nce. 0B 80 30 30 34 38 38 38 35 30 33 30 In Europe the Conference of European Post and Telecommunica- tions Administrations (CEPT) have produced specifications collec- tively known as NETs (Norme Europeene de Telecommunications) covering various areas to promote type approval across Europe. Figure 61.19 Typical display of a D Channel protocol NET3 covers the Basic Rate Access and NET5 the Primary Rate from a protocol analyser Access. Many manufacturers of protocol analysers have application programs available that allow them to carry out conformance tests with it SO that timing measurements or discrepancies can be deter- for the NETs and other conformance specifications. mined. ISDN also adds a new layer of complexity to protocol testing in that subtle effects of D channel call set up procedure can affect the 61.5.7.3 Performance testing protocol events occurring on the B channel. For this reason dual port protocol analysers are very popular in monitoring dual processes Performance testing requires the gathering and display of statistics simultaneously. In this way the user can simultaneously monitor the on the numbers of protocol units (frames, packets, messages and SO protocol events occurring on the same physical line but in different on) transmitted and received over a period of time between devices. channels, for example the D channel and a B channel. The goal is to discover deviations from normal operation or from a pre-defined specification, that point to underlying problems in the terminal or switching equipment or in the operation of the protocols 61.6 Introduction to cellular radio themselves. For ISDN, degrading performance of the D channel protocols, Mobile telephone systems based on the cellular network concept are such as longer set up times or a high number of unsuccessful calls, in use in most developed countries. can indicate a number of problems ranging from error at the termi- The key to satisfactory operation of these systems is a complex nal, to traffic overloading on the ISDN network. Monito