[SIPForum-discussion] 183 Session Progress without SDP

[Tomasz Zieleniewski]

Hi All,

I totally agree with Manish,
One more thing that came to my mind was that
gateway by sending this first 183 ASAP could assure that if for any
reason originating UAC on the whole sip downstream
path didn't receive the 100 trying response this will cause that this
INVITE transaction will move to Proceeding state and there would
no retransmissions.

Cheers
- Tomasz Zieleniewski

2009/4/9 Manish Aggarwal <maaggarwal at gmail.com>:
> Multiple provisional responses is allowed as per the protocol spec.
> This can be used to create an early dialogue.
>
> A UAS will send this, when its taking long time to process INVITE (and
> before sending 200 OK).
>
> Have heard of this behavior before though.
>
>
> -Manish
>
> On Thu, Apr 9, 2009 at 12:26 PM, nitin kapoor <nitinkapoorr at gmail.com>
> wrote:
>>
>> Dear All,
>>
>> We are facing one problem where we are getting two 183 session for 1
>> INVITE. UAC sending the INVITE to Switch and switch has forwarded the same
>> invite to UAS. Then UAS first send the 183 Session progress without SDP and
>> after 2 Sec its sends the another 183 Session Progress with SDP which is
>> something i am not able to understand.
>>
>> 1) Can you please tell me on which cases UAS sends the two 183 Session
>> progress like this.( with SDP & without SDP)?
>> 2) Is this the correct behaviour?
>>
>> I checked this on RFC3261 and another sip pdf but unable to search it.
>>
>> Please find the attached Traces.
>>
>> Thanks
>> Nitin Kapoor
>>
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>
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