Alcatel-Lucent 7950, Quality Of Service Manual, Page: 444 / 612

Egress Port-Based Schedulers
Page 444 7950 XRS Quality of Service Guide
14. Priority level 3 remaining offered load up to remaining priority rate limit
15. Priority level 2 remaining offered load up to remaining priority rate limit
16. Priority level 1 remaining offered load up to remaining priority rate limit
17. Priority level 1 remaining orphan offered load up to remaining priority rate limit (default
orphan behavior unless orphan behavior has been overridden in the scheduler policy)
When a queue is inactive or has a limited offered load that is below its fair share (fair share is
based on the bandwidth allocation a queue would receive if it was registering adequate activity),
its operational PIR must be set to some value to handle what would happen if the queues offered
load increased prior to the next iteration of the port virtual scheduling algorithm. If an inactive
queues PIR was set to zero (or near zero), the queue would throttle its traffic until the next
algorithm iteration. If the operational PIR was set to its configured rate, the result could overrun
the expected aggregate rate of the port scheduler.
To accommodate inactive queues, the system calculates a Minimum Information Rate (MIR) for
each queue. To calculate each queue’s MIR, the system determines what that queue’s Fair
Information Rate (FIR) would be if that queue had actually been active during the latest iteration
of the virtual scheduling algorithm. For example, if three queues are active (1, 2, and 3) and two
queues are inactive (4 and 5), the system first calculates the FIR for each active queue. Then it
recalculates the FIR for queue 4 assuming queue 4 was active with queues 1, 2, and 3 and uses the
result as the queue’s MIR. The same is done for queue 5 using queues 1, 2, 3, and 5. The MIR for
each inactive queue is used as the operational PIR for each queue.
Service/ Egress Port Bandwidth Allocation
The port-based egress scheduler can be used to allocate bandwidth to each service
or
associated
with the port. While egress queues on the service can have a child association with a scheduler
policy on the SAP or multi-service site, all queues must vie for bandwidth from an egress port.
Two methods are supported to allocate bandwidth to each service
or
queue:
1. Service
or
queue association with a scheduler on the SAP or multi-service site which is
itself associated with a port-level scheduler.
2. Service
or
queue association directly with a port-level scheduler.