Hsmda Features - Alcatel-Lucent 7450 Quality Of Service Manual

HSMDA Features

HSMDA Queue Groups
A fundamental concept on an HSMDA is the queue group. Queue groups are not directly
managed by the provisioner, they are indirectly assigned when creating SAPs or subscribers
on the XMA and MDA. A queue group has eight queue members. The queues within the
group are numbered from 1 through 8. When creating a SAP or subscriber associated with a
port on the XMA or MDA, an ingress and egress queue group is allocated to the object. Every
SAP and subscriber using the XMA or MDA has 8 ingress and 8 egress queues (whether they
are in use or not). In the SAP ingress and egress QoS policies, the HSMDA queues within the
group are represented by queue-id 1 through 8.
Each queue within the group has two RED slopes (managed by associating a slope policy to
the queue), an MBS defined in bytes, a byte offset parameter used to add or subtract bytes to
each packet handled by the queue for accounting purposes, a PIR and a CIR leaky bucket.
The queue group supports an aggregate shaper used to manage an aggregate rate limit for all
queues within the group. Scheduling for queues within the group is stopped and started based
on the rate set on the shaper.
Each queue group also supports 16 counter sets. Eight of the counters are the default counters
used by packets assigned to each queue respectively. The remaining eight are exception
counters and are named Counter 1 through Counter 8.
The number of queue groups available is dependent on the HSMDA variant. The ESS variant
supports up to 8K ingress and egress queue groups. The SR variant supports up to 20K ingress
and egress queue groups. The ability to utilize all available queue groups is dependent on the
type of IOM that is hosting the HSMDA.
Scheduling Classes
The HSMDA supports eight scheduler classes that are directly mapped to the queue-id (1
through 8) for each SAP and subscriber queue. The scheduler class is not an internal QoS
policy driven forwarding class. Forwarding classes within the system are used between the
ingress and egress forwarding complexes and help the system to manage packet marking or
remarking decisions and also are used to map each packet to an ingress and egress queue. It
is possible to have two different QoS policies, the first that maps forwarding class AF (for
example) to queue number 3 and the second may map AF to queue number 5. While the
system will make certain common decisions based on the AF forwarding class, the fact that
it is being mapped to different scheduler classes within the HSMDA will dictate that the
scheduling of AF will be different for the two QoS policies based on the scheduler behavior.
788 Quality of Service Guide