Described herein are systems and techniques for determining when excessive I/O response times are not the fault of a storage port, but rather are caused by other factors or components on a storage network, for example, over-utilization of a host port. For one or more host ports and/or storage ports, a payload idle time (PIT) may be determined for each I/O operation, the PIT being the amount of time during which a storage port is waiting for a host port to be ready to send or receive data of the respective I/O operation. It may be determined whether one or more of the PITs includes an excessive idle time (EIT), where the EIT may be an amount of the PIT that is more than a predefined acceptable amount of time. The cause of the EIT may be determined.