This Recommendation specifies the requirements for Deep Packet Inspection (DPI) in Next Generation Networks (NGN). This Recommendation primarily specifies the requirements for Deep Packet Inspection (DPI) entities in NGN, addressing, in particular, aspects such as application identification, flow identification, inspected traffic types, signature management, reporting to the network management system (NMS) and interaction with the policy decision functional entity. Although aimed at the NGN, the requirements may be applicable to other types of networks.