52 lines
2.2 KiB
HTML
52 lines
2.2 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<HEAD>
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<TITLE>Domain Name Servers</TITLE>
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</HEAD>
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<BODY LANG="EN">
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<A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node39.html">The DNS Database</A>
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<B>Up:</B> <A HREF="node34.html">The Domain Name System</A>
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<B> Previous:</B> <A HREF="node37.html">Name Lookups with DNS</A>
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<BR> <P>
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<H2><A NAME="SECTION004640000">Domain Name Servers</A></H2>
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Name servers that hold all information on hosts within a zone are
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called <em>authoritative</em> for this zone, and are sometimes referred
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to as <em>master name servers</em>. Any query for a host within this
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zone will finally wind down at one of these master name servers.
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<P>
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<A NAME="1601"></A>
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<A NAME="1602"></A>
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<A NAME="1603"></A>
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<A NAME="1604"></A>
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To provide a coherent picture of a zone, its master servers must be
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fairly well synchronized. This is achieved by making one of them the
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<em>primary</em> server, which loads its zone information from data
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files, and making the others <em>secondary</em> servers who transfer the
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zone data from the primary server at regular intervals.
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<P>
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One reason to have several name servers is to distribute work load,
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another is redundancy. When one name server machine fails in a benign
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way, like crashing or losing its network connection, all queries will
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fall back to the other servers. Of course, this scheme doesn't protect
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you from server malfunctions that produce wrong replies to all DNS
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requests, e.g. from software bugs in the server program itself.
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<P>
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<A NAME="1607"></A>
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Of course, you can also think of running a name server that is not
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authoritative for any domain.<A HREF="footnode.html#1748"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A> This type of server is useful nevertheless, as it is still able to
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conduct DNS queries for the applications running on the local network,
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and cache the information. It is therefore called a <em>caching-only</em>
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server.
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<P>
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<A NAME="1611"></A>
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<P>
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<BR> <HR>
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<P><ADDRESS>
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<I>Andrew Anderson <BR>
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Thu Mar 7 23:22:06 EST 1996</I>
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</ADDRESS>
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</BODY>
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</HTML>
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