the last_app, i.e. sofia/out/+919814440203@222.199.89.27 read_codec See Channel_Variables#read_codec sip_gateway_name See How does FreeSWITCH CDR determine which gateway was used in failover? sip_rtp_rxstat sip_user_agent sofia_record_file start_epoch UNIX epoch value when the call was started, eg. 1294060468 for Mon, 03 Jan 2011 13:14:28 GMT. start_stamp Timestamp when the call was started, in ISO 8601