Administrator Guide

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sFlow
Configuring sFlow is supported on Dell Networking OS.
Overview
The Dell Networking Operating System (OS) supports sFlow version 5.
sFlow is a standard-based sampling technology embedded within switches and routers which is used to
monitor network traffic. It is designed to provide traffic monitoring for high-speed networks with many
switches and routers. sFlow uses two types of sampling:
• Statistical packet-based sampling of switched or routed packet flows.
• Time-based sampling of interface counters.
The sFlow monitoring system consists of an sFlow agent (embedded in the switch/router) and an sFlow
collector. The sFlow agent resides anywhere within the path of the packet and combines the flow
samples and interface counters into sFlow datagrams and forwards them to the sFlow collector at regular
intervals. The datagrams consist of information on, but not limited to, packet header, ingress and egress
interfaces, sampling parameters, and interface counters.
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.
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.
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sFlow