Subject: RE: I-D ACTION:draft-ietf-webdav-quota-01.txt

From: "Clemm, Geoff" <[email-masked]>
Date: Tue, 25 Mar 2003 18:07:50 -0500

To help us in our categorization of errors, could you describe
how does a web spider responds differently to a 4xx or a 5xx?

Also, although it is good to know that one way is compliant and the
other is not (:-), it would be helpful to have some criteria to
to actually make that determination.  In particular, how do you
distinguish a client error category (making a bad request) from a
server error category (not satisfying a valid client request).
There are some obvious
cases (a syntactically ill-formed request), but many of the others
could fall in either category (the quota errors, in particular).

Cheers,
Geoff

-----Original Message-----
From: Roy T. Fielding [mailto:[email-masked]]
Sent: Tuesday, March 25, 2003 4:43 PM
To: Clemm, Geoff
Cc: WebDAV
Subject: Re: I-D ACTION:draft-ietf-webdav-quota-01.txt

> What I was asking was whether there was a client that
> generically handled 4xx codes (i.e. a 4xx code that it had no
> special handling for) in a significantly different way than
> it handles a 5xx code (i.e. a 5xx code that it had no special
> handling for).

Yes, web spiders that perform maintenance.

>   I.e., when we are deciding whether to put a
> specific code in the 4xx or 5xx range, does it matter which
> one we pick?

Yes. One way is HTTP compliant; the other is not.

....Roy

---

From: "Roy T. Fielding" <[email-masked]>
Date: Tue, 25 Mar 2003 16:08:24 -0800

> how does a web spider responds differently to a 4xx or a 5xx?

They have different correction procedures.  If you get a 5xx error,
header fields like retry-after become effective and further errors
are directed to the server administrator.  A 4xx error, OTOH, is
directed to the page owner of the referencing page or mechanism
that generated the request.  A 5xx is never seen as a failure of
the author of a reference.

> server error category (not satisfying a valid client request).

If the same identical request might succeed were it not for a
limitation on the server handling the request, then it is a 5xx.
Basically, there is nothing wrong with the request.

> could fall in either category (the quota errors, in particular).

Not really.  If the request would have succeeded but did not due
to an addition of bytes exceeding quota, then it is a 5xx.
If the request alone is sending a body greater than the quota max
(disregarding other content on the server), then the correct
response is not quota-exceeded but rather 413 (Request Entity Too
Large).

I haven't encountered a case that wasn't obvious.  I have encountered
many cases where extensions have tried to say too many different
things with one status code when two would be clearer.

....Roy

---

From: "Julian Reschke" <[email-masked]>
Date: Thu, 27 Mar 2003 20:34:46 +0100

> From: [email-masked]
> [mailto:[email-masked]]On Behalf Of Roy T. Fielding
> Sent: Wednesday, March 26, 2003 1:08 AM
> To: Clemm, Geoff
> Cc: WebDAV
> ...
> ...

For the record -- having read Roy's comment and looking again at RFC2616 --

	"Response status codes beginning with the digit "5" indicate cases in which
the server is aware that it has erred or is incapable of performing the
request."

I now agree that a 5xx code is the right one for "quota exceeded". However I
still think it's valuable to be able to distinguish between the various
reasons for 507 (Insufficient Storage), so I think we should have specific
condition (for marshalling in DAV:error) for the various conditions.

Julian

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