Detecting Sip Endpoint Disconnection; H323 Endpoint Disconnection Detection - Polycom RealPresence 1500 Administrator's Manual

Conference and Participant Monitoring

Detecting SIP Endpoint Disconnection

When an abnormal disconnection of SIP endpoints occurs because of network problems or client
application failures, SIP endpoints remain connected to the conference causing connection disruptions. For
example, the video freezes in the layout or blocks content for SIP endpoints when a quick re-connection is
performed. It can take several minutes to detect the SIP endpoint disconnection using the SIP standard
behavior.
In a normal SIP video call, audio and video (RTP and RTCP) messages are sent from the endpoints to the
MCU to detect the signaling of connected endpoints. Conversely, SVC endpoints might not send video RTP
messages to the MCU when a participant is not displayed in the video layout of any of the participants in the
conference. For SVC endpoints, the MCU will only verify audio RTP and RTCP messages and video RTCP
messages. Video RTP messages will not be checked.
To detect the disconnection of SIP endpoints in a reasonable amount of time, a new system flag can be
defined to specify the amount of time that the MCU should wait for an RTCP or RTP message from the SIP
endpoint before the endpoint starts the disconnection process. The system default value is automatically
set to 20 seconds.
The system flag, DETECT_SIP_EP_DISCONNECT_TIMER, contains the amount of time in seconds to wait
for an RTCP or RTP message to be received from the endpoint. When the time that was set in the system
flag has elapsed and no RTCP or RTP audio or video message has been received on either the audio or
the video channel, the MCU disconnects the SIP endpoint from the conference. A CDR event record is
created with a Call Disconnection Cause of SIP remote stopped responding.
The Microsoft Lync add-in endpoint opens audio and content channels. Lync endpoints can send
RTCP/RTP messages and empty RTP audio messages. When the time that was set in the system flag has
elapsed and no RTCP or RTP message has been received on the audio channel, the MCU disconnects the
endpoint from the conference.
SIP audio only endpoints use the audio channel only. When the time that was set in the system flag has
elapsed and no RTCP or RTP message has been received on the audio channel, the MCU disconnects the
SIP audio endpoint from the conference.
Configuring the System Flag
The time out used for SIP endpoint disconnection detection is controlled by the
DETECT_SIP_EP_DISCONNECT_TIMER System Flag which must be added to the System Configuration
to view or modify its value.
Range: 0 - 300
When the value is set between 0 and 14, the feature is disabled and SIP endpoints are not detected for
disconnection. When the value is set between 15 and 300, the feature is enabled.
Default: 20
For more information see Manually Adding and Deleting System Flags, and Modifying System Flags.

H323 Endpoint Disconnection Detection

In versions previous to version 8.4, when an H.323 endpoint disconnected, round trip messages were still
received, even when a gatekeeper was deployed. Because of this, the MCU failed to detect the endpoint
disconnection.
From version 8.4 onward, the MCU detects H.323 endpoint connection or disconnection by monitoring
RTCP/RTP messages reception using either the audio or video channels. When these messages are not
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