SIP/2.0 200 OK
Via:     SIP/2.0/UDP sip.ieee.org ;branch=3d8a50dbf5a28d.2
From:    A. Bell <sip:a.g.bell@bell-tel.com>;tag=3
To:      T. Watson <sip:t.watson@ieee.org>
Call-ID: 31415@c.bell-tel.com
CSeq:    1 CANCEL