1. Naming With the Domain Name System

2. Why Not Names? Requires more memory to store Requires more computation to manipulate

3. Structure Scheme is called DNS Hierarchical (most significant on right) No specification on number or segments

4. Top-Level Domains Specific values Controlled by ICANN (Internet Corporation for Assigned Names and Numbers) Registrars List of top-level domains on 465

5. Geographic Structure Additional structure allowed for geographic registration weld.co.us

6. Within in Organization Additional Hierarchy Optional computer.unco.edu computer.location.unco.edu

7. Service Names Computers named by the service they provide ftp www Not required

8. DNS Servers DNS Servers maintain database of addresses and names Applications are the clients

9. Server Hierarchy Root Servers know where to request info on computers on a lower level Follows naming hierarchy, but the structure may vary Single Server less viable in large organizations

10. Linked Servers DNS hierarchy not arbitrary Each Server responsible for all computers with a given suffix Subtrees can be moved Nodes cannot be split

11. Resolving a Name Contact Server with request Server gives answer or... Server becomes client of another server Repeat as needed

12. Optimizations Hopeless as is Two optimizations used Replication Caching

13. Types of Entries Name-Type-Value A for Address MX for Mail eXchange

14. CNAME Computer name aliasing Allows the switching of service machines Multiple Aliases

15. Consequence Type Matters Different application make different request types

16. Abbreviations Local computers contacted more often then remote Suffixes can be dropped Resolvers must be programmed to fix abbreviation