> This reverse traceroute is still helpful. The paths will be roughly the same, likely differing only in terms of which specific routers see your packet.
This is categorically incorrect. While the AS path is often the same, the actual peering points are almost always quite different. Most ASes use hot-potato routing - getting packets to the next AS at the closest peering point to the source of the traffic. (And even if cold-potato routing is used, that's still asymmetric). In addition if there are two options with the same AS-path-length hot-potato routing can lead to different AS paths. This can happen if there's two mutual transit providers between source and destination and various other situations.
Anecdotally, I've run a bunch of traceroutes and reverse traceroutes to different locations and they tend to follow the same AS paths — although sometimes the traceroute will surface more routing through your ISP (especially from college networks). In general you are correct, though, and I would love to explain more about hot-potato vs. cold-potato (and other interesting routing decisions) in the future. Either way, the results the reverse traceroute provides are good enough for the purposes of explaining the internet, IMO!
FYI what you described is hot-potato routing: each AS gets rid of it as soon as possible.
You may think this is unfair, and yes, it is, but it's also quite logical when you consider you don't know where the packet is going in the destination AS. If you have a network spanning Berlin and Hamburg and the packet is going to a different network that also spans Berlin and Hamburg, and you interconnect at both points, and you don't know which city it's actually going to, handing it off at the closest interconnect doesn't risk round-tripping it for no good reason.
I'm interested in your definition of fairness that makes hot potato routing unfair.
In my mind, hot potato is fair, every packet gets treated the same, and (mostly) every provider does the same thing.
> it's also quite logical when you consider you don't know where the packet is going in the destination AS. If you have a network spanning Berlin and Hamburg and the packet is going to a different network that also spans Berlin and Hamburg, and you interconnect at both points, and you don't know which city it's actually going to, handing it off at the closest interconnect doesn't risk round-tripping it for no good reason.
There are ways to help with this, BGP MED (multi-exit discriminator) or path extention can help guide towards the best place to deliver traffic. But especially for last mile traffic, you do want it on the destination network sooner than later; if traffic is genetated in Berlin, and the ultimate destination is Hannover and the Hannover endpoint is connected to both Berlin and Hamburg on the destination network, delivering at Berlin provides a better experience than delivering to Hamburg, even though Hamburg is closer to Hannover, because the transit to Hamburg was unnecessary. And if the destination is only connected to Hamburg, delivering in Berlin works about the same as delivering in Hamburg (depending on capacity and use from Berlin to Hamburg on both networks).
There's certainly situations where having options would be nice, but having options makes things complex, so typical users can't really influence routing. If you have v4 and v6, you may find that routing differs between the two and that does give you a bit of a choice.
> "You may have noticed that the traceroute progressively loads in lines above the bottom line. Web pages can only load forward. Since I didn’t want to use any JavaScript, I did the hackiest thing possible: every time I update the traceroute display, I embed a CSS block that hides the previous iteration! Since browsers render CSS as the page is loading, this made it look like the traceroute was being edited over time."
> Seems like this hit the Hacker News front page again, and the server's having some trouble pinging all of you. Feel free to read the article, but if you want to see your tracereoute you might need to bookmark and check back tomorrow :)
I have old components on my personal site that used to do a similar trick for streaming data without JavaScript but between nginx buffering and cloudflare I have not been able to sort out getting it to actually work these days. Worked fine on Apache in 2005 lol
Hmm, after several seconds it gave up and displayed raw markup ... I'm not sure exactly why in this case, but ...
One of the major infelicities of the web is that CSS is specified to ignore truncation, and there is no way to fix this. Now think about what happens if something like `display: inline-block` gets truncated before the `-`.
It's like when your uncle squeezes you at Christmas. You're glad to see him again, but it's just a liiiitttleee... too... much... for... your... lungssss,.,.,.,
This is categorically incorrect. While the AS path is often the same, the actual peering points are almost always quite different. Most ASes use hot-potato routing - getting packets to the next AS at the closest peering point to the source of the traffic. (And even if cold-potato routing is used, that's still asymmetric). In addition if there are two options with the same AS-path-length hot-potato routing can lead to different AS paths. This can happen if there's two mutual transit providers between source and destination and various other situations.
(EDIT: fixed hot/cold mixup)
You may think this is unfair, and yes, it is, but it's also quite logical when you consider you don't know where the packet is going in the destination AS. If you have a network spanning Berlin and Hamburg and the packet is going to a different network that also spans Berlin and Hamburg, and you interconnect at both points, and you don't know which city it's actually going to, handing it off at the closest interconnect doesn't risk round-tripping it for no good reason.
I'm interested in your definition of fairness that makes hot potato routing unfair.
In my mind, hot potato is fair, every packet gets treated the same, and (mostly) every provider does the same thing.
> it's also quite logical when you consider you don't know where the packet is going in the destination AS. If you have a network spanning Berlin and Hamburg and the packet is going to a different network that also spans Berlin and Hamburg, and you interconnect at both points, and you don't know which city it's actually going to, handing it off at the closest interconnect doesn't risk round-tripping it for no good reason.
There are ways to help with this, BGP MED (multi-exit discriminator) or path extention can help guide towards the best place to deliver traffic. But especially for last mile traffic, you do want it on the destination network sooner than later; if traffic is genetated in Berlin, and the ultimate destination is Hannover and the Hannover endpoint is connected to both Berlin and Hamburg on the destination network, delivering at Berlin provides a better experience than delivering to Hamburg, even though Hamburg is closer to Hannover, because the transit to Hamburg was unnecessary. And if the destination is only connected to Hamburg, delivering in Berlin works about the same as delivering in Hamburg (depending on capacity and use from Berlin to Hamburg on both networks).
There's certainly situations where having options would be nice, but having options makes things complex, so typical users can't really influence routing. If you have v4 and v6, you may find that routing differs between the two and that does give you a bit of a choice.
Love this
https://lamplightdev.com/blog/2024/01/10/streaming-html-out-...
Behind the keyboard of a large PC
Well, how did ip route here?
ssh watch.ascii.theater
> - Lexi, Nov 7, 3:16 PM PST
I read this title and that opening bass line just starts flowing.
One of the major infelicities of the web is that CSS is specified to ignore truncation, and there is no way to fix this. Now think about what happens if something like `display: inline-block` gets truncated before the `-`.
https://news.ycombinator.com/item?id=38531604
(sigh) I'm just thinking those thoughts right now.