Amer Networks SS3GR24i - Manual (Page 49)

SS3GR24i/SS3GR48i Layer3 Stackable Gigabit Switch User’s Guide
Mapping Domain Names to Addresses
Name-to-address translation is performed by a program called a
Name server. The client program is called a Name resolver. A
Name resolver may need to contact several Name servers to
translate a name to an address.
The Domain Name System (DNS) servers are organized in a
somewhat hierarchical fashion. A single server often holds names
for a single network, which is connected to a root DNS server –
usually maintained by an ISP.
Domain Name Resolution
The domain name system can be used by contacting the name
servers one at a time, or by asking the domain name system to do
the complete name translation. The client makes a query
containing the name, the type of answer required, and a code
specifying whether the domain name system should do the entire
name translation, or simply return the address of the next DNS
server if the server receiving the query cannot resolve the name.
When a DNS server receives a query, it checks to see if the name is
in its subdomain. If it is, the server translates the name and
appends the answer to the query, and sends it back to the client. If
the DNS server cannot translate the name, it determines what
type of name resolution the client requested. A complete
translation is called recursive resolution and requires the server to
contact other DNS servers until the name is resolved. Iterative
resolution specifies that if the DNS server cannot supply an
answer, it returns the address of the next DNS server the client
should contact.
Each client must be able to contact at least one DNS server, and
each DNS server must be able to contact at least one root server.
The address of the machine that supplies domain name service is
often supplied by a DCHP or BOOTP server, or can be entered
manually and configured into the operating system at startup.
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