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sFlow Configuration Overview
28-2
Definitions
ThefollowingtabledescribessomeofthemainsFlowtermsandconcepts.
sFlow Agent Functionality
PacketflowsamplingandcountersamplingareperformedbysFlowInst ances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.
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.