ZyXEL Communications NBG-417N, Руководство пользователя, Страница: 254 / 279

Appendix E Wireless LANs
User
’
s Guide
255
Fragmentation Threshold
A Fragmentation Threshold is the maximum data fragment size (between 256
and 2432 bytes) that can be sent in the wireless network before the AP will
fragment the packet into smaller data frames.
A large Fragmentation Threshold is recommended for networks not prone to
interference while you should set a smaller threshold for busy networks or
networks that are prone to interference.
If the Fragmentation Threshold value is smaller than the RTS/CTS value (see
previously) you set then the RTS (Request To Send)/CTS (Clear to Send)
handshake will never occur as data frames will be fragmented before they reach
RTS/CTS size.
Preamble Type
A preamble is used to synchronize the transmission timing in your wireless
network. There are two preamble modes:
Long and Short .
Short preamble takes less time to process and minimizes overhead, so it should
be used in a good wireless network environment when all wireless stations
support it.
Select Long if you have a ‘ noisy ’ network or are unsure of what preamble mode
your wireless stations support as all IEEE 802.11b compliant wireless adapters
must support long preamble. However, not all wireless adapters support short
preamble. Use long preamble if you are unsure what preamble mode the wireless
adapters support, to ensure interpretability between the AP and the wireless
stations and to provide more reliable communication in
‘ noisy ’ networks.
Select Dynamic to have the AP automatically use short preamble when all
wireless stations support it, otherwise the AP uses long preamble.
Note: The AP and the wireless stations MUST use the same preamble mode in order
to communicate.
IEEE 802.11g Wireless LAN
IEEE 802.11g is fully compatible with the IEEE 802.11b standard. This means an
IEEE 802.11b adapter can interface directly with an IEEE 802.11g access point
(and vice versa) at 11 Mbps or lower depending on range. IEEE 802.11g has
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