• March 2004 – present
Professor, The Ohio State University
• Nov. 1999 – March 2004
Vice President, Bell Labs Research
• Jan. 1998 - Nov. 1999
Director, Networking Research Department, Bell Labs Research
• July 1985 - Dec 1997
Member of Technical Staff, Bell Labs Research
• February 1982 to June 1985
Graduate Research Fellow, Department of Computer Science, Columbia University
• February 1980 to February 1982
Lecturer, Department of Mathematics, Hunter College, City University of New York