CTD is the time span between the sending time and the receiving time of a cell between two monitoring points (MP). CTD differs from one cell to another. The CTD has three segments: The primary type is Propagation delay is the time important to convey bits through the media that associates two network components. The second is Switching delay is the time interval between the appearance of a cell in one of the switch’s input ports and its accessibility in an output port. And the third one is the Queuing delay is the time interval that the cell stays inside the switches queues; this value relies upon the network load.