SNR S2989G-24TX-POE — настройка управления временем сети и DNS для повышения эффективности [488/553]

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S2989G-24TX Operation Manual

Chapter 9 Network Time Management Configuration

9-8

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 each domain to keep track of their own changes, avoiding the need for a

central register to be continually consulted and updated.

In general, the Domain Name System also stores other types of information, such as

the list of mail servers that accept email for a given Internet domain. By providing a world-

wide, distributed keyword-based redirection service, the Domain Name System is