A Paradox for Admission Control of Multiclass Queueing Network with   Differentiated Service
  In this paper, we present counter-intuitive examples for the multiclass queueing network system. In the system, each station may serve more than one job class with differentiated service priority, and each job may require service sequentially by more than one service station. In our examples, the network performance is improved even when more workloads are admitted for service. 
Heng-Qing Ye