Again, you are correct.
It seems that we have been in a circular argument on this list for a
while. The same old
arguments keep coming back.
Basically we have 3 groups of people:
1 - People who prefer the response to be very explicit (e.g., separate
error codes), and
tell "what URI Scheme is acceptable".
2 - People who prefer the response to be a "hard failure" with no
explicit indication
of the acceptable URI scheme provided, in order to not encourage
automatic
downgrades
3 - People who don't really care either way
The compromise that emerged from this is to use a single error code,
480, which is the
error used when the network cannot locate a contact for a particular
recognized AOR.
But, in addition, a Warning header field with one of 2 warn-codes is
provided, to indicate
the reason for the failure: SIPS Not Allowed or SIPS Required. This is
meant to provide
an indication to an Automata or an end user on the cause for the
failure.
It has the benefit that existing implementations or "simple
implementations" will behave
as desired, i.e, if they will treat it as a normal 480, and not harmful
downgrades occur.
So we achieve the goals of group 2 who want to avoid people shooting
themselves in the
foot.
Implementations that want to provide further indications of what went
wrong will be able
to use the Warn-Code to provide an indication of the problem (for
end-user, network
administrator, etc.). So we achieve the goals of group 1.
It seems to me that this is a good solution. I'd really like to put an
end to this
discussion and move on to something else.
> -----Original Message-----
> From: Alan Hawrylyshen [mailto:[EMAIL PROTECTED]
> Sent: Friday, July 27, 2007 08:27
> To: Kyzivat Paul; Mahy Rohan
> Cc: IETF SIP List; Audet, Francois (SC100:3055);
> [EMAIL PROTECTED]
> Subject: Re: [Sip] draft-ietf-sip-sips-05: 480 vs. 418
>
>
> On 27-Jul-2007, at 10:06 , Paul Kyzivat wrote:
>
> > I understand that if the user entered a sips URI then it
> should be the
> > user that must decide to downgrade. But if the user didn't know
> > whether to use sip or sips in the first place, and the UA
> decides to
> > try sips first then I see no problem in the UA having a policy that
> > causes it to downgrade.
>
> I was under the impression (based on meeting discussion) that :
> 1 - the downgrade was undesirable because it reveals
> (possibly) information about the targeted party in the clear, and;
> 2 - The 480 with a Warning header was an option to provide
> automata- friendly indication of the failure reason.
>
> Alan Hawrylyshen
>
> a l a n a t p o l y p h a s e d o t c a
>
>
>
>
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