Enterprise QoS refers to the ability of enterprises to offer differentiated services to their customers. Businesses require that mission-critical applications have priority over non-essential traffic during episodes of congestion. This article described why certain emerging applications require QoS. In order for QoS to be effective, there needs to be a consistent common framework infrastructure from the services offered by the service providers and the enterprise infrastructure. The sources of delays and where QoS fits in the overall end-to-end solution was described. Finally, the main functional components of a QoS capable device were described in order to provide you with an understanding of the commercial implementations.