[SIPForum-discussion] Need Info - UAC behavior

[Arnab Biswas]

Yes..this is a valid behavior. Because the initial offer was there in the
INVITE. The answer (inavlid) answer came in the 200 OK. After the 200 Ok,
your phone can't send any error response. It has to send ACK to acknowledge
the 200 Ok. But also it can't accept the offer. That is why it is sending an
immediate BYE to drop the call.


If you do the same thing in the reverse way, i.e. SIPp sends an invalid
INVITE to the SIP phone, the phone should send 488 Not Acceptable. You may
test it.

Thanks,
Arnab



On Wed, Jan 21, 2009 at 12:01 PM, Gowthaman Desingh <
gowtham_dgm at rediffmail.com> wrote:

> Hi All,
>   I would like to know the expected behavior of the UAC in the below
> mentioned scenario.
>
> Setup:
>         |SIP Phone | -------- |sipp|
>     I have connected a SIP phone back to back with SIPP.
>
> 1. I send an INVITE request from the SIP Phone to the sipp with the below
> mentioned SDP offer.
> **********************************
> v=0
> o=SIPUA 22986 0 IN IP4 9.7.40.253
> s=SIP Call
> t=0 0
> m=audio 19570 RTP/AVP 0 8 18 102 9 101
> c=IN IP4 9.7.40.253
> a=rtpmap:0 PCMU/8000
> a=rtpmap:8 PCMA/8000
> a=rtpmap:18 G729/8000
> a=fmtp:18 annexb=no
> a=rtpmap:102 L16/16000
> a=rtpmap:9 G722/8000
> a=rtpmap:101 telephone-event/8000
> a=fmtp:101 0-15
> a=sendrecv
> **********************************
>
> 2. Accept the call from sipp by sending 200 OK.
>   In the 200 OK sent by the sipp, I send the below mentioned SDP answer.
> The payload number mentioned in the m=line is "12345"(which is invalid). But
> the payload number mentioned in the attribute is valid (8 - PCMA).
> **********************************
> v=0
> o=user1 53655765 2353687637 IN IP4 9.7.40.50
> s=-
> t=0 0
> a=recvonly
> c=IN IP4 9.7.40.50
> *m=audio 6000 RTP/AVP 12345*
> c=IN IP4 9.7.40.50
> *a=rtpmap:8 PCMA/8000*
> a=sendonly
> ***********************************
>
>
> My phone is sending 200 OK followed by BYE to terminate the call. Is that a
> valid behavior.
>
> Thanks,
> Gowthaman D
>
>  u can reach me on my mobile @ +919886625873
>
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