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Domain Name System (DNS) Neil Tang 12/05/2008

Domain Name System (DNS) Neil Tang 12/05/2008. Survey. http://www.cs.montana.edu/survey/. Outline. An Example Basic Concepts Domain Hierarchy Name Server Name Resolution. An Example. Basic Concepts. Name space : the set of possible domain names.

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Domain Name System (DNS) Neil Tang 12/05/2008

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  1. Domain Name System (DNS)Neil Tang12/05/2008 CS440 Computer Networks

  2. Survey http://www.cs.montana.edu/survey/ CS440 Computer Networks

  3. Outline • An Example • Basic Concepts • Domain Hierarchy • Name Server • Name Resolution CS440 Computer Networks

  4. An Example CS440 Computer Networks

  5. Basic Concepts • Name space: the set of possible domain names. • DNS maintains the bindings of name to values (e.g., IP address). • Resolution Mechanism: a procedure which takes a name as the input and returns the corresponding value (e.g., IP address) • Name Server: a program which implements a specific resolution mechanism. CS440 Computer Networks

  6. edu com gov mil org net uk fr ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ princeton mit cisco yahoo nasa nsf arpa navy acm ieee cs ee physics ux01 ux04 Domain Hierarchy CS440 Computer Networks

  7. edu com gov mil org net uk fr princeton mit cisco yahoo nasa nsf arpa navy acm ieee ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ cs ee physics ux01 ux04 Zone • A domain hierarchy is partitioned to sub-trees called zones, each of • which is usually managed by an administrative Authority. CS440 Computer Networks

  8. Root name server Princeton Cisco ■ ■ ■ name server name server ■ ■ ■ CS EE name server name server Name Server • The name information contained in each zone is implemented in two or more identical name servers for the sake of redundancy. CS440 Computer Networks

  9. Information in Name Servers • A set of 5-tuple (Name, Value, Type, Class, TTL) records are maintained in each name server. • Type: A: the value field gives an IP address. NS: the value field gives the domain name of a host running the name server. CNAME: It is used to define aliases. MX: the value field gives the domain name for a mail server for the given domain. CS440 Computer Networks

  10. Information in Name Servers • Root name server: (princeton.edu, cit.princeton.edu, NS, IN) • (cit.princeton.edu, 128.196.128.233, A, IN) • (cisco.com, ns.cisco.com, NS, IN) • (ns.cisco.com, 128.96.32.20, A, IN) • Second level name server (cit.princeton.edu): • (cs.princeton.edu, gnat.cs.princeton.edu, NS, IN) • (gnat.cs.princeton.edu, 192.12.69.5, A, IN) • (ee.princeton.edu, helios.ee.princeton.edu, NS, IN) • (helios.ee.princeton.edu, 128.196.28.166, A, IN) • Third level name server (gnat.cs.princeton.edu): • (cs.princeton.edu, gnat.cs.princeton.edu, MX, IN) • (cicada.cs.princeton.edu, 192.12.69.60, A, IN) • (cic.cs.princeton.edu, cicada.cs.princeton.edu, CNAME, IN) • (gnat.cs.princeton.edu, 192.12.69.5, A, IN) • (www.cs.princeton.edu, 192.12.69.35, A, IN) CS440 Computer Networks

  11. Name Resolution CS440 Computer Networks

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