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11-DNS - CSE 265 System Network Administration DNS The...

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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison CSE 265: CSE 265: System & Network Administration System & Network Administration DNS – The Domain Name System History of DNS What does DNS do? The DNS namespace BIND software How DNS works DNS database Testing and debugging (tools)
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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison DNS History DNS History In original ARPANET, a single text file listed all machines Updates used significant portion of available bandwidth File was still constantly out of date DNS solves scalability problem Hierarchical host naming Distributed responsibility Caching of content } Major ideas!
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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison What does DNS do? What does DNS do? Provides hostname – IP lookup services www.lehigh.edu = 128.180.2.57 DNS defines A hierarchical namespace for hosts and IP addresses A distributed database of hostname and address info A “resolver” -- library routines that query this database Improved routing for email A mechanism for finding services on a network A protocol for exchanging naming information DNS is essential for any org using the Internet
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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison
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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison What uses DNS? What uses DNS? Any application that operates over the Internet Such as email Spam filters WWW FTP IRC, IM Windows update telnet, ssh
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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison The DNS namespace The DNS namespace A tree of “domains” Root is “.” (dot), followed by top-level (root-level) domains Two branches of tree One maps hostnames to IP addresses Other maps IP address back to hostnames Two types of top-level domain names used today gTLDs: generic top-level domains ccTLDs: country code top-level domains Some illustrations from O'Reilly's DNS & Bind
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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison Generic top-level domains Generic top-level domains See http://www.iana.org/gtld/gtld.htm Domain Purpose Domain Purpose com Companies Air transport industry Educational institutions Businesses gov (US) government agencies coop Cooperatives mil (US) military agencies info Unrestricted net Network providers jobs Human resources folks Nonprofit organizations museum Museums int International organizations name Individuals IP address lookup pro Professionals (attorneys, etc.) aero edu boz org arpa
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Spring 2008 CSE 265: System and Network Administration ©2004-2008 Brian D. Davison Common country codes Common country codes See http://www.iana.org/cctld/cctld-whois.htm Code Country Code Country au Australia hu Hungary br Brazil jp Japan ca Canada md Moldovia cc Cocos Islands mx Mexico ch Switzerland nu Niue de Germany se Sweden fi Finland tm Turkmenistan fr France tv Tuvalu hk Hong Kong us United States
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