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Re: Issue #73: definition of deflate encoding

From: Mark Nottingham <mnot@mnot.net>
Date: Thu, 30 Jul 2009 10:29:10 +0200
Cc: ietf-http-wg@w3.org
Message-Id: <454DA2C2-09AB-4FD1-8DFB-DDB98B93FAED@mnot.net>
To: David Morris <dwm@xpasc.com>
Could you forward me some of the URLs that you think fail? REDbot <http://redbot.net 
 > has gzip checking built-in and I'd like to verify it...


On 30/07/2009, at 7:17 AM, David Morris wrote:

> While doing some recent packet capture / object extraction work as  
> part of an effort to study the current degree of content-encoding by  
> live web sites, I needed to remove gzip encoding ... naively thought  
> I could just
> save the data as a *.gz file (tried .zip also) and post process it.  
> Found
> about 800 gzip encoded responses of about 2400 and decoded them all  
> assuming no gzip or zlib wrapper. I'm not 100% sure about my  
> conclusions
> (I probably could provide a couple example payloads still gzip-ed in  
> file form if someone with more knowledge would care to look), but it  
> appears to me that 'some incorrect' is likely 'most implementations  
> are incorrect'.
> Dave Morris
> On Wed, 29 Jul 2009, Henrik Nordstrom wrote:
>> http://trac.tools.ietf.org/wg/httpbis/trac/ticket/73
>> As most of you know our definition of deflate is somewhat  
>> contradictory
>> with the referenced RFCs definitions, as is already stated in our
>> definition:
>>  deflate
>>       The "zlib" format defined in RFC 1950 [31] in combination with
>>       the "deflate" compression mechanism described in RFC 1951 [29].
>> As result of this inconsistent name selection there is several
>> implementations that implement "deflate" to literally mean the  
>> deflate
>> encoding without the zlib wrapper.
>> Proposed solution is to add a note on this fact
>>               Note that some incorrect implementations may send
>>               deflate encoding without a zlib wrapper when using this
>>               encoding.
>> On a related note I should perhaps also remind you that gzip is  
>> actually
>> also deflate but with a gzip wrapper instead of zlib. To be  
>> consistent
>> or "deflate" term should really had been "zlib". And both are well
>> defined file format which also happens to be the same name of the
>> application/library creating the format in question.
>> Regards
>> Henrik

Mark Nottingham     http://www.mnot.net/
Received on Thursday, 30 July 2009 08:29:48 UTC

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