Alcatel-Lucent 7450 Quality Of Service Manual page 661

The unknown forwarding type usually tracks the multicast forwarding type definition. This command
overrides that default behavior.
The no form of this command sets the unknown forwarding type queue-id back to the default of
tracking the multicast forwarding type queue mapping.
Parameters queue-id — The queue-id must be an existing, multipoint queue defined in the the
cbs
Syntax cbs percent
no cbs
Context config>qos>shared-queue>queue
Description
The Committed Burst Size (cbs) command specifies the relative amount of reserved buffers for a
specific ingress network XMA or MDA forwarding class queue or egress network port forwarding
class queue. The value is entered as a percentage.
The CBS for a queue is used to determine whether it has exhausted its reserved buffers while
enqueuing packets. Once the queue has exceeded the amount of buffers considered in reserve for this
queue, it must contend with other queues for the available shared buffer space within the buffer pool.
Access to this shared pool space is controlled through Random Early Detection (RED) slope
application.
Two RED slopes are maintained in each buffer pool. A high priority slope is used by in-profile packets.
A low priority slope is used by out-of-profile packets. All Network-Control and Management packets
are considered in-profile. Assured packets are handled by their in-profile and out-of-profile markings.
All Best-Effort packets are considered out-of-profile. Premium queues should be configured such that
the CBS percent is sufficient to prevent shared buffering of packets. This is generally taken care of by
the CIR scheduling of Premium queues and the overall small amount of traffic on the class. Premium
queues in a properly designed system will drain before all others, limiting their buffer utilization.
The RED slopes will detect congestion conditions and work to discard packets and slow down random
TCP session flows through the queue. The RED slope definitions can be defined, modified or disabled
through the network-queue policy assigned to the XMA or MDA for the network ingress buffer pool
or assigned to the network port for network egress buffer pools.
The resultant CBS size can be larger than the MBS. This will result in a portion of the CBS for the
queue to be unused and should be avoided.
Default
The cbs forwarding class defaults are listed in
Quality of Service Guide
config>qos>sap-ingress context policer-output-queues profile. For the 7950 XRS, this is not
configurable in the policer-output-queues profile.
Values 25 to 32
Shared-Queue QoS Policies
Table 44.
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