若是該項服務包括語

音播放(Announcement) 、互動語音回應(Interactive Voice

Response；IVR)，此時SCP就會要求智慧型設備(Intelligent

Peripheral；IP)播放語音給發話端，同時偵測發話端的按鍵，並將

按鍵結果之DTMF回傳給SCP，用來決定該項服務的進行。



The Telephone Network (2/2)

5 Basic Components in Intelligent Networks

SSP/Service Switching Point

switching, signaling, routing, service invocation

STP/Service Transfer Point

signaling, routing

SCP/Service Control Point

service logic execution

SDP/Service Data Point

subscriber data storage, access

IP/Intelligent Peripheral

resources such as customized voice announcement,

voice recognition, DTMF digit collection

SSP

SCP SDP

STPIP

SSP

STP

TCAP messages

ISUP messages

Voice



Telephony Switches

Central offices All telephony lines terminated in a central office.

The central office (CO) offered only local services

Hierarchy of telephony exchanges (switches) Class 1 – Regional

Class 2 – Sectional

Class 3 – Primary

Class 4 – Toll

Class 5 – Central Office

Classes 1~4 switch connections only, have no

subscribers attached to them

The lower the class number and the bigger the

exchange



Introduction to Signaling

As you make a call to Kitty, image

How do you notify the CO to place a call ?

How do you know when to dial the Kitty’s telephone number ?

As you dial the digit, how does the CO know what you dial ?

How does the CO notify the Tendem switch to route the call to Kitty ?

How does Kitty know the call coming ? Even know it’s you in calling

her ?

How do the CO and Tendem switch know when the call terminate ?

The answers are all by Signaling

Signaling is a control information tx. mechanism in telecomm.

network. By which, the devices or systems can exchange necessary

information for completing the processing of a call.



Signaling Systems

Early signaling systems carried the control signals on the same circuit as the user traffic The older in-band analog systems

The newer signaling systems use a separate channel for signaling information Common Channel Signaling (CCS):

Use Dedicated Digital Channel for Signaling Transmission

SS7 (Signaling System Number 7)

Physical out-of-band signaling

ISDN (integrated Services Digital Network)

Physical in-band/ Logical out-of-band

B channel - user traffic; D channel - signaling



Comparison of Signaling

User Traffic

Signaling trafficSwitchA

SwitchB

User & Signaling TrafficSwitch

A

SwitchB

Physical out-of-band signaling (the SS7 approach)

Physical in-band/ Logical out-of-band signaling (the ISDN approach)

Signaling traffic backup



ISDN Channels

Logical channel 1

SwitchA

SwitchB

Logical channel 2

Logical channel n

The logical channels (conceptual view)

SwitchA

SwitchB

channel 1

On the physical channels (TDM/time division multiplexing)

channel 2 channel n

ISDN logical channels

D channel (signaling): 16 or 64 kbits/s

B channel (user data): 64 kbits/s

BRI (basic rate interface): 2B + D



Difference between SS7 & ISDN

Why does ISDN not use physical out-of-band?

ISDN usually implemented on local subscriber

loops running between a customer & the CO

Not cost-effective to use separate links

The ISDN approach represents a compromise

Physical channel is shared

Not provide for redundant links

Signaling System 7 (SS7) To enable a wide range of services

Caller ID, toll-free calling, call screening, …

the foundation for Intelligent Network



Placement of ISDN & SS7

Switch SwitchCPE CPE

CPE Customer premise equipmentNNI Network node interfaceUNI User-network interface

NNIUNI UNI

Network

SS7

analog

ISDN

SS7

analog

ISDN

SS7



Outline



SS7 Architecture

SS7 Protocol Suite


What is IN ?

IN Call Model


ITU-T IN Call Model




SS7 Network

Signaling Point

Each Signaling Point in SS7 Network is Uniquely

Identified by Point Code

Three Kinds of Signaling Point

SSP: Service Switching Point

STP: Signal Transfer Point

SCP: Service Control Point

Fault Tolerant

Mated Pair Configuration

Linkset

STP

STP

SCP

SCPSSP

SSP

SS7

LinksSS7

Links

Trunk



Signaling Point (SP)

Each node in an SS7 network is an SP.

The signaling address of the SP is known as a

signaling point code (SPC).

Linkset

Group of signaling links directly connecting

two SPCs

For capability and security reasons



SSP

Service Switching Point (SSP)

The Switch System in Telephone Network

Usually the Tandem Switch

Functionality = Voice Switch + SS7 Switch

Process Incoming Calls According to IN Call Model

If necessary, Create a Query Message to SCP

through SS7 Network

Determine the call Destination (maybe Advised by

SCP)

Set-up the Call

Service Deployment and Service Triggering

Mechanism



STP

Signal Transfer Point (STP)

Serve as Router in SS7 Network

Network Traffic Packets between Signaling Point

are Routed by STP

Global Title Translation --- A Procedure to

Determine the Packet’s Destination from the

Digits in the Signaling Message

SSP Can have no idea about the address of SCP but

send the query to STP directly

STP checks the dialed digit (or global title address,

e.g. 080xxxxxx), and determines the destination

signaling point code of SCP to which the query

packet will be sent to



STP

Switch

SPC 2

Switch

SPC 1

MSU , destination = SPC 2 MSU , destination = SPC 2

Message for SPC 2. That is me!

Message for me? No! Pass it on.

STP

SPC 3

To transfer messages from one SPC to another



SCP

Service Control Point (SCP)

A network entity that contains additional logic

and that can be used to offer advanced services

The switch sends a message to the SCP asking

for instructions.

The SCP, based upon data and service logic that

is available, will tell the switch which

actions need to be taken.

