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The Domain Name Server

The Domain Name Server. The domain name hierarchy is partitioned into zones. Each name server holds information relating to its zone. This zone information is implemented as a collection of records. Each record contains the following fields:. < Name, Value, Type, Class, TTL>. DNS Example.

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The Domain Name Server

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  1. The Domain Name Server The domain name hierarchy is partitioned into zones Each name server holds information relating to its zone This zone information is implemented as a collection of records. Each record contains the following fields: <Name, Value, Type, Class, TTL>

  2. DNS Example The .edu root server <princeton.edu, cit.princeton.edu, NS, IN, TTL-val> <cit.princeton.edu, 128.196.128.233, A, IN, TTL-val> . . Where value field names: NS = name server CNAME = canonical name (alias) A = address And class field name IN = internet

  3. DNS Example Princeton University name server <cs.princeton.edu, gnat.cs.princeton.edu, NS, IN, TTL-val> <gnat.cs.princeton.edu, 192,12.69.5, A, IN, TTL-val> <ee.princeton.edu, helios.ee.princeton.edu, NS, IN, TTL> <helios.princeton.edu, 128.196.28.166, A, IN, TTL-val> <jupiter.physics.princeton.edu, 128.196.4.1, A, IN, TTL>

  4. DNS Example Princeton CS department name server <cs.princeton.edu, gnat.cs.princeton.edu, MX, IN, TTL-val> <gnat.cs.princeton.edu, 192.12.69.5, A, IN, TTL-val> <gna.cs.princeton.edu, gnat.cs.princeton.edu, CNAME, IN, TTL> <www.cs.princeton.edu, 192.12.69.35, A, IN, TTL-val> . .

  5. DNS Example Iterative queries The example that follows illustrates a sequence of iterative queries that are used by the client’s local Name Server to locate the IP address of a remote URL. The sequence of iterative queries can be shortened it the Princeton Name Server in this example were to use recursive queries to return to the Marist Names server the IP address of the requested URL (and not just the next Name Server in the chain) The Marist Name Server will cache this URL for a period of time specified by the TTL field for future requests for this URL – requested URLs are likely to be requested again in the immediate future.

  6. Domain name server cicada.cs.princeton.edu princeton.edu, 128.196.128.233 Marist Name Server Princeton Name Server cs.princeton.edu, 192.12.69.5 cicada.cs.princeton.edu CS Name Server cicada.cs.princeton.edu cicada.cs.princeton.edu, 192.12.68.60 Cicada.cs.princeton.edu 192.12.69.60 192.12.69.60 Marist Client Princeton CS Web Server Iterative Requests

  7. Domain NameServer princeton.edu 128.196.128.233 cicada.cs.princeton.edu Marist NameServer Princeton NameServer cicada.cs.princeton.edu 192.12.69.60 cicada.cs.princeton.edu cicada.cs.princeton.edu cicada.cs.princeton.edu cicada.cs.princeton.edu 192.12.69.60 cicada.cs.princeton.edu 192.12.69.60 192.12.69.60 CS Web Server Marist Client CS NameServer Recursive Requests

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