ISDN (Integrated Services Digital Network) is a set of CCITT/ITU standards for digital transmission over ordinary telephone copper wire, as well as over other media.
Managed network services are networking applications, functions and services that enterprises outsource to be remotely operated, monitored and maintained by a managed service provider (MSP).
A network service provider (NSP) is a company that owns, operates and sells access to internet backbone infrastructure and services.
Path Computation Element (PCE) is a network component, application or node that can apply computational constraints and compute a network path or route based on a network graph. The PCE has access to topology information for the entire network and uses this in path computations.