Arunachala wrote:
> Doesn't RFC3960 talk about this very thing?
Yes. I knew that was out there, but didn't remember the number.
Thanks,
Paul
> -Arun
>
> On Wed, May 12, 2010 at 1:14 PM, Paul Kyzivat <pkyzi...@cisco.com> wrote:
>> Technically, SDP in any 18x only serves to indicate where media should
>> be *sent*, and has nothing to do with whether you should receive media,
>> play received media, etc.
>>
>> Nor does receiving a 180 mean you should play local ringback. It merely
>> says "the other end is being alerted". Nor does receiving a 183 after
>> receiving a 183 after a 180 mean you should *not* play local ringback.
>>
>> If you have received a 180, you may want to play something indicating
>> the called device is alerting. If you are receiving media that you are
>> willing to render, you might want to do so in lieu of locally generated
>> ringback.
>>
>> Unless you use ICE or SRTP, SIP doesn't really specify any way to
>> determine if media you are receiving is media the callee intended for
>> you to receive, rather than spam. As a result, some implementations
>> refuse to render received media unless it comes from the address they
>> are to send media to (symmetric RTP). You can do that if you feel you
>> must, but recognize that you may miss valid media from some implementations.
>>
>> There is no perfect answer here. You can do pretty much as you wish.
>> (E.g. you aren't *required* to render any of the media you receive, even
>> after the call is established.) But you can also have a crappy
>> implementation that doesn't interoperate well with others if you make
>> unreasonable assumptions.
>>
>> Thanks,
>> Paul
>>
>> Kanumuri, Sreeram wrote:
>>> Nitin,
>>>
>>>> I checked the TO tag for both 18x and noticed that both are the same.
>>>> Do you think, that after sending 180 ringing(where local ringing should
>>>> generate), if my UAS is sending 183 without SDP will stop the local
>>>> ringing?
>>> This is up to the implementation whether to play ringing (or) not.
>>>
>>> In this case, I feel you should stop the ringing after receiving 183 and
>>> show a different treatment to the originating UA (something like
>>> click,,click..) to indicate that the call is in progress...
>>>
>>>
>>> HTH,
>>> Sreeram.
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