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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.
3.12.1.1.
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 decision is made on whether or not to sample the packet.
•
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.
•
When a sample is taken, the counter indicating how many packets to skip before taking the next
sample is reset. The value of the counter is set to a random integer where the sequence of random integers
used over time is the Sampling Rate.
3.12.1.2.
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:
•
sFlow Agents keep a list of counter sources being sampled.
•
When a Packet Flow Sample is generated the sFlow Agent examines the list and adds counters to the
sample datagram, least recently sampled first. Counters are only added to the datagram if the sources are
within a short period, 5 seconds say, of failing to meet the required Sampling Interval.
•
Periodically, say every second, the sFlow Agent examines the list of counter sources and sends any
counters that must be sent to meet the sampling interval requirement.
The set of counters is a fixed set.
3.12.2.
Configuring sFlow
Summary of Contents for QuantaMesh QNOS5
Page 1: ...QuantaMesh Ethernet Switch Configuration Guide QNOS5 NOS Platform ...
Page 209: ...209 Table 7 8 IPv6 Neighbor Discovery Settings ...
Page 226: ...226 Table 8 2 L3 Multicast Defaults ...
Page 254: ...254 Appendix A Term and Acronyms Table 9 5 Terms and Acronyms ...
