On 22/11/2013 13:26, Randy Bush wrote:
>> 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.
Of course, the dual stack model only works while you still have enough
v4 space for one-per-customer. I wasn't intending to deny that. It still
boggles my mind that major ISPs failed to grok this in time. The ISPs that
did grok it are the ones happily running dual stack.
Brian