SIP Early Media Handling via Fork Detection
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Solution Overview
Problem
Current SIP standards do not effectively handle multiple provisional response messages and early media streams when calls are parallel or sequentially forked, leading to unexpected issues, particularly with simultaneous early media streams.
Innovation Solution
A communication device manages SIP INVITE messages by starting timers to detect forking, receiving and handling multiple provisional response messages, discarding unnecessary media streams, and playing local progress tones as needed to ensure proper media stream handling during call forking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If parallel forking is implemented to send SIP INVITE to multiple communication devices simultaneously, then call reachability is improved, but multiple provisional response messages and early media streams are generated causing system complexity and unexpected problems
Solution Approach 1:
The patent starts a timer immediately after sending the SIP INVITE message to detect sequential forking before it occurs. This preliminary timing mechanism allows the system to prepare for and properly handle multiple provisional response messages and early media streams by knowing when to expect them, thereby managing the complexity introduced by parallel forking.
Solution Approach 2:
The patent uses timer expiration as a feedback mechanism to detect whether sequential forking has occurred. When the timer expires without receiving a second provisional response message, the system knows the call has been sequentially forked and can appropriately manage the media streams. This feedback loop enables proper handling of multiple media streams without excessive complexity.
2Adaptability or versatility
If multiple early media streams are received from parallel forking, then more communication options are provided, but unexpected problems occur when multiple streams are played simultaneously
Solution Approach 1:
The patent extracts and identifies individual early media streams from multiple provisional response messages using SDP information. By separating and individually managing each media stream rather than handling them as a bulk group, the system can selectively play or discard specific streams, preventing the reliability issues that arise from simultaneous playback of multiple unmanaged streams.
Solution Approach 2:
The patent implements a mechanism to discard early media streams that are no longer needed based on timer expiration and call progression. When sequential forking is detected or when a call progresses to a later stage, the system discards early media streams appropriately, preventing unexpected problems from simultaneous playback while preserving necessary streams for continued communication.
3Productivity
If sequential forking is implemented to transfer calls if unanswered, then call completion rate is improved, but timing detection and media stream management become more complex
Solution Approach 1:
The patent starts a timer before sequential forking can occur to establish a time reference for detecting the forking behavior. This preliminary timing action simplifies the detection process by having a pre-established benchmark against which to measure whether sequential forking has occurred, reducing the overall timing detection complexity despite the improved call completion rate.
Data Source
AI summary
A communication device sends a Session Initiation Protocol (SIP) INVITE message to establish a call. In response, the call is forked. For example, in parallel forking, the SIP INVITE may be sent to two different communication devices. The forking causes each communication device to send at least one provisional response message. In this case, first and second SIP provisional response messages are received that include Session Description Protocol (SDP) information for a media stream. A first media stream associated with one of the first or second SIP provisional response messages is received and played. A second media stream associated with the other one of the first or second SIP provisional response messages is received within a first time period. In response to receiving the second media stream within the first time period, the first media stream is discarded and the second media stream is played.