KHALID AHMAD, PhD, is a senior research engineer in the Carrier Data Networking division of Nortel Networks, a leading global manufacturer of ATM, optical fiber, and FR network elements. Dr. Ahmad has been involved at the forefront of developments in ATM, FR, and MPLS technologies and interworking since their inception in the ITU-T, ATM Forum, and FR Forum. He earned his doctorate in solid-state physics from the Cavendish Laboratory, Cambridge University, U.K.