McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Chapter 18 Domain Name System (DNS)

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000CONTENTS NAME SPACE DOMAIN NAME SPACE DISTRIBUTION OF NAME SPACE DNS IN THE INTERNET RESOLUTION DNS MESSAGES TYPES OF RECORDS COMPRESSION EXAMPLES DDNS ENCAPSULATION

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 NAME SPACE 18.1

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 DOMAIN NAME SPACE 18.2

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-1 Domain name space

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-2 Domain names and labels

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-3 FQDN and PQDN

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-4 Domains

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 DISTRIBUTION OF NAME SPACE 18.3

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-5 Hierarchy of name servers

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-6 Zones and domains

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 A primary server loads all information from the disk file; the secondary server loads all information from the the primary server. When the primary downloads information from the secondary, it is called zone transfer.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 DNS IN THE INTERNET 18.4

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-7 DNS in the Internet

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-8 Generic domains

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-9 Country domains

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Inverse domain

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 RESOLUTION 18.5

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Recursive resolution

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Iterative resolution

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 DNS MESSAGES 18.6

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure DNS messages

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Query and response messages

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Header format

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure QR: Query/Response OpCode: 0 standard, 1 inverse, 2 server status AA: Authoritative TC: Truncated RD: Recursion Desired RA: Recursion Available rCode: Status of the error Flags fields

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 TYPES OF RECORDS 18.7

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Question record format

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure admin.atc.fhda.edu. Query name format

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Resource record format

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 COMPRESSION 18.8

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Format of an offset pointer

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 EXAMPLES 18.9

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Example 1 A resolver sends a query message to a local server to find the IP address for the host “chal.fhda.edu.”. We discuss the query and response messages separately.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Example of a query message

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Example of a response message

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Example 2 An FTP server has received a packet from an FTP client with IP address The FTP server wants to verify that the FTP client is an authorized client.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Example of inverse query message

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Example of inverse response message

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 DDNS 18.10

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 ENCAPSULATION 18.11

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 DNS can use the services of UDP or TCP using the well-known port 53.