1 Domain Name System (DNS)

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3 How DNS Works Application Transport Internet Network Application Transport Internet Network DNS Resolver Name Server Sockets

4 Domain Name Space Root-Level Domain New Zealand (NZ) COMEDUORG microsoft compaq purdue StudentSeattle Top-Level Domain Second-Level Domain Countries

5 Zones of Authority CORP R&D MKTG com Microsoft Name Servers Name Server Name Server Zone 1 Zone 3 Zone 2

6 Name Server Roles Primary Name Server Zone information in locally maintained files Secondary Name Server Zone information downloaded from a master name server Master Name Server Source of information for a secondary server; can be a primary or secondary server Caching Only Does not keep any zone information

7 Name Resolution Local Name Server Root Name Server gov Name Server whitehouse.gov Name Server DNS Client Recursive Query Iterative Queries

8 Inverse Queries Special Domain for Inverse Queries in-addr.arpa IP Addresses Reversed when Converted to DNS Inverse Queries becomes query for in-addr.arpa

9 Configuring the DNS Files Database File (zone.dns) Contains resource records for the zone Typically maps host names to IP addresses Reverse Lookup File ( z. y. w. x.in-addr.arpa) Maps IP addresses to host names Cache File (cache.dns) Names and addresses of root domain name servers Boot File Used by manual start-up method

10 The Database File Stores Resource Records RFC 1034 Compliant SOA, A, NS, PTR, CNAME, MX, HINFO Microsoft Specific WINS, WINS-R

11 The Reverse Lookup File Supports inverse queries For inverse queries for IP network , file name created: db in-addr.arpa Example resource record entry: in-addr.arpa. IN PTR mailsrv3.microsoft.com.

12 Review Domain Name System (DNS) Name Resolution Configuring the DNS Files Planning a DNS Implementation