Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 2084)

sFlow Introduction and Configuration
Software Reference for x310 Series Switches
80.4 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
Frame Sampling
As frames enter or leave an sFlow source port, they are sampled at a rate determined by
the
sflow sampling-rate command on page 81.13 for that particular port.
Sampling occurs every N frames (on average), where N is the rate value set via sflow
sampling-rate command. The sampling rate applies to ingress and egress frames
independently. For example, a value of 1000, will sample one frame in every 1000 frames
received, one in every 1000 frames sent from the specified port.
Data Confidentiality
Sampling operates by capturing the initial portion of frames (statistically) selected. The
portion sampled is set by the
sflow max-header-size command on page 81.10 , or SNMP.
If the maximum header size is greater than the actual headers in the sampled frames,
then portions of the user data (payload) will also be captured and encapsulated in the
datagrams sent to the collector. The amount of user data captured can be minimized by
careful selection of the maximum header size.
Counter Polling
The function of counter polling is to provide snapshots of various system counters. This
produces a series of data counter sets for each port, which can be independently polled at
user defined rates, and sent (once a second or less) to the collector. Allied Telesis switches
running AlliedWare Plus software support generic interface counters only. For more
information on the data types included in the sampling count, see
“sFlow Datagrams” on
page 80.13 .
Caution Setting the sFlow sampling rate to a very low value (frequent sampling)
can place a heavy load on the switch’s CPU. The severity of this loading will
increase with the number of ports configured for sampling, the port
speeds, and their data sampling rates.