Sometimes your multiple fiber paths end up in the same bundle, severed by the same backhoe. It's always a fun day when that becomes apparent.
For a major trans-oceanic backbone provider, at least 15ish years ago they had a mile or two between Detroit and Chicago where both ends were on the same side of the interstate highway.
But it's more frequent on DAS (Distributed Antenna Systems, AKA small-cell or micro-cell) networks.
Also the challenge of when fibers are leased (if that's still a thing, based on the networks I helped design I'd say 'probably').
They really are analogous to Lamport's "Distributed System" quip; A damaged fiber owned by a company you have never heard of can wreck your day.
Fibres on the Texas link die all the time (yearly) but that’s fine.
My circuits in the far east are often carried one via dues and one via the USA.
It is possible to guarentee diversity, you just need to get specific detail and have good contractual protections.
Yeah, FWIW the non-redundant DAS links we designed when I was in that industry, it was typically a case of the client telling us 'That is too expensive, we accept the risk'.
The Detroit-chicago thing, I don't know the story on that, it was something that fiber provider had already built.
Over ten years ago, my employer was spinning up a new DC across the state and had three links between it and the primary DC. Two were pretty direct, but we needed a third because at one point in the 300 mile path, the two main links went within 400 meters of each other.
So how national-security-adjacent critical systems like an airport system doesn't have a larger set of backup links, and validates that they are geographically separate up until the connections, and have realtime alerting on the connection status, is surprising to me.
This isn't relevant in this case. The problems occurred at different places. The backup fiber was, separately from the issues with the primary system, cut by a construction crew. It's not two fiber lines both cut at the same spot.
You can get two separate failures in short succession, where the first one hasn’t been fixed. For critical devices that’s why you have tertiary backups, ideally on different technology compel you. For one major event I had diverse fibre and satelite and microwave. Lost microwave and satelite to electronic warfare but the fibres were ok. Ofcom were really pissed about it, but nothing they could do.
No?
Like, okay, monitoring reports what there is no link.
Now what? Somebody gets a hi vis vest, a hard hat and goes along the cable to investigate the reason?
There is nothing monitoring could help, especially if the cable was cut recent enough.
> An RFTS enables fiber to be automatically tested from a central location. A central computer is used to control the operation of OTDR-like test components located at key points in the fiber network. The test components scan the fiber to locate problems. If a problem is found, its location is noted and the appropriate personnel are notified to begin the repair process.
If it's down for more than 15 minutes in country or 2 hours internationally it gets flagged for manual attention. Shorter outages are logged but only looked at monthly as part of the operational report process.
Now sure you can have two independent faults on the same day, but the reports are that they didn't know the backup line was down.
In your case you already have way more than monitoring. You have the infrastructure designed for resilience. You have that design implemented. You have the protocols to do if the things go north. You have automation to disregard minor events and to bring to the attention more serious things. You have way more than monitoring alone.
For mission critical stuff like airports I would like to think they're go for a more rigorous methodology than hope for the best on paths
Usually it’s a combo of a tier 1 that decides that a resell agreement is “good enough” and “well just eat the loss” and then by the time stuff like this rolls around “we’ll get back to you” + a bunch of silly explanations that boil down to “you’re not gonna sue us though” start coming out lol
Then there's another faction that doesn't trust a word suppliers say, who will insist on two different suppliers, as while in theory they could be sharing the same routes, it's far less likely.
Comes down to "do you trust contracts".
Of course this is for third tier sites like branch offices. Major sites require far more oversight, including visibility of cable routes and any hops on the internal network
Had a few issues in some lamdlpcked counties on occasion - Kabul had all traffic routing via the same route into Pakistan for a few years, Kathmandu had an earthquake knock out both ISPs within 30 seconds of each other.
Backups via starlink global roaming work well now in particularly challenging environments.
Luckily we were on Century Link so weren't affected by his stupidity. lol