Mark knows about the Internet architectures/protocols, multimedia communications/codecs, signaling, congestion controls, and many others.
Soo-Hyun designed and implemented real-time multimedia congestion control (CC) mechanisms, and related RTP/RTCP interfaces with CC mechanisms. He also modified a video codec for the use of CC mechanisms in real-time interactive video conferencing systems.
Piers knows about interactive multimedia conferencing systems, especially for Vic and Rat system. He also knows about RTP/RTCP protocol usages in a real system. He is interested in ECN exposure in the Internet.