Dr. Jennings was selected by the NomCom to serve on the ICANN Board from 2007-2010, serving as the board's vice-chair from 2009-2010. During his time with ICANN he also served as Chair of the Board Governance Committee. Dennis Jennings was appointed the consultant Project Leader for ICANN's IDN Variant Issue Project; he first took up that role at ICANN's 2011 meeting in San Francisco.
Dr. Jennings' career has seen him pursuing venture capital endeavors, investments, and serving on a variety of boards and within academia.
Dr. Jennings was the director of University College Dublin (UCD) Computing Services from 1977 to 1999; he was responsible for the university's IT infrastructure and a staff of over 90 people. In 1986, he took leave from the University and acted as interim President of the Consortium for Scientific Computing at the John von Neumann Centre (JvNC) in Princeton, New Jersey; he took charge of starting its super computer center. 
He co-founded 4th Level Ventures in 2002, and continues to work there. 4th Level Ventures is a 17 million pound Irish venture capital company; it aims to invest in companies that are commercializing opportunities arising form Irish research and academic institutions. As of 2007, Dennis and 4th Level's other founder, Ray Norton, had invested in over a dozen companies as angel investors, and he claims that about half of those investments are looking "very promising".
Mr. Jennings has been able to take time off from his academic career and develop 4th Level Ventures thanks to an early investment in Euristix in the 90s; that company was first purchased by Fore Systems for $81 million, and subsequently purchased by GEC-Marconi for $2.8 billion.
He was also integral in creating NSFnet, in 1985-86, which is the network that preceded the Internet. Thus, he was directly responsible for creating the internet as we know it; it was his decision to use the TCP/IP Protocols out of the military (DARPA) and select academic environments, where they exclusively existed, and link together 300+ universities. It was an ambitious move that he believes would have happened eventually; but, alas, he was the one responsible and, thus, he paved the way for the expansion of the network into the Internet as we know it. The initiative that he led cost the U.S. government some $17 million USD.
A selection of some of Dr. Jennings' more important roles:
- Founder of NSFnet
- Chair of the Board and General Assembly for CENTR
- Early proponent of ICANN
- Founder of IEDR
- President of EARN
- Board Member Ebone
- Chair of he Oversight Board of the Irish Centre for High-End Computing (ICHEC)
- Non Executive Board Director for Afilias
Dr. Jennings holds a 1st Class honours physics BSc degree from University College Dublin (1967), and a PhD degree obtained for research on high-energy gamma radiation from pulsars (neutron stars) (1972).
Dennis enjoys opera and classical music, and is the chairman of the UCD Choral Scholars Board of Management.