He is an invited researcher at Korea Advanced Institute of Science (KAIST) since 2016. From 2009 to 2012 and He worked as a researcher in Electronics and Telecommunication Research Institutes (ETRI). He founded a venture company, Raonet Systems, Inc. in 2000 and served as the CEO till 2009. From 1992 to 2001 he worked as a professor of computer engineering in Chungnam National University (CNU). He received B.E and M.E degree in Computer Engineering from Seoul National University (SNU) in 1982 and 1984 respectively. He received his Ph. D. degree in Information and Computer Sciences from University of Delaware (UD) in 1992. His major research areas include the Internet/Future Internet and protocol engineering. His current research topic is identifier based communication networking and trustworthy communications.