Alcatel-Lucent 7450 Quality Of Service Manual page 523

Each statistics gathering operation requires a show or read followed by a clear. The shorter
the time between the two, the more accurate the information about the congestion state of the
EPS will be.
If the clear operation is not executed after the show or read operation, the external statistics
gathering entity (external server) would need to perform additional operations (such as,
subtract statistics between the two consecutive reads) in order the obtain the delta between
the two reads.
The recommended minimum polling interval at a higher scale (high number of monitoring
entities) is 15 minutes per monitoring entity.
If statistics are obtained via SNMP, the relevant MIB entries corresponding to the show
command are:
Clearing of the statistics can also be performed through a common MIB entry, corresponding
to a clear command: tmnxClearEntry.
Restrictions
The scalability and performance is driven by the number of entities for which congestion
monitoring is enabled on each line card.
Quality of Service Guide
• tPortEgrVPortMonThrEntry
• tPortEgrMonThrEntry
• EPS congestion monitoring is supported only on Ethernet ports.
• If EPS is applied under Vports, the congestion monitoring mechanism does not
provide any indication of whether or not the physical port was congested. For
example, if the physical port is congested, it will distribute less bandwidth to its
Vports than it otherwise would. Therefore, the Vport offered load will appear as less
than it actually is, giving an impression of no congestion.
• Changing EPS parameters dynamically does not automatically update congestion
monitoring statistics. Therefore, it is recommended that the congestion monitoring
statistics are cleared after changing the values of EPS parameters.
• If EPS is configured under a LAG, the failure of the active link causes an interruption
in statistics collection.
QoS Scheduler Policies
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