Configuring and Managing MPE/iX Internet Services (MPE/iX 6.5)

118 Chapter8
DNS BIND/iX
Explanation of Terms
Explanation of Terms
BIND, which stands for Berkeley Internet Name Domain, is the most
commonly used implementation of DNS.
DNS is essentially a distributed data base, with control of the different
elements of the data base maintained by individuals responsible for the
domain served by that DNS server. The data is used by DNS servers to
assist one host in identifying the location of another host anywhere in
the system, translating a host name to its IP address, and visa versa.
The DNS distributed data base is much like a directory. It is organized
in an inverted tree fashion, much like the unix directory structure, with
the most inclusive node, or domain, at the top, with multiple levels of
sub-domain names below, until at the end are the actual host names.
Information about each domain, specifying the sub-domains or hosts
below it, are maintained in the DNS data base files. The convention is
to call these files “db files” in BIND 4.X, and “zone files” in BIND 8.x.
These files are made known to the respective DNS server through a
configuration file, named.conf. In earlier versions of BIND, it was called
named.boot.
When fully formed, a host name is made up of a sequence of labels
separated by dots. When read from right to left, as DNS parses it, it
describes a path leading from the most inclusive domain in its tree,
through successively more local domains, until its own host name is
reached.
Using the full host domain name, this is how a DNS server traverses
the DNS data base, starting at the right-most, most inclusive domain,
following data maintained by the various DNS administrators in their
respective data files, until it finds the target host name, and its IP
address.
A domain name is also made up of a sequence of labels separated by
dots. Rather than describing a host, it describes a domain, under which
other sub-domains and/or hosts exist. It can be located in the DNS data
base by DNS servers the same way as was the host domain name.
Sometimes a particular DNS server will not manage an entire domain.
Rather, the domain will be broken up into pieces, called “zones”.
Responsibility for these various zones is “delegated” to other DNS
servers, and their respective DNS administrators. So, in DNS
configuration files, instead of describing a domain for which it is
responsible, the more general term “zone” is used.
It is also common, in fact recommended, for a DNS Server to have at
least one “backup”, another machine that will respond to queries when
the main server is down. The main server is knows as the “master” and
the backup as the “slave”. In previous versions of BIND, they were