An good example – toll-free 800 number



SCP

Service Control Point (SCP)

SCP is a computer with real-time database

The database stores the routing information of

the IN subscribers

Different kind of IN services are provided by

executing different service logic on SCP

Examples of IN service:

Advanced Free Phone

VPN

Intelligent Call Routing

One Number (099…)



Special IN Components

4 Special Components in IN

SCE/Service Creation Env.

Provide tools to assist in

creating services in SCP

SMS/Service Management Syst.

Manage database that

controls IN services

NAP/Network Access Point

No IN function, just for

access SS7 network

AD/Adjunct

Configured for 1/few

services for a single switch

Others use AD through the

connected SSP

SSP SSP

SCPSMSSCE

SS7Backbond

STP

IP

Adjunct

AD

NAP

NetworkAccessPoint



Service Switching Point

The SSP provides the users with the interface

to the IN functions

Tasked with detection capabilities

Detect user requests for IN services

Can have dialogues with different SCPs

trigger point defines required service in calls

interconnections via Signaling Transfer Points

Dialogues with SCPs based on SS7 signaling - no

actual payload is transmitted

The SSP contains CCF and SSF, and CCAF if it

acts as a local exchange



Service Control Point

The SCP are connected to the SSPs, and contains Service Logic Programs (SLPs) and associated data to provide the IN services.

Services are run in Service Logic Execution Environment e.g. OS, runtime modules, management procedures etc.

The SCP contains a SCF and a SDF. The SCP can also be connected to IPs.

Service data (SDP) can be located in Service Data Point ie. (relational) database

usually integrated to SCP

can be a commercial product (Oracle,Sybase)

Service interfaces to SSP abstracted with TCAP and INAP (OSI application layer)



NAP & SSCP

The network access point (NAP) contains only the CCAF and CCF.

The NAP is not a fully functional IN node. It does not communicate with an SCF,

but it is able to determine if IN services are

to be invoked to support a user request.

If such an event occurs, NAP sends these calls

to an SSP

The service switching and control point (SSCP) is combined SCP and SSP operating in a single node It contains SCF, SDF, CCAF, CCF, SSF



Adjunct & IP

AD is Functionally equivalent to SCP, but has

direct communications link to an SSP

supports one-to-one relationship with SSP

usually small geographical coverage

The intelligent peripheral (IP) contains the SRF

Manages resources such as

announcements

speech recognition

digit collection

Controlled by SSP or SCP (or SN)

interface to SSP incl. both signaling and data,

but to SCP (or SN) only signaling



Service Node

The SN provides interaction with users as well

as control IN services.

can have the functionality of both SCP & IP

The SN Contains an SCF, SDF, SRF, and an

SSF/CCF

The SSF/CCF is not accessible by external SCFs

and is closely coupled to the specific SCF

operating within the SN.

The SCF receives messages from the SSP and

executes SLPs.

The SRF allows the SN to interact with users in

a fashion similar to that of the IP



Service Management Syst.

SMS Supports both commercial and technical IN

service management

operator can load new services to the SCP

operator can gather statistics and billing

data to the OSS (Operations Support System)

Handles service management in the distributed IN

systems

data consistency in SCPs’ databases (SDPs)

Usually closely coupled with the SCP

no standard SMS-SCP interface protocols exist



Service Creation Environ.

Framework for defining, developing and testing

SLPs e.g.

graphical SIB-based ‘drag and drop’

graphical SDL-based

high level, 4GL language based

low level C-language based with special

resources e.g. libraries and runtimes

proprietary graphic and/or text based

Services are loaded via SMS to SCPs



GUI SCE (App. Generator)



Outline



SS7 Architecture

SS7 Protocol Suite


What is IN ?

IN Call Model


ITU-T IN Call Model




SS7 Protocol Overview

Common Channel Signaling System No. 7

ITU-T

ANSI and Telcordia Variants --- North American

ETSI Variant --- Europe, Asia,...

SS7 Usage

Basic Call Set-up, Management, Tear-Down

Wireless Services

PCS, Roaming, Subscriber Authentication

Local Number Portability

IN Services, e.g. 800/900 Wireline Services

Enhanced Call Features

Caller-ID, Three Way-Calling, Call Forwarding

Telecommunications Efficiency and Security



SS7 Protocol Suite

Message Transfer Part (MTP) 1



Signaling Connection Control Part (SCCP)

Transaction Capabilities Application Part (TCAP)

Opera

tion,

Adm

inis

tration,

and M

anagem

ent

Part

(O

AM

P)

Mobile A

pplication

Part

(M

AP)

IN A

pplication P

art

(I

NAP)

ISD

N U

ser

Part

(IS

UP)

Tele

phony U

ser

Part

(TU

P)

OSI Layers

Application

Presentation

Session

Transport

Network

Data Link

Physical



MTP Levels 1 & 2

Message Transfer Part

Level 1

Handling the issues related to the signals on

the physical links between one signaling node

and another

Level 2

Dealing with the transfer of messages on a

given link from one node to another

Providing error detection/correction and

sequenced delivery of the SS7 messages



備忘稿

MTP (Message Transfer Part) 是 SS7 protocol

stack 中最下面的三個層級(layers)，主要是分別對應到Open Systems Interconnection (OSI) seven-

layer model 中的最下面三個層級：Network Layer,

Data Link Layer, 以及 Physical Layer。

MTP Level 1 的功能就是實體層上如何搭載 signaling

的問題；而 Level 2 則是負責處理一個 link 中如何傳送到網路中的下一個節點，同時也提供偵錯、更正以及依序傳輸的功能；MTP Level 3 則是處理整個 signaling

網路的 routing 問題，也就透過先前提到的 STP 來當做中繼點(intermediate nodes)來傳送封包。



MTP Level 3

Signaling message handling

Providing message routing between signaling

points in the SS7 network

Signaling network management

Rerouting traffic to other SS7 signaling links

in the case of link failure, congestion or node

failure

Load-sharing



TUP and ISUP

Telephone User Part (TUP)

