All ringing and established calls in the Ring Group drop

Symptom

All calls currently ringing and all calls in progress in the a Simultaneous Ring Group will all drop at the same time.
Physical phones in the Ring Group then appear to go out of service for about 1 or 2 minutes.

Applies To

• 8x8 Ring Groups

Resolution

This issue can occur if the Total time to alert a member option is set to the maximum 180 seconds and a call reaches this limit.

Set this timer to 175 seconds or less.

Cause

The 8x8 SBCs (Session Border Controllers), that monitor calls sent out to endpoints (physical and soft phone devices), have a session limit of 180 seconds if no response is received.

The SBC considers no response after 180 seconds an indication that the SIP endpoint (physical phone, softphone) is no longer available and updates the controlling PBX with this information.
The PBX then drops any connections to theses devices along with their registrations. This is what renders the phones un-usable for about 2 minutes as they re-connect and re-register with the PBX.
If the RG is Simultaneous ring then this would be every phone that was ringing with a call that reached 180 seconds.
If the Notify members even if busy option is enabled then users on established calls will also be dropped. 

In most cases the Ring Group no answer forwarding will pull the call back prior to the SBC declaring the phones unreachable but not always.

Additional Information

A future release of Admin Console will be limiting the Total time to alert a member to 120 seconds to completely remove the possibility of this error and to also align Ring Groups with the no answer forwarding for Call Queues.