VoIP Active Calls
The number VoIP Active Calls has exceeded threshold. Depending on the capacity of the call manager (e.g., the SIP proxy server or the H.323 gateway), large numbers of simultaneous calls can lead to loss of voice quality and delays in call setup.
Possible reasons for this event:
There is simply a high volume of call activity currently.
The VoIP call manager (e.g., the SIP proxy server) is under a Denial of Service (DoS) attack. You should be able to configure your firewall to block the traffic after using Observer to examine the suspicious call setup/teardown requests.