When a call is connected using the Twilio Voice JavaScript SDK (formerly "Twilio Client"), the client and server exchange periodic messages verifying that the call is alive. If these message exchanges fail, it could indicate a problem with the connection to Twilio. Previously such errors were returned to your server as unspecified errors, they now manifest as the following :

• ICE liveness checks failed: This error implies that the browser had a media session with Twilio, but had trouble exchanging information to keep the media session active. In this case, the call will continue, although it could imply that network connectivity has degraded.
• ICE negotiation with Twilio failed: This means that the browser made a TCP connection to Twilio for signaling, but could not establish UDP/RTP media connectivity. This can happen if network connectivity is poor, or if UDP is being blocked, or if a network policy prevents UDP to/from IP addresses in Amazon's public range. When this error occurs please ensure that the Twilio Voice JavaScript and Mobile SDK Network Connectivity and Bandwidth Requirements are taken into consideration. If you have verified connectivity requirements, but these errors persist, please contact our Support team.