Overview
24-2 sFlow Configuration
Definitions
ThefollowingtabledescribessomeofthemainsFlowtermsandconcepts.
sFlow Agent Functionality
PacketflowsamplingandcountersamplingareperformedbysFlowInstancesassociatedwith
individualDataSourceswithinthesFlowAgent.Packetflowsamplingandcountersamplingare
designedaspartofanintegratedsystem.Both typesofsamplesarecombinedinsFlowdatagrams.
Packetflowsamplingwillcauseasteady,but
random,streamofsFlowdatagramstobesenttothe
sFlowCollector.Countersamplesmaybetakenopportunisticallyinordertofillthesedatagrams.
Inordertoperformpacketflowsampling,ansFlowSamplerInstanceisconfiguredwitha
samplingrate.Thepacketflowsamplingprocessresultsinthegenerationof
packetflowrecords.
Inordertoperformcountersampling,ansFlowPollerInstanceisconfiguredwithapolling
interval.Thecountersamplingprocessresultsinthegenerationofcounterrecords.ThesFlow
AgentcollectscounterrecordsandpacketflowrecordsandsendsthemintheformofsFlow
datagramsto
sFlowCollectors.
Sampling Mechanisms
TwoformsofsamplingareperformedbythesFlowAgent:statisticalpacket‐basedsamplingof
switchedorroutedpacketflows,andtime‐basedsamplingofcounters.
Table 24-1 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 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.
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