Windows Media Station file (*.nsc) is the session description file for Microsoft's Media Stream Broadcast (MSB) protocol.
Introduced with Microsoft NetShow 2.0, the file extension NSC comes from NetShow Channel. NSC files are text files that contain stream configuration information enabling NetShow clients to connect to a multicast stream coming from a NetShow server. NetShow 2.0 was the first commercial streaming media system to support multicast streaming. Windows Media Services is Microsoft's latest product for generating multicast streams and these proprietary, partially encrypted NSC files are still used.
NetShow was Microsoft's framework for network broadcasting, just like Real's RealMedia. Components include NetShow Player (merged with Windows Media Player), NetShow Media Services (merged with Windows Media Services), etc.