WESM zl Management and Configuration Guide WT.01.28 and greater

13-2
sFlow Agent
Overview
Overview
The Procurve Wireless Edge Services zl Module contains an sFlow agent. The sFlow
agent samples traffic, treating the traffic that arrives on each adopted RP radio as a
separate flow. In other words, the module’s sFlow agent monitors each radio much
as a switch might monitor each physical interface.
The sFlow agent forwards traffic information to an sFlow collector. Another term for
an sFlow collector is an sFlow receiver. For the rest of this chapter, this guide will
use the term “sFlow receiver.”
The agent can create six separate instances for each flow, and forward the information
for each instance to a different sFlow receiver.
The Wireless Edge Services zl Module supports the two sampling mechanisms of
sFlow, which are designed to work together to produce an accurate picture of network
traffic:
■ flow sampling
■ counter polling
An advantage of the module’s sFlow capabilities is that the picture not only details
how much traffic radios handle, but also the types of traffic and the devices that
generate it.
Flow Sampling by the sFlow Agent
Traffic analysis techniques differ in the way that agents collect and process traffic.
Some techniques have the agent copy all traffic to the receiver, but this strategy can
create prohibitive overhead. with other techniques, the agent groups traffic into flows,
summarizes information about each flow, and sends the summary to the collector.
However, this approach requires the agent to inspect all traffic and consumes
significant resources within the agent.
The sFlow technology, rather than requiring the agent to inspect every packet that
passes through, uses sample-based profiling. That is, the agent inspects approxi-
mately every “nth” packet from each data source available to sFlow. The sampling
algorithm is designed to give a high certainty that the sampled traffic mirrors the total
traffic within a small margin of error.