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Module 12: Domain Name System (DNS)

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Presentation on theme: "Module 12: Domain Name System (DNS)"— Presentation transcript:

1 Module 12: Domain Name System (DNS)

2 Overview Domain Name System (DNS) Name Resolution
Configuring the DNS Files Planning a DNS Implementation

3 Domain Name System (DNS)

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

5 Domain Name Space Countries COM EDU ORG New Zealand (NZ) Seattle
Root-Level Domain Countries Top-Level Domain COM EDU ORG New Zealand (NZ) Second-Level Domain Seattle Student microsoft compaq purdue

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

7 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

8 Name Resolution 2 3 4 5 6 1 8 7 Local Name Server Root Name Server gov
Iterative Queries Root Name Server 2 3 4 gov Name Server 5 6 1 8 Recursive Query 7 Name Server DNS Client

9 Inverse Queries Special Domain for Inverse Queries
IP Addresses Reversed when Converted to DNS Inverse Queries becomes query for

10 Caching and TTL DNS Servers Cache Iterative Queries
Each Cached Entry Is Given a Time to Live (TTL) When the TTL Expires, the Entry Is Flushed from the Cache The Remaining TTL Is Sent to the Resolver in the Recursive Response

11 Configuring the DNS Files
Database File (zone.dns) Contains resource records for the zone Typically maps host names to IP addresses Reverse Lookup File ( 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

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

13 The Reverse Lookup File
Supports inverse queries For inverse queries for IP network , file name created: db Example resource record entry: IN PTR

14 The CACHE File Contains Names and Addresses for Root Domain Servers
Windows NT 4.0 Provides the Cache File for the Internet Example entry: IN NS A.ROOT-SERVERS.NET. A.ROOT-SERVERS.NET A

15 The BOOT File Not RFC-Based, Part of BIND Implementation
Controls Start-up Behavior of BIND-Compliant DNS Server Microsoft DNS Server Can Be Configured to Use Boot File Boot File Commands: Directory Cache Primary Secondary

16 Planning a DNS Implementation
Small Companies Can use ISP DNS servers for queries and to store company domain names Larger Companies Maintain their own DNS servers Two DNS Servers Recommended Primary name server Secondary name server

17 Registering with the Parent Domain
Second-Level Domain Contact InterNIC Seattle Student Contact Domain Administrator

18 Lab 16: Planning DNS Server Implementation

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

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