The point of demarcation between the public carrier network and the customer premises. At the demarc there typically is a physical interface between the local loop, on the network side, and the subscriber's inside wire and cable system and customer premises equipment (CPE).The demarc, whether physical or logical in nature, constitutes a boundary of responsibility, with the carrier being solely responsible for the network side and the customer being primarily, if not solely, responsible for the subscriber side. In a public network connecting to a residential or small business subscriber via an electrical local loop, the physical interface commonly is described as a network interface unit (NIU) or network interface device (NID), and includes a surge protector. If the subscriber is a larger business, the demarc is positioned at the Minimum Point of Entry (MPOE), defined as the closest logical and practical point within the customer domain. In a high-rise office building, for example, it typically is defined as a point of the entrance cable 12 inches from the inside wall. See also CPE, local loop, and protector.
Origin of demarc