Dynamic Mbs For Egress Queue Group Queues - Alcatel-Lucent 7450 Quality Of Service Manual

When the local-limit is used the percent-rate is relative to the queue's parent scheduler rate
or the agg-rate rate at egress, when the port-limit is used the percent-rate is relative to the rate
of the port (including the ingress-rate/egress-rate setting) to which the queue is attached. port-
limit is the default.
For policers, the percent-rate rate is always relative to the immediate parent root policer/
arbiter rate or the FP capacity.
SAP-Egress QoS Policy:
*B:Dut-A>config>qos>sap-egress# queue 1 percent-rate
- no percent-rate
- percent-rate <pir-percent> [cir <cir-percent>] [port-limit | local-limit]
<pir-percent> : [0.01..100.00]
<cir-percent> : [0.00..100.00]
<port-limit | local-*> : keyword
*B:Dut-A>config>qos>sap-egress# policer 1 percent-rate
- no percent-rate
- percent-rate <pir-percent> [cir <cir-percent>]
<pir-percent> : [0.01..100.00]
<cir-percent> : [0.00..100.00]

Dynamic MBS for Egress Queue Group Queues

Dynamic MBS is used to constrain the maximum delay experienced by the traffic forwarded
through an egress queue group queue when the operational PIR of the queue is modified as
part of the HQoS algorithm.
The approximate maximum delay of traffic through a queue due to the length of the queue
which is not using HQoS is relative to its administrative PIR and can be approximated as
(MBS[kB] × 8) / PIR[kbps]) in seconds. A queue's PIR is set to max, its administrative PIR
is set to the rate of the port to which the queue is attached.
When using HQoS, the PIR is modified by the HQoS algorithm to give an operational PIR
that is equal to or lower than the administrative PIR. As the operational PIR changes, the
delay through the queue can also change if the length of the queue is fixed. Reducing the
operational PIR could increase the delay, while increasing the operational PIR could reduce
the delay. Enabling dynamic MBS on a queue allows the system to change the administrative
MBS of the queue in a ratio of operational PIR to administrative PIR, giving an operational
MBS, which aims to maintain the maximum queue delay. A queue's high-prio-only, hi-low-
prio-only, and WRED slope parameters are defined as percentages of the MBS and are
therefore adjusted accordingly.
Quality of Service Guide
Service Egress and Ingress QoS Policies
193