QoE is a measure of the overall quality of a particular entity. The entity in question can range from a supplier off services down to a single service. In the former case QoE is a measurement of the organisation providing the service as a whole. In the latter it is a measure of the single service. Different delivery models between these two extremes can also be measured using QoE metrics. QoE differs from Quality of Service monitoring. The former is a measure of everything involved in the delivery of a service from the consumer of the services point of view, while that latter is a measure of the physical robustness of the service delivery infrastructure.