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Re: Transfer-Encoding in a HEAD response

From: Wenbo Zhu <wenboz@google.com>
Date: Wed, 14 Apr 2010 17:22:34 -0700
Message-ID: <g2q83c4e7ff1004141722s6ee1d908ybb7ac3466ea90403@mail.gmail.com>
To: "Roy T. Fielding" <fielding@gbiv.com>
Cc: Mark Nottingham <mnot@mnot.net>, ietf-http-wg@w3.org
On Tue, Apr 13, 2010 at 11:08 PM, Roy T. Fielding <fielding@gbiv.com> wrote:
> On Apr 13, 2010, at 10:39 AM, Wenbo Zhu wrote:
>
>> On Tue, Apr 13, 2010 at 2:38 AM, Mark Nottingham <mnot@mnot.net> wrote:
>>> On 13/04/2010, at 6:36 PM, Wenbo Zhu wrote:
>>>
>>>>>> While rfc-2616 doesn't require all the headers appear in the HEAD
>>>>>> response, the confusion here mostly lies in whether Transfer-Encoding
>>>>>> is applicable for a HEAD response (as it is the case for
>>>>>> Content-Length).
>>>>>
>>>>> See:
>>>>>  http://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-09#section-3.4
>>>>>
>>>>> which should clarify this.
>>>> Well, this is not directly related to HEAD response.
>>>
>>> See step 1:
>> Well, this brings up my original question: if C-L is considered a
>> valid header for HEAD response, then transfer-encoding should be too,
>> i.e. in the context of 3.4 Message Length.
>
> Content-length provides useful information for resource testing.
> Transfer-encoding does not.  Moreover, T-E is almost always
> generated by the server's messaging subsystem, not the resource
> handler, and requires an elaborate test of HTTP versioning prior
> to use.  It is mainly for the latter reason that servers do not
> send T-E in a response to a HEAD request.
This seems to be aligned with the definition of HEAD request - i.e.
its response contains metainformation of the resource, which shouldn't
include T-E .

>
> I see no reason to change this behavior in Apache httpd, so my
> preference would be to clarify in the spec that there is no need
> to send T-E in a response to HEAD regardless of the value it
> might have for a GET.
Such a clarification will be useful, given all the different
implementations that exist today.

- Wenbo

>
> ....Roy
>
>
Received on Thursday, 15 April 2010 00:23:05 GMT

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