INVITE sip:alice@wonderland.com SIP/2.0
Via: SIP/2.0/UDP h.caller.com
From: <sip:charlie@caller.com>;tag=5
To: Alice <sip:alice@wonderland.com>
Call-ID: 27182@caller.com
CSeq: 2 INVITE
Contact: sip:charlie@h.caller.com