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DNS Name Server Data Storage: Resource Records and Classes
(Page 1 of 4)
One of the most important jobs performed
by name servers is the storage of name data. Since the authority for
registering names is distributed across the internetwork using DNS,
the database of name information is likewise distributed. An authoritative
server is responsible for storing and managing all the information for
the zones of authority it is assigned.
Each DNS server is, in essence, a
type of database server. The database contains many kinds of information
about the subdomains and individual devices within the domain or zone
for which the server is responsible. In DNS, the database entries that
contain this name information are called resource records (RRs).
A specific set of RRs is associated with each node within the zone.
Binary and Text Representations of Resource Records
The entire point of DNS is to allow
humans to work with names and computers to work with numbers, and we
see this principle further reflected in the two very different representations
that exist for the DNS resource records themselves:
- Resource Record Field Format (Binary) Representation:
Name servers are required to respond to queries for name information
by sending resource records within DNS messages. Obviously, we want
to do this in as efficient a way as possible, so each resource record
is internally stored using a special field format that is similar to
the many field formats we have seen used for messages in other protocols.
All resource records use a general field format for some of their fields,
and then have a unique portion that is specific to the resource record
- Master File (Text) Representation: Computers
are happy to exchange binary-encoded field formats and have no problem
remembering that, for example, resource record type 15 corresponds to
a mail exchange (MX) record. However, human administrators want to be
able to quickly and easily maintain DNS information without having to
remember cryptic codes or work with binary values. For this reason,
DNS uses a master file format for its user-machine interface,
which allows resource records to be specified in text form for easier
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Version 3.0 - Version Date: September 20, 2005
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