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Airlines are running out of 4-digit flight numbers

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Re: Airlines are running out of 4-digit flight numbers

#381

Post by kelnos »

drdaeman wrote: post #371
lxgr wrote: post #155

Earlier quoted context omitted.

Having multiple prefixes per airline doesn't seem trivial, given that this historically wasn't a thing. I could imagine a bazillion code snippets of if flightNumber.startsWith(OUR_AIRLINE_CODE) that might be incredibly painful to fix on short notice.

Searching a large codebase for a constant (like "DL", plus tracing all related variable use if something is assigned this or related value), and replacing the logic is a relatively easy kind of change. Especially in the modern day when we got all those nice semantic analysis and code transformation tools. Especially if they got proper tests. Certainly way easier than replacing use of a deprecated API (and people do t…

I think you have an unreasonably optimistic view of the current state of most of these code bases.

Re: Airlines are running out of 4-digit flight numbers

#383

Post by kelnos »

account42 wrote: post #314
delfinom wrote: post #254

Earlier quoted context omitted.

The marketing carrier, aka the one with the airline code on the ticket becomes liable for certain things in most countries. Codeshare is one way who is responsible is known to outside parties immediately. It also impacts automatic luggage transfers for layovers. Not to mention, there are bits where if I buy a JAL ticket for AA internationally, I get 2 free checked bags while the same AA sold and operated flight has n…

Most airlines already have vastly different baggage rules for different seat classes so I doubt this really needs to be determined by the flight number.

I feel like you have it backwards: that's exactly the point. You buy the flight under the code share flight number, and you buy the seat class based on the code share airline's (not the operator airline's) seat class name. Then the code share airlines baggage rules for that seat class flow into that.

Re: Airlines are running out of 4-digit flight numbers

#384

Post by kelnos »

immibis wrote: post #344
ReptileMan wrote: post #310

Earlier quoted context omitted.

Roughly 20 years ago a network engineer I worked with said - "We took a look and IPv4 had everything we want and need but the address space". Why the committees didn't just made it 128 bit and be done with it is beyond me.

They basically did. All the other changes are minor cleanups like getting rid of fields nobody uses, and realigning header bytes. Except SLAAC, but that wasn't part of the original design anyway. That was an accident when some major vendor implemented SLAAC before it implemented DHCPv6. The plan was to keep DHCP.

The idea that IPv6 is basically just "IPv4 with more address bits" is so wildly incorrect I'm not even sure where to start.

Re: Airlines are running out of 4-digit flight numbers

#385

Post by rvnx »

Macha wrote: post #343
rvnx wrote: post #333

Earlier quoted context omitted.

This is the point, instead of rewriting a full stack, I would rather change the prototype of these APIs. To store 999.999.999.999, then you are totally fine with a 64-bits INT (QWORD), and there is no struggle to backward-compatibility store a 32-bits INT (DWORD) into it. It's more of a matter of doing #ifdef IPV4_EXTENDED #define DWORD QWORD #endif and add an extra IP field inside the IP header packet itself that sa…

So you need to send a message from your host 5.6.7.8 to one of these newly enabled hosts 500.600.700.800. You update the software on your host, and your target's ISP is updated, and your target updates, and we'll even hand wave and assume your ISP is updated despite apparently having enough legacy addresses to allocate you one. The message goes out to your ISP router, who then sends it to their upstream ISP, who look…

(I'm not pushing this idea to the max, I mean, now IPv6 is here so we'll just go with it, but this is for the mental and engineering exercise).

To answer your question, in my model, the legacy IPv4 field contains the IP addresses of "IPv4 to IPv4 Extended bridges".

Let's imagine you want to connect to [example.com]:

Clients who speak IPv4 Extended and their ISP is compatible, get the IPv4 Extended answer:

425.223.231.123 A+ example.com

and directly to it

Clients who speak IPv4 Extended but don't have an IPv4 Extended compatible ISP, add that extra IPv4 Extended header and speak to the bridges.

