The growing use of clusters in diverse applications, many of which have real-time constraints, requires Qualityof-Service (QoS) supporr from the underlying cluster interconnect. In this paper; propose an analytical model that captures the characteristics of a QoS capable wormhole router; which is the basic building block of cluster networks. The model captures the behavior of integrated trafic in a cluster and computes tht: average deadline missing probability for real-time trafic. The cluster interconnect, considered here, is a hypercube network. Comparison of Deadline Missing Probability (DkfP) using the proposed model with that of the simulation shows that our analytical model is accurate and useful.