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

cir" loops, one for each of the eight priority levels. The second tier "above-cir" loop provides
bandwidth to the third tier "above-cir" loops for each of the eight priority levels.
The "within-cir" loop for each priority level on the third tier supports an optional rate limiter used
to restrict the maximum amount of "within-cir" bandwidth the priority level can receive. A
maximum priority level rate limit is also supported that restricts the total amount of bandwidth the
level can receive for both "within-cir" and "above-cir". The amount of bandwidth consumed by
each priority level for "within-cir" and "above-cir" is predicated on the rate limits described and
the ability for each child queue or scheduler attached to the priority level to use the bandwidth.
The priority 1 "above-cir" scheduling loop has a special two tier strict distribution function. The
high priority level 1 "above-cir" distribution is weighted between all queues and schedulers
attached to level 1 for "above-cir" bandwidth. The low priority distribution for level 1 "above-cir"
is reserved for all orphaned queues and schedulers on the egress port. Orphans are queues and
schedulers that are not explicitly or indirectly attached to the port scheduler through normal
parenting conventions. By default, all orphans receive bandwidth after all parented queues and
schedulers and are allowed to consume whatever bandwidth is remaining. This default behavior
for orphans can be overridden on each port scheduler policy by defining explicit orphan port
parent association parameters.
Ultimately, any bandwidth allocated by the port scheduler is given to a child queue. The
bandwidth allocated to the queue is converted to a value for the queue's PIR (maximum rate)
setting. This way, the hardware schedulers operating at the egress port level will only schedule
bandwidth for all queues on the port up to the limits prescribed by the virtual scheduling
algorithm.
The following lists the bandwidth allocation sequence for the port virtual scheduler:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
7950 XRS Quality of Service Guide
Priority level 8 offered load up to priority CIR
Priority level 7 offered load up to priority CIR
Priority level 6 offered load up to priority CIR
Priority level 5 offered load up to priority CIR
Priority level 4 offered load up to priority CIR
Priority level 3 offered load up to priority CIR
Priority level 2 offered load up to priority CIR
Priority level 1 offered load up to priority CIR
Priority level 8 remaining offered load up to remaining priority rate limit
Priority level 7 remaining offered load up to remaining priority rate limit
Priority level 6 remaining offered load up to remaining priority rate limit
Priority level 5 remaining offered load up to remaining priority rate limit
Priority level 4 remaining offered load up to remaining priority rate limit

QoS Scheduler Policies

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