Aggregate Rate Limits For Directly Attached Queues - Alcatel-Lucent 7450 Quality Of Service Manual

required for proper bandwidth allocation between queues and service schedulers. If this value
is not attainable, another approach is to artificially lower the maximum rate of the port
scheduler to represent the average port framing overhead. This, in conjunction with a zero or
low value for avg-frame-overhead, will ensure that the allocated queue bandwidth will
control forwarding behavior instead of the low level hardware schedulers.

Aggregate Rate Limits for Directly Attached Queues

When all queues for a SAP, multi-service site or subscriber or multi-service site instance are
attached directly to the port scheduler (using the port-parent command), it is possible to
configure an agg-rate-limit for the queues. This is beneficial since the port scheduler does not
provide a mechanism to enforce an aggregate SLA for a service or subscriber or multi-service
site and the agg-rate-limit provides this ability. Queues may be provisioned directly on the
port scheduler when it is desirable to manage the congestion at the egress port based on class
priority instead of on a per service object basis.
The agg-rate-limit is not supported when one or more queues on the object are attached to an
intermediate service scheduler. In this event, it is expected that the intermediate scheduler
hierarchy will be used to enforce the aggregate SLA. Attaching an agg-rate-limit is mutually
exclusive to attaching an egress scheduler policy at the SAP or subscriber or multi-service
site profile level. Once an aggregate rate limit is in effect, a scheduler policy cannot be
assigned. Once a scheduler policy is assigned on the egress side of a SAP or subscriber or
multi-service site profile, an agg-rate-limit cannot be assigned.
Since the sap-egress policy defines a queue's parent association before the policy is
associated with a service SAP or subscriber or multi-service site profile, it is possible for the
policy to either not define a port-parent association or define an intermediate scheduler
parenting that does not exist. As stated above, queues in this state are considered to be
orphaned and automatically attached to port scheduler priority 1. Orphaned queues are
included in the aggregate rate limiting behavior on the SAP or subscriber or multi-service site
instance they are created within.
SAP Egress QoS Policy Queue Parenting
A sap-egress QoS policy queue may be associated with either a port parent or an intermediate
scheduler parent. The validity parent definition cannot be checked at the time it is provisioned
since the application of the QoS policy is not known until it is applied to an egress SAP or
subscriber or multi-service site profile. It is allowed to have port or intermediate parenting
decided on a queue by queue basis, some queues tied directly to the port scheduler priorities
while other queues are attached to intermediate schedulers.
Quality of Service Guide
QoS Scheduler Policies
531