What is SPT Service point trigger

Unveiling SPT: The Trigger Mechanism in IMS Routing

Within the realm of IP Multimedia Subsystem (IMS), a key technology for voice and video calls over internet protocol (VoIP/VoIP), Service Point Trigger (SPT) plays a crucial role in call routing. It acts as a set of conditional statements that define when a specific route or service application server should be chosen for an incoming session. Here's a detailed explanation of SPTs and their functionality in IMS networks:

Core Functionality:

• An IMS network utilizes Trigger Points (TPs) to route incoming sessions (calls, messages) to the appropriate service application server.
• Each TP consists of one or more SPTs, which are essentially conditional statements. These statements specify criteria that the session must meet for the TP to be triggered.
• SPTs can be based on various parameters extracted from the SIP (Session Initiation Protocol) messages associated with the session, such as:
  • Request Method (e.g., INVITE for calls): Identifies the type of SIP request.
  • Request URI: Specifies the destination of the call (phone number, SIP address).
  • SIP Headers: Contain additional information like caller ID, call type (voice, video), or presence information.
  • Session Case: Distinguishes between Mobile Originated (MO) or Mobile Terminated (MT) calls.

Logical Operators:

• Multiple SPTs within a TP can be combined using logical operators (AND, OR) to create more complex routing rules.
• For instance, a TP might be triggered if the request method is "INVITE" (call initiation) AND the request URI matches a specific phone number prefix.

Benefits of SPTs:

• Flexible Routing: SPTs enable dynamic and flexible routing of sessions based on pre-defined criteria, allowing for efficient call routing and service delivery.
• Improved Service Delivery: By directing sessions to the appropriate service application server, SPTs ensure that calls and messages are handled by the correct service logic.
• Scalability: The modular design of TPs with SPTs allows for easy addition of new routing rules as network requirements evolve.

Technical Considerations:

• SPTs are typically defined in an XML format within IMS network configuration files.
• The specific criteria used in SPTs depend on the network operator's configuration and service offerings.
• Various network elements, like the Serving Call Session Control Function (SCSCF), are responsible for evaluating SPTs and triggering the appropriate TP based on the incoming session characteristics.

Comparison with Other Routing Mechanisms:

• Static Routing: Pre-defined routes for specific destinations, less flexible than SPT-based routing.
• Policy Routing: Routing based on broader network policies, might not offer the same level of granularity as SPTs.

Conclusion:

Service Point Trigger (SPT) serves as a cornerstone for dynamic and flexible call routing within IMS networks. By leveraging conditional statements based on SIP message parameters, SPTs ensure efficient delivery of voice, video calls, and other multimedia services to the appropriate application servers. The use of SPTs contributes to a seamless user experience for VoIP and other IMS-based communication services.