Re: Our ALPN protocol IDs

On 5 December 2013 00:59, Carsten Bormann <> wrote:
> So how would the negotiation of the minor version be done?

For which version(s)?

For HTTP/1.x, the negotiation between HTTP/1.1 and HTTP/1.0 (and 0.9)
uses rules already established.

For HTTP/2.x, the negotiation between HTTP/2.0 and a hypothetical
HTTP/2.1 would use ALPN and "h2" and maybe "h2.1".  Any unique string
would suffice.

> I don’t see how that is done in HTTP/2.0 (except when upgrading from 1.1).

Yes, HTTP/2.0 explicitly doesn't allow version negotiation "within"
the protocol.  We have ALPN and intend to use it ...and nothing else.

> Maybe it is worth adding a section that explains the protocol evolution model of HTTP/2.0.

Like this?

  Any new, incompatible version of HTTP will use a different
identifier string.  For instance, a hypothetical HTTP/2.1 might be
identified by the string "DUCK".

Received on Thursday, 5 December 2013 17:40:13 UTC