Named Pools - Alcatel-Lucent 7450 Quality Of Service Manual

Named Pools

When buffer pools are being created or deleted, individual queues may need to be moved to
or from the default pools. When a queue is being moved, the traffic destined to the queue is
first moved temporarily to a 'fail-over' queue. Then the queue is allowed to drain. Once the
queue is drained, the statistics for the queue are copied. The queue is then returned to the free
queue list. A new queue is then created associated with the appropriate buffer pool, the saved
stats are loaded to the queue and then the traffic is moved from the fail-over queue to the new
queue. While the traffic is being moved between the old queue to the fail-over queue and then
to the new queue, some out of order forwarding may be experienced. Also, any traffic
forwarded through the fail-over queue will not be accounted for in billing or accounting
statistics. A similar action is performed for queues that have the associated pool name added,
changed or removed. This only applies to where fail-over queues are currently supported.
The first step in allowing named pools to be created for an XMA or MDA is to enable
'named-pool-mode' at the IOM level (config card slot-number named-pool-mode). Named
pool mode may be enabled and disabled at anytime. When MDAs are currently provisioned
on the IOM, the IOM is reset to allow all existing pools to be deleted and the new default,
named XMA or MDA and named port pools to be created and sized. If MDAs are not
currently provisioned (as when the system is booting up), the IOM is not reset. When named
pool mode is enabled, the system changes the way that default pools are created. The system
no longer creates default pools per port, instead, a set of per forwarding plane level pools are
created that are used by all queues that are not explicitly mapped to a named pool.
After the IOM has been placed into named pool mode, a named pool policy must be
associated with the ingress and egress contexts of the XMA or MDA or individual ports on
the XMA or MDA for named pools to be created. There are no named pools that exist by
default.
Each time the default pool reserve, aggregate XMA or MDA pool limit or individual pool
sizes is changed, buffer pool allocation must be re-evaluated.
Pools may be deleted from the named pool policy at anytime. Queues associated with
removed or non-existent pools are mapped to one of the default pools based on whether the
queue is access or ingress. The queue is flagged as 'pool-orphaned' until either the pool
comes into existence, or the pool name association is changed on the pool.
An ingress or egress port managed buffer space is derived from the port's active bandwidth.
Based on this bandwidth value compared to the other port's bandwidth value, the available
buffer space is given to each port to manage. It may be desirable to artificially increase or
decrease this bandwidth value to compensate for how many buffers are actually needed on
each port. If one port has very few queues associated with it and another has many queues
associated, the commands in the port's "modify-buffer-allocation-rate" CLI context may be
used to move one port's bandwidth up, and another port's bandwidth down. As provisioning
levels change between ports, the rate modification commands may be used to adapt the buffer
allocations per port.
Quality of Service Guide 721