Gonzalo Camarillo is the Principal Systems Expert with the Advanced Signaling Research Lab of Ericsson in Helsinki, Finland. An active participant in the IETFs SIP Working Group since its inception, he co-authored several contributions on SIP-related matters. He is also a frequent speaker at VoIP conferences and the Ericsson representative in the SIP Forum. He received an M.Sc. degree in Electrical Engineering from Universidad Politecnica de Madrid and another M.Sc. degree¿also in Electrical Engineering¿from the Royal Institute of Technology in Stockholm. He is continuing his studies as a Ph.D candidate at Helsinki University of Technology.