Configuring flow export

Introduction

Correct configuration of Flow Exporting Devices (FED) is key to Flow Based Network Analysis. In most cases, errors made during configuration will result in missing or duplicate data. It may be difficult to spot that because of this the flow data is compromized. Device vendors are not making it easy and most of them use different methods to enable network flow exports to the collector (in our case TVF or TVA).

Furthermore, some collectors require a special setting on FED in order to undersand its flow records correctly.

This article is trying to decribe the idea behind network flow reporting and we hope it will help you to determine the correct procedure on how to confgure your FEDs.

 

Solution

Definitions

FED

AFlow Enabled Device is any layer three and in some cases layer two device configured to send flow records to a collector.

Flow

A flow is defined as a stream of packets between a given source and a given destination.

For example, in client-server computing a TCP sessions consists of two flows: one flow from client to server and the second flow from server to client.

Flow record

A flow record is a protocol data unit that describes the flow. The most significant parameters are source and destination address, protocol and port, duration of the flow, class of service marking and the physical or virtual interface where the packets entered and exited the FED.

Sensor

A flow sensor is deployed on an interface basis. A flow sensor will "read" the packets going accross the interface and "compose" the flow record.