It can be used to locate and then throttle some traffic (e.g. traffic from P2P file sharing), thus providing better QoS for the other OTT services offered via public Internet access. Overall, one may note that DPI is implemented in different ways by different ven- dors of Internet network equipment (e.g. routers, gateways). However, the importance of DPI is also considered by the ITU-T in its next generation network (NGN) series of recommendations. The requirements regarding DPI in NGN [35] are targeted (but are not limited to) to perform application identification by inspecting application payload, to support various kinds of policy rules, to be in line with IETF standards for IP flow information exports [36], and SO on. The potential use of DPI for QoS and performance measurements according to the ITU's framework for DPI [37] is given in Table 2.3. As one may note from Table 2.3, the DPI framework includes different depths of packet inspection, considering all headers from layer 2 up to layer 7 (according to the OSI pro- tocol layering model with seven layers), and application payload (which is added by the sending application on the sender's side, and used by the receiving application at the recipient's side). So, one may distinguish deep header inspection (DHI), based on inspec- tion of all headers from layer 3 to layer 7, and deep application identification (DAI), based on layer 7 payload inspection. Performance measurement (locally or remotely) uses DHI and DAI (only layer 2 is excluded here because it refers to the link-layer header, not to a header or payload which is transferred end-to-end). For QoS support, such as traffic management techniques, DHI can be used for traffic-shaping purposes. Further, for network analysis regarding user behavior or usage patterns, headers from layer 3 up and layer 7 as well as application payload can be used. Similar use of DPI can be consid- ered for SLAs between the end-user as a customer and the service provider. Inspection of all packet headers including layer 2 (the 