Description
Start of Authority
Host
Name Server
Mail Exchanger
Canonical Name (an alias)
Class
Internet (IN)
Internet (IN)
Internet (IN)
Internet (IN)
Internet (IN)
TTL
Default TTL is 60 minutes
Zone (SOA)
TTL
Zone (SOA)
TTL
Zone (SOA)
TTL
Zone (SOA)
TTL
Type | Data | |
SOA | Owner Name, | |
| Primary Name Server | |
| DNS Name, Serial | |
| Number, | |
| Refresh Interval, | |
| Retry Interval, | |
| Expire Time, | |
| Minimum TTL |
AOwner Name (Host DNS Name),
Host IP Address
NS | Owner Name, |
| Name Server DNS Name |
MX | Owner Name, |
| Mail Exchange Server |
| DNS Name, Preference |
| Number |
CNAME | Owner Name (Alias |
| Name), |
| Host DNS Name |
Distributing the Database: Zone Files and Delegation
A DNS database can be partitioned into multiple zones. A zone is a portion of the DNS database that contains the resource records with the owner names that belong to the contiguous portion of the DNS namespace. Zone files are maintained on DNS servers. A single DNS server can be configured to host zero, one or multiple zones.
Each zone is anchored at a specific domain name referred to as the zone’s root domain. A zone contains information about all names that end with the zone’s root domain name. A DNS server is considered authoritative for a name if it loads the zone containing that name. The first record in any zone file is a Start of Authority (SOA) RR. The SOA RR identifies a primary DNS name server for the zone as the best source of information for the data within that zone and as an entity processing the updates for the zone.
Names within a zone can also be delegated to other zone(s). Delegation is a process of assigning responsibility for a portion of a DNS namespace to a separate entity. This separate entity could be another organization, department or workgroup within your company. In technical terms, delegating means assigning authority over portions of your DNS namespace to other zones. Such delegation is represented by the NS record that specifies the delegated zone and the DNS name of the server authoritative for that zone. Delegating across multiple zones was part of the original design goal of DNS. Following are the main reasons for the delegation of a DNS namespace:
Windows 2000 White Paper | 6 |
