Charging Triggering Function for SIP Session Modifications
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Solution Overview
Problem
Current charging systems in IP Multimedia Subsystems, such as those in UMTS networks, lack full traceability of unsuccessful SDP negotiations due to the absence of charging information for non-2xx SIP responses, which are not considered in 3GPP TS 32.260, thereby preventing comprehensive charging and usage tracking.
Innovation Solution
Implementing a method and apparatus within the telecommunications network to send charging information to a charging function upon receiving an unsuccessful SIP response, specifically a non-2xx SIP response, allowing for correlation with ongoing charging sessions using session identifiers, enabling both online and offline charging mechanisms to account for rejected SIP requests like SIP re-INVITE and SIP UPDATE operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charging information is not sent for unsuccessful SIP responses (non-2xx), then the charging system operates according to existing standards, but charging traceability is incomplete and billing accuracy is reduced
Solution Approach 1:
The charging information is segmented into different types based on SIP response codes. Successful responses (2xx) continue to be handled by existing charging mechanisms, while unsuccessful responses (non-2xx) are routed to a new charging data function. This segmentation allows the system to maintain existing operations while adding targeted functionality for incomplete charging scenarios.
Solution Approach 2:
A charging triggering function acts as an intermediary between SIP signaling and charging functions. This intermediary intercepts SIP responses, determines whether they are successful or unsuccessful, and routes them to appropriate charging handlers. The intermediary enables comprehensive charging traceability without requiring modifications to the core SIP protocol or existing charging systems.
2Reliability
If charging information is sent for all SIP responses including unsuccessful ones, then complete billing coverage is achieved, but additional charging processing overhead is introduced
Solution Approach 1:
The charging triggering function performs preliminary classification of SIP responses before they reach charging functions. By pre-identifying unsuccessful responses and routing them appropriately, the system avoids unnecessary processing of already-handled successful responses, thereby maintaining processing efficiency while ensuring comprehensive billing coverage.
Solution Approach 2:
Different charging processing qualities are applied to different SIP response types. Successful responses receive standard charging processing, while unsuccessful responses receive enhanced processing through the charging data function. This local quality differentiation ensures billing accuracy for critical cases without uniformly increasing processing overhead for all responses.
3Loss of information
If non-2xx SIP responses are ignored in charging, then the system follows current 3GPP specifications, but traceability of rejected session modifications is lost
Solution Approach 1:
The charging information for unsuccessful SIP responses is extracted from the main SIP signaling flow and handled separately by a dedicated charging data function. This extraction ensures that information about rejected session modifications is captured and preserved without complicating the main charging system implementation, as it uses a separate, specialized handling path.
Data Source
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AI summary
A method is disclosed for use in a telecommunications network in which that makes use of the Session Initiation Protocol (SIP). The method comprises sending (S2) charging information to a charging function (20) of the network in response to the receipt (S1) of an unsuccessful SIP response to a SIP request. The SIP request may relate to a request to modify an established SIP session. The SIP request may relate to a request to modify the media of an established SIP session, for example by adding, removing or changing the media. The SIP request may be a SIP UPDATE request. The SIP request may be a SIP re-INVITE request. The unsuccessful SIP response may be a non-2xx SIP final response. The network may be a Universal Mobile Telecommunications System comprising an IP Multimedia Subsystem, IMS. The charging function (20) may comprise an IMS Charging Data Function, CDF, or an IMS Online Charging System, OCS. The method may be performed by a Charging Triggering Function of the network.