SCF SSF CommunicationService Program
CTRTYPE BLOCK
3.20 Appendix Description of SSF interfacing APT Subsystems
Group Switching Subsystem (GSS)
The Group Switching Subsystem (GSS) performs switching between time multiplexed buses and sets up paths between telecommunications devices. It also provides timing signals for its own synchronisation and for network synchronisation.
The GSS consists of both hardware and software, and it works with other subsystems to switch calls of different types between subscribers - for example local, trunk and transit calls.
The GSS functions are to:
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Select, connect and disconnect speech or signal paths through the Group Switch.•
Supervise disturbance in the hardware.•
Supervise the traffic.•
Supervise the PCM links to the Group Switch•
Maintain a stable clock frequency. This clock frequency is used for synchronisation in the Group Switch, and can also be used to synchro- nise the network.Charging Subsystem (CHS)
Charging is a key function since it is the means of translating network traf- fic into revenue and cost. It is essential that accurate and detailed charging data is available for billing and statistical purposes.
Within AXE, charging and accounting are controlled by the Charging Sub- system (CHS) which is responsible for:
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Basic Charging Function - CHS provides the data to charge subscribers for their calls.•
Accounting - CHS provides the data to settle accounts between cooper- ating network operators (national or international)•
Additional Services - these services are in addition to ‘normal’ call charging. For example, the charging for user-to-user data transfer in signalling messages sent over the D-channel.Traffic Control Subsystem (TCS)
The Traffic Control Subsystem (TCS) is the central traffic control subsys- tem in AXE. TCS consists of software only.
The main TCS functions are divided into:
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Basic Core Functions, including basic call set-up, call supervision and release, and storing of subscriber categories.•
Analysis Functions, including B-number, A-number and analysis to determine which ISDN service is requested.•
Administrative Functions, performs administration tasks associated with the Analysis functions. For example, they include the commands for changing, handling and printing data in the B-number analysis tables in the DA block.•
Service Functions, including semi-permanent connections and Trunk offering which allows the operator to get into speech position with a busy subscriber to offer an incoming call.Common Channel Signalling Subsystem (CCS)
The Common Channel Signalling Subsystem (CCS) contains both hard- ware and software. Its main function is to handle CCS7 signalling.
CCS7 speeds up call set-up time and improves trunk efficiency by sending the signalling information for numerous speech circuits on a few high- speed signalling links. CCS7provides the signalling backbone for IN.
Operation and Maintenance Subsystem (OMS)
An AXE exchange is provided with operation and maintenance functions that guarantee a high quality of service OMS is implemented in central and regional software, as well as some hardware.
The main OMS functions are:
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Supervision, which continually supervises the trunk and subscriber lines. if a fault or a disturbance is detected, an alarm is generated.•
Test and Fault Localisation, this contains diagnostic and test functions,which are used in conjunction with alarms and reports to localise faults, both internal and external to the exchange.
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Administration, enables exchange personal to change exchange data, connect and disconnect subscribers and services.•
Statistics, is used for measurement and printout of data such as the vol- ume and type of traffic flowing through the exchange. This information is important for the planning and configuration of exchanges.Statistics and Traffic Measurement Subsystem (STS)
The Statistics and Traffic Measurement Subsystem (STS) collects, stores, process and presents measurement data (statistics) on, for example, traffic flow and network performance. STS is implemented in the Support Proc- essor (SP) but belongs to the APT system. STS consists of software only The following operations are performed by STS:
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Counters in the traffic system are read and data collected at specific intervals.•
At defined intervals report programs read data form the measurement database and produce easy-to-read reports for network management/ exchange personnel.3.21 Module Summary
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SES is divided into two functional elements, 1. Service Switching Function (SSF) 2. Service Control Function (SCF).•
The SSF provides the set of capabilities required for interaction between the Call Control Function (CCF) and the Service Control Function (SCF) in order to access and process services for subscribers in an Intelligent Network.•
The Service Control function controls the processing of IN services. It contains the service programs, which constitutes the IN services, and provides for the execution of these.•
The IN Service Trigger (IST) is a result of B-number analysis in TCS which, if present, indicates that the call is to be routed to the service switching function (SSF).•
Trigger Detection Points are points in the basic call process where an IN service could be invoked, starting by sending the operation Ini- tialDP.•
Dialogue Control controls how dialogues are initiated, maintained, closed and coordinated by SSF to the SCF.•
IN Call Control is responsible for the interface to the call processing functions of the exchange.3.22 Abbreviations
AD Assisting Dialogue
BCD Binary Coded Decimal
BCSM Basic Call State Model
CID Call Instance Data
CS1 Capability Set
CS1+ Ericsson superset of CS1 CTRTYPE Control type
DM Data Module
ETSI European Telecommunications Standards Institute
FE Functional Entity
HD Handoff Dialogue
ID Initiating Dialogue
IN Intelligent Network
INAP IN Application Protocol
INM IN Management interface
INPM IN Protocol Manager
IOG Input Output Group
IP Intelligent Peripheral
ISDN Integrated Services Digital Network
LLA Low Level Action
MCS Man-machine Communication Subsystem
NCRD Non Call Related Dialogue
OCS Open Communications Subsystem
PHF Protocol Handler Function
SA Service Administrator
SC Service Customer
SCF Service Control Function
SCEF Service Creation Environment Function
SDF Service Data Function
SDFD SDF Dialogue
SES SErvice provision Subsystem
SIB Service Independent Building Block
SDM Service Data Module
SL Service Logic
SLM Service Logic Module
SLP Service Logic Program
SLPI Service Logic Program Instance
SMAS Service Management Application System
SMF Service Management Function
SDF Service Data Function
SRF Specialized Resources Function SSCP Service Switching and Control Point
SSF Service Switching Function
SSP Service Switching Point
SSI Service Script Interpreter