As a user, you notice when your application is lagging, and it’s frustrating. As a network engineer, this lag — network latency — is cause for investigation and resolution. Network latency is how long it takes a packet of data to reach its destination. It is typically measured in round-trip time (RTT) from the sender to the receiver and back, and includes additional delays like propagation delay, processing delay, queuing delay, and encoding delay. Plus, network congestion can add a dynamic element.