Intelligent Network - SS7 Architecture

SS7 Architecture

The main concepts (functional view) surrounding IN services or architecture are connected with SS7 architecture:

• Service Switching Function (SSF) or Service Switching Point (SSP) This is co-located with the telephone exchange itself, and acts as the trigger point for further services to be invoked during a call. The SSP implements the Basic Call State Machine (BCSM) which is a Finite state machine that represents an abstract view of a call from beginning to end (off hook, dialing, answer, no answer, busy, hang up, etc.). As each state is traversed, the exchange encounters Detection Points (DPs) at which the SSP may invoke a query to the SCP to wait for further instructions on how to proceed. This query is usually called a trigger. Trigger criteria are defined by the operator and might include the subscriber calling number or the dialed number. The SSF is responsible for entertaining calls requiring value added services.

• Service Control Function (SCF) or Service Control Point (SCP) This is a separate set of platforms that receive queries from the SSP. The SCP contains service logic which implements the behaviour desired by the operator, i.e., the services. During service logic processing, additional data required to process the call may be obtained from the SDF. The logic on the SCP is created using the SCE.

• Service Data Function (SDF) or Service Data Point (SDP) This is a database that contains additional subscriber data, or other data required to process a call. For example, the subscribers prepaid credit which is remaining may be an item stored in the SDF to be queried in real time during the call. The SDF may be a separate platform, or is sometimes co-located with the SCP.

• Service Management Function (SMF) or Service Management Point (SMP) This is a platform or cluster of platforms that operators use to monitor and manage the IN services. It contains the management database which stores the services configuration, collects the statistics and alarms, and stores the Call Data Reports and Event Data Reports.

• Service Creation Environment (SCE) This is the development environment used to create the services present on the SCP. Although the standards permit any type of environment, it is fairly rare to see low level languages like C used. Instead, proprietary graphical languages have been used to enable telecom engineers to create services directly. The languages usually belong to 4G languages, the user can use Graphical Interface to manipulate between different functions to formulate a service.

• Specialized Resource Function (SRF) or Intelligent Peripheral (IP) This is a node which can connect to both the SSP and the SCP and delivers additional special resources into the call, mostly related to voice data, for example play voice announcements or collect DTMF tones from the user.