> On Aug 21, 2019, at 12:56 PM, Masataka Ohta <mohta@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Once a full routing table is available on all the end systems, it is > easy for the end systems try all the destination addresses, from the > most and to the least favorable ones, based on the routing metric. Ohta-san: I'm familiar with the paper "End to end arguments in system design" as well. I'm also familiar with John Day, although I suspect I have learned more from him than he has learned from me. That said, we don't operate on the end2end principle in the Internet, in the sense of the application determining the route its packets will take to a destination. Applications know the addresses they might send packets to, but they have no idea by what path said packets might be routed - and probably wouldn't know how to interpret them if they did. That is separately determined by every AS the packet goes through, and can change in a clock tick. The network is intelligent - it uses routing protocols scubas BGP, OSP, and IS-IS to determine the routing of packets without the application being aware or involved. Yours very humbly, Fred
