CE — customer premises equipment dedicated to one particular business/enterprise
PE — service provider router that connects to a CE to provide a business VPN service to the associated business/enterprise
CSC-CE — an ASBR/peering router that is connected to the CSC-PE of another service provider for purposes of using the associated CsC IP VPN service for backbone transport
CSC-PE — a PE router belonging to the backbone service provider that supports one or more CSC IP VPN services