Polycom RealPresence 1800 Administration Manual page 372

Appendix - Media Traffic Shaping
Polycom integrated traffic shaping capabilities into the RealPresence Collaboration Server to enable
deploying Collaboration Server systems in networks limiting packet bursts within 100ms time intervals (or
more). Setting router policies to limiting of bandwidth within a time interval, causes the router to drop packets
exceeding the allowed bandwidth within this interval. Therefore, using this feature enables the Collaboration
Server to flatten the traffic, and minimize traffic bursts, without exceeding the bandwidth allowed within the
time interval.
Though the Collaboration Server supports high level network features, high quality of service requires
end-to-end video network operation. The Collaboration Server traffic shaping capabilities cannot
compensate for network level violations/limitations generated by elements outside the Collaboration Server,
such as endpoints, routers, etc.
Traffic shaping can flatten a momentary burst (meaning, within a 100ms time interval). However, it cannot
"flatten" longer bursts resulting from endpoints sharing content in video switching conferences. Similarly, this
feature helps reducing packets dropping by routers following momentary traffic bursts, yet it does not resolve
packet lost by faulty network connections or network congestion.
Note that during VSW content sessions, should source endpoint exceed the negotiated content rate for over
100ms, the Collaboration Server can flatten the video channel but not the incoming content channel.
Traffic Shaping Guidelines
● Traffic shaping is applied in the following conferencing modes and scenarios:
 AVC conferences (both CP and VSW)
 Mixed CP and SVC conferences - applied only on AVC endpoints
 Content VSW
This feature is not applied on TIP endpoints.
● Traffic shaping code is embedded in the DSP ART modules thus requiring enlarging PCI memory size
to 18Mbps, and content memory size to that of video.
● Should license port capacity be lower than the number of hardware ports, the unlicensed ports are
used for traffic shaping to decrease capacity reduction.
● Traffic shaping is applied on the aggregation of both content and people channels.
● Delays due to traffic shaping, if any, are limited to 10ms.
● This feature is not applied on audio, since the encoder output audio rate is constant.
● When LPR is enabled, traffic shaping is applied following packets repair and prior to packets sending.
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