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RE: NEW ISSUE: 13.1.2's Definition of 1xx Warn-Codes

From: Travis Snoozy (Volt) <a-travis@microsoft.com>
Date: Tue, 2 Jan 2007 12:27:19 -0800
To: "William A. Rowe, Jr." <wrowe@rowe-clan.net>
CC: Mark Nottingham <mnot@mnot.net>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Message-ID: <86EDC3963F04D546BED8996F77D290F6049D117E48@NA-EXMSG-C138.redmond.corp.microsoft.com>

William A. Rowe, Jr. said:
> Travis Snoozy (Volt) wrote:
> > Mark Nottingham said:
> >> Added as i54;
> >>
> http://www.w3.org/Protocols/HTTP/1.1/rfc2616bis/issues/index.html#i54
> >>
> > <snip>
> >
> > The modified proposal (after discussion) is as follows (should fix all
> three problems mentioned):
> >
> > "A cache MUST NOT generate 1xx warn-codes for any messages except cache
> > entries, and MUST NOT generate 1xx warn-codes for a cache entry except
> > in response to a validation attempt for that entry. 1xx warn-codes MUST
> > NOT be generated in Request messages."
> Explain again how any code is passed as a Request message?  The original
> language, "MUST NOT be generated by Clients" was correct.

To answer your question:

2xx warn-codes could be added to a Request, e.g., by a proxy that is
transforming requests between the user-agent and the origin server. This is
perfectly valid, and desirable, though likely uncommon.

To the original language is incorrect:

Clients should be allowed to generate 1xx warn-codes in Responses -- all the
client has to do is implement a cache, and the client will need the ability
to add 1xx warn-codes to its cached Responses. Thus, the original language
("1XX warn-codes MAY be generated by a cache only when validating a cached
entry. It MUST NOT be generated by clients.") is incorrect, unless the
intent is to effectively prohibit clients (including proxies) from
implementing a cache. Such a prohibition, given the context of the rest of
the spec, is so silly as to be laughable; thus, the wording here needs to be

The proposed wording means that clients (and everything else) MUST NOT
generate 1xx warn-codes in Request messages (because it's nonsense). Clients
(and everything else) can generate 1xx warn-codes in Response messages,
though cache subsystems (in clients or otherwise) have some extra rules to
follow. There's no reason to have a blanket prohibition on clients
generating 1xx warn-codes in Responses.

On further reflection, there is an issue that I have with the above proposed
wording: the context might imply that "1xx warn-codes MUST NOT be generated
in Request messages" _by caches_, instead of by anything.


-- Travis
Received on Tuesday, 2 January 2007 20:27:40 UTC

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