REGISTER sip:example.com SIP/2.0
To: sip:null-%00-null@example.com
From: sip:null-%00-null@example.com;tag=839923423
Max-Forwards: 70
Call-ID: escnull.39203ndfvkjdasfkq3w4otrq0adsfdfnavd
CSeq: 14398234 REGISTER
Via: SIP/2.0/UDP host5.example.com;rport;branch=z9hG4bKkdjuw
Contact: <sip:%00@host5.example.com>
Contact: <sip:%00%00@host5.example.com>
L:0