A New Approach to Support Delay-Sensitive VBR Video 
                     in Packet-Switched Networks

			    Hui Zhang 
		      Carnegie Mellon University

			  Edward Knightly
			  EECS Department
		  University of California, Berkeley

Previous approaches to supporting video on packet-switched networks
include deterministic service, statistical service, predicted service,
and feedback-based schemes. These schemes represent different tradeoffs
in quality of service (QOS), achievable network utilization, and method
of dealing with overload.  In this paper, we propose a new service that
attempts to strike an efficient balance with the above tradeoffs. The
approach is based on deterministic guarantees with client controlled
renegotiation of QOS parameters and graceful adaptation during overload
periods. We evaluate the scheme using two traces of MPEG-compressed
video and show that, even with simple renegotiation polices and
relatively low renegotiation frequencies, high network utilization in
the range of 50% to 80% can be achieved. For traffic that is bursty
over long intervals, this represents a 100% to 150% improvement in
network utilization compared to deterministic service. Compared to
statistical and predicted service, our approach allows more graceful
and client-controlled QOS degradation during overload period.