Using CDRTool, search for Call Detail Records. Click on the Index of
particular calls to see more details related to signalling, media or rating.
Click on SIP Session id to access the full SIP trace of the SIP session.

The SIP facility uses a MySQL database for storage. The data is stored in
the sip_trace table, for the precise location check the MySQL_URI_siptrace
setting in /etc/openser/config/settings.m4

The data can grow very fast on a busy system. It is advisable to store the
traces on separate database servers to avoid any impact on other database
related tasks when purging the sip_trace table.

To purge the sip_trace table, do the following:

1. Stop OpenSER tracing: /etc/init.d/openser siptrace-off
2. Optionally backup the data offline
3. Purge the table using mysql command: delete from sip_trace;
4. Start OpenSER tracing: /etc/init.d/openser siptrace-on

For heavy loaded systems it is advisable to stop the SIP trace system by
default by setting define(`TRACING', 0) in /etc/openser/config/settings.m4

You may enable the SIP trace facility on a per user basis at any time
without restarting the SIP proxy by placing the SIP account, using the
provisioning functions, into the group "intercept".

You can also trace sip messages on the server console using ngrep command:

sudo ngrep -d eth0 -W byline STRING port 5060

Replace eth0 with the name of the public interface of the SIP Proxy.
STRING is optional and can be used to filter SIP messages.