SIP

Initial Filter Criteria (IFC) are used in the IMS (IP Multimedia Subsystem) architecture, specifically within the CSCF (Call Session Control Function), to route incoming sessions (like voice or video calls) and trigger services in external Application Servers (AS) based on predefined conditions. The SIP AEF also called ISC AEF is a tool to rapidly depoy tne external AS in the IMS network.

Here’s a high-level overview of how IFCs are used in the process:

• Session initiation: When an IMS-based session is initiated (such as a voice or video call), the CSCF intercepts the signaling (typically SIP messages) and looks for the Initial Filter Criteria (IFC). These criteria are defined by the HSS (Home Subscriber Server) or external entities to identify specific types of sessions (e.g., a VoLTE call or a video conference).
• IFC matching: The CSCF checks the incoming session against the IFC rules, which are conditions like caller identity, called party identity, service type, or network conditions. These filters are part of the session’s setup information and are used to determine which external Application Server (AS) should be involved in the session.
• Triggering services: If a session matches an IFC rule, the CSCF triggers a service or application in an external Application Server (AS). This could involve various services such as: Call forwarding, Video conferencing, RCS (Rich Communication Services) features
  VoLTE-specific features like supplementary services. The CSCF communicates with the AS using SIP protocol to trigger the service, passing along the necessary information to the AS to process the request.
• Execution of services: The Application Server processes the request and applies the required logic. For instance, it might decide to route a call differently, initiate a video session, or invoke a feature like call recording or voicemail. The AS then communicates back to the CSCF with instructions on how to proceed, such as modifying the session, allowing the service to proceed, or applying specific user preferences.
• Session continuation or termination: After the service has been applied (or if no service is needed), the CSCF continues processing the session, either continuing the call or terminating it, based on the service logic from the AS.

MNO (Mobile Network Operator) would most typically expose APIs to MVNOs (Mobile Virtual Network Operator) to enable better integration and interoperability between their services. By exposing APIs, MNO can allow MVNO to access its network resources, such as billing, authentication, provisioning, and customer care. This can benefit both parties by reducing operational costs, improving customer satisfaction, and creating new revenue streams. For example, MVNO can offer customized plans and features to its subscribers using MNO’s network infrastructure, while MNO can leverage MVNO’s market reach and brand loyalty.