This paper describes the initial goals behind the creation of the Domain Name System, or DNS. Originally, mappings of host names to addresses was maintained in one single centrally-located HOSTS.TXT file. Understandably, this approach became unwieldy and needed to be distributed somehow.
The new DNS approach was designed to adhere to the following constraints: provide the same information as HOSTS.TXT, allow distributed management, and flexibly interoperate across environments including the DARPA Internet, all while providing "tolerable" performance and imposing few limits on size of names or other components associated with it.
DNS requires the use of name servers, which store information and answer queries, and resolvers, which interact with client programs to find the right name server to connect to. Resolvers can choose to cache query responses. DNS has an internal name space in the form labels concatenated together from a variable-depth tree, allowing organizations flexibility to organize themselves and expand internally.
I found it amusing to hear that the Berkeley community was somewhat resistant to the change to DNS. As this paper was written over 20 years ago, I wonder if HOSTS.TXT is still used by many systems; I know I personally use a hosts mapping file in Linux to build shortcuts on top of DNS, but to be at all usable, HOSTS.TXT really needs to be an extra layer in addition to DNS to handle special cases at local levels.
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