Ingress Access Port Queue Group Hardware Queue Allocation - Alcatel-Lucent 7450 Quality Of Service Manual

The situation is different for a shared or port-queuing model that is based on policing color
packets that conform or exceed a static rate before the single queue and that use WRED or
drop tail functions to essentially reserve room for the conforming packets.
In this model, there is no way for the conforming packets to go to the head of line in the view
of the port scheduler. Another advantage of per-SAP queuing is the ability for the SAP queues
to perform shaping to control burst sizes and forwarding rates based on the SAPs defined
SLA. This is especially beneficial when a provider is enforcing a sub-line rate bandwidth
limit and the customer does not have the ability to shape at the CE.
However, there are cases where per-SAP queuing is not preferred. Per SAP queuing requires
a more complex provisioning model in order to properly configure the SAPs ingress and
egress SLAs. This requires service awareness at some points in the network where an
aggregation function is being performed. In this case, a shared queuing or per-port queuing
model will suffice. Creating ingress and egress access queue groups and mapping the SAPs
forwarding classes to the queues within the queue group provides this capability.
A further use case is where a set of ingress SAPs, which may represent a subset of the total
number of ingress SAPs, is to be shaped or policed on an aggregate per-forwarding class basis
when those SAPs are spread across a LAG on multiple ingress ports, and where color-aware
treatment is required so that explicitly in-profile traffic is honored up to CIR, but above which
it is marked as out of profile
The above scenarios can be supported with access queue groups. A single ingress queue
group is supported per access port, while multiple ingress queue group instances are
supported per IOM/IMM/XMA forwarding plane. To provide more flexibility on the egress
side of the access port, multiple egress access queue group queue-group instances are
supported per egress access port.
Since queue redirection is defined per forwarding class, it is possible to redirect some
forwarding classes to a queue group while having others on the SAP use the SAP local
queues. This is helpful when shared queuing is only desired for a few applications such as
VOIP or VOD while other applications still require queuing at the SAP level.
Ingress Access Port Queue Group Hardware Queue
Allocation
When ingress access port queue groups are configured, hardware queues are allocated to each
switch fabric destination for each queue configured in the queue group template.
The allocation of ingress access port queue group hardware queues has been optimized for
the 7950 XRS-20 systems to avoid allocating ingress hardware queues to XCMs in slots 11
and above.
Quality of Service Guide
Queue Sharing and Redirection
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