QTECH QSW-8300 Инструкция по настройке - Manual (Page 348)

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Chapter 41 DNSv4/v6 Configuration
41.1 Introduction to DNS
DNS (Domain Name System) is a distributed database used by TCP/IP applications to
translate domain names into corresponding IPv4/IPv6 addresses. With DNS, you can use
easy-to-remember and signification domain names in some applications and let the DNS
server translate them into correct IPv4/IPv6 addresses.
There are two types of DNS services, static and dynamic, which supplement each other in
application. Each time the DNS server receives a name query it checks its static DNS
database first before looking up the dynamic DNS database. Some frequently used addresses
can be put in the static DNS database, the reduction the searching time in the dynamic DNS
database would increase efficiency. The static domain name resolution means setting up
mappings between domain names and IPv4/IPv6 addresses. IPv4/IPv6 addresses of the
corresponding domain names can be found in the static DNS database when you use some
applications. Dynamic domain name resolution is implemented by querying the DNS server. A
user program sends a name query to the resolver in the DNS client when users want to use
some applications with domain name, the DNS resolver looks up the local domain name cache
for a match. If a match is found, it sends the corresponding IPv4/IPv6 address back to the
switch. If no match is found, it sends a query to a higher DNS server. This process continues
until a result, whether success or failure, is returned.
The Domain Name System (DNS) is a hierarchical naming system for computers, services, or
any resource participating in the Internet. It associates various information with domain names
assigned to such participants. Most importantly, it translates humanly meaningful domain
names to the numerical (binary) identifiers associated with networking equipment for the
purpose of locating and addressing these devices world-wide. An often used analogy to
explain the Domain Name System is that it serves as the "phone book" for the Internet by
translating human-friendly computer hostnames into IP addresses.
The Domain Name System makes it possible to assign domain names to groups of Internet
users in a meaningful way, independent of each user's physical location. Because of this,
World-Wide Web (WWW) hyperlinks and Internet contact information can remain consistent
and constant even if the current Internet routing arrangements change or the participant uses
a mobile device. Internet domain names are easier to remember than IP addresses such as
208.77.188.166(IPv4) or 2001:db8:1f70::999:de8:7648:6e8 (IPv6). People take advantage of
this when they recite meaningful URLs and e-mail addresses without having to know how the
machine will actually locate them.
The Domain Name System distributes the responsibility for assigning domain names and
mapping them to Internet Protocol (IP) networks by designating authoritative name servers for