Fluke Networks - Characterizing Network Failover Time in an Industrial Ethernet Network

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Redundancy in Industrial Ethernet Industrial
Ethernet networks must be highly reliable and continue to operate during harsh environmental conditions, accidental network disruptions, and equipment failures. Network downtime can be dangerous and expensive. Network reliability is largely achieved by the use of redundancy for all critical links. There are four popular redundancy schemes for Ethernet: Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), Link Aggregation (Trunking), and proprietary ring topology.

Independent of the redundancy scheme, EtherScope coupled with a LinkRunner provides precise measurement of failover recover time with submillisecond accuracy. The characterization is performed under load, up to full gigabit line rate, to ensure worst cast measurement conditions.

Characterizing Network Dead Time using EtherScope
Dead time characterizes the maximum that a network goes quiet and is useful for measuring breaks like ring failover or access point handoff times. There are 2 methods to measure dead time, either by a loss of frames, or the maximum frame interarrival time.

Measurement Resolution
In both methods, the accuracy and load of the measurement can be controlled using an RFC test frame rate. Depending on the deployment phase of the network, the user may wish to test dead time at maximum throughput, up to a gigabit, or with light loading in the case of a production network. For example, if 1 ms timing accuracy is desired then 1000 frames per second (fps) must be generated. To do this with minimum load, 64 byte frames can be used. To generate 1000 fps with 64 byte frames, a rate of 672 Kbps is used. Frame Loss Configure an RFC throughput test to run for duration longer than the total test time required to capture the break, for example 60 seconds...

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