The notion of quality of service
The term MPLS (an acronym for "MultiProtocol Label Switching) represents a collection of specifications defined by the IETF (Internet Engineering Task Force) consisting of equipping the frames circulating the network with a label which indicates to the routers the path that the data must follow. So MPLS serves the management of quality of service by defining 5 Classes of Service, known as CoS.
- Video. The class of service for transporting video has a higher priority level than classes of service for data.
- Voice. The class of service for transporting voice has a priority level equivalent to that of video, i.e. higher than classes of service for data.
- High priority data (D1). This is the class of service with the highest priority level for data. It is used in particular for applications which are critical in terms of performance, availability and band width.
- Priority data (D2). This class of service relates to non critical applications which have particular requirements in terms of band width,
- Non priority data (D3), representing the lowest priority class of service.
MPLS specifications operate at layer 2 of the OSI Model and can notably function on IP, ATM or frame relay networks.