User’s Guide FUJITSU PSWITCH
December/2018 111
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, a sFlow Sampler Instance is configured with a
Sampling Rate. Packet Flow sampling results in the generation of Packet Flow
Records. And currently this software only supports Packet Flow Data type with Raw
Packet Header. To perform Counter Sampling, a 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.
3.1.6.2.2. Packet Flow Sampling
The Packet Flow Sampling mechanism 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. -
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.
A sample method which to take one packet from N coming packets is not
adopted. Instead, chip uses a user-configurable 'probability' to sample the traffic.
For each coming packet, chip will apply the probability on this packet to decide
whether to sample it.
3.1.6.2.3. Sampling in Hardware
On platforms where sFlow packet sampling is supported in hardware, the hardware
can send sampled packets to a configured remote-agent and can copy the sampled
packet to the CPU (local agent).
3.1.6.2.4. Counter Sampling
The primary objective of Counter Sampling is to efficiently, periodically export
counters associated with Data Sources. A maximum Sampling Interval is assigned
to each sFlow instance associated with a Data Source.
Counter Sampling is accomplished as follows:
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