Alcatel-Lucent 7750 SR OS Service Manual page 513

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.
If the CBS value is larger than the MBS value, an error will occur, preventing the MBS change.
The no form of this command returns the MBS size assigned to the queue.
Default
default
Parameters
size-in-kbytes — The size parameter is an integer expression of the maximum number of kilobytes of
mbs
Syntax mbs {size-in-kbytes | default}
no mbs
Context config>service>vpls>sap>ingress>queue-override>queue
Description
This command can be used to override specific attributes of the specified queue's MBS parameters.
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 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 con-
trolled 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.
If the CBS value is larger than the MBS value, an error will occur, preventing the MBS change.
The defined high-prio-only value cannot be greater than the MBS size of the queue. Attempting to
change the MBS to a value smaller than the high priority reserve will generate an error and fail execu-
tion. Attempting to set the high-prio-only value larger than the current MBS size will also result in an
error and fail execution.
The no form of this command
Default
default
Parameters
size-in-kbytes — The size parameter is an integer expression of the maximum number of kilobytes of
7750 SR OS Services Guide
buffering allowed for the queue.For a value of 100 kbps, enter the value 100. A value of 0 causes
the queue to discard all packets.
Values
0 — 131072 or default
buffering allowed for the queue. For a value of 100 kbps, enter the value 100. A value of 0 causes
the queue to discard all packets.
Values
0 — 131072 or default
returns
the MBS size assigned to the queue to the default value.
Virtual Private LAN Services
Page 513