I saw the talk version of that and it has lodged in my memory. The point he made was that "health.gov" was made by a bunch of teams that made sure that their part worked, but nobody was in charge of making the whole thing work.
This is sadly "normal" for large bureaucracies.
Every time I see a giant, multi-million dollar catastrophe, it's always "proper", "documented", "enterprise", "by the book", and... "a total failure". The reason is always that nobody actually cares about the final outcome, only the paperwork in front of them that they need fill out, the checkbox that needs to be ticked, or the compliance requirement that needs to be met.
This, in my opinion, is some part of how we are schooling people - do as you are told and follow the rules and some part of not having stakes in the outcome.
They're pretty readable, I recommend that second one (though it leaves some questions I have unanswered). It's a good example of how latent issues with a large system can go unrecognised for a long time before a seeming unrelated change can trigger a cascading failure
One thing it doesn't make clear – the GPS card only supported the original L1 signal, which is what causes the GPS week rollover issue. The newer L2C signal has a much longer rollover period (157 years vs 19.6 years), which means no rollover until next century. If the GPS card had supported the newer L2C signal, then likely this would not have happened even if the other misconfigurations had still occurred.
Is it really so that Time Division Multiplex timing in cellular networks is based on NTP time? I stopped reading after the article implied this - it doesn't sound plausible at all.
I would assume it’s similar to dab etc, and it’s ptp that carried that data on IP. In the broadcast tv world we use ptp, or more traditionally black and burst, or word clocks in audio.
The source is still the same - your grandmaster (ptp) or sync generator (b+b) is fed from a good timing source - often GPS, with one or two inputs, but sometimes local atomic clocks.
I’ve seen issues before with 40ms audio gaps when a GPS antenna has died and the coders can’t cope with frame drift so they incentive a 40ms silence in the audio every 40 minutes or so as the source and destination clocks are different speeds by about 1 part in 60,000.
In DAB the tolerances are far lower, there was a problem about 10 years ago due to a GPs satellite being a few microseconds off
No. The official report seems to suggest that software in IMS core (the subsystem that controls VOIP signalling in the mobile network) bugged out after the time was shifted back 20 years. That doesn't narrow down the specific failure that stopped calls from going through very much. IMS core is full of timers, but it could also have been a license server issue for all the report said about it.
Human made summary: A telecom company had time synchronisation issues in a location of their infrastructure. They eventually used a single hardware GPS clock that fixed the issues but became their only authoritative clock in this location.
One day, the clock was turn off and on and it went 1024 weeks backwards because the time GPS time protocol sucks and use a week counter with too few bits.
Apparently a GPS clock can keep track of the time if it’s up and running when the week counter overflows, otherwise it has to take a wild guess. Apparently their hardware GPS clock used a hardcoded start time from its firmware instead of trusting a less reliable existing clock.
The article finishes with some AI looking suggestions to prevent such an issue to happen again.
Mine would be to have bought one or two more GPS clocks and not from the same provider.
22 comments
[ 2.7 ms ] story [ 20.3 ms ] thread>This design from 2010 had at the top stratum 1 sources at Australia's National Measurement Institute (NMI)
>Among otherwise comparable candidates, the lower stratum carries more weight.
This is the perfect description of Telstra as a company.
I saw the talk version of that and it has lodged in my memory. The point he made was that "health.gov" was made by a bunch of teams that made sure that their part worked, but nobody was in charge of making the whole thing work.
This is sadly "normal" for large bureaucracies.
Every time I see a giant, multi-million dollar catastrophe, it's always "proper", "documented", "enterprise", "by the book", and... "a total failure". The reason is always that nobody actually cares about the final outcome, only the paperwork in front of them that they need fill out, the checkbox that needs to be ticked, or the compliance requirement that needs to be met.
https://www.telstra.com.au/exchange/what-we-ve-learned-from-...
https://www.telstra.com.au/content/dam/tcom/dynamic-media-pr...
It happened twenty years ago...
;-)
That timing requires a very tight time, frequency and phase reference. It’s derived from local high stability GNSS-disciplined time references.
The source is still the same - your grandmaster (ptp) or sync generator (b+b) is fed from a good timing source - often GPS, with one or two inputs, but sometimes local atomic clocks.
I’ve seen issues before with 40ms audio gaps when a GPS antenna has died and the coders can’t cope with frame drift so they incentive a 40ms silence in the audio every 40 minutes or so as the source and destination clocks are different speeds by about 1 part in 60,000.
In DAB the tolerances are far lower, there was a problem about 10 years ago due to a GPs satellite being a few microseconds off
https://www.radioworld.com/trends-1/gps-anomalies-caused-pro...
One day, the clock was turn off and on and it went 1024 weeks backwards because the time GPS time protocol sucks and use a week counter with too few bits.
Apparently a GPS clock can keep track of the time if it’s up and running when the week counter overflows, otherwise it has to take a wild guess. Apparently their hardware GPS clock used a hardcoded start time from its firmware instead of trusting a less reliable existing clock.
The article finishes with some AI looking suggestions to prevent such an issue to happen again.
Mine would be to have bought one or two more GPS clocks and not from the same provider.
Runs in my loft, what a time to be alive.
https://lectronz.com/products/gps-ntp-server