SIP Refer Call Correlation via Global Call Identifier
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Solution Overview
Problem
Private Branch eXchange (PBX) systems struggle to recognize and correlate calls established using the Session Initiation Protocol (SIP) refer method, leading to difficulties in tracking call efficiency and customer service performance metrics, as new calls appear as separate requests rather than continuations of original calls.
Innovation Solution
A network device attaches a header with a Global Call Identifier (GCID) to outgoing refer messages and modifies table entries to correlate incoming invite messages with original calls, enabling the PBX to identify and link transferred calls to their original counterparts, thereby updating databases to track customer issues and generate performance statistics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the SIP refer method is used to transfer calls, then call transfer functionality is enabled, but the PBX cannot recognize and correlate transferred calls with original calls
Solution Approach 1:
The system performs preliminary action by attaching a Global Call Identifier (GCID) header to the refer message before it is sent to the transferee. This header contains the original call's identifier, allowing the PBX to pre-establish the correlation context before the actual call transfer completes, ensuring the transferred call is recognized as a continuation of the original call.
Solution Approach 2:
The Global Call Identifier (GCID) header acts as an intermediary carrier that transmits call correlation information between the transferor and transferee. This intermediary element bridges the information gap that would otherwise exist between the original call and the transferred call, enabling the PBX to correlate them properly.
2Adaptability or versatility
If call transfer is implemented using SIP refer, then operational flexibility is improved, but tracking call efficiency and customer service performance becomes difficult
Solution Approach 1:
The system implements feedback by having the PBX monitor incoming invite messages and use the GCID header information to correlate transferred calls with their original calls. This feedback mechanism allows the PBX to track call efficiency and customer service performance metrics accurately, resolving the measurement precision issue while maintaining operational flexibility.
3Adaptability or versatility
If the PBX monitors incoming invite messages without GCID headers, then compatibility with existing systems is maintained, but call correlation capability is lost
Solution Approach 1:
The system applies partial action by selectively adding GCID headers only to refer messages that require call correlation, rather than modifying all SIP messages universally. This approach maintains compatibility with existing systems that don't support the extended header format while enabling call correlation capability where needed, balancing both requirements.
Data Source
AI summary
In one embodiment, a network device attaches a header including an identifier for an original call to an outgoing refer message and may also modify a table entry for a consultative call to include the identifier. The network device then monitors incoming invite messages for a header containing the identifier and observes that an incoming invite message containing the header correlates to the original call. When a header is not included, the network device extracts information from the incoming invite messages and compares the extracted information to the modified table entry to correlate one of the incoming invite messages to the original call.