Chapter 32: Packet Throttling
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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A new shaper block is implemented immediately before the output queue. When the shaper receives a packet, it places it
into a time-bin in a calendar queue scheduler, which releases the packet upon completion of the delay that was calculated
by the policing block.
Note: Packets arriving from the fabric for PacketCable voice and Unsolicited Grant Services (UGS) flows are not shaped.
They are placed in a separate queue and are serviced in a strict priority manner before the calendar queue packets.
Shaping versus Policing Summary
Traffic shaping gives preference to PacketCable voice and UGS flows over all other traffic. No other prioritizing is done by
the CAM when shaping is enabled. The CAM does not implement any new dropping mechanisms, such as WRED.
Traffic policing calculations are still the primary method of limiting bandwidth on individual flows, and the back pressure
mechanism of the RCM fabric is still used to trigger WRED in the fabric for congestion control and Tmin rate enforcement.
Traffic Shaping Implementation
The implementation of traffic shaping can be summarized as follows:
Traffic shaping applies only to downstream traffic.
Packets that must be held more than two seconds in order to conform to the shaping norms are dropped.
Disabling policing on the C4/c CMTS also disables traffic shaping on the DCAM because policing determines whether a
flow is conforming or not.
Traffic shaping does not affect PacketCable voice and UGS packets.
Traffic Shaping CLI Commands
The commands in the following section relate to traffic shaping.
Set Peak Traffic Rate for DOCSIS 1.1 COS
Use the following command as a guide for setting the peak traffic rate for DOCSIS 1.0 cable modems that have been
mapped to a DOCSIS 1.1 Class of Service:
configure cos-mapping down-peak-traffic-rate 96000