Final answer:
A Tier 1 ISP connects National ISPs together and is typically operated by large common carriers such as Sprint and AT&T. The net neutrality debate is intertwined with the concept of ISPs as common carriers and regulatory practices. The evolution of telecommunications shows the changing landscape on the definition of utilities.
Step-by-step explanation:
The subject of the question is identifying the appropriate kind of Internet Service Provider (ISP) that connects National ISPs together, which is referred to as Network Service Providers (NSPs). Given the characteristics provided in the question - about a dozen in the US, run by common carriers like Sprint and AT&T, the correct answer is Tier 1 ISP. Tier 1 ISPs represent the top level of the Internet's infrastructure, interconnecting with each other without needing to purchase transit agreements, and thus forming the backbone of global Internet connectivity.
The net neutrality debate mentioned in various excerpts from the context provided discusses the idea that Internet data should be treated equally by providers, without creating 'fast' and 'slow' lanes that could benefit larger corporations over smaller local businesses. This connects to the discussion on whether these entities should be considered as common carriers and the regulatory implications that follow.
Lastly, the historical context about the evolution of telecommunications, highlighting the shift from monopolistic practices to a more diverse technology-based environment, underscores the fluid definition of what constitutes a utility based on the available technology.