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Cisco SCE 8000 10GBE Software Configuration Guide
OL-30621-02
Chapter 7 Configuring Line Interfaces
Counting Dropped Packets
Counting Dropped Packets
•
About Counting Dropped Packets, page 7-37
•
Disabling the Hardware Packet Drop, page 7-37
About Counting Dropped Packets
By default, the Cisco SCE platform hardware drops WRED packets (packets that are marked to be
dropped due to BW control criteria). However, this presents a problem for the user who needs to know
the number of dropped packets per service. To be able to count dropped packets per service, the traffic
processor must see all dropped packets for all flows. However, if the hardware is dropping red packets,
the traffic processor will not be able to count all dropped packets and the user will not get proper values
on the relevant MIB counters (
tpTotalNumWredDiscardedPackets
).
Note
The MIB object
tpTotalNumWredDiscardedPackets
counts dropped packets. The value in this counter is
absolute only when hardware packet drop is disabled (not the default mode). When hardware packet drop
is enabled (default mode), this MIB counter provides only a relative value indicating the trend of the
number of packet drops, with a factor of approximately 1:6.
The user can disable the drop-wred-packets-by-hardware mode. This allows the application to access
existing per-flow counters. The application can then retrieve the number of dropped packets for every
flow and provide the user with better visibility into the exact number of dropped packets and their
distribution.
Note that counting all dropped packets has a considerable effect on system performance, and therefore,
by default, the drop-wred-packets-by-hardware mode is enabled.
Disabling the Hardware Packet Drop
Use the following command to disable the drop-wred-packets-by-hardware mode, enabling the software
to count all dropped packets.
By default hardware packet drop is enabled.
Note
Disabling this feature may have both delay and performance implications.
From the SCE(config if)# prompt, type:
Command
Purpose
no accelerate-packet-drops
Disables hardware packet drop.
accelerate-packet-drops
Enables hardware packet drop.