N = Number of requests in the system
X = Throughput
R = Response Time
B Utilization law
U = X * S
U = Utilization
X = Throughput
S = Service Time
c Stretch Factor
Stretch Factor=1/ (1-U) =response time/service time
where U is the utilization of the server.
The analytic formula for estimating stretch factor assumes the following:
There are an infinite number of customers
The arrival times are exponentially distributed
The service times are exponentially distributed