 is typically in the range of Kbit/s due to TCP Slow Start and Con- gestion Avoidance mechanisms). Generally, Web browsing is used over public Internet access, based on the network neutrality principles. However, the Web has become a graphical user interface (GUI) for various real-time services, such as video streaming services and IPTV. In such cases, when the Web is used as GUI for QoS-enabled ser- vices, normally such Web traffic also is transferred over the managed IP network (not 6.4 QoS for Popular Internet Services Table 6.6 Standardized HTTP QoS parameters. HTTP QoS parameter Definition HTTP service Probability that a subscriber cannot access the service non-accessibility [%] successfully HTTP setup time [s] Time period needed to access the HTTP service successfully, from starting the connection (that is sending TCP segment with SYN bit set to one, from the HTTP client to HTTP server) to the point of time when the content is sent or received HTTP IP-service access failure Probability that a subscriber would not be able to establish a ratio [%] TCP/IP connection to the server of a service successfully HTTP IP service setup time [s] Time period needed to establish a TCP/IP connection to the server of the Web service, from sending the initial query to a server to the point of time when the content is sent or received HTTP session failure ratio [%] Proportion of uncompleted HTTP sessions and HTTP sessions that were started successfully HTTP session time [s] Time period needed to successfully complete HTTP data session HTTP mean data rate [Kbit/s] Data transfer rate measured throughout the entire connect time to the service. The HTTP data transfer shall be successfully terminated. HTTP data transfer cut-off Proportion of incomplete data transfers and data transfers that ratio [%] were started successfully Table 6.7 Trigger points for QoS parameter HTTP service non-accessibility. Event from abstract equation Trigger point from user's point of view Web service access attempt Start: User initiates the Web service