Alcatel-Lucent 7450 Quality Of Service Manual page 763

The discard counters are incremented during enqueuing discarded events and the forward
counters are incremented during scheduled dequeuing events.
For standard ingress queues, the offered stats-per-queue are counted by the ingress
forwarding plane. For standard egress queues, the offered stats are derived by adding the
hardware per-queue discard and forward stats. This means packets waiting to be scheduled in
a standard egress queue will not be counted until it is forwarded. The HSMDA queue-offered
stats operate the same as the standard egress queues where the discard and forwarded stats are
combined to derive the offered stats for an HSMDA queue.
The decision on the counter to use is made per packet by HSMDA ingress hardware or by the
egress forwarding plane hardware. The default behavior is to use the counter-id that
corresponds to the queue-id to which the packet is mapped. This means the packets destined
to queue 2 will be accounted for by counter set 2 within the same queue group. This sets aside
the first eight counter sets as the default counters for the queue group. The remaining eight
are available as counter override decisions.
A counter override can be performed within the ingress QoS classification rules wherever an
HSMDA is installed.
The eight counter sets used as exception counters are identified as counter 1 through counter
8. While the discard and forwarding statistics can be overridden based on exception criteria,
the offered statistics are maintained per queue. This means that the offered statistics for a
queue includes all packets offered to the queue, but the discard and forwarding statistics only
reflect packets handled by the queue that have not been associated with exception counters.
It is possible to estimate the number of packets not represented by the queue statistics by
subtracting the discard and forwarding statistics from the queue-offered statistics. The
resulting number may be off slightly if packets are still in the queue when the statistics where
collected, but this error is minimized when calculated over an appropriate amount of time and
can be completely eliminated if the queue is allowed to drain prior to performing the
calculation. When the queue statistics and the exception statistics are considered as a whole,
all packets handled by the queue group are accurately represented by the counters.
Quality of Service Guide
• Discarded out-of-profile (low priority) packet
• Discarded out-of-profile (low priority) octet
• Discarded in-profile (high priority) packet
• Discarded in-profile (high priority) octet
• Forwarded out-of-profile packet
• Forwarded out-of-profile octet
• Forwarded in-profile packet
• Forwarded in-profile octet
High Scale Ethernet MDA Capabilities
765