The time from the source sending a packet to the destination receiving it.
Latency is the time it takes for a message, or a packet, to travel from its point of origin to the point of destination. That is a simple and useful definition, but it often hides a lot of useful information — every system contains multiple sources, or components, contributing to the overall time it takes for a message to be delivered, and it is important to understand what these components are and what dictates their performance.
Amount of time required for a message to travel from the sender to receiver, which is a function of distance over speed with which the signal propagates.
Amount of time required to push all the packet’s bits into the link, which is a function of the packet’s length and data rate of the link.
Amount of time required to process the packet header, check for bit-level errors, and determine the packet’s destination.
Amount of time the packet is waiting in the queue until it can be processed.