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Re: Multiple header fields with the same field name - unwritten assumption about quoted commas in values?

Mark Nottingham <mnot@mnot.net> Wed, 16 January 2013 00:02 UTC

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From: Mark Nottingham <mnot@mnot.net>
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Date: Wed, 16 Jan 2013 11:01:22 +1100
Cc: Karl Dubost <karld@opera.com>, Julian Reschke <julian.reschke@gmx.de>, Piotr Dobrogost <p@ietf.dobrogost.net>, ietf-http-wg@w3.org
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To: Nico Williams <nico@cryptonector.com>
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Subject: Re: Multiple header fields with the same field name - unwritten assumption about quoted commas in values?
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On 16/01/2013, at 10:57 AM, Nico Williams <nico@cryptonector.com> wrote:

> On Tue, Jan 15, 2013 at 5:47 PM, Mark Nottingham <mnot@mnot.net> wrote:
>> On 16/01/2013, at 10:37 AM, Nico Williams <nico@cryptonector.com> wrote:
>> 
>>> On Tue, Jan 15, 2013 at 5:28 PM, Mark Nottingham <mnot@mnot.net> wrote:
>>>> We're talking about HTTP/1.x here, not 2.0. We can't retroactively make implementations non-conformant.
>>> 
>>> Ah, yes.  But we could stop encouraging implementors to merge multiple
>>> header instances.  Then we only have to say that it happens and
>>> explain the pitfalls.
>> 
>> It's extremely common to do something like:
>> 
>> Cache-Control: max-age=60, must-revalidate
>> 
>> Are you really saying that this should be discouraged?
> 
> No.  I'm saying that it's OK for apps to do that but not any other
> entities (middleboxes), mostly because middleboxes can't possibly know
> about headers that hadn't been registered when they were implemented.


OK. Is this an actual problem you've encountered? 

I'm fine with adding some clarifying text if it helps implementers, but I haven't seen this confusing any middlebox vendors; they tend to leave the bits alone...

--
Mark Nottingham   http://www.mnot.net/

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