This read-only TimeStamp records the start time of the ABR call, the moment its Setup Message (or Add Party Message) was first received on this interface. An administrator uses this to determine how long a specific ABR connection has been active, useful for correlating its start against a network event or configuration change. For example, an operator investigating a cluster of ABR quality complaints checks whether the affected calls' cwspAbrCallStartTime values cluster around a recent change.