This Recommendation defines a set of general quality of service (QOS) parameters for public data networks (PDNs). The parameters have two essential characteristics: 1) they focus on performance efsects which are observable at the network interfaces, rather than their causes within the network; and 2) their definitions are based on protocol-independent events (e.g. access request) rather than protocolspecific interface events (e.g. issuance of an X.21 call request signal). These characteristics m&e the parameters independent of application, network, and service. With proper specialization, they may be used to specify or measure the quality of any data communication service, irrespective of network internai design or network access protocol. Examples of data communication services to which the parcmeters may he applied are circuit-switched services, packet-switched services, and leased circuit services. The parruneters are applicable to both connection-oriented and connectionless services.