Telecommunications and Internet Protocol Harmonization over Networks (TIPHON) Release 3; End-to-End Quality of Service in TIPHON Systems; Part 2: Definition of Speech Quality of Service (QoS) Classes (V2.1.2)
"The present document defines five classes of Quality of Service for characterizing the speech performance of TIPHON compliant IP voice telephony networks. The classes of service apply to all the defined TIPHON Scenarios and are specified in terms of the following parameters: ? ""Overall Transmission Quality Rating""; ? ""Listener Speech Quality"" (one-way non-interactive speech quality); and ? ""End-to-end Delay""."