Support Basic Call Set-up and Tear Down

TUP Handles Analog Circuits Only

Replaced by ISUP Gradually

ISDN User Part (ISUP)

To Set-up, Manage, and Release Trunks that

Carry Voice and Data between Terminating Line

Exchange

Used for both ISDN and Non-ISDN Calls



ISUP

Used as the protocol for setting up and tearing down

phone calls between switches

Initial Address Message (IAM)

To initiate a call between two switches

Address Complete Message (ACM)

To indicate that the call party’status

Answer Message (ANM)

To indicate that a call has been accepted by the

called party

Release Message (REL)

To initiate call disconnection

Release Complete Message (RLC)



備忘稿

在 MTP 層之上是 ISDN User Part (ISUP) 以及Signaling Connection Part (SCCP)。

嚴格來說，ISUP 主要是用於 Integrated Services

Digital (ISDN) 應用。不過事實上，ISUP 目前多使用為建立/關閉通話的 signaling protocol。

常見的 ISUP 訊息包括了 Initial Address Message

(IAM；在兩個switches間建立一個通話)、 Answer

Message (ANM；指出通話已被受話方接受）、以及Release Message (REL；通話結束)



ISUP Signaling

SSP

Calling Party Called Party

STP SS7 Link STP

SSP

1. IAM 7. REL

2. IAM

3. ACM

4. ACM

5. ANM

6. ANM

8. REL 9. RLC10. RLC

Voice Circuit Id Code = 5



Call Establishment

Calling Called

IAMSetup

IAMSetup

Originating

SSP

Terminating

SSP

AlertingACM

ACMAlerting

ConnectANMANM

Connect

Tandem

Switch



Call Release

Calling Called

REL

Disconnect

REL

Disconnect

Originating

SSP

Terminating

SSP

RLCRLC

Release

Release

Tandem

Switch



Call Establish & Release

IAM

IAM

ACM

ACM

One-way audio

CPG

CPG

ANM

ANM

Two-way speech path

REL

REL

RLC

RLC

a

b

c

d

e

f

g

h

i

j

k

l

m

n

What is

the difference?



備忘稿建立通話，發話端的交換機會送出 IAM。IAM 帶有發話人電話號碼、收話

人電話號碼、傳輸的輸求、發話人種類（一般通話、系統商通話、付費電費）等資訊。

經由 STP 傳輸到收話端的交換機後，會回傳一個 ACM (Address Complete Message)來告知發話端：「通話已經連接到了目的地。」而ACM 會開啟一個由收話端到發話端的單向音訊路徑，如果收話端可以接聽的話，發話端即可聽到撥話時的嘟嘟聲(ring-back tone)。嚴格來說，ACM是一個 optional 的訊息，如果不回傳 ACM 就不會開啟單向音訊路徑，而發話端必須等到完整的通話建立之後才會知道通話已經建立，並不會影響到通話建立的成功率。但是當撥話之後，如果發話端能先聽到 ring-back tone 就好像收話端可以即時的 response （雖然尚未完全建立通話），因此大多數的通話建立時仍然會回傳 ACM。

CPG (Call Progress) 訊息也是一個 optional 的訊息，主要是用於提供額外的資訊給發話端的交換機。

收話端接起電話時，收話端的交換機會回傳一個 ANM (Answer Message) ，而這個訊息有兩個功能：開啟雙向的音訊路徑以及開始對通話計費。

通話結束之後，當兩端有使用者掛下電話時，該方交換機會送出 REL (Release) 訊息，另一方的交換機收到後則會送出 RLC (Release Complete) 的訊息。在 RLC 回傳到對方的交換機之後，通話便結束了。



SCCP

Signaling Connection Control Part

Used as the transport layer for TCAP-based

services

freephone (800/888), calling card, wireless

roaming

Both connection-oriented and connectionless

Mostly connectionless signaling

Global title translation (GTT) capabilities

The destination signaling point and subsystem

number is determined from the global title



TCAP, MAP and INAP

TCAP (Transaction Capabilities Applications

Part)

Supporting the exchange of non-circuit related

information between signaling points

Queries and responses sent between SSPs and

SCPs are carried in TCAP messages

INAP (IN Application Part)

MAP (Mobile Application Part)



Outline



SS7 Architecture

SS7 Protocol Suite


What is IN ?

IN Call Model


ITU-T IN Call Model




IN Introduction

Two names: IN and AIN (Advanced IN)

IN – ITU-T Model (Intl. Telecom. Union – Telecom.

Standardization Sector)

AIN – Bellcore Model

Both terms convey the idea of a network that provides

a platform to deploy user services in a fast and

efficient manner.

The goal is to build a software platform that

consists of programs that are reusable across

applications.

application independent

Undergone revisions & different releases(beyond CS-4)

ITU-T Capability Set 1 (CS1) & Bellcore AIN 0.1

More prevalent in commercial products at this time



IN Goals

To support the creation of services for the end

customer in a rapid manner.

The IN

uses the Signaling Systems Number 7 (SS7), and

add its functionality at the application layer

to achieve these key goals

Timely creation of new services for the customer

Support a wide range of services (generic & tailored)

Efficient maintenance of the IN system

Require a seamless environment between vendors’

Automate services that entail operator intervention



What is an IN Service ?

The term IN service is misleading

Because IN designed to be service independent

The value of IN

Standardizes the procedures and protocols to

provide IN services to a customer

IN or AIN in commercial products ?

Most vendors/manufactures are implementing both

Why we need IN ?

