Compaq WL110, Руководство пользователя

Страница: 72 / 144

6-12 Optimizing Performance
Figure 6-4 Medium Reservation “Clear to Send”
Note: In most networking environments it is very unlikely that you will need
to enable RTS/CTS medium reservation on the Access Point to prevent
collisions.
Since all stations connected to the Access Point are typically within
range of that Access Point, they should be able to sense whenever the
Access Point is using the medium to transmit messages via the wireless
medium.
Enabling RTS/CTS medium reservation on the Access Point would
require the Access Point to ask for a CTS for every message that it
wishes to forward to stations within its range, even if it is forwarding
traffic between stations that belong to the same wireless cell.
This might cause redundant network overhead that could negatively
affect the throughput performance instead of providing a remedy.
If you insist on enabling RTS/CTS medium reservation on the Access Point, you
will notice that the configuration of this option for Access Points is slightly
different from that of stations.
The Access Points allow you to customize the sensitivity of the RTS/CTS
mechanism. By entering a user-defined frame length value in the
RTS/CTS Medium
Reservation Threshold
field (in the edit mode, select
Interface
tab, then click the
Advanced
button), you can influence when the Access Point should apply the
RTS/CTS mechanism. For example:
■
When a message is shorter than the RTS/CTS medium reservation
threshold, the Access Point will not initiate an RTS to the addressed station,
but use the CSMA/CA protocol: i.e. it will immediately transmit the
message when it senses that the medium is free.
■
When the length of a message exceeds the RTS/CTS medium reservation
threshold, the Access Point will first send an RTS to the addressed station
and defer transmission until the addressed station has responded with a CTS
message.