On Fri, Jan 27, 2023 at 9:49 PM Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp> wrote:
That multihomed sites are relying on the entire Internet for computation of the best ways to reach them is not healthy way of multihoming.
This was studied in the IRTF RRG about a decade ago. There aren't any other workable ways of multihoming compatible with the TCP protocol, not even in theory. Every other mechanism imagined failed some basic system constraint, usually the requirement that packets have administrative permission to cross an intermediate network. So, another way of multihoming critically depends on replacing the layer-4 protocols with something that doesn't intermingle the IP address with the connection identifier. For clarity: TCP's connection identifier consists of the source and destination IP addresses plus the source and destination ports. Those four elements, unique when combined, identify exactly one ongoing TCP connection. Because of this, the connection must fail if the source or destination IP addresses are no longer available to the source or destination hosts. From this fact, we get the requirement that the entire Internet learn when a particular IP address has changed its position within the network. Regards, Bill Herrin -- For hire. https://bill.herrin.us/resume/