RealPresence Collaboration Server (RMX) 800s/Virtual Edition Administrator’s Guide
Polycom®, Inc.
209
Packet Loss
Packet Loss
refers to the failure of data packets, transmitted over an IP network, to arrive at their
destination. Packet Loss is described as a percentage of the total packets transmitted.
Causes of Packet Loss
Network congestion within a LAN or WAN, faulty or incorrectly configured network equipment or faulty
cabling are among the many causes of Packet Loss.
Effects of Packet Loss on Conferences
Packet Loss affects the quality of:
●
Video – frozen images, decreased frame rate, flickering, tiling, distortion, smearing, loss of lip sync
●
Audio – drop-outs, chirping, audio distortion
●
Content – frozen images, blurring, distortion, slow screen refresh rate
Lost Packet Recovery
The
Lost Packet Recovery
(
LPR
) algorithm uses
Forward Error Correction
(
FEC
) to create additional
packets that contain recovery information. These additional packets are used to reconstruct packets that are
lost, for whatever reason, during transmission.
Dynamic Bandwidth Allocation
(
DBA
) is used to allocate the
bandwidth needed to transmit the additional packets.
Lost Packet Recovery Guidelines
●
If packet loss is detected in the packet transmissions of either the video or Content streams:
LPR is applied to both the video and Content streams.
DBA allocates bandwidth from the video stream for the insertion of additional packets containing
recovery information.
●
LPR is supported in H.323 and SIP networking environments only.
●
In LPR-enabled Continuous Presence conferences:
Both LPR-enabled and non-LPR-enabled endpoints are supported.
The LPR process is not applied to packet transmissions from non-LPR-enabled IP (H.323 and
SIP) endpoints.
Non-LPR-enabled endpoints can be moved to LPR-enabled conferences.
LPR-enabled endpoints cannot be moved to non-LPR-enabled conferences.
●
When connecting via an Entry Queue:
A participant using an LPR-enabled endpoint can be moved to a non-LPR-enabled conference.
The participant is connected with LPR enabled.
Enabling Lost Packet Recovery
LPR
is enabled or disabled in the
Conference Profile
dialog box.
●
CP Conferences – LPR is enabled by default in the
New Profile – Advanced
dialog box.
For more information, see
Defining New Profiles
.
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