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Re: Expect header 'understand' vs 'meet'

From: Jan Algermissen <jan.algermissen@nordsc.com>
Date: Wed, 7 Sep 2011 22:03:16 +0200
Cc: HTTP Working Group <ietf-http-wg@w3.org>
Message-Id: <1758DCA6-3CB3-401E-90FC-9CD1156046F4@nordsc.com>
To: Julian Reschke <julian.reschke@gmx.de>
Hi Julian,


On Sep 7, 2011, at 9:58 PM, Julian Reschke wrote:

> On 2011-09-07 21:38, Jan Algermissen wrote:
>> Dear WG,
>> 
>> I have a question on the Expect header section 9.2 in HTTPbis 16[1]
>> 
>> Is my understanding correct:
>> 
>> 1. A proxy that finds an expectation extension in the Expect header that it does understand but cannot meet must respond 417
>> 2. A proxy that finds an expectation extension in the Expect header that it does not understand ignores the extension
>> 
>> 
>> Jan
>> 
>> [1] http://www.ietf.org/id/draft-ietf-httpbis-p2-semantics-16.txt
> 
> "The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST return a 417 (Expectation Failed) status code if it receives a request with an expectation that it cannot meet."
> 
> I think that implies 417 for unknown extensions; how would the proxy "meet" the expectation when it doesn't know what it is?


fair enough.

But this means an extension can only be successfully defined and used when all intermediaries understand it - which is: never.

Or am I getting this wrong?

Jan

> 
> Best regards, Julian
> 
> 
> 
Received on Wednesday, 7 September 2011 20:03:46 GMT

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