TCP/IP Configuration and Management Manual

Configuration Reference
TCP/IP Configuration and Management Manual—427132-004
A-4
Domain Name Server (DNS)
servers: a primary master and one (or more) secondary masters to provide backup
service if the primary is unavailable or overloaded. A server may be a master for
multiple domains, primary for some domains, and secondary for others. The functions
of each type of server are:
Caching-Only Server
All servers are caching servers, meaning that the server caches the information it
receives for use until the data expires. A caching-only server is a server that is not
authoritative for any domain. This server services queries and asks other servers that
are authoritative for the information needed. All servers keep data in their cache until
the data expires. The expiration time is based on a time-to-live field (the time after
which the data in the cache becomes invalid) associated with the data when it is
received from another server.
Remote Server
A remote server is an option given to people who would like to use a domain name
server on their workstation or on a machine that has a limited amount of memory and
CPU cycles. By using this option you can run all the networking programs that use the
domain name server without having to run the domain name server on the local
machine. All queries are serviced by a domain name server running on another
machine on the network.
Slave Server
A slave server is a server that always forwards to a fixed list of forwarding servers
those queries it cannot satisfy locally, instead of interacting with the master name
servers for the root and other domains. The queries to the forwarding servers are
recursive queries. There may be one or more forwarding servers, and they are tried in
turn until the list is exhausted.
A slave and forwarder configuration is typically used when you do not want all the
servers at a given site to interact with the rest of the Internet servers. A typical scenario
would involve a number of workstations and a departmental timesharing machine that
has Internet access. The workstations might be administratively prohibited from having
Internet access. To give the workstations the appearance of access to the Internet
domain system, the workstations could be slave servers to the timesharing machine,
Primary Server A primary master server loads its data from a disk file. This
server also can delegate authority to other servers in its domain.
Secondary
Server
A secondary master server is delegated authority and receives
its data from a primary master server. At startup time, a
secondary server requests all the data for the given zone from
the primary master server. The secondary server periodically
checks with the primary server to see if the primary needs to
update its data.