Subject: HTTP substatus error codes (403.9, 500.20, etc.)

From: "Larry Masinter" <[email-masked]>
Date: Sun, 23 Mar 2003 10:39:01 -0800

IIS has a feature for "substatus" error codes, at least
according to the document I can find, but how are these
communicated back to the client?

One of the complaints about HTTP error messages is
that they're not very extensible, but it looks like
the "substatus error codes" is some kind of
extensibility message.

(I think "403.9 Forbidden: Too many clients are trying
to connect to the Web server" is probably inappropriate,
since it's a temporary failure and not a permanent
one, but that's another story).

How are substatus codes sent back to the client,
or are they? Only to IE user agents? In the
message body?

Larry

---

From: Alex Rousskov <[email-masked]>
Date: Sun, 23 Mar 2003 14:06:56 -0700 (MST)

On Sun, 23 Mar 2003, Larry Masinter wrote:

> IIS has a feature for "substatus" error codes, at least according to
> the document I can find, but how are these communicated back to the
> client?

I am not a Microsoft user or administrator, but according to [1],
substatus error codes are NOT communicated back to the client.
According to the information I could find, these codes are used on the
server side only, to customize the content of error messages
(generated by a customized server) or to provide server admins more
info (through server log files).

Hopefully, somebody with first-hand IIS knowledge will respond to
confirm or deny the above.

> One of the complaints about HTTP error messages is that they're not
> very extensible, but it looks like the "substatus error codes" is
> some kind of extensibility message.

The content of an error message is fully "extensible". HTTP does not
even define what the content should be! The status codes themselves
are as extensible as an integer code can be. Several popular protocols
(WebDAV, ICAP?) use extension codes to implement protocol-specific
features.

HTH,

Alex.

[1] http://www.microsoft.com/technet/prodtechnol/windowsserver2003/proddocs/server/log_substatus.asp

-- 
                            | HTTP performance - Web Polygraph benchmark
www.measurement-factory.com | HTTP compliance+ - Co-Advisor test suite
                            | all of the above - PolyBox appliance