[Freeswitch-users] SDP With T.38 in INVITE Problem

[Steve Underwood]

Hi Michael,

On 02/23/2010 12:49 AM, ivdreg ivdreg wrote:
> Hi Michael,
>
> As I said in a previous mails I know exactly what is happening.
> In working setup:
>
> ITSP ---> YATE (GW - Frontend) ---> FreeSwitch (routing 
> server/xml_curl) ---> YATE (GW - SIP Interop) ---> OpenSIPS ---> 
> Subscriber.
>
> I prefer to change YATE (GW - Frontend) and YATE (GW - SIP Interop) 
> with FreeSwitch for some reasons. The problem is:
>
> INVITE comes from ITSP and goes to subscriber via OpenSIPS. INIVITE 
> between FreeSwitch (routing server) and YATE (GW - SIP Interop) 
> contains SDP:
> m=audio 21108 RTP/AVP 18 4 8 0
> c=IN IP4 10.10.1.110
> a=rtpmap:18 G729/8000
> a=rtpmap:4 G723/8000
> a=rtpmap:8 PCMA/8000
> a=rtpmap:0 PCMU/8000
> m=image 21108 udptl t38
> c=IN IP4 10.10.1.110
> a=T38FaxVersion:0
> a=T38MaxBitRate:14400
> a=T38FaxUdpEC:t38UDPRedundancy
> a=T38FaxRateManagement:
> transferredTCF
>
> And reply 200 OK contains in SDP:
> *m=audio 34788 RTP/AVP 8*
> a=rtpmap:8 PCMA/8000
> a=silenceSupp:off - - - -
> a=ptime:20
>
> Reply 200 OK SDP between YATE (GW - SIP Interop) and OpenSIPS contains 
> in SDP:
> *m=audio 16330 RTP/AVP 8*
> a=rtpmap:8 PCMA/8000
> a=silenceSupp:off - - - -
> a=ptime:20
> *m=image 0 udptl 19*
>
> In this case everything works fine. Line *m=image 0 udptl 19 *is 
> removed by YATE.
> But same test with FreeSWITCH on the place of YATE (GW - SIP Interop) 
> *"m=image 0 udptl 19" *call brakes as you can see in my first mail.
>
> I don't want to compare or discus YATE and FS functionality or 
> something else. I just see difference in behavior and because I'm not 
> a big expert don't know witch implementation is more accurate 
> according standards. And second: Is it impossible for me to upgrade 
> all CPE so only thing I can do is to fix it on server side. That is 
> because I ask for a help.
You said the the broken line "m=image 0 udptl 19" goes from OpenSIPS to 
YATE. Do you know if it originates from the OpenSIPS box or the 
subscriber? If it originates from the OpenSIPS box it should be reported 
to them. If its from the subscriber, well...... your chances of getting 
anything fixed are usually small.

Steve