Name Service Administration 7-3
7
Figure 7-1 Example of DNS Domains
Every domain has two or more systems that keep a database of DNS names for
that domain. These systems also contain the DNS names of the subdomains,
unless this responsibility is delegated to systems in the subdomain. Thus, there
are several systems that contain the database for the domain net. In that
database, there is a delegation entry pointing to a system that keeps the
database for tv. The DNS database for tv contains entries for delegating the
domains soap and comedy. The database for comedy contains the host address
for ren.
The DNS system of resolving names is strictly hierarchical. Using the previous
example, the system that acts as the DNS server for the domain tv translates a
host name to a host address only if that host name exists directly within the
domain. All other host names are forwarded to the appropriate sub-domain for
resolution. (Thus, the name ren.comedy.tv.net is forwarded from tv’s
DNS server to the DNS server for the subdomain tv for resolution.
ren
net
tv
comedy
soap
myworld
isp
— A sub-domain of the domain net
— A sub-domain of tv.net, isp.net, or myworld.net
local
green
access
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