Alcatel-Lucent 7950 Quality Of Service Manual page 281

network-queue command.
The no form of this command restores the default high priority reserved size.
Parameters
percent — The percentage reserved for high priority traffic on the queue. If a value of 10KBytes is desired,
enter the value 10.
Values
mbs
Syntax mbs size [bytes | kilobytes]
no mbs
Context config>qos>sap-egress>queue
config>qos>sap-ingress>queue
Description
The Maximum Burst Size (MBS) command provides the explicit definition of the maximum amount of
buffers allowed for a specific queue. The value is given in bytes or kilobytes and overrides the default value
for the context.
The MBS value is used by a queue to determine whether it has exhausted all of its buffers while enqueuing
packets. Once the queue has exceeded the amount of buffers allowed by MBS, all packets are discarded until
packets have been drained from the queue.
The sap-ingress context for mbs provides a mechanism for overriding the default maximum size for the
queue.
The sum of the MBS for all queues on an ingress access port can oversubscribe the total amount of buffering
available. When congestion occurs and buffers become scarce, access to buffers is controlled by the RED
slope a packet is associated with. A queue that has not exceeded its MBS size is not guaranteed that a buffer
will be available when needed or that the packets RED slope will not force the discard of the packet. Setting
proper CBS parameters and controlling CBS oversubscription is one major safeguard to queue starvation
(when a queue does not receive its fair share of buffers). Another is properly setting the RED slope
parameters for the needs of services on this port or channel.
The no form of this command returns the MBS size assigned to the queue to the value.
Default default
Parameters size [bytes | kilobytes] — The size parameter is an integer expression of the maximum number of bytes or
kilobytes of buffering allowed for the queue. The default unit is kilobytes; to configure the MBS in
bytes specify the bytes parameter. A value of 0 causes the queue to discard all packets. The queue MBS
maximum value used is constrained by the pool size in which the queue exists and by the shared pool
space in the corresponding megapool.
Values
7950 XRS Quality of Service Guide
0 — 100, default
0 — 131072 or default
Minimum configurable non-zero value
Minimum default value
1byte
maximum of 10ms of PIR or 64Kbytes
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