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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 UTC

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