Well, if the called party takes a while to pick up the phone and a final 
response is not recieved at the UAC in that time,  and no inermediate 
responses are received either (because the RINGING was dropped for 
example), I suppose the client transaction on the UAC would time out. 
Whereas, it would seem that if the INVITE did get to the UAS and the 
phone is indeed ringing, it would make sense to send periodic RINGING 
while the phone is indeed ringing at the UAS.

I suppose one can use provisional reliable response for that purpose if 
that is really an issue but I was wondering why a single RINGING 
suffices and if so, what is the purpose of even sending that one RINGING 
if it can be dropped.

Ranga

Paul Kyzivat wrote:

> What do you expect the UAC to do differently when it receives 
> subsequent 180s that it wouldn't do if it didn't get them?
>
>     Paul
>
> M. Rangnathan wrote:
>
>> Hello
>>
>> I want to make a UAS send periodic RINGING responses as the phone is 
>> being alerted. Are there any guidelines for what the interval between 
>> such responses should be ?
>>
>> Thanks
>>
>> Ranga
>>
>


-- 
M. Ranganathan 

Advanced Networking Technologies Division,
National Institute of Standards and Technology (NIST),
100 Bureau Drive, Stop 8920, Gaithersburg, MD 20899. 
tel:301 975 3664 , fax:301 590 0932 http://w3.antd.nist.gov/
Advanced Networking Technologies For the People!  


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