Re: p1: Upgrade ordering (possible HTTP/2 impact)

Willy Tarreau <w@1wt.eu> Tue, 23 April 2013 08:13 UTC

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Date: Tue, 23 Apr 2013 10:12:09 +0200
From: Willy Tarreau <w@1wt.eu>
To: Mark Nottingham <mnot@mnot.net>
Cc: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
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Subject: Re: p1: Upgrade ordering (possible HTTP/2 impact)
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Hi Mark,

On Tue, Apr 23, 2013 at 05:38:59PM +1000, Mark Nottingham wrote:
> Proposal - add to p1 6.7:
> 
> """
> When occurring in a request, Upgrade's value indicate the protocol(s) the
> client would like to upgrade to, in order of relative preference. When
> occurring in a 101 (Switching Protocols) response, there will usually only be
> one protocol indicated in Upgrade. When occurring in any other response,
> Upgrade indicates the protocol(s) the server is capable of upgrading to, in
> order of relative preference.
> """

I'm OK in the principle, though I think this should be fused into existing
text, probably that way :

   The "Upgrade" header field is intended to provide a simple mechanism
   for transitioning from HTTP/1.1 to some other protocol on the same
   connection.  A client MAY send a list of protocols in order of relative
   preference in the Upgrade header field of a request to invite the server
   to switch to one or more of those protocols before sending the final
   response.  A server MUST send an Upgrade header field in 101 (Switching
   Protocols) responses to indicate which protocol(s) are being switched
   to, and MUST send it in 426 (Upgrade Required) responses to indicate
   acceptable protocols in order of relative preference.  A server MAY
   send an Upgrade header field in any other response to indicate that
   they might be willing to upgrade to one of the specified protocols for
   a future request, in order of relative preference.

Willy