Peace, Now, speaking of compromises, On Sun, Aug 8, 2021 at 1:09 AM Robert Raszuk <robert@xxxxxxxxxx> wrote: > Every second routing may decide for you to prefer some other BGP path and your anycast destination may end up in different destination naturally only by following the destination routing paradigm. In my opinion, this is a perfect sample of a bad engineering approach. Here's why. In practice, routing on the Internet does never change this way. A single BGP route announcement takes some 30 seconds to propagate, and sometimes a route withdrawal takes more than 4 minutes. Severe routing changes by an AS are just not expected to happen more frequently than a few times in an hour, and massive changes shouldn't happen more often than once in a few hours, because they might cause routing loops, weird routing issues, and prolonged network unavailability otherwise. This is the limitation to rely on for an application, or, somewhat worse, for a transport protocol. Engineering is basically a process of developing compromises over limitations. You need to thoroughly understand the latter to build a system. Engineers don't build houses capable of resisting the energy of an intergalactic meteor landing. Your car would break and kill you if you smash it into the wall cruising 900 mph, and I don't even need to know the make to tell you that, because I already know your car certainly isn't a Batmobile, and it's therefore built on compromises, over limitations, and there are warning signs on every road because of that. An attempt to pretend the Internet engineering doesn't have to keep any limitations in mind just leads to bad engineering practices. There's always a compromise, and you need to know the limitations. And there are no limitations on the Internet of the past, present, or the future, which could possibly make the anycast impractical. Application designs may do, because of poor engineering practices, but that's it. -- Töma
