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Overview
Definitions
The following table describes some of the main sFlow terms and concepts.
Table 24-1 sFlow Definitions
Term
Data Source
Packet Flow
Packet Flow Sampling
Sampling Rate
Sampling Interval
sFlow Instance
sFlow Agent
sFlow Collector
sFlow Datagram
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.
24-2 sFlow Configuration
Definition
A Data Source refers to a location within a Network Device that
can make traffic measurements. Possible Data Sources include
interfaces and VLANs.
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 refers to the random selection of a fraction
of the Packet Flows observed at a Data Source.
The Sampling Rate specifies the ratio of packets observed at the
Data Source to the samples generated.
The time period between successive Counter Samples.
An sFlow Instance refers to a measurement process associated
with a Data Source.
The sFlow Agent provides an interface for configuring the sFlow
Instances within a device.
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.
An sFlow Datagram is a UDP datagram that contains the
measurement data, and information about the measurement
source and process.
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