[Spce-user] No audio, could truncated SIP message be the cause?

[Andrew Pogrebennyk]

Hi Abel,

The initial SDP offer/answer looks OK to me, check the INIVTE to the
callee (packet #60, click in Packet Details on Message Body and then
Session Description Protocol) and 200 OK to caller (packet #102).

However the caller sends another re-INVITE immediately after call is
established, which perhaps looks strange.
This was in initial invite #45 from the caller:

v=0
o=root 722560047 722560047 IN IP4 192.254.96.5
s=Asterisk PBX 1.8.20.0
c=IN IP4 192.254.96.5
t=0 0
m=audio 10604 RTP/AVP 0 101
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=sendrecv

The re-INVITE #107 from the caller has new IP address:

v=0
o=root 722560047 722560048 IN IP4 196.12.161.225
s=Asterisk PBX 1.8.20.0
c=IN IP4 196.12.161.225
t=0 0
m=audio 33244 RTP/AVP 0 101
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=sendrecv

proxy forwards it towards callee in packet #126 and it gets a new port
33490 vs 33486. Not sure if this is correct, but there is RTP stream
from callee, so I suppose this is not the cause of the issue you are
having. IMHO you should check a few things on *caller* device here.

1) why it changes IP and port in re-INVITE? The IP is a private one in
initial INVITE as you see and public in the re-INVITE. Does asterisk
have something like STUN enable (NAT mapping discovery)? Is there a
router with SIP ALG in between?
2) why caller is not sending any media?

BTW, since the media should flow via sipwise mediaproxy-ng, you have
some RTP statistics in /var/log/ngcp/rtp.log (it has side A and side B
statistics - side A would be zero in this case).

P.S. You can you -s0 option with tcpdump to capture whole packets no
matter the size.

Hope this helps.

Andrew

On 12/04/2013 05:42 AM, Abel Alejandro wrote:
> Actually I realized the limit to the truncated packet was tcpdump
> itself. I increased the packet to 2100 bytes and now it doesnt appear
> truncated. However I do not see media info there.
> 
> You can download the 2100 byte packet capture
> at https://dl.dropboxusercontent.com/u/41014173/no-audio-2100framesize.pcap