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

2. 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

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

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

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

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

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

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

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

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

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

12. 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.

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

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

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

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

17. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-10 Inverse domain

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

19. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-11 Recursive resolution

20. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-12 Iterative resolution

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

22. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-13 DNS messages

23. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-14 Query and response messages

24. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-15 Header format

25. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-16 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

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

27. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-17 Question record format

28. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-18 admin.atc.fhda.edu. Query name format

29. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-19 Resource record format

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

31. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-20 Format of an offset pointer

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

33. 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.

34. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-21 Example of a query message

35. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-22 Example of a response message

36. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Example 2 An FTP server has received a packet from an FTP client with IP address 153.2.7.9. The FTP server wants to verify that the FTP client is an authorized client.

37. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-23 Example of inverse query message

38. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 18-24 Example of inverse response message

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

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

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