On Fri, May 10, 2019 at 12:51 PM Eric Rescorla <ekr@xxxxxxxx> wrote:
There seem to be two main equilibria:1. There's a critical mass of very strict implementations; in this case it's very hard for a non-conformant implementation to enter the ecosystem.2. There's a critical mass of non-conformant implementations; in this case it's very hard for a strict implementation to enter the ecosystem.Once you're in one equilibrium or the other, it's very hard to get out.
And from the perspective of the IETF as a standards body, an additional question may be whether an equilibrium has yet been reached. If it has not, and the implementing groups are actively participating in the standards effort, then I believe Martin's analysis suggests Postel's principle is still correct, though incomplete. Be conservative in what you send; be liberal in what you accept; be communicative about what went wrong.
The advantage of that during the development process is that it allows you to test past the error to see if other parts of the implementation are correct and behaving as you expect. Hard fails very early turn the testing process into a fully serial process, which may be too slow. But this approach also comes with a very obvious cost, in that it forces implementing groups to participate in the process at least enough to know how to reach out to those whose implementations they are testing. That tends to favor the well-funded and the well-connected over others, and it may mean that those who cannot participate will also find an equilibrium already set before they get to play.
Lowering that cost is important, as is being honest about whether an effort is currently in an exploratory phase or documenting an as-built system. Having chaired working groups which moved between those two without an intervening RFC publication, this is not as easy as looks, though I believe we are working on some better signposts.
regards,
Ted
