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Re: HTTP/2 Header Encoding Status Update

From: Mark Nottingham <mnot@mnot.net>
Date: Thu, 28 Feb 2013 19:22:27 +1100
Cc: James M Snell <jasnell@gmail.com>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Message-Id: <F809C9BF-C1F8-428C-84D5-C9CB2ACF47DD@mnot.net>
To: Julian Reschke <julian.reschke@gmx.de>

On 28/02/2013, at 6:27 PM, Julian Reschke <julian.reschke@gmx.de> wrote:

> On 2013-02-28 00:00, James M Snell wrote:
>> On Wed, Feb 27, 2013 at 2:45 PM, Mark Nottingham <mnot@mnot.net> wrote:
>>> Hi James,
>>> 
>>> [snip]
>>> So, the biggest concern here, I think, is that the conversion of a UTF-8 value to ASCII/Latin-1 -- to be able to forward the header on a HTTP/1.x hop -- requires knowledge of the header.
>>> 
>>> Would you want to define a standard way to encode UTF-8 in Latin-1 (e.g., percent-encoding) for headers that use this? It would constrain the headers (and likely rule out any existing headers from using UTF-8), but I don't see how this is going to be viable otherwise.
>>> 
>> 
>> Yes, I think that is reasonable. One key thing is that existing
>> headers would need to be explicitly redefined to take advantage of the
>> new encoding options so it would be technically invalid to take any of
>> the existing headers and encode them as UTF-8 unless their definition
>> has been changed in spec. That said, a standard mapping like you
>> suggest would be good in the cases we do have to drop down from http/2
>> to /1. Percent-encoding seems to be perfectly reasonable.
>> ...
> 
> That's not going to work for existing header fields and existing code on HTTP/1.1.
> 
> This is a hairy problem. If it wasn't, we would already have solved it.

I think what's being suggested is that *new* headers can opt-in to a format whereby the entire value is percent-encoded where needed when expressed in Latin-1, but not when it's in UTF-8. Existing headers wouldn't be able to do so (unless they already fit this convention).

Cheers,




--
Mark Nottingham   http://www.mnot.net/
Received on Thursday, 28 February 2013 08:22:56 GMT

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