Market prediction

Traditional telephony service not growing much

Looking for new service to meet customers’ needs



Precursors to IN

The 800 service (Freephone or Green Number)

Existed since 1976

Provide toll-free service

Before CCS(common channel signaling) & SS7

SSP

SCP

STP

SMS/800

1. Dial 800#

SSP recognizes the 800 number,suspends normal call processing,forms an SS7 message, and sends …

2. 800#3. 800#4. Query (SCP 800 database)5. Response (to define how to handle the call)6. Dest & routing data7. Dest & routing data8. Dest9. Ring

Network1.

2.

3.

4.

7.

6.

5.

8. 9.

(provisioning)

SCP Service Control PointSMS Service Manag. Syst.STP Signaling Transfer PointSSP Service switching point

Not participate in call operationsInteracts with the customer



IN Service Examples (1/3)

Example of an AIN 800 Service

SSP

Central Office

Location A

Pizza-A-Go-Go

SCP/Adjunct: to discover the nearest location

Residence

SubscriberLocation B

Pizza-A-Go-Go

SSP

Central Office

1. 800-1234

2. Query

3. Response4. Place call




“Do Not Disturb/Call Screening” Service

SSP

SCP

1. Activation Digits

Activating the service

2. Collect & analyze digits3. Suspend call processing

4. Query Message

5. Response Message

6. Confirm

SCP

4. Query Message

6. Response Message

SSP1. Dial


5. Because “Do Not Disturb” is active,Calling party is not blocked.

7. Connect

Allowing a call to be connected




SCP

4. Query Message

6. Response Message

SSP

1. Dial


5. Because “Do Not Disturb” is active,Calling party is blocked.

Disallowing the call

IP

7. Announcement

8. Announcement

9. Digits

10. Voice Message

Voice MailSystem

“Do Not Disturb + Voice Mail” Service



How IN Evolved (1/5)

Early System

Switch Switch

Switch

Basic call processing programs

Control data

Supplementary service programs

Switching and routing programs

All-in-One approach 1. Created duplication switches

2. Change/update cumbersome

3. Each vendor had a different approach

Interworking of equipment difficult

4. Hard to timely create new services

Database




The Intelligent Network Architecture

Move and distribute functions into specialized

modules and specialized machines

Mid-1980s, 800 number in the SCP

Switch Switch

SCP

The interface tailored to each service,

i.e., customized messages created.

Database

Service specific

Service specific

A common Resource

Easy to maintain

Switch Switch

SCPDatabase

Basic call processing

Switching and routing


Control data

Supplementary service




The Intelligent Network Architecture (cont.)

Steps in obtaining a supplementary service

Switch Switch

SCP

Database

1.

2.

3. 4.

5. SCP performs basic call processing,

Step2 : with several messages exchanged

before the supplementary service obtained

That consumes considerable resource.

1. Dial-in to network

2. Set up connection then make request

3. Return reply

4. Set up connection






Remove the overhead involved in setting up

connections between the switch and the SCP

1. Dial-in to network

2. Make request on a common signaling channel

(out-of-band connectionless channel)

3. Return reply on a common signaling channel



Switch Switch

SCPDatabase


Switching and routing


Control data

Supplementary service

Further distribution of functions

Less overlap of processes

More specilized

More modular





The publication & acceptance of SS7 in 1984

Switch Switch

SCP

Instead of tailored messages for a service

Database

Generic interface

Generic interface



History of IN Standards

70s/80s

centralize database used for 800 and credit card

calls in the USA [IN1]

mid 85

Bellcore starts development of IN1 & IN2

88

multi-vendor interaction forum in the USA begins the

Advanced IN

IN standardization begins in ETSI & ITU-T (CCITT)

92

Bellcore produces definitions for AIN 0.1, 0.2 and

0.3

ITU-T produces Recommendations for IN CS-1



The ITU-T IN Model

IN Model

published in ITU-T Recommendation Q.1201

Supplementary info in Q.1203, Q1204, Q.1213

Used as a tool in the development

IN Capability Set (CS)

Organized around 3 principal elements


Conventional operation of call setup & disconnect

Hooks

the interface between BCP & IN services modules

IN service logic

Software modules to provide the IN services



ITU-T Recommendations (1/2)

The INCM defined in the ITU recommendations

Glossary of Terms Used in the Definition of IN Q.1290

General Aspects of the IN Application Protocol Q.1208

IN Physical Plane Architecture Q.1205

IN Distributed Functional Plane ArchitectureQ.1204

IN Global Functional Plane ArchitectureQ.1203

IN Service Plane Architecture Q.1202

Principles of the IN Architecture Q.1201

General Series IN Recommendation Structure Q.1200

RecommendationNumber



ITU-T Recommendations (2/2)

The structure for defining each CS-x, x = 1, 2, 3

IN User Guide for CS-x Q.12x9

IN Interface Recommendations for CS-x Q.12x8

IN Physical Plane Architecture for CS-x Q.12x5

IN Distributed Functional Plane Architecture for CS-x Q.12x4

IN Global Functional Plane Architecture for CS-x Q.12x3

IN Service Plane Architecture for CS-x (not for CS-1) Q.12x2

Introduction to IN CS-xQ.12x1

Structure of IN CS-x Q.12x0

RecommendationNumber



Capability Sets of IN (1/2)

CS-1 (Capability Set 1) supports “Type A” services only

CS-2 supports “Type A + Type B” services

Type A Single-ended (Applies to only one party).

Single point of control (only influenced by one SCF).

E.g.

Abbreviated Dialing

Freephone

Premium Rate

Televoting

VPN



Capability Sets of IN (2/2)

Development in phases

CS1

published 1993

CS2

published 1999

specifies management interfaces and call-unrelated

switching functions

CS3

design started 1997

focus on mobility management

CS1

CS2CS3



Acronyms

Standard Bodies CCITT: International Consultative Committee on

Telegraphy and Telephony

ITU-T: International Telecommunications Union-

Telecommunications Standardization Sector

ETSI: European Telecommunications Standards

Institute

Standards AIN: Advanced Intelligent Network.

