"Are networks behind NAT/ALG or that use RFC 1918 or the v6 equivalent address space, part of the 'Internet' or are they in networks where access to addresses/service ports must be explicitly granted?"

RFC4084 (Terminology for Describing Internet Connectivity)<http://tools.ietf.org/html/rfc4084>, IMHO, does a decent job of trying to enumerate/unpack these kinds of questions. I'm sure it's not uncontroversial, but may provide some common vocabulary. Tony