Was there indeed a major reconfiguration of the affected system ?

Since Scottish Mil will have needed a chunk of new connectivity to both the outside world and locally within Swanwick I think it is a fair punt that a large config change would have been needed. Changes to configs is one of the more likely causes of this type of failure as it is virtually impossible to test every possible combination that the new config can make available to the user.

I'd want to know whether or not Scottish Mil are using VCS before I'd take that punt.

I'd love to see HD's technical solution in use at Swanwick. I suspect NATS might have to build some rather large walls to put all the switches on though.

Having worked for many years on the Frequentis 3020 in our system;it would be interesting to know if new software had just been installed.

Te procedures we developed would have us have had us take down one of the parallel / redundant switches, (leaving the operation with no redundancy within the switch, but we had completely independent backup system to provide all comms just in case) and load and TEST the software while that switch was offline. If all went according to plan the switch with the new software was brought on line and the switch with the old software taken offline (making sure that the two versions of software didn't try to talk to each other)

If the new software proved itself under real world use for a while then the other switch was updated, and tested, then switched back on line. The fact that the 3020 allowed either switch to fully support the operation on its own made helped make upgrades a lot easier. In dozens of software upgrades I don't think we ever left the operation stranded, a couple of times we had to switch back to the old software due to problems that never seem to show up in the lab but are happy to raise their ugly little heads when used in anger.

Would be interesting to hear what process NATS used for the upgrade.

Okay, Guv. It's a fair cop. It was I what done it.

Cheers, Murph.

But I knows a bloke who can fix it. But t'aint me. It's an expert! :E

If the new software proved itself under real world use for a while then the other switch was updated, and tested, then switched back on line.

Fine for the core switch code but what about the configuration data ? If you need to change the configuration because of new positions or because the other stations you are connecting to change that option isn't going to be available.

I didn't go into great detail in the original blurb, but first, testing configuration changes would have been lab tested using a redundant switch. Secondly, as part of our on site testing once the new software had been loaded into one of the switches we would switch a few unused (all this was done on the midnight shift, so there were plenty of spare positions) positions over to the updated switch and "played around" with a number of tests.

With our setup, configuration changes did not involve a software update per se, they were created and loaded locally and did not require taking either side of the system down.