Hello, I got a mobile to mobile call working for signalling only. Two RTP channels are being established successfully. But there are only a few pattern sent over these channels (1 byte 0x23 as UDP payload). Is there a setting I am missing in the configuration files? Please find attached a .zip file with pcap and cfg files.
Thanks, Kristian
On 08 Dec 2016, at 11:29, Kristian Martens kristian.martens@ng4t.com wrote:
Hello,
Hi!
I got a mobile to mobile call working for signalling only. Two RTP channels are being established successfully. But there are only a few pattern sent over these channels (1 byte 0x23 as UDP payload). Is there a setting I am missing in the configuration files? Please find attached a .zip file with pcap and cfg files.
I didn't look at the trace yet but have you seen my comment about the SDP file?
[0;m<000b> mgcp_protocol.c:830 Got media info via SDP: port 5502, payload 112 (GSM), duration 20, addr 192.168.17.100 [0;m<000b> mgcp_transcode.c:170 Checking transcoding: GSM (3) -> GSM (112)
Why would one use a dynamic payload type for GSM FR1? I am not sure if the mgcp_mgw is optimized to avoid doing transcoding if input and output codec are the same but use different payload types. I would think it is.
The 0x23 UDP payload is to establish a NAT state to be able to send traffic (e.g. ringtone) to a call for a BSC behind a NAT (all traffic will go from network->NAT/Firewall->MGCP MGW) and the only way to know the port is to have the BSC send some data.
So in your trace I don't see:
* UDP traffic from BTS to bsc_mgcp_mgw * UDP traffic from bsc_mgcp_mgw to 192.168.17.100:5500 * UDP traffic from 192.168.17.100:5500 to ...
you get the point. Maybe start looking for where the BTS is sending the traffic to and take it from there?
holger
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Holger Freyther -
Kristian Martens