Grade of service also known as TSF is a metric used by BPO outsourcing to calculate the probability of a call being blocked or delayed more than a specified interval and expressed as a decimal fraction. It is the probability that a call will not be connected to the system as all lines are busy. It helps in determining whether to accept customer calls, reroute the call to an alternative equipment or to reject the call. Rejected calls occur as a result of heavy traffic loads (congestion) on the system and can result in the call either being delayed or lost. If a call is delayed, the user simply has to wait for the traffic to decrease, however if a call is lost then it is removed from the system. This may hamper the call center service.
GoS is the percentage of calls answered within the time frame specified by businesses. The Grade of Service is one aspect of the quality a customer can expect to experience when making a telephone call.
Grade of Service is measured according to the following formula:
GoS = number of blocked calls/ number of offered calls
Grade of service is traffic congestion that occurs in telephone network. Congestion in network results in lost call scenario. Hence traffic carried equals to total traffic offered minus total traffic lost.