Users Guide

Application-specific integrated circuits (ASICs) typically complete packet sampling. sFlow collector analyses
the sFlow datagrams received from different devices and produces a network-wide view of traffic flows.
Figure 126. sFlow Traffic Monitoring System
Implementation Information
Dell Networking sFlow is designed so that the hardware sampling rate is per line card port-pipe and is
decided based on all the ports in that port-pipe.
If you do not enable sFlow on any port specifically, the global sampling rate is downloaded to that port and is
to calculate the port-pipe’s lowest sampling rate. This design supports the possibility that sFlow might be
configured on that port in the future. Back-off is triggered based on the port-pipe’s hardware sampling rate.
For example, if port 1 in the port-pipe has sFlow configured with a 16384 sampling rate while port 2 in the
port-pipe has sFlow configured but no sampling rate set, Dell Networking OS applies a global sampling rate
of 512 to port 2. The hardware sampling rate on the port-pipe is then set at 512 because that is the lowest
configured rate on the port-pipe. When a high traffic situation occurs, a back-off is triggered and the
hardware sampling rate is backed-off from 512 to 1024. Note that port 1 maintains its sampling rate of 16384;
port 1 is unaffected because it maintains its configured sampling rate of 16484.
To avoid the back-off, either increase the global sampling rate or configure all the line card ports with the
desired sampling rate even if some ports have no sFlow configured.
Important Points to Remember
• The Dell Networking OS implementation of the sFlow MIB supports sFlow configuration via snmpset.
sFlow 974