Dell PowerEdge M420 Configuration Manual page 401

Dell powerconnect m8024-k user's configuration guide

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Table of Contents

sFlow Sampling

The sFlow Agent in the PowerConnect M6220/M6348/M8024/M8024-k

switch software uses two forms of sampling:

Statistical packet-based sampling of switched or routed Packet Flows

Time-based sampling of counters

Packet Flow Sampling and Counter Sampling are performed by sFlow

Instances associated with individual Data Sources within an sFlow Agent.

Both types of samples are combined in sFlow datagrams. Packet Flow

Sampling creates a steady, but random, stream of sFlow datagrams that are

sent to the sFlow Collector. Counter samples may be taken opportunistically

to fill these datagrams.

To perform Packet Flow Sampling, an sFlow Sampler Instance is configured

with a Sampling Rate. Packet Flow sampling results in the generation of

Packet Flow Records. To perform Counter Sampling, an sFlow Poller Instance

is configured with a Polling Interval. Counter Sampling results in the

generation of Counter Records. sFlow Agents collect Counter Records and

Packet Flow Records and send them as sFlow datagrams to sFlow Collectors.

Packet Flow Sampling

Packet Flow Sampling, carried out by each sFlow instance, ensures that any

packet observed at a Data Source has an equal chance of being sampled,

irrespective of the Packet Flow(s) to which it belongs.

Packet Flow Sampling is accomplished as follows:

A packet arrives on an interface.

The Network Device makes a filtering decision to determine whether the

packet should be dropped.

If the packet is not filtered (dropped) a destination interface is assigned by

the switching/routing function.

A decision is made on whether or not to sample the packet.

The mechanism involves a counter that is decremented with each packet.

When the counter reaches zero a sample is taken.

Monitoring Switch Traffic