Rosewill RNX-N400LX - Manual (Page 56)

Wireless Router RNX-N400LX User Manual
encryption keys that both source and destination stations can use to alert frame bits to
avoid disclosure to eavesdroppers. WEP relies on a secret key that is shared between a
mobile station (e.g. a laptop with a wireless Ethernet card) and an access point (i.e. a base
station). The secret key is used to encrypt packets before they are transmitted, and an
integrity check is used to ensure that packets are not modified in transit.
10. What is Fragment Threshold?
The proposed protocol uses the frame fragmentation mechanism defined in IEEE 802.11
to achieve parallel transmissions. A large data frame is fragmented into several fragments
each of size equal to fragment threshold. By tuning the fragment threshold value, we can
get varying fragment sizes. The determination of an efficient fragment threshold is an
important issue in this scheme. If the fragment threshold is small, the overlap part of the
master and parallel transmissions is large. This means the spatial reuse ratio of parallel
transmissions is high. In contrast, with a large fragment threshold, the overlap is small
and the spatial reuse ratio is low. However high fragment threshold leads to low fragment
overhead. Hence there is a trade-off between spatial re-use and fragment overhead.
Fragment threshold is the maximum packet size used for fragmentation. Packets larger
than the size programmed in this field will be fragmented. If you find that your corrupted
packets or asymmetric packet reception (all send packets, for example). You may want to
try lowering your fragmentation threshold. This will cause packets to be broken into
smaller fragments. These small fragments, if corrupted, can be resent faster than a larger
fragment. Fragmentation increases overhead, so you'll want to keep this value as close to
the maximum value as possible.
11. What is RTS (Request to Send) Threshold?
The RTS threshold is the packet size at which packet transmission is governed by the
RTS/CTS transaction. The IEEE 802.11-1997 standard allows for short packets to be
transmitted without RTS/ CTS transactions. Each station can have a different RTS
threshold. RTS/CTS is used when the data packet size exceeds the defined RTS threshold.
With the CSMA/CA transmission mechanism, the transmitting station sends out an RTS
packet to the receiving station, and waits for the receiving station to send back a CTS
(Clear to Send) packet before sending the actual packet data. This setting is useful for
networks with many clients. With many clients, and a high network load, there will be
56