Virtual Private LAN Services
Page 700 7750 SR OS Services Guide
cbs
Syntax cbs size-in-kbytes
no cbs
Context config>service>vpls>sap>egress>queue-override>queue
config>service>vpls>sap>ingress>queue-override>queue
Description This command can be used to override specific attributes of the specified queue’s CBS parameters.
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 potential large number of
service queues and the economy of statistical multiplexing the individual queue’s CBS setting 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 drop packets.
If the CBS value is larger than the MBS value, an error will occur, preventing the CBS change.
The no form of this command returns the CBS size to the default value.
Default no cbs
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).
Values
0 — 131072 or default
high-prio-only
Syntax high-prio-only percent
no high-prio-only
Context config>service>vpls>sap>egress>queue-override>queue
config>service>vpls>sap>ingress>queue-override>queue
Description This command can be used to override specific attributes of the specified queue’s high-prio-only
parameters. The high-prio-only command configures the percentage of buffer space for the queue,
used exclusively by high priority packets.
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 network-queue command.
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
execution. Attempting to set the high-prio-only value larger than the current MBS size will also
result in an error and fail execution.
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