s of 6 MB for bitrates below 30 Mbit/s and file sizes of 12 MB for bitrates in the range 30-50 Mbit/s, while for higher speeds above 50 Mbit/s the HTTP connection for download/upload is required to last at least 10 seconds, which requires a file size of approximately 60 MB (per test) Measurement server Whitebox gateway Internet Laptop Customer network ISP - Internet service provider PC - Personal computer Figure 7.12 SamKnows measurement probe. 7.10 Discussion Table 7.10 Primary quality metrics in SamKnows platform. Target for measurement Primary quality metrics Web browsing The total time to retrieve a reference Web page from one of the popular websites. Voice over IP (VoIP) Uplink and downlink packet loss and jitter, and RTT delay. Speed Downlink and uplink bitrate (Mbit/s), measured separately in each direction with several (e.g. three) concurrent TCP connections for more realistic measurement (based on user experience, where single broadband access is concurrently used for more several Web client-server connections). UDP delay Average RTT obtained through a series of randomly transmitted UDP packets. UDP packet loss Percentage of UDP packets lost (obtained from UDP delay tests). DNS resolution The time measured for the recursive DNS resolvers (used by the ISP) to return IP address from resolving a popular website domain name (e.g. www.google.com) or more [31]. However, the data cap (maximum volume of traffic included in the IAS package on daily, weekly, or monthly basis) can be an obstacle for such measurements if the Internet traffic due to measurements is not differentiated (and hence not included in the data cap, i.e. not charged) by the ISP. 7.10 Discussion The QoS measurements are influenced by different methods used. While passive QoS measurements (based on user traffic sniffing) may provide valuable statistical data, QoS measurements are typically provided with active measurement because the measure- ment procedures can be specified or standardized and the results are repeatable and comparable. However