What causes an ICE Connection State to transition from Failed to Connected?

[Rahul Behera]

According to the ICE States listed at the W3C Spec, it's possible for an ICE Connection State to go from the failed state to the disconnected state. What could possibly cause this to happen?

In our tests we are unable to reproduce this. Any suggestions would be helpful

[Christoffer Jansson]

Hi,

According to the spec the following is true:

failed

The ICE Agent is finished checking all candidate pairs and failed to find a connection for at least one component. Connections may have been found for some components.

Which suggests that the ICE state can enter disconnected if the "non failed" candidates are disconnected when at least one candidate has failed.

+Peter Thatcher maybe you have a better explanation.

There is an ongoing discussion about ice states here, maybe that can shine some light on this.

/Chris

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[Peter Thatcher]

Fist, that diagram is non-normative and misleading in many respects, so don't use that as your source of truth.  Use the text.

Second, the text says for failed "checking all candidate pairs", and it's not at all clear what that means and is a topic of discussion in the standards body at this very moment.  I recently  posted a message to discuss-webrtc asking for input from developers to see what the want the API to do.  For example: is "failed" permanent (until and ICE restart)?  It's not clear right now.

If "failed" is not permanent, then going from "failed" to "disconnected" is possible if:

1. You were once connected.

2. You became disconnected but continued checking (which is not the checking state)

3. All the candidate pairs failed, so you went to "failed"

4. You received a check from the remote side, so you start checking back.  Now you go to the "disconnected" state.