RNS2).(1 - IPERNS3) (1 - IPERNSn}} (4.1) Loss ratio. The UNI-UNI performance regarding the IPLR parameter can be estimated by inverting the probability of successful packet transfer across n network sections on the path end-to-end, given as follows: IPLRUNI-UNI = 1 - {(1 - - - IPLRNSn)} (4.2) The units of IPLR values should have a resolution of at least 10 to include different types of transport technologies, including the optical transport networks as dominant ones, which have the lowest loss ratio (in the range of 10-9). 4.5.2 QoS Classes by the ITU Network QoS classes are specified by ITU-T [32], based on the requirements of the main applications/services such as telephony, digital TV, and video streaming on demand, 4.5 End-to-End QoS Network Design Table 4.8 ITU QoS classes. Upper bound Upper bound on IPTD on IPDV Upper bound Upper bound QoS Class (milliseconds) (milliseconds) on IPLR on IPER Class-0 Class-1 Class-2 Unspecified Class-3 Unspecified Class-4 Unspecified Class-5 Unspecified Unspecified Unspecified Unspecified Class-6 Class-7 data applications based on use of reliable TCP (e.g. Web, email), and others. The QoS classes and their upper bounds on the main QoS network parameters are shown in Table 4.8. In general, one may use the defined QoS classes for certain types of application con- sidering their QoS requirements, given as follows: Class-0 and Class-1 are appropriate for real-time applications that are sensitive to mean delay and delay variations (e.g. VoIP, video telephony services) where Class-0 has a lower bound on the IPTD parameter and hence it can be used for voice (without video), gaming, or some time-critical smart services (e.g. driverless vehicles). Class-2 and Class-3 are targeted at transaction data, from which class-2 is intended for signaling traffic, while class-3 is for interactive applications. Class-4 is targeted at short transactions, video streaming, or bulk data. Class-5 is unspecified (regarding all performance parameters) and is targeted at tra- ditional best-effort Interne