ter observed and studied. This is the variance of the time interval between the samples. This has a similar effect on the human operator as the RTT in case of TCP. Before each measurement, the data link is investigated with a bandwidth and reliability test (loss of packets, delays) using a dedicated tool, Iperf (with the Jperf graphical interface) for measuring max- imum TCP/UDP bandwidth [20]. For bandwidth measurement (and for other QoS parameters) Ethereal/WireShark [21] was also used. Jperf Bandwidth and the Ethereal I/O Graphs are expressed in kbps (Y-kbps, X-s). The samples are read from the memory buffer and then transmitted to the client via IP-TCP with its own error detection mechanism and UDP with simple error detection (the connection is ended when samples are lost). In this process, the sam- ples are not altered in any way and SO at the client we will have the same metrologi- cal characteristics as those of the digital oscilloscope used. Service Delivery Platforms 12.1.2.4 Probe and Client Programs In order to program the data transmission and reception at the probe and client level it was employed LabVIEW [22], which can also run on smartphones (many times throughout the implementations of this chapter, the HTC P3600-GSM- GPRS-EGDE/3G-UMTS-HSDPA/WiFi/Bluetooth/IrDA/GPS/Windows Mobile 5.0-running LabVIEW for PDA-Pocket PC was used). Data streaming was done via TCP or UDP by the already established PDP (Packet Data Protocol) between the mobile terminal and the PLMN (GGSN) using the defined LabVIEW func- tions for TCP and UDP Transport. Using these functions, four peered virtual instruments (VIs) were developed for client DL and probe UL transmission on TCP or UDP. From the "Probe" front panel (see Figure 12.5), the number of points (samples) to be sent can be chosen. The maximum value is 5000. All tests were done with 200 samples. For the VI-s at client side, an example is presented in Figure 12.6 (the front panel) and Figure 12.7 (the diagram-including contextual details). At the "probe" (the server s