WIKIPEDIA: http://en.wikipedia.org/wiki/Symbian

EXCERPTS:

The Base Services Layer is the lowest level reachable by user-side operations; it includes the File Server and User Library, the Plug-In Framework which manages all plug-ins, Store, Central Repository, DBMS, and cryptographic services. It also includes the Text Window Server and the Text Shell, the two basic services from which a completely functional port can be created without the need for any higher layer services.

The article did not cover whether Symbian provides software for broadband services from wired, wireless and radio, although it would seem that such access would be vital to Symbian. Maybe I missed that part of the discussion.