IP Router Configuration
Router Configuration Guide 25
QPPB Interaction with SAP Ingress QoS Policy
When QPPB is enabled on a SAP IP interface the forwarding class of a packet may change
from fc1, the original fc determined by the SAP ingress QoS policy to fc2, the new fc
determined by QPPB. In the ingress datapath SAP ingress QoS policies are applied in the first
P chip and route lookup/QPPB occurs in the second P chip. This has the implications listed
below:
• Ingress remarking (based on profile state) is always based on the original fc (fc1) and
sub-class (if defined).
• The profile state of a SAP ingress packet that matches a QPPB route depends on the
configuration of fc2 only. If the de-1-out-profile flag is enabled in fc2 and fc2 is not
mapped to a priority mode queue then the packet will be marked out of profile if its
DE bit = 1. If the profile state of fc2 is explicitly configured (in or out) and fc2 is not
mapped to a priority mode queue then the packet is assigned this profile state. In both
cases there is no consideration of whether or not fc1 was mapped to a priority mode
queue.
• The priority of a SAP ingress packet that matches a QPPB route depends on several
factors. If the de-1-out-profile flag is enabled in fc2 and the DE bit is set in the packet
then priority will be low regardless of the QPPB priority or fc2 mapping to profile
mode queue, priority mode queue or policer. If fc2 is associated with a profile mode
queue then the packet priority will be based on the explicitly configured profile state
of fc2 (in profile = high, out profile = low, undefined = high), regardless of the QPPB
priority or fc1 configuration. If fc2 is associated with a priority mode queue or policer
then the packet priority will be based on QPPB (unless DE=1), but if no priority
information is associated with the route then the packet priority will be based on the
configuration of fc1 (if fc1 mapped to a priority mode queue then it is based on
DSCP/IP prec/802.1p and if fc1 mapped to a profile mode queue then it is based on
the profile state of fc1).
Table 2 summarizes these interactions.
Table 2: QPPB Interactions with SAP Ingress QoS
Original FC
object
mapping
New FC
object
mapping
Profile Priority (drop
preference)
DE=1
override
In/out of profile
marking
Profile mode
queue
Profile mode
queue
From new
base FC
unless
overridden
by DE=1
From QPPB, unless
packet is marked in or
out of profile in which
case follows profile.
Default is high priority
From new
base FC
From original FC
and sub-class
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