Domain Name Server category

Original article from http://blog.sina.com.cn/s/blog_4bd58fae0100091c.html
The DNS server is the core of the DNS service network. Strictly speaking, a DNS server is called a DNS name server, which stores DNS region data. DNS servers are classified into the following types based on their working methods.
Domain Name Server (DNS) is also called "DNS name server "?
1. primary DNS Server
The primary DNS server is the DNS server that created the region. The region data is readable and changeable. The region data in the primary DNS server is also called the original region data.
In a DNS service network, multiple primary DNS servers can be created to provide fault tolerance for the DNS service.
2. Secondary DNS Server
The secondary DNS server does not create a region. The region data is copied from the primary DNS server. Therefore, the region data can only be read and cannot be modified, also known as the copy region data.
When the secondary DNS server is started, the secondary DNS server will contact the primary DNS server and copy data from the primary DNS server.
When the secondary DNS server is working, it regularly updates the copy region data to ensure data consistency between the copy and the original region as much as possible. In addition to data replication from the primary DNS server, the secondary DNS server can also replicate regional data from other secondary DNS servers.
Setting multiple secondary DNS servers in one region can provide fault tolerance, share the burden on the primary DNS server, and speed up DNS resolution.
3. Master DNS Server
Whether it is the primary DNS server or the secondary DNS server, if it provides the regional data replication service to other secondary DNS servers, it is called the DNS server as the primary DNS server.
If DNS server a provides data replication service to DNS server B, DNS server a is called the master DNS server.
4. cache-only Server
Cache-only server does not have any region data. It only helps the DNS client to query other DNS servers, and then stores the queried data in a cache, responds to the client's query request.
The cache-only server is only responsible for querying data. When the client queries data, if there is data in the cache, the cache can quickly feedback the results to the client.
5. DNS forwarding Server
A dns forwarding Server is a special type of DNS server.
In a DNS Network, if the domain name resolved by the client to the specified DNS server fails, the DNS server can send the client's resolution request to a DNS forwarding server, the DNS forwarding server forwards domain name requests to other DNS servers.
Note: The gray sentence is what I said.