Feature: Switch an active call to another device

[deepakjaiswal1]

Summary

Allow a user to move an in-progress call (active media session) from one device to another (e.g. from a desktop softphone to a mobile softphone) without dropping the call.

Motivation

Softphones are decoupled from any single device. A user with the same subscriber identity registered on more than one device expects to continue an ongoing call when they pick up on a different device. This is about live call continuity, not about managing registrations.

Proposed capability

• Hand off an in-progress media session (identified by mediaSessionId) from the current device to another device belonging to the same subscriber.
• The call continues uninterrupted on the target device.
• Define the behaviour of the original device's session after handover (e.g. it is released once the target device takes over).

Scope

• In scope: transferring the active media session between devices.
• Out of scope: creating, moving, or otherwise managing registrations. Each device is expected to already have its own registration; this feature operates at the call/session level only.

Open questions for the WG

• New action/operation on webrtc-call-handling referencing the existing mediaSessionId and a target device?
• How is the target device identified and selected (e.g. an existing registrationId/deviceId under the same subscriber)?
• Media continuity: is the existing media session preserved via SDP renegotiation to the new device, or re-established?
• Authorization: confirming both source and target are under the same subscriber/token context.
• Notifications to affected endpoints via webrtc-events.