Subject: Re: Warning Codes (was: Re: Missing Warning reasons to SIP)

From: "Scott Petrack"<[email-masked]>
Date: Fri, 3 Jul 1998 12:08:09 +0200

From: Scott Petrack@VOCALTEC on 07/03/98 12:08 PM

Sorry, my mailer is insane (well, retarded is more medically accurate:
Lotus Notes).

>I have tentatively added
>3xx warning, did not cause request to fail
>4xx error, caused failure status
This is sort of a "severity score" rather than giving some idea of what the
error was. Could I suggest the following
warning codes:

3xx    -- SIP syntax warning
4xx    -- SIP semantics warning (parsed the SIP fine, but didn't understand
something)
5xx    -- Payload Syntax Warning (can't parse the Payload, includes "don't
recognize the content-type of payload").
6xx    -- Payload Semantics warning (could parse the payload, but didn't
understand something in it).

I would suggest that we already specify:

50x   -- SDP syntax warning
60x   -- SDP semantics warning

And within this we can place all of the nice specific warnings that we have
already defined.
Henning, your "severity scores"  are fine, but maybe they could be
subcodes, as in

60x.1   -- an SDP semantic problem that caused a failure   (e.g. I didn't
understand a tag in the a=rtpmap: line)

If we really want to keep an eye on a future merging with HTTP, we could
call the 3xx and 4xx Warnings
"Header Syntax Warning" and "Header Semantics Warning".   Then we would
define 31x and 41x to refer to
SIP-specific headers. ( maybe we'll reserve 30x and 40x for HTTP headers
and 31x, 41x for SIP-specific headers).

This makes the four codes defined very nice
and generic, but still extremely useful (at least to me) -- for example, it
allows the warnings about the payload
to be passed to the tool which generated or parses the payloads in an
automatic way.

BTW, I have not yet been able to download SIP v7, so I apologize if this is
there. I am sort of assuming that
in SIP v7 there is just the 3xx and 4xx that Henning suggests.

Finally, it may be that we want four digit codes 3xxx, 4xxx, 5xxx, 6xxx,
etc.

Scott

I might as well come clean and say that I am going to need to extend these
a bit for PINT, e.g. so that when a client
sends a BYE but 3 out of 4 fax pages have already been sent the server can
warn the client of this fact. I think that
I will want to add a complete separate category of warnings for this case
(say 7xxx meaning "media session status warnings" -- generically it
includes a warning about the status of a media session. I think this is
reasonable since
even if SIP is not about SDP, it is about sessions, and SIP can now be used
to change sessions that are in progress,
so it is reasonable to include Warnings about the status of ongoing
sessions).

---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 14 Jul 1998 21:30:44 -0400

> understand something in it).

I don't think we really need (at least initially) any SIP
syntax/semantics warnings. The 4xx codes do just fine for indicating SIP
syntax (400) and semantics problems (such as invalid call-id, no
response that matches Accept (406) or invalid session description
(415)). Thus, the warnings are really only needed for indicating
problems with processing the session description, where more detailed
information is valuable and where multiple, "parallel" error conditions
can be more readily identified.

Given our lack of experience in this area, I would tread carefully in
trying to cover every possible condition. Warning codes can be trivially
extended by IANA registration should they be needed.