[SIPForum-discussion] Reg: SDP offer

[Leks™]

Its a special case.
SDP Can have media ports as 0.
This specifies continuing existing session by disabling that specific codec.

in this case re-INVITE offer is disabling the payload type 8.

refer rfc4317 for example SDP offer answer

-Raaz


On Wed, Apr 8, 2009 at 4:34 PM, prem ranjan <prem.behera at gmail.com> wrote:

> Hi,
> I have the following scenario:
> A calls B
> A sends INVITE with the following SDP:
>
> *v=0
> o=780 409699 409699 IN IP4 192.168.0.20
> s=-
> c=IN IP4 151.98.90.197
> t=0 0
> m=audio 41270 RTP/AVP 8 18 4 96
> a=rtpmap:96 telephone-event/8000
> a=ptime:20
> a=SilenceSupp:off
> a=fmtp:96 0-15
> a=nortpproxy:yes*
>
>
> B answers the following SDP in 180 Ringing:
>
> *v=0
> o=- 38000001 1239174750 IN IP4 151.98.90.196
> s=SDP Data
> c=IN IP4 151.98.90.196
> t=0 0
> m=audio 18990 RTP/AVP 8 96
> a=rtpmap:96 TELEPHONE-EVENT/8000
> a=ptime:20
> a=sqn:0
> a=cdsc:1 image udptl t38
> a=cpar: a=T38FaxVersion:0
> a=cpar: a=T38MaxBitRate:14400
> a=cpar: a=T38FaxRateManagement:transferredTCF
> a=cpar: a=T38FaxMaxBuffer:280
> a=cpar: a=T38FaxMaxDatagram:260
> a=cpar: a=T38FaxUdpEC:t38UDPRedundancy
>
> *After this Call is successful.
> Now B wants to send a FAX. For this it creates a Re-Invite with the
> following SDP:
>
> *v=0
> o=- 38000001 1239174761 IN IP4 151.98.90.196
> s=SDP Data
> c=IN IP4 151.98.90.196
> t=0 0
> m=audio 0 RTP/AVP 8
> a=ptime:10
> m=image 33815 udptl t38
> a=T38FaxVersion:0
> a=T38MaxBitRate:14400
> a=T38FaxRateManagement:transferredTCF
> a=T38FaxMaxBuffer:1800
> a=T38FaxMaxDatagram:260
> a=T38FaxUdpEC:t38UDPRedundancy
> *
> Now my question is, can we have the value "Zero" in the audio port. Is this
> RFC compliant???
>
> Kind Regards,
> Prem Ranjan Behra
> _______________________________________________
> This is the SIP Forum discussion mailing list
> TO UNSUBSCRIBE, or edit your delivery options, please visit
> http://sipforum.org/mailman/listinfo/discussion
> Post to the list at discussion at sipforum.org
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sipforum.org/pipermail/discussion/attachments/20090409/0cd16c67/attachment-0002.html>