On Mon, Apr 4, 2022 at 10:41 AM Vasilenko Eduard via NANOG <nanog@nanog.org> wrote:
240.0.01.1 address is appointed not to the router. It is appointed to Realm. It is up to the realm owner (ISP to Enterprise) what particular router (or routers) would do translation between realms.
Please forgive me as I work this out in my head for a moment. If I'm a global network with a single ASN on every populated continent on the planet, this means I would have a single Realm address; for the sake of the example, let's suppose I'm ASN 42, so my Realm address is 240.0.0.42. I have 200+ BGP speaking routers at exchange points all over the planet where I exchange traffic with other networks. In this new model, every border router I have would all use the same 240.0.0.42 address in the Shaft, and other Realms would simply hand traffic to the nearest border router of mine, essentially following a simple Anycast model where the nearest instance of the Realm address is the one that traffic is handed to, with no way to do traffic engineering from continent to continent? Or is there some mechanism whereby different instances of 240.0.0.42 can announce different policies into the Shaft to direct traffic more appropriately that I'm not understanding from the discussion? Because if it's one big exercise in enforced Hot Potato Routing with a single global announcement of your reachability... ...that's gonna fail big-time the first time there's a major undersea quake in the Strait of Taiwan, which cuts 7/8ths of the trans-pacific connectivity off, and suddenly you've got the same Realm address being advertised in the US as in Asia, but with no underlying connectivity between them. https://www.submarinenetworks.com/news/cables-cut-after-taiwan-earthquake-20... We who do not learn from history are doomed to repeat it...badly. :( Matt