[Linphone-developers] No audio in uplink direction and STUN request/response change RTP port communication

[amit Kumar]

Hi Linphone Developer,

we are using linphone library for our voip app.we are using "rtpproxy" to traverse the RTP traffic over NAT(in case of client is behind NAT).Some of the time we have observed that called party were not able to hear anything.on daignoisis we have seen there were no voice/RTP traffic in uplink direction.Following are the SIP REQUEST-RESOPNSE.

As per below SDP negatation, we were expecting follwing traffic flow.

DOWNLINK DIRECTION=>

(RTP PROXY)70.205.110.110:16644 =rtp=> 172.55.54.20:7078 (LINPHONE CLIENT)

UPNLINK DIRECTION=>

172.55.54.20:7078 (LINPHONE CLIENT) =rtp=> (RTP PROXY)70.205.110.110:16644


But After call connect, we see an  STUN binding request on PORT 16644 from LINPHONE CLIENT 172.55.54.20:31751.

Could someone exlplain what does this mean, becuase after the above request I see below RTP FLOW. How come STUN request can be fullfilled at PORT 16644.??


DOWNLINK DIRECTION=>

(RTP PROXY)70.205.110.110:16644 ==rtp=> 172.55.54.20:31751 (LINPHONE CLIENT)

UPNLINK DIRECTION=>[here this uplink direction I see no RTP flow]

172.55.54.20:31751 (LINPHONE CLIENT) =NO RTP=> (RTP PROXY)70.205.110.110:16644

Can someone explain why port has been changed when in (LINPHONE CLIENT) SDP it was 7078.and how STUN request drive it to change.
also after that I see no uplink traffic. Could you please provide some pointer to find root cause(ie its a bug or setting required in linphone)

INVITE  TO LINPHPNE CLIENT...

INVITE sip:address@hidden:41235;transport=udp SIP/2.0
SDP CONTENT:

v=0
o=Sonus_UAC 408177 17457 IN IP4 70.205.110.110
c=IN IP4 70.205.110.110
t=0 0
m=audio 16644 RTP/AVP 0 18 96 101
a=rtpmap:0 PCMU/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:96 iLBC/8000
a=fmtp:96 mode=30
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=sendrecv
a=ptime:30
a=nortpproxy:yes

RESPONSE FROM  LINPHPNE CLIENT PUBLIC IP(172.55.54.20)

SIP/2.0 200 OK

SDP CONTENT:

v=0
o=35066040 1110 19 IN IP4 10.192.190.50
s=Talk
c=IN IP4 10.92.189.50
b=AS:380
t=0 0
m=audio 7078 RTP/AVP 18 0 101
a=fmtp:18 annexb=yes
a=rtpmap:101 telephone-event/8000

Thanks,

amit