# Erlang B Calculator

The Erlang B formula is useful for solving some of the exercises in the textbook Optical Network Design and Planning.

### Assumptions:

• Arrival Process: Interarrival times are exponentially distributed.  lambda = arrival rate (connections per unit of time)
• Service Process: Service times are exponentially distributed.     mu = service rate (connections per unit of time)
• Traffic Intensity: rho = lambda/mu.   Must be less than 1 for a stable system.
• If all servers are busy upon arrival of a connection request, the request is Dropped.
The calculator operates in one of two ways:
• For a specified lambda, mu, and blocking probability, the calculator determines the number of servers that are needed to yield a blocking rate that is lower than or equal to the specified threshold
• For a specified lambda, mu, and number of servers, the calculator determines the blocking probability

 Arrival Rate and Service Rateare Required Fields Arrival Rate (lambda) Service Rate (mu) Enter one of the following fields,and then calculate the other -------------------- Blocking Probability Number of Servers