WESM zl Management and Configuration Guide WT.01.28 and greater

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sFlow Agent
Configuring sFlow Using the Web Browser Interface
Figure 13-5. Flow Sampling Configuration Screen
4. From the Receiver Instance drop-down menu, choose the receiver index number
associated with the sFlow receiver to which the module should send the samples.
To easily track which settings apply to a specific sFlow collector, match the
sFlow instance number to the receiver instance number. However, matching the
numbers is not mandatory. Although you can choose one and only receiver for
each flow, you can map multiple flows, even on the same radio, to the same
receiver. For example, you could map different sFlow instances to the same
receiver, but choose a different sampling rate for the flows.
5. Enter a value between 50 and 65535 in the Packet Sampling Rate field.
The value determines how often the radio sends the sFlow agent a packet to be
sampled. In other words, the radio sends every “nth” packet, and “n” is the value
entered in the Packet Sampling Rate field. For example, if you enter 100, the
radio sends one percent of the packets to be sampled.
The accuracy of a sample increases as the absolute number of samples increases.
One general guideline is to set the rate so that the radio sends about one sample
per second. To determine the necessary rate, consider roughly how much traffic
the radio typically handles. For example, if the radio handles about 1000 packets
a second, you can set the rate to 1000. On the other hand, if the radio, on average,
handles only 100 packets a second, it must sample traffic more frequently to
achieve the same accuracy; set the rate to 100.
Of course, the activity on a radio changes over time, so there are no absolute
rules for determining the best sampling rate.