RFC 3176 (rfc3176) - Page 2 of 31

InMon Corporation's sFlow: A Method for Monitoring Traffic in Switched and Routed Networks

RFC 3176               InMon Corporation's sFlow          September 2001


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1. Overview

   sFlow is a technology for monitoring traffic in data networks
   containing switches and routers.  In particular, it defines the
   sampling mechanisms implemented in an sFlow Agent for monitoring
   traffic, the sFlow MIB for controlling the sFlow Agent, and the
   format of sample data used by the sFlow Agent when forwarding data to
   a central data collector.

   The architecture and sampling techniques used in the sFlow monitoring
   system are designed to provide continuous site-wide (and network-
   wide) traffic monitoring for high speed switched and routed networks.

   The design specifically addresses issues associated with:

   o Accurately monitoring network traffic at Gigabit speeds and higher.

   o Scaling to manage tens of thousands of agents from a single point.

   o Extremely low cost agent implementation.

   The sFlow monitoring system consists of an sFlow Agent (embedded in a
   switch or router or in a stand alone probe) and a central data
   collector, or sFlow Analyzer.

   The sFlow Agent uses sampling technology to capture traffic
   statistics from the device it is monitoring.  sFlow Datagrams are
   used to immediately forward the sampled traffic statistics to an
   sFlow Analyzer for analysis.

   This document describes the sampling mechanisms used by the sFlow
   Agent, the SFLOW MIB used by the sFlow Analyzer to control the sFlow
   Agent, and the sFlow Datagram Format used by the sFlow Agent to send
   traffic data to the sFlow Analyzer.

2. Sampling Mechanisms

   The sFlow Agent uses two forms of sampling: statistical packet-based
   sampling of switched flows, and time-based sampling of network
   interface statistics.








Phaal, et al.                Informational