INVITE sip:user@domain SIP/2.0
VIA: SIP/2.0/UDP host.test.com
from: Caller <sip:caller@domain.com>
To: Callee <sip:callee@domain>
CaLl-Id: 86888aab87@10.0.1.1
CSEq: 0 INVITE
COnTeNt-length: 0