Qos Scheduler Policies - Alcatel-Lucent 7950 Quality Of Service Manual

The command can be applied on any tier 1 scheduler within an egress scheduler policy or within
any agg-rate node (except when using the HS-MDA) and affects all queues controlled by the
object.
When LUB is enabled, the LUB second pass is performed as part of the HQoS algorithm The
order of operation between HQoS and LUB is as follows:
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When LUB is enabled on a scheduler rate or aggregate rate, a LUB context is created containing
the rate and the associated queues the rate controls. Because a queue may be controlled by multiple
LUB enabled rates in a hierarchy, a queue may be associated with multiple LUB contexts.
LUB is applied to the contexts where it is enabled. LUB first considers how much of the aggregate
rate is unused by the aggregate rates of each member queue after the first pass of the HQoS
algorithm. This represents the current bandwidth that may be distributed between the member
queues. LUB then distributes the available bandwidth to its member queues based on each queue's
LUB-weight. A queue's LUB-weight is determined as follows:
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The resulting operational PIRs are then set such that the scheduler or agg-rate rate is not exceeded.
To achieve the best precision, queues must be configured to use adaptation-rule pir max cir max
to prevent the actual queue rate used exceeds that determined by LUB.
Example
Taking a simple scenario with 5 egress SAP queues all without rates configured but with each
queue parented to a different level in a parent scheduler which has a rate of 100Mb/s, see
Figure
7950 XRS Quality of Service Guide
Queue offered rate calculation.
Offered rate modifications based on adv-config-policy offered-measurement
parameters.
HQoS Bandwidth determination based on modified offered-rates.
LUB second pass to ensure aggregate rates are not exceeded where LUB enabled.
Bandwidth distribution modification based on adv-config-policy bandwidth-
distribution parameters.
Each queue's operational PIR is then modified.
If a queue is using all of its default H-QoS assigned rate then its LUB-weight is 0. It is not
participating in the bandwidth distribution as it cannot accept more bandwidth.
Else if a queue has accumulated work then its LUB-weight is set to 50. The work is
determined by the queue having built up a depth of packets, or its offered rate is increasing
since last sample period. The aim is to assign more of the unused bandwidth to queues
needing more capacity. No attempt is made to distribute based on a queues relative priority
level or weight within the hierarchy.
Otherwise, a queue's LUB-weight is 1
22.

QoS Scheduler Policies

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