Lawful Intercept Mediation Function Correlation Number Extension
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Solution Overview
Problem
In Lawful Intercept systems, delivering correlation information in TDM format for VoIP sessions is challenging due to the lack of provisioning of correlation information over HI3, making it difficult to correlate intercepted calls with the correct Intercept Related Information, especially when using existing Circuit Switched Monitoring Centers and networks.
Innovation Solution
The solution involves using an extension of the calling or called party number to provide the correlation number, which is inserted in an SIP call initiated by the Mediation Function to the Border Gateway Control Function, allowing correlation information to be sent over HI3 and HI2 interfaces, enabling efficient correlation without impacting the operator network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If correlation information is not provided over HI3 interface, then the existing CS MC and network infrastructure can be reused without modification, but the ability to correlate intercepted CC with correct IRI is lost
Solution Approach 1:
The correlation number is nested within the calling or called party number field of the SIP message. Instead of creating a separate correlation information field, the solution embeds the correlation number inside the existing party number structure, allowing correlation data to be transmitted without adding new interface elements or modifying the HI3 protocol structure.
Solution Approach 2:
The MF acts as an intermediary that generates and inserts the correlation number into the SIP message's party number field. This mediator function bridges the gap between the need for correlation information and the limitation of the existing HI3 interface, allowing correlation data to flow through the established protocol without direct modification.
2Reliability
If SIP-I or customization of SIP interface is used to provide correlation information, then correlation capability is achieved, but great impacts on existing core network are caused
Solution Approach 1:
The existing party number field in the SIP message is made multi-functional. It not only identifies the calling or called party but also carries the correlation number. This universal use of the field eliminates the need for separate correlation signaling mechanisms and avoids impacting the core network infrastructure.
Solution Approach 2:
The solution changes the parameter structure of the party number by adding the correlation number as an extension or additional parameter within the existing number format. This allows correlation information to be transmitted using the same SIP interface without requiring protocol customization or new interface standards.
3Ease of manufacture
If TDM format is used for CC delivery to CS MC, then cost reduction and hardware reuse are achieved, but provisioning of correlation information over HI3 is lost
Solution Approach 1:
The correlation number is extracted from the packet-switched domain and embedded into the circuit-switched compatible SIP message format. By placing the correlation number in the party number field of the SIP invitation, the solution extracts the essential correlation data and makes it compatible with TDM-based CS MC delivery without requiring PS-specific correlation mechanisms.
Data Source
AI summary
The present disclosure relates to the problem to deliver correlation information, CN, in case of CC delivery in TDM format to a Monitoring Centers, MC in a circuit switched network and achieving a minimal impact to MCs and/or no impact on the operator network at all. Said problem is solved by using the extension field of calling or called party number for providing the correlation number to a MC from a Mediation Function entity.