IRIX 6.5 Applications 2002 November/SGI IRIX 6.5 Applications 2002 November.iso/dist/gateway.idb/usr/WebFace/Source/20-NetworkServices/dns/description.frm.z/description.frm

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<H1><A NAME="_wmh1_828407857">Domain Name Service</A></H1>
<P>
The Domain Name Service (DNS) is a decentralized database service that
resolves hostnames and addresses on the Internet. DNS organizes the
Internet into a hierarchy of administrative units called <EM>domains</EM>.
The <EM>root domain</EM> at the top of the hierarchy has authority over the
entire Internet. Descending the hierarchy, subordinate domains are decreasingly
comprehensive, so that a local domain usually serves a single organization
(such as your local network). Large domains are frequently organized into
<EM>subdomains</EM> to further distribute the maintenance task.
</P>
<P>
<STRONG>Note:</STRONG> All sites connected to the Internet are required
to have two systems that answer requests for their domain.
</P>
<P>
The <EM>named</EM> process supports DNS on a <I>WebForce Internet Gateway</I>
server (see the named(1M) reference page for details). A system running
<EM>named</EM> is referred to as a <EM>name server</EM>. If a domain contains
subdomains, several name servers are used. In this case, the
<EM>primary name server</EM> is the designated authority; it contains
the master database for the domain. <EM>Secondary servers</EM> contain
a copy of the database that is maintained on the primary server, and
<EM>clients</EM> relay name and address requests to primary or
secondary servers to be resolved.
</P>
<P>
When <EM>named</EM> receives a request for a domain for which it is neither
primary nor a secondary server, it forwards the request to another name
server for resolution. The addresses of such servers are maintained in
a <EM>forwarder</EM> address list. The DNS protocol provides support for
dynamically locating authoritative servers.  If you do not wish to use this
feature, you can limit all forwarding to the specified forwarder list.
<P>
All hosts operate as DNS clients, including DNS servers. To request
domain information from DNS servers, all applications use a set of
routines collectively called the <VAR>resolver</VAR>. The resolver determines
the order in which name services are to be used and the name servers and
domain names to be queried in name lookups.
</P>
<P>
Use these forms to configure DNS:
</P>
<UL>
<LI><A HREF="index.dns1.shtml" TARGET="left">DNS Name Server</A>
<LI><A HREF="index.dns2.shtml" TARGET="left">DNS Resolver</A>
</UL>
<P>
For additional information, see Chapter 6 of <CITE>IRIX Admin:
Networking and Mail</CITE>. Also see the resolver(4) and named(1M)
reference pages.
</P>
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