QoS Overview
Page 44 7210 SAS D, E, K OS Quality of Service Guide
To illustrate how the adaptation rule constraints minimum, maximum and closest are evaluated in
determining the operational CIR or PIR for the 7210 SAS, assume there is a queue where the
administrative CIR and PIR values are 90Kbps and 150 Kbps, respectively. If the adaptation rule is
minimum, the operational CIR and PIR values will be 128Kbps and 192Kbps respectively, as it is
the native hardware rate greater than or equal to the administrative CIR and PIR values. If the
adaptation rule is maximum, the operational CIR and PIR values will be 64Kbps and 128Kbps. If
the adaptation rule is closest, the operational CIR and PIR values will be 64Kbps and 128Kbps,
respectively, as those are the closest matches for the administrative values that are even multiples
of the 64 Kbps rate step.
Committed Burst Size
The committed burst size (CBS) parameters specify the amount of buffers that can be drawn from
the reserved buffer portion of the queue’s buffer pool. Once the reserved buffers for a given queue
have been used, the queue contends with other queues for additional buffer resources up to the
maximum burst size.
The CBS is provisioned on ingress and egress service queues within service ingress QoS policies
and service egress QoS policies, respectively. The CBS for network queues are defined within
network queue policies based on the forwarding class. The CBS for a queue is specified in Kbytes.
For 7210 SAS-D and 7210 SAS-E, the CBS for the queues is not configurable. The CBS value for
the queues is set to appropriate default values which takes care of specific FC needs in terms of
maintaining the differential treatment. The default values used on different ports is available on
Table 10 on page 49.
On 7210 SAS-K, the CBS for the queues is user configurable. By default, software assigns a
default value. It can be modified by the user as per their needs. The default value are specified in
the command description.
Maximum Burst Size
The maximum burst size (MBS) parameter specifies the maximum queue depth to which a queue
can grow. This parameter ensures that a customer that is massively or continuously
oversubscribing the PIR of a queue will not consume all the available buffer resources. For high-
64kbps
67100 - 134180 kbps
128kbps
134190 - 268360 kbps
256kbps
268370 - 536730 kpbs
512kbps
536740 - 1000000 kbps
Hardware Rate Steps Rate Range (kbps)
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