Fritz! Fon WLAN 7390 Installation, Configuration And Operation page 178

Glossary
DDNS
Dynamic IP
address
Fixed IP address
FRITZ!Box Fon WLAN 7390
abbreviation for Dynamic Domain Name System
DDNS is a service which allows a computer always to be
reached under the same domain name despite constantly
changing public IP addresses. This means the home net-
work can always be reached from the Internet, regardless
of the user's location. Even private users have an econom-
ical way of placing their own Internet offers on their com-
puter at home.
Every time the Internet connection is established, the In-
ternet provider assigns a new public IP address.
Each time the IP address changes, the current IP address
is transmitted to a special DDNS server. Except for the few
seconds between the cancellation of the old IP address
and the notification of the new IP address, the computer
can always be reached at the selected domain name.
A dynamic IP address is an IP address valid only for the
duration of one Internet or network session.
Every computer participating in the Internet must have a
uniquely assigned public IP address. Since only a limited
number of such IP addresses is available, they must be
used sparingly. That is why most of the Internet partici-
pants who dial in to the Internet receive a dynamic IP ad-
dress. They are called dynamic because every participant
receives a new public address that has not been assigned
yet each time he or she dials in to the Internet.
By contrast, dynamic addresses are usually used in local
IP networks because they are easy to handle, and because
using them avoids incorrect IP address entries or uninten-
tional double assignments. The DHCP service is responsi-
ble for assigning unique dynamic IP addresses.
Fixed IP addresses are IP addresses which are permanently
assigned to a computer or another device like a network
printer.
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