20 mar 2010 kl. 19.45 skrev Pranab Bohra:
> In my opinion, the decision on whether to respond with 183 or 180,
> with or without SDP and other things related to early media should be
> taken on case-by-case basis.
> In case of analog termination, as in the present case, ring-tone or
> progress indication tone is always inband. Hence the UAC should be
> ready to receive RTP packets once it receives 183 + SDP.
>
> While dealing with Digital interfaces like ISDN, the gateway can
> inspect the Progress Indicator IE of the call signalling messages like
> ALERT and PROGRESS to decide whether to pass early media to the UAC or
> let it render out-of-band ringtone.
Fully agree. Why I keep being persistent here is that too many applications
assume that 183 means ringing. They just don't understand the importance of the
state change of the call in the network - "the user will hear the ringing".
Audio
is not the only way to alert.
/O
>
> On Sat, Mar 20, 2010 at 10:44 PM, Olle E. Johansson <o...@edvina.net> wrote:
>>
>> 20 mar 2010 kl. 16.40 skrev Iñaki Baz Castillo:
>>
>>> 2010/3/20 Olle E. Johansson <o...@edvina.net>:
>>>
>>>>> For example, some TDM nodes fake the ringing and generate real audio.
>>>>> When such TDM signaling arrives to a SIP-PSTN gateway, it must
>>>>> generate a 183 with SDP :(
>>>
>>>> NO, IT can generate 180 with SDP as default...
>>>
>>> IMHO there is no difference at all between a 180 and 183 both with SDP.
>> "180 ringing" is a state that I can relay to other protocols - we know that
>> there's
>> something out there that is in fact alerting the callee. 183 can be anything,
>> normally translated as PROGRESS. In many apps, the ringing state is
>> very important and it will be missed if we get no 180.
>>
>>>
>>> Does a 180 with SDP mean that the UAC could choose to render the real
>>> audio or internal artificial ringing?
>> Remember that the rendering might be something very different than audio.
>>
>>> If so, how the UAC would know if the received early media is just a
>>> real ringing or a voice message "you have no credit to call, please
>>> pay or die" ?
>> Well, in my head the 180 with SDP means I'll get a ring signal in audio.
>>
>> 183 with SDP is something I would like to be limited to operator messages
>> before an error code in the implementations, or just an informationial
>> message before proceeding with ringing ("You need to refill your account
>> soon"). Today, it's very often used for ringing and I can't determine if we
>> actually have someone that is alerted on the other end.
>>
>> Especially with gateways to deaf people, it is very important to get an
>> alert confirmation so that we can render the ringing in some way that works
>> and we can move to a state where we are more prepared to activate a
>> translator service. Sending 183 with audio doesn't help at all.
>>
>> /O
>> _______________________________________________
>> Sip-implementors mailing list
>> Sip-implementors@lists.cs.columbia.edu
>> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>>
---
* Olle E Johansson - o...@edvina.net
* Cell phone +46 70 593 68 51, Office +46 8 96 40 20, Sweden
_______________________________________________
Sip-implementors mailing list
Sip-implementors@lists.cs.columbia.edu
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
