Analysis of server logs from multimedia servers, a FTP server, and a web server suggest that irrespective of the content type and protocol used to retrieve it, the small percentage of files that account for the most load on the server exhibit a very dynamic popularity behavior. This observation has implications for content dissemination techniques like caching, server replication, content distr...

We consider a parallel server system that consists of several customer classes and server pools in parallel. We propose a simple robust control policy to minimize the total linear holding and reneging costs. We show that this policy is asymptotically optimal under the many-server heavy traffic regime for parallel server systems when the service times are only server pool dependent and exponenti...

We consider a generalized Jackson network with reneging customers in heavy traffic. In particular, each customer joining a particular station may abandon the network if his service does not begin within a station-dependent, exponential amount of time. We establish that in heavy traffic this system can be approximated by a multi-dimensional regulated Ornstein-Uhlenbeck process.