Alcatel-Lucent 7950 Quality Of Service Manual page 280

Service Queue QoS Policy Commands
cbs
Syntax cbs size-in-kbytes
no cbs
Context config>qos>sap-egress>queue
config>qos>sap-ingress>queue
Description This command provides a mechanism to override the default reserved buffers for the queue. It is
permissible, and possibly desirable, to oversubscribe the total CBS reserved buffers for a given access port
egress buffer pool. Oversubscription may be desirable due to the potentially large number of service queues
and the economy of statistical multiplexing the individual queue's CBS settings into the defined reserved
total.
When oversubscribing the reserved total, it is possible for a queue depth to be lower than its CBS setting and
still not receive a buffer from the buffer pool for an ingress frame. As more queues are using their CBS
buffers and the total in use exceeds the defined reserved total, essentially the buffers are being removed from
the shared portion of the pool without the shared in use average and total counts being decremented. This
can affect the operation of the high and low priority RED slopes on the pool, causing them to miscalculate
when to start randomly dropping packets.
If the CBS value is larger than the MBS value, the CBS is capped to the value of the MBS or the minimum
CBS value. If the MBS and CBS values are configured to be equal (or nearly equal) this will result in the
CBS being slightly higher than the value configured.
The no form of this command returns the CBS size to the default value.
Default
default
Parameters
size-in-kbytes — The size parameter is an integer expression of the number of kilobytes reserved for the
queue. If a value of 10KBytes is desired, enter the value 10. A value of 0 specifies that no reserved
buffers are required by the queue (a minimal reserved size can still be applied for scheduling purposes)
The CBS maximum value used is constrained by the pool size in which the queue exists.
Values
high-prio-only
Syntax high-prio-only percent
no high-prio-only
Context config>qos>sap-ingress>queue
config>qos>sap-egress>queue
Description
The high-prio-only command configures the percentage of buffer space for the queue, used exclusively by
high priority packets. The specified value overrides the default value for the context.
The priority of a packet can only be set in the SAP ingress QoS policy and is only applicable on the ingress
queues for a SAP. The high-prio-only parameter is used to override the default value derived from the
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0 — 104857 or default
Minimum configurable non-zero value
Minimum non-zero default value
6Kbytes on an FP2 and 7680 bytes on an FP3
maximum of 10ms of CIR or 6Kbytes on an FP2
and 7680 bytes on an FP3
7950 XRS Quality of Service Guide