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Trailers and intermediaries

From: Mark Nottingham <mnot@yahoo-inc.com>
Date: Mon, 13 Aug 2007 20:00:49 +1000
Message-Id: <D6FE3198-7D0B-4B10-B61C-EDED8ADC8D03@yahoo-inc.com>
To: HTTP Working Group <ietf-http-wg@w3.org>

Regarding trailers, section 3.6.1 says:

> The trailer allows the sender to include additional HTTP header  
> fields at the end of the message. The Trailer header field can be  
> used to indicate which header fields are included in a trailer (see  
> section 14.40).
>
> A server using chunked transfer-coding in a response MUST NOT use  
> the trailer for any header fields unless at least one of the  
> following is true:
>
> a) the request included a TE header field that indicates "trailers"  
> is acceptable in the transfer-coding of the response, as described  
> in section 14.39; or,
>
> b) the server is the origin server for the response, the trailer  
> fields consist entirely of optional metadata, and the recipient  
> could use the message (in a manner acceptable to the origin server)  
> without receiving this metadata. In other words, the origin server  
> is willing to accept the possibility that the trailer fields might  
> be silently discarded along the path to the client.
>
Read strictly, this doesn't seem to give an intermediary along the  
path to the client the wiggle room necessary to preserve those  
trailers if the request doesn't have a TE: trailers. Something like  
this might help;

c) the server is an intermediary, the forwarded request did not  
include a TE header field that indicated "trailers", and the trailers  
are being forwarded.


--
Mark Nottingham       mnot@yahoo-inc.com
Received on Monday, 13 August 2007 10:01:17 GMT

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