SIP/2.0 200 OK
Via: SIP/2.0/UDP nm;branch=foo;rport=26810;received=224.221.3.28
To: <sip:nm2@nm2>;tag=a8638129
From: <sip:nm@nm>;tag=root
Call-ID: 50000
CSeq: 42 OPTIONS
Accept: application/sdp
Accept-Language: en
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REGISTER, SUBSCRIBE, NOTIFY, REFER, INFO, MESSAGE, UPDATE
Supported: replaces, timer
Allow-Events: message-summary, dialog, call-info, line-seize
Content-Length: 0