Sflow; Flow Sampling By The Sflow Agent - HP ProCurve 530 NA (J8986A) Management And Configuration Manual

Special Features

sFlow

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sFlow

The Access Point 530 contains an sFlow agent. The sFlow agent samples
traffic flow, treating the traffic that arrives on each of the radios or on the
ethernet interface as a separate flow.
The sFlow agent forwards traffic information to one or more sFlow collectors.
The agent can create three separate instances for each flow, and forward the
information for each instance to a different sFlow collector. The three
instances are contained in three separate Receiver Tables.
The Access Point 530 supports both sampling mechanisms of sFlow, which
are designed to work together to produce an accurate picture of network
traffic:
Flow sampling
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■ Counter polling
sFlow settings for the Access Point 530 can only be configured over SNMP.

Flow Sampling by the sFlow Agent

sFlow technology, instead of requiring the agent to inspect every packet that
passes through, as some other flow sampling methods do, 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 total traffic within a small margin of error.
On the Access Point 530, data sources are the interfaces, and "n", the packet-
sampling rate, is configurable per-interface and per-sampling instance (up to
three per interface). When sFlow is enabled, the interfaces send every "nth"
packet to the sFlow agent to be sampled, packaged, and sent to the collectors.
Only 802.11 data frames are sampled. The sFlow agent management and
control frames such as beacons.
The sFlow agent packages samples into small datagrams which include,
among other information:
A sampled packet's decrypted header
■
■ A sampled packet's inbound or outbound interface
■ Information about the how a sampled packet is being forwarded.