Enterasys Networks 9034313-07 manual Definitions, SFlow Agent Functionality, Sampling Mechanisms

sFlow Configuration Overview

Definitions

The following table describes some of the main sFlow terms and concepts.

Table 28-1 sFlow Definitions

Term	Definition
Data Source	A Data Source refers to a location within a Network Device that
	can make traffic measurements. Possible Data Sources include
	interfaces, physical entities within the device such as the
	backplane, and VLANs.
Packet Flow	A Packet Flow is defined as the path or trajectory that a packet
	takes through a Network Device (That is, the path that a packet
	takes as it is received on one interface, is subjected to a switching/
	routing decision, and is then sent on another interface).
Packet Flow Sampling	Packet Flow Sampling refers to the random selection of a fraction
	of the Packet Flows observed at a Data Source.
Sampling Rate	The Sampling Rate specifies the ratio of packets observed at the
	Data Source to the samples generated.
Sampling Interval	The time period between successive Counter Samples.
sFlow Instance	An sFlow Instance refers to a measurement process associated
	with a Data Source.
sFlow Agent	The sFlow Agent provides an interface for configuring the sFlow
	Instances within a device.
sFlow Collector	An sFlow Collector receives sFlow Datagrams from one or more
	sFlow Agents. The sFlow Collector may also configure sFlow
	Instances using the configuration mechanisms provided by the
	sFlow Agent.
sFlow Datagram	An sFlow Datagram is a UDP datagram that contains the
	measurement data, and information about the measurement
	source and process.

sFlow Agent Functionality

Packet flow sampling and counter sampling are performed by sFlow Instances associated with individual Data Sources within the sFlow Agent. Packet flow sampling and counter sampling are designed as part of an integrated system. Both types of samples are combined in sFlow datagrams. Packet flow sampling will cause a steady, but random, stream of sFlow datagrams to be sent to the sFlow Collector. Counter samples may be taken opportunistically in order to fill these datagrams.

In order to perform packet flow sampling, an sFlow Sampler Instance is configured with a sampling rate. The packet flow sampling process results in the generation of packet flow records. In order to perform counter sampling, an sFlow Poller Instance is configured with a polling interval. The counter sampling process results in the generation of counter records. The sFlow Agent collects counter records and packet flow records and sends them in the form of sFlow datagrams to sFlow Collectors.

Sampling Mechanisms

Two forms of sampling are performed by the sFlow Agent: statistical packet‐based sampling of switched or routed packet flows, and time‐based sampling of counters.

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