Hi Jari

See inline

[Jari] If I start from the top of the list, there are high tone and low
tone, which I have no idea what they are. Then the next one is dial
tone, so let's concentrate on this. Dial tone is a tone which is given
to the caller when he/she picks up the phone, before making any
dialling. By hearing the dial tone, the caller knows the "line is free".
This is implemented only in legacy fixed phones, e.g. mobile phones do
not have a dial tone. What meaning the sending of the dial tone could
have in INVITE or 180? Once the INVITE hits the callee, the playing of
the dial tone to the caller has been discontinued a long time ago. How
about 180, does it indicate that the dial tone should be played to the
caller in alerting phase?  

[DA] The tones were just for information to see if there is any interest
in defining some. That is why I added them to the e-mail and not to the
draft.
I would like to hear more opinions on the tones issue. If there will be
no support for the tone definitions I can drop them entirely from the
draft.

[Jari] Yes, let's use 181+180, or if that is not sufficient for some
reason (which reason I would like to read from the I-D), 180 with
Alert-Info with a CW indication.

[DA] I generally don't think that it is a good idea to overload the
semantic of the 182 to include the CW meaning. The cost of the urn
implementation is minimal and an explicit solution is more future proof
that an overloaded one. 

Let me ask the other way - what issues do you see with a urn?

Greetings,
Denis Alexeitsev
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