1. Fall 2006Computer Networks25-1 Chapter 25. Domain Name System 25.1 Name Space 25.2 Domain Name Space 25.3 Distribution of Name Space 25.4 DNS in the Internet 25.5 Resolution 25.6 DNS Message 25.7 DDNS 25.8 Encapsulation

2. Fall 2006Computer Networks25-2 Domain name space Flat name space, Hierarchical name space

3. Fall 2006Computer Networks25-3 Domain names and labels

4. Fall 2006Computer Networks25-4 FQDN and PQDN FQDN (Fully Qualified Domain Name) PQDN (Partially Qualified Domain Name)

5. Fall 2006Computer Networks25-5 Domains Domain: Subtree of the domain name space

6. Fall 2006Computer Networks25-6 Hierarchy of name servers

7. Fall 2006Computer Networks25-7 Zones and domains Zone: What s server is responsible for, or has authority over

8. Fall 2006Computer Networks25-8 Root Server A root server is a server whose zone consists of the whole tree. Primary and Secondary Servers A primary server loads all information from the disk file; the secondary server loads all information from the primary server.

9. Fall 2006Computer Networks25-9 DNS in the Internet

10. Fall 2006Computer Networks25-10 Generic domains Generic domains define registered hosts according to their generic behavior Each node in the tree defines a domain, which is an index to the domain name space database.

11. Fall 2006Computer Networks25-11 Generic domain labels LabelDescription comCommercial organizations eduEducational institutions govGovernment institutions intInternational organizations milMilitary groups netNetwork support centers orgNonprofit organizations

12. Fall 2006Computer Networks25-12 New generic domain labels LabelDescription aeroAirlines and aerospace companies bizBusinesses or firms (similar to com) coopCooperative business organizations infoInformation service providers museumMuseums and other nonprofit organizations namePersonal names (individuals) proProfessional individual organizations

13. Fall 2006Computer Networks25-13 Country domains

14. Fall 2006Computer Networks25-14 Inverse domain

15. Fall 2006Computer Networks25-15 Resolution Name-address resolution: a name to address/an address to a name Resolver: DNS client called by a host Recursive resolution and iterative resolution

16. Fall 2006Computer Networks25-16 Iterative resolution Caching

17. Fall 2006Computer Networks25-17 Query and response messages DNS has two types of messages

18. Fall 2006Computer Networks25-18 Header format