Re: [TLS] "Draft Version" extension

[Alexey Melnikov <[e-mail]>]

On 11/08/2014 17:53, Eric Rescorla wrote:
> Experience with HTTP 2 has shown that it's convenient to be able to
> distinguish which draft version you're implementing so you don't end
> worrying about interop between various I-D versions. Accordingly,
> for TLS 1.3 I'd like to define a temporary extension that indicates which
> TLS 1.3 draft it implements. The idea here is that the client would signal
> TLS 1.3 and then "draft 3" and the server would only negotiate 1.3 if
> it had a compatible draft. Otherwise it would fall back to TLS 1.2.
>
> My proposed extension would be as follows:
>
> struct {
>   uint16 draft_version;
> } DraftVersionExtension;
>
> And would have a code point in the (unofficially) experimental range: 
> 0xff02.
> We would not need a permanent allocation since once TLS 1.3 ships you
> would  send no extension at all.
>
> I've implemented this in NSS and it's trivial to do.
Sounds like a good idea. I implemented similar extensions for other 
protocols.
>
> Thoughts?
> -Ekr