Bug#365588: Error message

[Philipp Klaus Krause]

It seems the behaviour in case the provider doesn't support the option
is undefined. This is what upstream said:

> there are plenty of possibilities a provider can behave when he
> fails to handle this (completely legal!) option correctly. with
> sipgate.de e.g. the voicebox refuses to accept calls after "not
> avail"-time expired, and your online-status isn't displayed
> correctly to other sipgate users.
> you simply can't conclude reliably from behavior of provider to the
> problem he might have with "unique contact header". and twinkle is a
> softphone, no expert system database to analyze probable causes of
> manyfold error symptoms.
> 
> best way to avoid these problems is not to use the option unless you
> _know_ you need it.

another upstream developer replying to the above:

> Thanks Joerg, I couldn't have said it better. The root cause
> is a SIP incompliance at the operator side in this case.
> I am not going to implement error message for misbehaviour
> of a SIP proxy. And with newly created profiles since verions
> 0.7 this problem should not happen anymore.
> 
> joerg.greoj wrote:
>> there are plenty of possibilities a provider can behave when he
>> fails to handle this (completely legal!) option correctly. with
>> sipgate.de e.g. the voicebox refuses to accept calls after "not
>> avail"-time expired, and your online-status isn't displayed
>> correctly to other sipgate users.
>> you simply can't conclude reliably from behavior of provider to the
>> problem he might have with "unique contact header". and twinkle is a
>> softphone, no expert system database to analyze probable causes of
>> manyfold error symptoms.
>>
>> best way to avoid these problems is not to use the option unless you
>> _know_ you need it.