CANOGA PERKINS 9145EMP NID Software Version 4.0 - Manual (Page 217)

9145EMP NID Software User’s Manual Bandwidth Profiling
Queue size and yellow packet thresholds
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• Total dropped green packets and total dropped yellow packets (packets dropped due to
shaping)
For shaping purposes, yellow packets are marked with the DE bit set in the outer tag.
13.4 Queue size and yellow packet thresholds
Each egress queue has a configured frame size which indicates the number of bytes that can be
held in the queue while awaiting transmission. In this release, a new parameter, yellow packet
threshold, is configured on each queue, expressed as a percentage. Once a queue is full at the
specified yellow threshold, then only green packets are accepted in the queue. The yellow
packets (that is, packets with DE bit set, as defined by the policer) are dropped. For example, for
a queue of a size of 1000 bytes, with a yellow threshold at 70%, yellow frames will no longer be
accepted in the queue when the queue is full more than 700 bytes. A yellow threshold of 100%
indicates that no discrimination is made between yellow and green frames.
Packets accepted in the queue are sent out at CIR rate, as long as the queue occupancy is
below the yellow threshold. Once the queue occupancy is above the yellow threshold, the frames
are transmitted faster, at EIR rate, until the queue occupancy decreases under the yellow
threshold. Frames sent under the EIR rate are marked as yellow (that is, DE bit set) regardless of
the color determined by the policer. The yellow frames marked as such by the policier are not
remarked to green by the shaper, regardless of the queue occupancy at the time of transmission.