link layer which is limited to a network link or segment) is usually performed for layer 2 related policy conditions. In general, one may distinguish [37] between link-layer DPI (limited to the L2 network domain) and network-layer DPI (which covers network information on L3, i.e. the network layer, and higher protocol layers). Overall, the use of DPI is not mandatory in telecommunication networks. However, it has a variety of possible uses and then it is up to the network designers to decide whether DPI is needed and should be used or not. DPI also draws certain privacy con- cerns regarding end-users, SO legislation may be needed to regulate the purposes for which DPI can be used and the purposes for which it is not allowed (e.g. for sniffing user behavior and the type of content a given user consumes over the public Internet). 2.10 Basic Inter-Provider QoS Model Table 2.3 Framework for DPI on QoS. Deep packet inspection (DPI) Deep header inspection (DHI) application identification Shallow packet Medium-depth Network application (DAI) inspection packet inspection (SPI) (MPI) Layer 2 Layer 3, 4 Layer 4+ header header header Layer 7 inspection inspection inspection payload (L2HI) (L3,4HI) (L4+HI) inspection Performance measurements (key performance indicators [KPIs]) Collection of remote measurements Generation of local measurements Usage parameter monitoring Service level agreements Traffic parameter control L3 policing (peak rate, sustainable rate, burst size) L7 policing ("application payload" size, byte rate) QoS support Traffic shaping (L3 byte shaping) Network analysis User behavior Usage patterns Charging/billing support Time-based information Traffic volume-based information Event-based information (associated with content) Link-oriented DPI Layer 2-related policy conditions Basic Inter-Provider QoS Model The QoS model which is used inside the given network provider's domain (e.g. given tele- com operator, either fixed or mobile) is targeted to a limited number of services offered to end-users (e.g. VoIP as