The size of this table and the frequency of updates has reached the limits of manageability. The domain system uses a distributed database and software to perform the same functions as the host table. In this system, host resolvers query domain servers for name resolution. They may cache answers for performance improvement. The domain servers each maintain a portion of the hierarchical database under separate administrative authority and control.
Redundancy is obtained by transferring data between cooperating servers.
All host names were converted from a simple, flat namespace to a structured name consistent with domains. In the second step, servers acting as the root of the database hierarchy were put in place. In the next step, hosts are moving away from host table usage. All hosts will not change from host table to domain server usage at one time. Accordingly, three stages of conversion to the domain system are envisaged.