INAP: Intelligent Network Application Protocol.

CS: Capability Set.

ITU-T Q.12xy(x = 0 for General, CS-x for CS-x):

definition of IN architecture.



Outline



SS7 Architecture

SS7 Protocol Suite


What is IN ?

IN Call Model


ITU-T IN Call Model




The Call Model Procedures

The Call Model

A sequence of procedures executed by an IN to set up,

manage, and clear an IN session between IN

components.

Defines the interfaces, states, and events that

associated with each type IN service.

Provides an environment for the fast creation of

services, independent of vendor-specific architecture

Two Types of ITU-T IN Services

Type A – no interactions of SCPs

Type B – require the interactions of several SCPs

CS-1 supports only type A




PIC (Point-in-Call)

An entry point

An exit point

DP (detection Point)

Where BCP suspended,

and message sent to

another node.

DPs Associated with

Triggers.

A trigger lists a set

of criteria and the

address of the node to

receive the message.

Null(on-hook)

Originating

Dialing

Talking

Point-in-call (PIC) 1




Entry event (on-hook)

Exit event (user,off-hook)

Entry event (switch sees off-hook)

Exit event (user hears dialtone)

Entry event (user dials 1st digit)

Exit event (user hears ringing tone)

Entry event (user ringing stopped)

Exit event (user hangs up)

DP

DP

DP

DP Origination attempt

Origination attempt authorized

Information analyzed



Detection Points & Triggers

DP can consist of one to many operations and their

associated triggers.

If satisfied, suspension of call processing, and sending of

a message to the relevant recipient node.

Dialing

Talking

DP

Featurecode

CustomizedDirectory Number

Special Service

Code

TriggerCriteria

External AIN

Host ID

*123/voice SCP-02

888-8888 SCP-01

737-1111 SCP-02

411 Adjunct



AIN OCM & TCM

The AIN Call Model

divided into two parts

OCM (Originating Call Model)

Performs call validation of the calling party

Responsible for controlling the call to its completion

TCM (Terminating Call Model)

Validates the called party

Responsible for terminating the call

An AIN operation begins with the invocation of the

OCM, and then the TCM is started based on the

satisfaction of trigger criteria.

Once the TCM starts, both the OCM and TCM operate in

parallel, although the specific instance of the OCM

may be suspended when the TCM operating.



Example of AIN Operations (1/4)

An incoming call is processed through OCM

module by executing the logic with PIC & DP.

AIN call processing Trigger 1 - XTrigger 2 - XTrigger 3 - O

Collect data for AIN message

Build (encode) AIN messageSend it to SCP

Suspend call Processing

Invoke the trigger logic

1. SSP receives info

(dialed number)

2. It executes the PICs

until info analyzed DP

reach

3. Invokes the trigger

logic

4. Various trigger criteria

are analyzed, and

trigger 3 criteria are

satisfied.

CallingParty

1

2

3 4

OCM in SSP




If trigger criteria satisfied, the TCAP query msg

is sent to the relevant SCP.






5. Based on satisfying the

trigger 3 criteria, SSP

assembles the required

info to build a query

message

6. This message is coded

into the SS7 TCAP

message, and sent to the

relevant SCP

7. SSP suspends call

processing

CallingParty

1

2

3 4

Decode AIN message The relevant

SCP

5

6

7

Sends TCAPto SCP




The operations at the SCP are straightforward.

Decode AIN message

Direct to service_logic

Service_logicGenerates info.

Build (encode) infoInto AIN message

Decode AIN message

Resume callprocessing

SS7 TCAP Message

8

9

10

11

8. SCP decode the TCAP Msg

9. Executes the specific

software module to serve the

query

10. The module generates the

parameters to create the

response

11. Sends the TCAP msg to SSP




When the response arrives at the SSP, the

suspended call is activated.





Decode AIN message


Instruct SSP where to activate the call processing


12. The msg is decoded,

which may entail the

execution of other

actions. The info

instructs the SSP where

it should begin the

activation of the call

processing.

13. It may resume

processing at a

different PIC.12

13



Example of AIN Operations

The call model defines the exchange of info

between an SSP and an SCP.





Decode AIN message

Direct to service_logic

Service_logicGenerates info.

Build (encode) infoInto AIN message

Decode AIN message


SS7 TCAP MessageInstruct SSP where to activate the call processing


1

2

3 4

5

6

7

8

9

10

11

12

13



OCM of Bellcore AIN (1/2)

OCM (Originating Call model)

Null

Authorizing orig attempt

Collecting info

Analyzing info

Selecting route

Authorizing call setup

Call processing

Origination attempt

Info collected

Info analyzed

Network busy

Disconnect Exception NULL line/trunk interface idle (no

call exists), switch provides

supervision.

Authorizing org attempt switch

verifies authority of the user

to place a call.

Collecting info switch collects

initial info from user.

Analyzing info switch interprets and

translates the collected info

according to the numbering plan.

Selecting route switch selects the

outgoing route.

Authorizing call setup switch checks

toll restrictions.

Call processing Notifies the

termination.



OCM of Bellcore AIN (2/2)

OCM (Originating Call model)

Null


Collecting info

Analyzing info

Selecting route

Authorizing call setup

Call processing

Origination attempt

Info collected

Info analyzed

Network busy

Disconnect Exception Origination attempt used for

situations where a message is to

be sent to the SCP as soon as

user goes off hook (for hot line

type service).

Info collected used for situations

where a message is to be sent to

the SCP unless an escape code is

dialed.

Info analyzed used for situations

where the type of digits dialed

must be ascertained before

message can be sent to SCP.

Network busy used to send message to

SCP requesting overflow routes

(where all routes known to SSP

are busy).



