The Domain Name Service (DNS) is an Internet-wide service for converting numeric IP addresses to host names and back. It may also be used on networks without an Internet connection; indeed, setting up DNS is a worthwhile investment, because it simplifies integrating a local network into the Internet when a connection becomes available.
By the end of this module, you will be able to:

1. Describe the organization of the DNS namespace
2. Define the top-level subdomains of the DNS
3. Describe the process of converting IP addresses into names
4. Define the concept of zones as used in the DNS namespace
5. Describe the three classes of name servers
6. List the steps required when a name server sends a query up the DNS hierarchy
7. Describe the purpose and usefulness of caching-only name servers
8. Identify the types of Resource Records
9. Describe the general format of a zone file
10. Describe the format of SOA, A, PTR, HINFO, CNAME, and NS records