Dr. Cullen Jennings is a Distinguished Engineer in the Voice Technology Group at Cisco. Cullen came to Cisco from Vovida Networks which developed an open-source toolkit for Voice-over-IP. He is also an author of O'Reilly's title "Practical VoIP" and the co-chair of the IETF IPTEL Working Group. Currently Cullen is focusing on conferencing, security, and firewall and NAT traversal. Still active in the SIP and open source communities,
Cullen recently contributed a prototype Instant Messaging and Presence client which integrates strong end-to-end security.