425.223.231.123 A+ example.com

34.23.12.2 BR example.com (the bridge)

Clients who speak IPv4 only but don't speak IPv4 Extended don't have to think about IPv4 Extended at all, since they will go through the usual layer-7 (typically HTTP) reverse-proxy, or a routing based on rules (ip/port pair).

Cloudflare does search large scale reverse proxies, it works fine in practice.

If someone has an incentive to run such bridges or reverse proxies solution, first it's yourself, to save your preciouses IPv4.

To the end user the promise is "you will connect faster to the internet if you are in native IPv4 Extended (because you skip these intermediate bridges)"

We actually have a nice mechanism that we could reuse for knowing which bridges to use, it's reverse DNS lookup.

https://www.cloudflare.com/learning/dns/glossary/reverse-dns...

In reality this intermediate state with the bridge, is not even necessary, so the migration could be even easier.

Re: Airlines are running out of 4-digit flight numbers

#386

Post by Green-Man »

indus wrote: post #284

In 2010, Indian railways switched from a four-digit numbering system to five digits. They were running out of train numbers. Indian railways today operates 13,000 trains daily. There is a PDF that talks about the problem, the solution, exceptions, and a rollout plan. One fine day, IT systems seamlessly transitioned—-took some time to wipe the old numbers from passengers memories.

I looked up the nickname of the author of the commentary. Now I feel recursion is still running inside my brain

Re: Airlines are running out of 4-digit flight numbers

#387

Post by pasc1878 »

FeepingCreature wrote: post #234
nottorp wrote: post #196

Earlier quoted context omitted.

> IPv6 is seen and used directly by professionals, not the general public Yes, that's the problem. It's unusable on your fucking home network. Please, don't post again the 10 "concise" 50+ page documents that you "just" need to read to set up ipv6...

I don't really understand. My router gives me an IPv6 address...

Mine does not

Re: Airlines are running out of 4-digit flight numbers

#388

Post by drivers99 »

snapcaster wrote: post #228
jll29 wrote: post #227

> Here’s the full answer, along with how they triage the problem – for instance by assigning the same flight number to more than one flight a day (although that means they need for it to be flights that would never both be in the air at the same time, such as where the same plane is used and can’t reasonably be substituted) This sounds like it's calling for trouble! Whenever I hear that any IDs could be "recycled", I…

>Whenever I hear that any IDs could be "recycled", I make a mental note to replace the person making such a proposal from all teams that I am involved in. Couldn't agree more, not even interested in debating it

This whole argument reminds me of something. Found it. (Can't believe that was only 2 months ago.)

You'll regret using natural keys https://news.ycombinator.com/item?id=40580549 (554 comments)

Re: Airlines are running out of 4-digit flight numbers

#389

Post by tivert »

delta_p_delta_x wrote: post #292
ryukoposting wrote: post #259

Earlier quoted context omitted.

I'm certain each flight has its own completely unique ID buried somewhere in a database. But, shorter codes can be spoken into a radio faster and with lower probability of misinterpretation - both critical features for air traffic control. Those shorter codes will necessarily be reused, it's just a question of the time interval between re-uses of any particular code. I faintly recall seeing two Southwest flights from…

> I'm certain each flight has its own completely unique ID buried somewhere in a database There is. It's called the Globally Unique Flight Identifier (GUFI), and it's essentially a UUIDv4[1]. [1]: https://docs.fixm.aero/#/general-guidance/flight_identificat...

>> I'm certain each flight has its own completely unique ID buried somewhere in a database

> There is. It's called the Globally Unique Flight Identifier (GUFI), and it's essentially a UUIDv4[1].

Great, step one cleared.

Now have all the legacy systems everywhere that use 4-digit flight numbers been updated or replaced?

Re: Airlines are running out of 4-digit flight numbers

#390

Post by alfalfasprout »

gentle wrote: post #83

I love that so many people here think they can think about the problem for 10 seconds and come up with a solution that hasn't already been considered a thousand times and discarded.

Yep. Of course there are ton of solutions that seem better at a glance. More digits! Alphanumeric!

Problem is decades and decades of software with the assumption of 4 digit flight numbers baked in.

My hunch would be an additional airline code would probably be the easiest solution.

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