Crossed-Invite Session Handling via Priority Comparison
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Solution Overview
Problem
In multimedia session establishment, 'crossed-invite' situations occur when both devices attempt to set up a session with each other, leading to failed connections as both devices reject incoming invites after sending their own, due to lack of priority determination.
Innovation Solution
Implement a method at a local device to handle crossed-invites by determining the priority of incoming and outgoing session invites, canceling the lower priority invite, and presenting the higher priority invite for acceptance, using identifying information such as SIP URI or priority values assigned by the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both devices refuse incoming invites during session setup, then session conflicts are avoided, but crossed-invite situations cause session establishment to fail
Solution Approach 1:
The patent changes the parameter of invite handling by introducing priority values and timestamps. Instead of uniformly refusing all incoming invites during session setup, devices now compare priority parameters to determine which invite should be accepted, resolving the crossed-invite problem while maintaining simple operation.
Solution Approach 2:
The patent introduces an intermediary mechanism (priority comparison and timestamp evaluation) between the two devices. This intermediary logic resolves the conflict by determining which device should accept the incoming invite based on objective criteria, rather than direct peer-to-peer refusal.
2Productivity
If a device accepts any incoming invite during session setup, then session establishment succeeds, but session conflicts and ambiguity arise
Solution Approach 1:
The patent introduces priority parameters and timestamps to invites, transforming the simple accept/refuse decision into a parameter-based comparison. This allows rapid automated decision-making while ensuring reliable conflict resolution through objective priority evaluation.
3Ease of operation
If devices use standard busy message rejection, then incoming invites are refused during active session attempts, but crossed-invite situations are not distinguished from other busy scenarios
Solution Approach 1:
The patent implements feedback by having devices exchange priority information and timestamps in their invites. This feedback loop allows each device to understand whether it is in a crossed-invite situation and make appropriate decisions, preserving information that would otherwise be lost in standard busy message rejection.
Data Source
AI summary
A method and devices for handling crossed-invite situations in set-up of IP-based sessions. A local device receives an incoming session invite after sending an outgoing session invite before the outgoing session invite has been accepted. It then determines that the incoming session invite was sent by the remote device to which the outgoing session invite is also addressed. The method includes determining a remote device priority value from identifying information contained in the incoming session invite, comparing the remote device priority value with a local device priority value to determine whether the remote device or the local device is higher priority and, if the remote device is higher priority, canceling the outgoing session invite and displaying an incoming call answer screen for the incoming session invite, and if the local device is higher priority, waiting for cancelation of the incoming session invite and acceptance of the outgoing session invite.