Maximum Burst Size; High Priority Only Buffers - Alcatel-Lucent 7450 Quality Of Service Manual

Queue Parameters

Maximum Burst Size

The maximum burst size (MBS) parameter specifies the maximum queue depth to which a
queue can grow. This parameter ensures that a customer that is massively or continuously
over-subscribing the PIR of a queue will not consume all the available buffer resources. For
high-priority forwarding class service queues, the MBS can be relatively smaller than the
other forwarding class queues because the high-priority service packets are scheduled with
priority over other service forwarding classes.
The MBS is provisioned on ingress and egress service queues within service ingress QoS
policies and service egress QoS policies, respectively. The MBS for a queue is specified in
Kbytes.
The MBS for network queues are defined within network queue policies based on the
forwarding class. The MBS for the queues for the forwarding class are defined as a
percentage of buffer space for the pool.

High Priority Only Buffers

High priority (HP) only buffers are defined on a queue and allow buffers to be reserved for
traffic classified as high priority. When the queue depth reaches a specified level, only high-
priority traffic can be enqueued. The HP only reservation for a queue is defined as a
percentage of the MBS value.
On service ingress, the HP only reservation for a queue is defined in the service ingress QoS
policy. High priority traffic is specified in the match criteria for the policy.
On service egress, the HP only reservation for a queue is defined in the service egress QoS
policy. Service egress queues are specified by forwarding class. High priority traffic for a
given traffic class is traffic that has been marked as in-profile either on ingress classification
or based on interpretation of the QoS markings.
The HP only for network queues are defined within network queue policies based on the
forwarding class. High priority traffic for a specific traffic class is marked as in-profile either
on ingress classification or based on interpretation of the QoS markings.
26 Quality of Service Guide