TCM of Bellcore AIN

TCM (Terminating Call model)

Null

Authorizing termination

Hunting facility

termination attempt

Disconnect Exception NULL line/trunk interface idle (no

call exists), switch provides

supervision.

Authorizing termination switch

verifies authority to route this

call to the termination access.

Hunting facility the busy/idle

status of the termination access

of the call is determined.

Termination attempt used for

situations where a message is to

be sent to the SCP before the

SSP attempts to terminate the

call.



Example of Bellcore OCM (1/2)

Pizza-a-Go-Go

Null


Collecting info

Analyzing info

Origination attempt

Info collected

Info analyzed

After info is collected and analyzed,

the info analyzed trigger

detection point (TDP) is reach.

Info analyzed the called digits are

compared to specific criteria

(conditions) called the

Specific_Digit_String.

The match causes the SSP to suspend the

call processing and send an

Information_Analyzed query msg

(containing the calling and called

party numbers) to the SCP.

The SCP search the database for the

record of the called party number,

correlates this number with the

calling number, and send a

Forward_DN msg back to the SSP.

The msg tells the SSP to connect the

call to the nearest Pizza-a-Go-Go

location.

SCP

Information_Analyzed

Forward_DN

OCM in Originating SSP



Example of Bellcore OCM (2/2)

Activate “do not disturb feature”

Null


Collecting info

Analyzing info

Origination attempt

Info collected

Info analyzed

The AIN subscriber goes off-hook and dials

the activation digits.

Info analyzed discovers that the caller

subscribes to a trigger at the TDP.

Compares the dialed digits against the

conditions in the subscriber AIN

trigger.

The match causes the SSP to suspend call

processing and send an

Information_Analyzed query msg

(containing the calling number and

dialed digits) to the SCP.

The SCP uses the DN to access the

subscriber’s records and marks the do

not disturb service as active.

The SCP send a Send_to_resource msg that

instructs the SSP to inform the user

of the feature activation with a tone

or an announcement (IP).

SCP

Information_Analyzed

Send_to_resource

OCM in Originating SSP



Example of Bellcore TCM (1/2)

Pass call through

Null

Authorizing termination

Hunting facility

termination attempt

TCM in Terminating SSP

SCP

Termination_attemp

Authorized_termination

The SSP (as terminating SSP for the call)

recognizes the terminating line is

marked as an AIN subscriber.

Termination_attempt the SSP suspends call

processing and sends an

Termination_Attempt query msg

(containing the calling DN and the

called digits) to the SCP.

The SCP uses the called DN to access the

subscriber’s control records where it

is ascertained that the feature is

active. In addition, the associated

subscriber list, pertaining to pass-

through calls, is checked and a match

is found on the calling DN.

The SCP send a authorized_termination msg

that instructs the SSP to complete the

call.

The SSP connects this caller to the AIN

subscriber.



Example of Bellcore TCM (2/2)

Authorize call termination

Null

termination attempt

TCM in Terminating SSP

SCP

Termination_attemp

Send_to_resource

Termination_attempt as before the SSP sends

an Termination_Attempt query msg to

the SCP. However, the calling number

is not stored in the subscriber’s

control record. The SCP create a

send_to_resource msg that directs the

SSP to play an announcement to the

caller & to collect additional digits.

SSP connects the call to IP that is

responsible for playing this

announcement and collecting collecting

the additional digits. Next, the IP

send a report to the SSP.

SSP sends the additional digits to the SCP in a

resource_clear msg. The SCP analyzes it, and discovers that the calling party dialed an authorization code.

The SCP send a authorized_termination msg

to the SSP.

IP Play this announcement Collect the additional digits

Resource_clear

Authorized_termination



Call Model at Switches

The switch serving the

calling/called party

executes most of the

OCM/TCM logic.

SSF

SCF

OCM TCM

calling party called party

trigger trigger

SSF

SCF

OCM TCM

calling party

trigger trigger

SSF

SCF

OCM TCM

called party

trigger trigger



Basic Call State Model

BCSM Half Call Concept O-BCSM (Originating BCSM)~OCM

T-BCSM (Terminating BCSM)~TCM

Point In Call (PIC) state

Detection Point (DP) Implementation of point of

initiation POI defined at GFP

Hand over control to the SCF

A DP can be armed/disarmed in

order to notify an IN service

logic instance.

Arming mechanism:

Static & Dynamic SSF

SCF

O-BCSM T-BCSM

calling party called party

trigger trigger

DPa

PICi

DPb

PICj

event m..

event n

exit eventsare shownon line

BCSMTransition



DP Arming Mechanism

Arming Mechanism Two kinds of service requested

Trigger detection points (TDPs) – Static

Set statically at the time of deployment of a service

or when a user subscribes to it

Event detection points (EDPs) – Dynamic

Set dynamically by service logic during the course

of a call

Two kinds of actions

Request

Suspends call processing

Notification

Continues without waiting for a response

DP Action: TDP-R, TDP-N, EDP-R, EDP-N



Detection Point Processing

Four types: TDP-R, TDP-N, EDP-R, EDP-N

CCF SSF SCFInterface Interface

Basic Call Process(PIC i)

PIC i+1

PIC i+j

DP

DP

DP

DP

DP Processing-Traffic Management-Trigger Criteria-Feature Interaction-Message Formulation

Service Logic

TDP-NTrigger

Notification

TDP-RTrigger Request

InstructionsResponding Instructions &

Request for EDP-R

Perform Instructions

Arm EDP-R

Responding Instructions &Request for EDP-N

EventRequest

Instructions

Arm EDP-N

EDP-R

EDP-N

Event Notification



Service Example: AAB (1/2)

Network Architecture (in Physical Plane)

The automatic alternative billing (AAB) service

allows the user to make a call from any

telephone and charge the call to an account

specific to the service.

