What is join time, gathering delay, connectivity check delay, setup delay and TTFM?

• Join time: The time at which each participant joins the call. Joining time of first participant will always be zero
• Gathering delay: Collecting all interfaces/ICE candidates of the local machine
• Connectivity check delay: All the negotiation delay for the ICE candidates.
• Setup delay: Total time to setup a conference for the participant. The time when the user joins until the chosen candidate pair is connected. 
• TTFM: Time To First Media, is the first instance of time when the media sent by the participant.

The example above shows all the events happening linearly. However, in reality, the connection check can start when the ICE candidate gathering starts or the chose pair can be connected after the connection check ends. 

Further conference setup details are explained in our blogpost Metrics for WebRTC Conference Setup.