Ethernet fault timing analysis tool

Fremont, CA—GarrettCom Inc. reports that it’s offering industrial Ethernet users its Fault Timing Analysis (FTA) software free of charge.

By Control Engineering Staff September 1, 2004

Fremont, CA— GarrettCom Inc. reports that it’s offering industrial Ethernet users its Fault Timing Analysis (FTA) software free of charge. An e-mailed request sent to, with no subject line or message required, will generate an autoreply e-mail containing download instructions. GarretCom manufactures industrial Ethernet switches and connectivity tools.

Fault timing data are critical to implementing redundant networks in high-availability in-dustrial applications. However, accurate fault timing has been subject to trial-and-error analysis, which is why GarretCom decided to make FTA available. FTA works with both mesh and ring topologies.

‘Our objective in releasing the FTA tool free of charge is to allow industrial Ethernet users to determine for themselves the fault recovery time they can expect in their self-healing LAN installations,’ says Frank Madren, GarrettCom’s president. ‘We want users to have the information available to make the choice that is best for them.

‘The technology of fault recovery is not yet mature. This means that users are faced with simplistic, statistically impossible claims about how fast different products can achieve fault recovery, such as precisely 50 or 250 milliseconds (ms). In reality, even the same test using the same LAN equipment and set-up will have statistically significant variances from one test to the next. In sensitive control applications, the range of response times is critical to avoid errors under operating conditions, and to plan for successful fault recovery. Our FTA software gives users an easy and tested way to determine the fault response range in their own application.’

GarrettCom has been testing FTA in-house and with customers for more than a year. It has also been used hands-on by show attendees at events including the ISA Expo 2003 and SuperComm 2004.

Ease of use GarrettCom adds that FTA is easy to use because a clock window displays the elapsed time, in thousandths of seconds, from the start of the test. FTA operates by sending a rapid sequence of pings over the target network, timed by a 1-ms counter. A ping response shows that the network is working normally at that instant.

When the user initiates a fault in the network, the ping response is not returned and the connection is considered broken. A ms counter window tracks the elapsed time from fault detection to recovery, when ping responses are again received, and then updates the on-screen postings for the fault times measured, the number of fault incidents recorded, and the fault-recovery minimum/average/maximum statistics at the bottom of the FTA screen. FTA is downloaded as a 700 Kb zipped file; the FTA.exe file is a 1Mb Windows-executable file.

Fault recovery vs. path recovery Madren adds that a critical distinction is between path recovery and fault recovery. Path recovery is fairly straightforward, he says. It is defined as the operating state where a new node can come on, and find a working path enabling use of the ring elements to communicate with another new node.

Meanwhile, fault recovery is defined as the operating state where all existing nodes that previously communicated using the ring elements can communicate again. Fault recovery can be skewed because of differences in how network devices behave. If the ping target device sends regular packets announcing its presence on the network, then inaccurate fault recovery times will be noted. Since an announcement packet forces switches in the network to relearn the sender’s location, the measured test result will be less than or equal to the true fault recovery. Devices that do not regularly announce their presence, however, are not accessible for packet transmittal until intervening switches have flushed their buffers, and relearned all node addresses in the network, i.e., full fault recovery. Elapsed time for full fault recovery may take as long as five minutes in most off-the-shelf Ethernet switches, according to GarretCom.

More information about FTA operation and fault timing analysis is available in GarrettCom’s “LAN Fault Timing Analyzer (FTA) Software User Information” guide, which may be downloaded at .

Control Engineering Daily News DeskJim Montague, news