;tag=[call_number] To: Call-ID: [call_id] CSeq: 1 INVITE Contact: sip:alice@[local_ip]:[local_port] Max-Forwards: 5 Expires: 1800 User-Agent: SIPp/Linux Content-Length: 0 ]]> ;tag=[call_number] To: Call-ID: [call_id] CSeq: 2 INVITE Contact: sip:alice@[local_ip]:[local_port] [authentication username=alice password=alice realm=localhost]; Max-Forwards: 5 Expires: 1800 User-Agent: SIPp/Linux Content-Length: 0 ]]>