Latency is the delay measured between the time a frame first starts to leave the source device and the time the first part of the frame reaches its destination.
A wide variety of conditions can cause delay as a frame travels from source to destination:
• Media delays caused by the finite speed that signals can travel
through the physical media.
• Circuit delays caused by the electronics that process the signal
along the path.
• Software delays caused by the decisions that software must make
to implement switching and protocols.
• Delays caused by the content of the frame and influenced by the frame switching decisions to be made. For example, a device cannot route a frame to a destination until the destination MAC address has been read