Which Quality of Service (QoS) parameter is defined as a variable delay that can be measured in different ways?

Jitter is defined as the variation in packet arrival times, representing a variable delay. This parameter is crucial in quality of service measurements, particularly for applications that require a consistent stream of data, such as VoIP or video conferencing. Jitter can be measured in several ways, including the difference in time between the arrival of packets or the deviation from the average latency over time.

In contrast, latency generally refers to the time it takes for a packet to travel from the sender to the receiver, which is typically a fixed value rather than a variable one. Packet loss indicates the percentage of packets that are not delivered to their destination, and bandwidth refers to the maximum rate at which data can be transferred over a network connection, neither of which directly addresses variable delay. Thus, jitter stands out as the QoS parameter that specifically focuses on variability in delay, making it the correct answer in this context.