Resuming IFC Evaluation After Request-URI Changes
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Solution Overview
Problem
The existing mechanism for handling Initial Filter Criteria (IFC) evaluation in IP Multimedia Subsystem networks interrupts the process when the Request-URI is changed by an Application Server, which is not suitable for scenarios requiring continued evaluation, such as multiple user equipment sharing or address changes between SIP and Tel URIs.
Innovation Solution
A method and apparatus for evaluating Initial Filter Criteria at a terminating Call Session Control Function that determines whether to resume IFC evaluation based on changes to the Request-Uniform Resource Identifier, using indicators like target change override, allowing continued evaluation even after URI changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the S-CSCF interrupts IFC evaluation when the Request-URI is changed by an Application Server, then the call forwarding service can alter the destination address, but the IFC evaluation cannot continue for scenarios requiring further service handling
Solution Approach 1:
The patent introduces a dynamic mechanism where the S-CSCF can selectively resume IFC evaluation based on the type of Request-URI change detected. When the new Request-URI still belongs to the same user (e.g., different endpoint or address format), evaluation resumes. When it points to a different user, evaluation stops. This dynamic decision-making resolves the contradiction by adapting the evaluation behavior to the specific scenario.
Solution Approach 2:
The patent changes the parameter being monitored from simply 'Request-URI modification' to 'Request-URI modification type'. By analyzing whether the change is within the same user's address space or to a different user, the system determines the appropriate action. This parameter refinement allows the system to distinguish between call forwarding (stop evaluation) and endpoint selection/address format conversion (resume evaluation).
2Adaptability or versatility
If the S-CSCF continues IFC evaluation after Request-URI changes, then multi-UE scenarios and address conversions can be handled, but the call forwarding service mechanism becomes less reliable
Solution Approach 1:
The patent applies local quality by making the IFC evaluation resumption behavior specific to the type of Request-URI change. Instead of a uniform approach, the system evaluates the local context of the URI change (same user vs. different user) and applies different rules. This allows call forwarding to reliably stop evaluation while multi-UE scenarios can resume evaluation, resolving the contradiction through localized rule application.
Solution Approach 2:
The patent segments the Request-URI change detection into two distinct cases: changes within the same user's address space and changes to a different user. By segmenting the detection logic, the system can apply different evaluation resumption rules to each segment, ensuring call forwarding reliability while enabling multi-UE scenario support.
3Measurement precision
If the S-CSCF checks all IFCs in priority order, then service selection accuracy is improved, but the message processing time increases
Solution Approach 1:
The patent implements skipping by allowing the S-CSCF to interrupt IFC evaluation when a Request-URI change indicates call forwarding. Instead of checking all remaining IFCs in priority order, the system rushes through the remaining checks when the change type indicates the user's intent to forward the call, thereby reducing unnecessary processing time while maintaining accuracy for cases requiring full evaluation.
Data Source
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AI summary
A method of evaluating Initial Filter Criteria at a terminating Call Session Control Function in an IP Multimedia Subsystem network. A Session Initiation Protocol comprising a destination Uniform Resource Identifier is received. As a result of applying an Initial Filter Criterion to the message, the message is sent to an Application Server evaluation of further Initial Filter Criteria is suspended. The returned message is received from the Application Server, and a determination is made of whether the Uniform Resource Identifier has been changed by the Application Server. If the Uniform Resource Identifier has been changed by the Application Server, then a determination of whether to resume evaluation of Initial Filter Criteria is made, and if the Uniform Resource Identifier has not been changed by the Application Server, then resuming evaluation of Initial Filter Criteria.