We now have a new problem with our newly created Name Server concept.
To fix this problem the concept of Primary and Secondary Name Servers (many systems allow tertiary or more Name Servers) was born.
If the Primary Name Server does not respond a host can use the Secondary (or tertiary etc.).
Thus us would be the Domain Name of mycompany which was delegated from the state of Mary Land in the US.
This was the delegation model until around 2006 when both countries changed their registration policies and adopted an essentially flat delegation model.
Each layer in the hierarchy may delegate the authoritative control to the next lower level.
In the case of cc TLDs countries like Canada (cc TLD .ca) and the US (cc TLD .us) and others with federal governments decided that they would administer at the national level and delegate to each province (Canada) or state (US) a two character province/state code, for example, = Quebec, = New York, md = Maryland etc..
Finally, since 2011 the TLD policy is essentially unrestricted, if you pay enough money and adopt the operating procedures laid down anyone can register a sponsored TLD.
Look forward to a whole set of new TLDs like .singles, .kitchen and .construction arriving. Figure 1-1 Domain Structure and Delegation What is commonly called a Domain Name is actually a combination of a domain-name and a TLD and is written from LEFT to RIGHT with the lowest level in the hierarchy on the left and the highest level on the right.
With a Name Server present in the network any host only needs to know the physical address of a Name Server and the name of the resource it wishes to access.
Using this data it can find the address (or any other stored attribute or property) of the resource by interrogating (querying) the Name Server.
Remember that the Internet (or any network for that matter) works by allocating every point (host, server, router, interface etc.) a physical IP address (which may be locally unique or globally unique).