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> BGP just makes sure your packets get to the right location. I think I wasn't clear enough. Yes, BGP will route the packet to the nearest POP for that IP if i

> BGP just makes sure your packets get to the right location. I think I wasn't clear enough. Yes, BGP will route the packet to the nearest POP for that IP if it was announced in different locations, that's how "anycast IP" works, thanks to how BGP works. OP asked: > or something in front of Caddy So I've described what is it and how it works in simple terms. > If routing shifts in the middle of a TCP connection, there's no magic that makes a new machine that didn't SYN+ACK the original connection pick up where the old machine left off. If you are talking only about BGP then of course you are right but I was not talking about solving this using only BGP. You can tunnel the packet to your other POP which was origin, as I mentioned in my answer. So if you have a session established after 3 way handshake in POP B client <-> POP B and suddenly you are routed via POP A then just tunel all packets for that session: client <-> POP A <-> POP B or you could use MPTCP to solve this if supported etc.

tptacek 4y ago
... and now we're talking about contraptions you'd have to put in front of Caddy to make this work, which was what the commenter above was interested in hearing about. I don't care either way, except that the implication that BGP4 solves this problem set me off. Obviously, in reality, people mostly rely on geography to deal with this: you're just unlikely to get randomly rerouted from a Singapore rack to a Sydney rack, and so the issue doesn't come up. But if you care about it --- as the previous commenter does --- you want a real answer.
- lossolo 4y ago
  > But if you care about it --- as the previous commenter does --- you want a real answer. Yeah, I wasn't clear enough in my first comment, my last comment was more detailed so I guess it should match "a real answer" now. > Obviously, in reality, people mostly rely on geography to deal with this: you're just unlikely to get randomly rerouted from a Singapore rack to a Sydney rack, and so the issue doesn't come up. Yeah, most of the time it doesn't come up, anecdotally it's also more specific to some regions, in Europe for example I've seen this to occur more often (between POPs in EU) than in other regions.

tptacek 4y ago

... and now we're talking about contraptions you'd have to put in front of Caddy to make this work, which was what the commenter above was interested in hearing about. I don't care either way, except that the implication that BGP4 solves this problem set me off. Obviously, in reality, people mostly rely on geography to deal with this: you're just unlikely to get randomly rerouted from a Singapore rack to a Sydney rack, and so the issue doesn't come up. But if you care about it --- as the previous commenter does --- you want a real answer.

lossolo 4y ago
> But if you care about it --- as the previous commenter does --- you want a real answer. Yeah, I wasn't clear enough in my first comment, my last comment was more detailed so I guess it should match "a real answer" now. > Obviously, in reality, people mostly rely on geography to deal with this: you're just unlikely to get randomly rerouted from a Singapore rack to a Sydney rack, and so the issue doesn't come up. Yeah, most of the time it doesn't come up, anecdotally it's also more specific to some regions, in Europe for example I've seen this to occur more often (between POPs in EU) than in other regions.