His research interests are in network architectures, protocol design, and networked systems, from modeling to implementation and experimentation. His current research areas include network and system architectures, robust networking, mobile networked systems, adaptive real-time communication, and network measurements. In the IETF, was co-chair of the MMUSIC working group from 1997 through 2009 and co-chaired the SIP working group from its foundation in 1999 to October 2002, in the IRTF he co-chaired DTNRG. He has served the networking community as Treasurer of ASCM SIGCOMM, Vice-chair of IEEE Comsoc TCCC, General Co-Chair of several conferences (incl. ACM SIGCOMM 2012, ACM MobiSys 2018, ACM CoNEXT 2021) and a TPC co-chair of numerous conferences and workshops.