. The tempo of the dy- namics will depend on the application or the purpose of the device under interaction. In the context of Internet applications like web browsing, the response time will depend on the type of information requested and the quality of the link as well as protocols in use. Delay sensitive applications will demand faster interaction, e.g. emergency devices, system controls, etc. Other applications such location services, games, passive informa- tion centres, etc., will operate within flexible round trip delays. In the forthcoming sec- tion we cover other applications. 6.4.4 Background While the background class still grows with innovative solutions, it remains as one of the traditional data communications techniques. It serves for e-mail, SMS, database inquiry, and information service platforms. Delay does not have critical consequence in this class, although delays of more than a minute will be highly noticeable. But despite the non-demanding round-trip delays, accuracy becomes critical. Thus, the background users expect error-free communications. For example, control mechanisms measuring performance or monitoring actions will need a reliable accuracy when send- ing or transmitting information. 6.4.5 Sensitivity to IP Transmission Impairments To conclude the UMTS traffic classes, in the following we briefly outline some criteria for different applications in the context of the aforementioned classes. Packet Loss Conversational Streaming Interactive Background Dynamic Interaction Responsive Timely Non-critical Conversational Voice / video at Voice and video medium tempo Streaming audio/video/ background 100 ms 1 sec messaging transmission 10 sec 100 sec Do not tolerate Command/ contro Transactions Back net. action packet lost e.g. telnet, inter. games E-commerce, downloading e.g. email delivery Figure 6.5 Sensitivity of applications to delay in IP environments. From the algorithmic representation of delays (x-axis) and linear scale of packet loss estimation (y-axis) in Figure 6.5, we can see the 