MEF 23.1 is a specification developed by the Technical Committee of the MEF that provides an Implementation Agreement for Carrier Ethernet Class of Service.
"This Implementation Agreement (IA) specifies a set of Class of Service Names called CoS Labels that can be used by Operators, Service Providers and their Subscribers to indicate the performance expectations to be associated with a given set of frames that comprise a CoS Frame Set. This CoS IA includes standards for CoS and Color identification as well as performance objectives and supporting requirements. The CoS Labels are envisioned as a subset of all of the Class of Service Names an Operator may provide. The MEF CoS IA facilitates: Ethernet service interoperability and consistency between Operators, use of a common CoS Label set for Subscribers to utilize and use of performance objectives that support key applications. The terms CoS Label, CoS Name, CoS Frame Set and others are defined in Section 2 of this IA."