Wireless/Redundant Edge Services xl Module Management and Configuration Guide WS.02.xx and greater

14-2
sFlow Agent
Overview
Overview
The Procurve Wireless Edge Services xl 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 xl 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
approximately 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.