SSP

STP

SCP

SSP

STP

SCP

IP

The Calling Party The Called Party

Dial060 (access code)850689 (account #)123456 (PIN)912333 (destination)

850687 xxxxxx 400

850688 xxxxxx 200

850689 123456 500

912333

SDP



Service Example: AAB (2/2)

Call Flow in Distributed Function Plane

Collect Info

Analyze_Info

2

3

1

Analyzed_Info

Routing & Alerting

NULL & Auth._Orig._Att.

7

O_Active

SDFSCFSRFCCF/SSF

Initial DPReq. Instr.

Connect_To_Resource

Setup_Resp

Setup

Collected_UI

Prompt_Collect

Query_Resp

Query

Disc_Fwd_Conn.

Apply_Chg_Report

Disconnect

Furn_Chg_Info

Connect

Apply_Chg

Query_Resp

Query



Outline



SS7 Architecture

SS7 Protocol Suite


What is IN ?

IN Call Model


ITU-T IN Call Model




Revisions

AIN 0.1

Bellcore TR-NWT-001284

Most widely-used implementation

Modified in 1992

AIN 0.2

1996 Bellcore AIN Release – No longer used

AINGR

The latest revision

AIN Generic Requirement: Switching Systems

GR-1298-CORE, Issue 3, July 1996

Revision 1, November 1996



Bellcore AIN Summary

AIN defines

The detailed operations of advanced intelligent

networks

Based on Half-call model

Originating BCM, Terminating BCM

Basic call model defines

Detection points

Triggers

Points in call

Messages that flow between the SSP and SCP



Bellcore AIN 0.1 (1/3)

Overview

SSP recognizes a call that requires AIN processing by

an SCP but not make any assumptions about the service

that is to be provided

SSP temporarily suspends the call processing and

sends a query to SCP

SCP provides the SSP with info about how to continue

the processing of the call

Bellcore basic call model

Originating BCM – Figure 6-1

Terminating BCM – Figure 6-2

PICs - Table 6-1

TDPs – Table 6-2




Query

SSP sends a query to SCP over an SS7 channel

Must be sent as a TCAP query message

Query messages correspond to TDPs

Caller Interaction

After receiving SSP query message, SCP may send

back to SSP a TCAP conversation message

Prompts SSP to collect additional info from the

caller, i.e., DTMF

SSP returns the info back to SCP in a TCAP

conversation package message




Trigger Activation & Deactivation

SCP can request SSP to activate or deactivate certain

triggers by sending a TCAP query or conversation

package message

SSP must respond with either a TCAP response or a

TCAP conversation package message that indicates if

the request was successful

SCP Response

SCP response provides info about how to continue the

processing of the call

Can also indicate that it wishes to be notified when

the call ends (notify with unidirectional message)

SCP may also send SSP a TCAP query message which

directs it to monitor certain facilities; SSP must

report the state of these facilities using a TCAP

conversation or response message.



AIN 0.1 Basic Call Model

Feature Request

O_Mid_Call T_Mid_Call

T_Term Seized

11. T_Null

14. Present Call

Term. Attempt

Term. Reso. Available

Exception

12. Authorizing Termination

Term. Auth.

13. Select Facility

Term. Denied

T_Busy

Presentation Failure

15. T_AlertingT_No Answer

T_Answer

16. T_Active

T_Disconnect

17. T_Disconnect

T_Disconnect Complete

Called party reconnected

T_Abandon &T_Calling PartyDisconnect

1. O_Null

4. Analyze Info

5. Select Route

Orig. Attempt

Info. Collected

Info. Analyzed

Network Busy

Exception

2. Authorizing Orig. Attempt

Orig. Attempt Auth.

3. Collect Info

Route Selected

Orig. Denied

Collect Timeout

Invalid Info

6. Authorize Call SetupAuth. Failure

Orig. Authorized

7. Send CallO_Called_Party Busy

O_Term Seized

8. O_AlertingCleared

O_Answer

9. O_Active

Cleared

10. O_Disconnect

O_Disconnect Complete

O_Abandon &O_Called PartyDisconnect SS7 Failure Occurs



Bellcore AIN 0.2

Capabilities beyond AIN 0.1

Triggering

Four new triggers, …

Querying

New query message to support new triggers

Parameters added to some messages in AIN 0.1

Others

Procedures added to align with ITU-T CS-1 release

Provides IP interface

Automatic message accounting (AMA) functions

added for more statistics on call durations and no

response



Bellcore AINGR

New Capabilities Service Data Function (SDF)

Provides the ability for SCP/adjunct to access data associated with customers

Create-Call Function

Provides the ability for SCP/adjunct to create a call

A new message Create_Call is sent from SCP/adjunct to SSP

Others

Includes Additional AMA operations

Enhanced call party handling

Remote access capabilities

Aligned with ITU-T CS-2, a subset of CS-2



AINGR Basic Call Model

O_Feature Request

O_Mid_CallT_Mid_Call

Call Accepted

11. T_Null

14. Present Call

Term. Attempt

Term. Reso. Available

Exception

12. Authorizing Termination

Call Presented

13. Select Facility

Term. Denied

T_Busy

Call Rejected

15. T_AlertingT_No Answer

T_Answer

16. T_Active

T_Suspended

17. T_Suspended

Called party reconnected

T_Abandon

1. O_Null

4. Analyze Info

5. Select Route

Orig. Attempt

Info. Collected

Info. Analyzed

Network Busy

Exception

2. Authorizing Orig. Attempt

Orig. Attempt Auth.

3. Collect Info

Route Selected

Orig. Denied

Collect Timeout

Invalid Info

6. Authorize Call SetupAuth. Failure

Call Setup Auth.

