Lesson 12

This module introduced the Domain Name Service (DNS), an Internet-wide service for converting numeric IP addresses to host names and back.
Now that you've completed this module, you should 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

In this module, we used the following terms:

1. Address (A) record: An A record is a type of Resource Record that specifies an IP address-to-host name mapping.
2. Canonical (CNAME) record: A CNAME record is a type of Resource Record that defines an alias.
3. caching-only name server: A caching-only name server is a name server process with no authoritative information of its own. Instead, it relies entirely on information obtained by recursion.
4. DNS: Domain Name Service (DNS) is an Internet-wide service for converting numeric IP addresses to host names and back.
5. domain: A domain is a distinct piece of the DNS namespace that is managed by a single administrative entity. A domain consists of a root domain, a top-level domain, a second-level domain, and a series of subdomains.
6. Fully Qualified Domain Name (FQDN): The Fully Qualifed Doman Name (FQDN) is the full path from the root of the DNS tree to that entity.
7. Host information (HINFO) record: An HINFO record is a type of Resource Record that gives the operating system and architecture for the specified host.
8. Mail Exchange (MX) record: An MX record is a type of Resource Record that defines a mail exchange host.
9. name server: A name server is a process that accepts queries into the DNS database. It is also fairly common usage to refer to the computer on which this process is running as a name server.
10. Name Server (NS) record: An NS record is a type of Resource Record that declares a machine to be a name server for a specified zone.
11. Pointer (PTR) record: A PTR record is a type of Resource Record that specifies a host name-to-IP address mapping.
12. primary server: Every zone must have exactly one associated primary name server. This name server is the unique location which has the official or authoritative information on its zone.
13. recursive queries: The distributed DNS database is bound together into a single unit by the process of recursive queries. Whenever a name server receives a query it cannot directly answer, then it generates a query of a name server higher in the DNS hierarchy.
14. Resource Records: Resource Records are the individual records in a zone file.
15. reverse lookup: Reverse lookup is a way to find a host\'s name by using that host\'s numeric IP address. The DNS system can convert IP addresses into names by associating a domain name with a network address.
16. root server: The root servers are the servers for the root domain. They are operated by the InterNIC and play a crucial role in binding together the DNS database through the mechanism of recursion.
17. secondary server: In addition to its primary server, a zone may have one or more secondary servers. A secondary server provides an alternative source for information on the zone.
18. State of Authority (SOA) record: An SOA record is a type of Resource Record that sets basic parameters for a DNS zone of authority and marks the beginning of a zone. Every zone or subzone must have exactly one SOA record and the zone continues until another SOA record is encountered.
19. subdomain: A subdomain is any domain under the authority of another domain. For example, a top-level domain is a subdomain of the root domain, a second-level domain is a subdomain of a top-level domain, and so on.
20. zone: A zone is a branch of the DNS name space under the administrative control of some entity.
21. zone file transfer: Secondary servers obtain their data from the authoritative server by periodically downloading a copy of the authoritative server's zone files. This is called zone file transfer.
22. zone files: The data in the DNS database is stored in files, called zone files, which reside on the hosts running authoritative name servers for the zone.

Click the Quiz link below to take a multiple-choice quiz covering what you have learned in this module.
Domain Name Service - Quiz