Networking: What is a CSN?

I always have to login to a CSN at work, what is a CSN?

CSN Definition

Connectivity Service Network (CSN) The Connectivity Service Network (CSN) consist of network functions which offer IP Services and comprises a number of network entities such as AAA servers, interworking gateway devices and user databases for authentication. It provides following functions: Roaming, AAA Services, Inter-CSN tunneling for roaming Internet Access, Security Authentication, Billing and inter-operator agreement, Inter-ASN mobility…