When determining the number of service circuit channels for your system, ensure that all traffic estimates reflect the volume of traffic anticipated during the system's busy hour . Traffic volume is measured in a numeric value. This value indicates the average number of simultaneously existing calls. The Erlang is the basic unit of measurement for traffic used in traffic tables. Traffic tables offer a means for determining the number of service circuits or channel DS0s needed to carry a given volume of traffic in relation to a stated probability of loss.
Users generate their calls independently of each other.
Expected traffic density is the same for every user. Number of sources is significantly large-approaches infinity. Holding times are constant and equal. Theodore Frankel's book includes a Master Flow Chart for selecting the proper traffic tables. The duration of time the service circuit channel is required to complete a call setup transaction.