Frequently Used QoS Terms
Quality of Service Guide 889
The CIR rate for ingress queues controls the in-profile and out-of-profile policing and
ultimately egress in-profile and out-of-profile marking. Queue CIR rates also define
the hardware fairness threshold at which the queue is no longer prioritized over other
queues.
A child’s (queue or scheduler) CIR is used with the CIR level parameter to determine the
child’s committed bandwidth from the parent scheduler. When multiple children are at the
same strict CIR level, the CIR weight further determines the bandwidth distribution at that
level.
CIR Level
The CIR level parameter defines the strict level at which bandwidth is allocated to the child
queue or scheduler during the within CIR distribution phase of bandwidth allocation. All
committed bandwidth (determined by the CIR defined for the child) is allocated before any
child receives non-committed bandwidth. Bandwidth is allocated to children at the higher
CIR levels before children at a lower level. A child CIR value of zero or an undefined CIR
level results in bandwidth allocation to the child only after all other children receive their
provisioned CIR bandwidth. When multiple children share a CIR level, the CIR weight
parameter further defines bandwidth allocation according to the child’s weight ratio.
CIR Weight
The CIR weight parameter defines the weight within the CIR level given to a child queue or
scheduler. When multiple children share the same CIR level on a parent scheduler, the ratio
of bandwidth given to an individual child is dependent on the ratio of the weights of the active
children. A child is considered active when a portion of the offered load is within the child’s
defined CIR rate. The ratio is calculated by first adding the CIR weights of all active children
and then dividing each child’s CIR weight by the sum. If a child’s CIR level parameter is not
defined, that child is not included in the within CIR distribution and the CIR weight parameter
is ignored. A CIR weight of zero forces the child to receive bandwidth only after all other
children at that level have received their ‘within CIR’ bandwidth. When several children
share a CIR weight of zero, all are treated equally.
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