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: 0ha0isndaksdj@10.0.0.1
CSeq: 8 REGISTER
Via: SIP/2.0/UDP 135.180.130.133
Expires: Thu, 01 Dec 2040 16:00:00 GMT