From the point of view of IANA and root name server administrators, the particular TLD manager maintains the relevant TLD. From the end user’s point of view and especially from the point of view of an ISP, this situation is not as simple. We have to bear in mind that the TLD manager also ensures the registration of Second Level Domains (SLDs), which are widely used in many countries. The registration of an SLD requires quite a large agenda, which in turn means that a larger office is needed. In many countries, this office is called the Network Information Center (NIC).
We are most likely to encounter one of the following types of SLD registration:
There is one authority that registers SLDs. This authority operates name servers for the relevant TLD, registers SLDs, and at the same time tries to settle disputes in those cases where two or more people argue about a certain domain.
The central authority only operates the central SLD register and name servers...