> From the apps point of view, that's true; hence we end up with > heuristics such as Happy Eyeballs. I was referring to ISP > (or campus) infrastructure, where people have been running > dual stacks for many years. as the saying goes, it sucks less >> (2) The non-straightforward version requires that applications, at >> least TCP-based applications, be able to make rather complex route >> optimization decisions about which protocol and addresses to use and >> make those decisions in a way that completely violates clean layering >> models. We have, in general, never figured out how applications are >> supposed to do that, nor how to make the needed information available >> to them. > Probably because there is no general solution to that problem, but > IMHO you can't fix that without a time machine that takes you back to > about 1977. it sucks really badly > Actually, in the MIF/Homenet world you will find a lot of discussion > of the need for source/destination based routing. "this is a really steaming pile. let's shovel more dren on top of it to cover it up." >> Now I'm obviously missing, or misunderstanding, something that allows >> you to assert that straightforward dual stack is the clear market >> choice and works well despite the above. Could you explain what it >> is? > As I said, I'm talking about ISP infrastructure, where the issue is > how to deliver both v4 and v6 service to the customer side of the CPE > box. For years, ISPs that do this by simply running both protocols > have been saying that it's straightforward. i thought this fantasy was killed a decade or more ago. it requires an ipv4 address for every cpe. welcome to a+p, it sucks too. randy