What is a Flow?

Stateful Flow Management

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Napatech SmartNIC
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User Guide

The definition of a flow is relatively fluid, and Napatech provides support for many variants.

Flow definitions

A flow can be described by any of these definitions:
  • A sequence of packets from a source to a destination (host, multicast group or broadcast domain)
  • An artificial, logical equivalent to a call or connection
  • A sequence of packets sent from a particular source to a particular unicast, anycast or multicast destination that the source desires to label as a flow. A flow can consist of all packets in a specific transport connection or media stream. A flow is not necessarily mapped 1-to-1 to a transport connection
  • A set of IP packets passing an observation point in the network during a certain time interval

Flow examples

Napatech Stateful Flow Management supports flows that are defined in many ways, including subsets and groups of flows. These are examples of some of the supported flows:
  • 5-tuple flow or similar (4-tuple, 2-tuple). The most common parameters for flow identification are the 5-tuple (source IP, destination IP, source port, destination port, protocol).
  • Subset of a flow (for example, 5-tuple/2-tuple and VLAN tag)
  • Groups of flows (for example, layer-2 flow: all packets between two MAC addresses)

This is an example of a 5-tuple flow:


Flow info extract with source IP, destination IP, source port, destination port and protocol

This is an example of an alternative flow:


Two alternative flow info extracts with 1) destination MAC, source MAC and 2) source IP, destination IP, VLAN 1 and VLAN 2