REGISTER sip:company.com SIP/2.0
To: sip:user@company.com
From: sip:user@company.com
Contact: sip:user@host.company.com
Call-ID: k345asrl3fdbv@10.0.0.1
CSeq: 1 REGISTER
Via: SIP/2.0/UDP 135.180.130.133
Contact: <sip:user@example.com?Route=%3Csip:sip.example.com%3E>
