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Exposed Host
Exposed host refers to a PC outside the firewall.
See also: DMZ
F
Firewall
You can use a firewall to protect your network against unauthorised external access.
This involves combining various measures and technologies (hard and/or software) to
control the flow of data between a private network you wish to protect and an unpro-
tected network (e.g. the Internet).
See also: NAT.
Firmware
Device software in which basic information is saved for the functioning of a device. A
new version of the firmware can be loaded into the device's memory (firmware update)
to correct errors or update the device software.
Flat rate
System of billing for an Internet connection. The Internet service provider charges a set
monthly fee. There are no additional charges for the duration of the connection or
number of connections.
Fragmentation
Data packets that are too big are split into smaller packets (fragments) before they are
transferred. They are put together again when they reach the recipient (defragmented).
Full duplex
Data transmission mode in which data can be sent and received at the same time.
G
G711 a law, G711 µ law
Standard for a Codec.
G711 delivers a very good voice quality that corresponds to that in the ISDN fixed net-
work. As there is little compression, the necessary bandwidth is around 64 kbit/s per
voice connection, but the delay caused by coding/decoding is only 0.125 ms.
"a law" describes the European standard and "µ law" describes the North American/Jap-
anese equivalent.
G726
Standard for a Codec.
G726 delivers a good voice quality. It is inferior to the quality with Codec G711 but bet-
ter than with G729.
G729A/B
Standard for a Codec.
The voice quality is rather less with G729A/B. As a result of the high level of compres-
sion, the necessary bandwidth is only around 8 kbit/s per voice connection, but the
delay is around 15 ms.
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