974 | sFloww w w . d e l l . c o m | s u p p o r t . d e l l . c o m Figure 47-1. sFlow Traffic Monitoring SystemImplementation InformationDell Force10 sFlow is designed so that the hardware sampling rate is per line card port-pipe and is decidedbased upon all the ports in that port-pipe. If sFlow is not enabled on any port specifically, then the globalsampling rate is downloaded to that port and is to calculate the port-pipe’s lowest sampling rate. Thisdesign supports, then, the possibility that sFlow might be configured on that port in the future. Back-off istriggered based on the port-pipe’s hardware sampling rate.For example, if port 1 in a the port-pipe has sFlow configured with a 16384 sampling rate while port 2 inthe port-pipe has sFlow configured but no sampling rate set, FTOS applies a global sampling rate of 512 toport 2. The hardware sampling rate on the port-pipe is ten set at 512 because that is the lowest configuredrate on the port-pipe. When a high traffic situation occurs, a back-off is triggered and the hardwaresampling rate is backed-off from 512 to 1024. Note that port 1 maintains its sampling rate of 16384; port 1is 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 thedesired sampling rate even if some ports have no sFlow configured.Important Points to Remember• The FTOS implementation of the sFlow MIB supports sFlow configuration via snmpset.• Collection through management interface is supported on E-Series only• Dell Force10 recommends that the sFlow Collector be connected to the Dell Force10 chassis through aline card port rather than the RPM Management Ethernet port.• E-Series TeraScale sFlow sampling is done on a per-port-pipe basis.• E-Series ExaScale, C-Series, and S-Series sFlow sampling is done on a per-port basis.sFlow CollectorsFlow AgentSwitch/RouterSwitch ASICsFlow DatagramsPoll InterfaceCounters InterfaceCountersFlow Samples
