UPC and NPC

Usage Parameter Control (UPC) and Network Parameter Control (NPC) are functions performed in a computer network at the User-Network Interface (UNI) or the Network-Node Interface (NNI), respectively, that check and limit network traffic flows from a network host (user) or from another network for conformance to the expected levels. Generally the functions performed by UPC and NPC are the same. In the ITU-T's definition, for their use in Asynchronous Transfer Mode (ATM) networks, they state that "Their main purpose is to protect network resources from malicious as well as unintentional misbehaviour which can affect the Quality of service (QOS) of other already established connections by detecting violations of negotiated parameter values or procedures [i.e. detecting excessive or excessively bursty traffic] and taking appropriate actions." UPC and NPC may involve traffic shaping, where traffic is retimed to conform to the expected levels and timing, or traffic policing, where non-conforming traffic is discarded or reduced in priority (so that it may be discarded downstream in the network if congestion occurs).