From the largest global telecommunications service providers to the smallest regional players, there is no such thing as a “stand-alone” network. Telecom networks are comprised of a complex web of fiber optic cables, transport gear, switches, routers, gateways, servers, and datacenters that provide the path over which telecom packets flow and data are stored. To support the services subscribers desire such as internet, mobile smartphone, voice, telemetry, streaming video services, and others, telecom service providers interconnect with the networks of other telecom service providers who in turn connect to yet more thus creating access to the global subscriber base and the internet in its entirety.

There are many hand-off points in today’s networks and these are often referred to as demarcation points. These include external demarcations between two different service providers, between the telecom service provider and the end-customer, and they include internal demarcations that are needed for other purposes, for example crossing the border between two countries in transition, between logical portions of the network, for example between core networks and wireless backhaul and between network and between metro and access networks.

The most prevalent use-case is between the network and the customer premise.

In almost all cases Network Interface Devices (NIDs) are installed for the purposes of testing, monitoring, and segmentation of networks during troubleshooting. Instead of sending out a service technician to each demarcation location with a test instrument, the NID provides an automated way of providing a loopback or in fact even generating test patterns.