OPTIONS sip:bob@example.com SIP/2.0
Via: SIP/2.0/UDP 172.21.40.44;branch=z9hG4bKitIIzAialKS
Via: SIP/2.0/UDP [3ffe:1200:3012:c000:210:a4ff:fe8d:6a46]:5062
     ;branch=z9hG4bKJv+PsUQdfOb
     ;received=172.21.40.24
Record-Route: <sip:bob@example.com;maddr=172.21.40.44>
Record-Route: <sip:bob@example.com
     ;maddr=[3ffe:1200:3012:c000:210:a4ff:fe8d:6a46]>
From: <sip:alice@example.com>;tag=ud6a29947
To: <sip:bob@example.com>
Call-ID: f3359e42-5109-11d6-998d-0010a47e1c0f
CSeq: 1 OPTIONS
Contact: <sip:[3ffe:1200:3012:c000:210:a4ff:fe8d:6a46]:5062>
Content-Length: 0
Accept:
Allow: