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Polycom® RealPresence Collaboration Server (RMX) 1500/2000/4000 Administrator’s Guide
13-36 Polycom, Inc.
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
When you want to change the system default value of 20 seconds, the system flag,
DETECT_SIP_EP_DISCONNECT_TIMER, can be manually added to the System Flags
configuration to detect the disconnection of SIP endpoints. For more information on adding
system flags, see the Manually Adding and Deleting System Flags section in the RealPresence
Collaboration Server (RMX) Administrator’s Guide.
The value range is from 0 to 300 seconds. 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.