Multistage interconnection networks (Banyan networks) are proposed as connections in multiprocessor systems and in high-bandwidth network switches. In order to achieve suitable solutions when designing such networks to fit a given task, performance evaluation plays a crucial part. This paper presents an approximative analytical modeling approach that offers a performance measure (in addition to mean throughputs and delay times) that is considered important in real-time communications scenarios: distribution of delay times, for which no analytically tractable exact method exists.