SIP Reinvite Mechanism for Call Routing and Media Parameter Updates
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Solution Overview
Problem
Current network switches in IP communications systems reuse outdated media parameters during call routing, leading to inefficiencies in bandwidth usage and call quality, especially in call forking and call progress tones applications, violating the offer-answer model and wasting wire and processing bandwidth.
Innovation Solution
Implementing a 'double Reinvite' mechanism that sends a SIP Reinvite command with no SDP to one endpoint, reestablishing media negotiation by querying new media parameters, and then sending an official offer to the second endpoint, maintaining media streams without violating RFC 3264, and allowing ring-back connections without SIP transfer methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If network switches reuse originally sent media parameters during call routing, then call routing can be performed without re-negotiation, but the media parameters may no longer be valid on the connection or may not provide the best bandwidth solution
Solution Approach 1:
The system changes the media parameters by sending a Reinvite message with updated SDP offer containing new media parameters (codecs, bandwidth, ports) to the called party, who responds with an answer. This ensures the media parameters are current and optimized for the connection while maintaining call routing efficiency through automated negotiation.
2Adaptability or versatility
If SIP transfer methods are used to route calls to different endpoints, then call destination can be changed, but SIP transfer methods are not allowed on the wire and require patch-up of audio
Solution Approach 1:
The invention extracts the media parameter negotiation from the SIP transfer process by using a Reinvite message with SDP offer-answer model. This separates the media negotiation function from the complex SIP transfer mechanisms, allowing call destination changes without requiring SIP transfer methods on the wire or audio patch-up operations.
3Adaptability or versatility
If media streams are switched during call to reach new endpoint, then call can be redirected, but wire and processing bandwidth is wasted due to terminating and resending media
Solution Approach 1:
The system performs preliminary media parameter negotiation by sending a Reinvite message with SDP offer before the call is fully redirected. This allows the new endpoint to be prepared with correct media parameters in advance, enabling seamless call redirection without terminating and resending media streams, thus conserving bandwidth and processing resources.
Data Source
AI summary
A communications session call is established between first and second call devices. A SIP Reinvite command is sent to the second call device without any SDP media parameters to gain new and current media parameters. The second call device acknowledges the Reinvite command as corresponding to the first SDP offer with new and current media parameters. A third call device is sent a SIP Reinvite command as a second SDP offer using new and current media parameters. The third call device acknowledges the SIP Reinvite command as corresponding to the first SDP answer to the first SDP offer. The second call device acknowledges as a second SDP answer to the second SDP offer. The call with the first call device is terminated to change the destination of the call and maintaining any media stream between the second and third call devices.