7. Send CallO_Called_Party Busy

O_Term Seized

8. O_AlertingO_No_Answer

O_Answer

9. O_Active

O_Suspended

10. O_Suspended

O_Abandon

O_Disconnect

T_Feature_Requestl

SS7 Failure Occurs



Outline



SS7 Architecture

SS7 Protocol Suite


What is IN ?

IN Call Model


ITU-T IN Call Model




Description

Examination of basic call state model (BCSM)

Description of each PIC as did in Bellcore AIN

How the BCSM is used in CS-1

User operations in relation to the CS-1 BCSM

Interactions between the CS-1 O-BCSM & T-BCSM



ITU-T BCSM (1/3)

ITU-T BCSM

Figures 7-1 & 7-2 depict the O-BCSM & T-BCSM

Quite similar to its counterpart,

Bellcore AIN 0.1 (Figures 6-1 & 6-2)

Table 7-1 (PICs for ITU-T, similar to Table 6-1)



ITU-T BCSM (2/3)



ITU-T BCSM (3/3)



ITU-T CS-1 BCSM (1/3)

CS-1 Call Model

CS-1 O-BCSM in Figure 7-3

CS-1 T-BCSM in Figure 7-4

Alter BCSM for CS-1 (pp.124~127)



User Interaction to BCSMs

Assumption

The originating & terminating users are

communicating with the network with an ISDN

interface, and the Q.931 protocol

Appendix E (Figure E-1, p.195) provides a brief

overview of the Q.931 messages used

Originating User Interaction with O-BCSM

Figure E-1(p.195) & Figure 7-5

Terminating User Interaction with T-BCSM

Figure E-1(p.195) & Figure 7-6



Q.931 for ISDN Connection



User Interaction with O-BCSM



User Interaction with T-BCSM



Interactions betw. BCSMs

Figure 7-7

Shows interactions that occur between the

originate and terminate BCSMs

Combined with user interaction with BCSM

Figures 7-5 & 7-6

The call setup information flow

O-user ~ O-BCSM ~ T-BCSM ~ T-user

Q.931 – SS7 ISUP – Q.931



Interaction between BCSMs



Outline



SS7 Architecture

SS7 Protocol Suite


What is IN ?

IN Call Model


ITU-T IN Call Model




CS-1 Limitations

Limitations of CS-1

CS-1 assumes that the network is controlled by

a single operator

No internetworking service

CS-1 does not offer sufficient features for

multiparty & multimedia comm.

CS-1 has only limited features for mobility

User authentication, location updating

CS-2 Target

Lift some of these limitations

Maintain backward compatible with CS-1



CS-2: CS-1 extension

The extension to CS-1

The service logic and data can be distributed, and

services can be controlled across operator domains.

Handles call more than two parties

One service logic instance in the SCF can control more than one BCSM at a time.

Allows user interactions to take place outside the

context of a call

Create a basic call-unrelated state model (BCUSM) for BCUP in addition to BCSM for BCP

Allows user interactions to use out-channel signaling

connections (not related to the call)

GSM short message

Generalizes the service-creation concept

Refine the concept of SIBs and make it recursive



CS-2 BCSM

Many PICs have remained the same, but some were split up in finer PICs

O_Null&Authorize_Origination_Attempt

Routing&Alerting

Select_Facility&Present_Call

2 new PICs

O_Suspended

T_Suspended

These new PICs represent a half call that is

neither active nor released

When a party is put on hold

New DPs



CS-2 O-BCSM

Source: ITU-T Q.1224



CS-2 T-BCSM

Source: ITU-T Q.1224



CS-2 – Intra Switch BCSM



CS-2 Basic CU State Model

Idle and AuthorizeActivation/Association Req.

Active Componentreceived

Activation receivedand authorized

Release

Association releaserequested

Activationfailed

Released

Basic Call-Unrelated State Model

Represents user interactions taking place

outside the context of a call.



CS-2 Call Party Handling

in CS-1

It was only possible to setup and release a

call between two parties

The call and the connection set up as the

result of the call were the same thing

in CS-2

It is possible to manipulate the individual

parties in a call and their connections

Within the context of a call, CS-2 lets you add

or drop call parties and connections

The addition of CPH makes CS-2 much more

complex than CS-1

Not so apparent at GFP level (only Split & Join SIBs)



CS-3

CS-3 should be regarded more as an updated version of

CS-2 than as a new capability set Many of refinements and corrections to the CS-2

during the specification of CS-3

CS-3 Features Does not introduce new concepts in the INCM

no documents Q.1232~Q.1235 (SP, GFP, DFP, and PP)

Does improve CS-2 facilities for interworking

with mobile network, broad/narrow-band ISDN, Internet

Most important

redefinition of the INAP protocol in Q.1238

New facilities

number portability

Multiple point of control (single point in CS-2)

more work on Conflict is still needed



New Additions in CS-4 CS-4

Voice, video, multimedia, data communications

Possibly involving multiple parties

Possibly involving mobile terminals

Using packet-based transmission rather than switched

connections

The only part of the INCM updated in CS-4 is the DFP (Q.1244)

The most important new features in CS-4 is the support for communication over the Internet

CS-4 DFP introduces the session manager (SM) for handling

voice and multimedia sessions on the Internet (using H.323

or SIP)

SM look like (1) H.323 gatekeeper, or (2) SIP proxy

Integration of telephony services

PINT – set up IN calls from Web sites

SPIRITS – Internet call waiting support



Beyond CS-4

JAIN (Java APIs for Integrated Networks)

Promotes a Java framework for implementing

value-added services

Parlay

Produces interfaces for opening up network

control to third-party software

OSA (Open Service Access)

3GPP and ETSI proposed service architecture for

3G mobile networks

TINA

A complete telecom architecture built on

distributed object-oriented middleware

Mobile All-IP Networking LaboratoryDepartment of Computer Science & Information Engineering

Any Question?


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