User guide

Optimizing Performance
6-13
Alvarion
! Upon receipt, the Base Station will respond with a CTS message to all
stations within its range to:
" notify all other stations to defer transmissions for the time-frame of
the requested transmission.
" confirm the requestor station that the Base Station has checked the
medium for availability, and has reserved it for the time-frame of
the requested transmission.
The CTS process is shown in Figure 6-26.
Figure 6-26: Medium Reservation “Clear to Send”
Since all stations connected to the Base Station are typically within range of
that Base Station, they should be able to sense whenever the Base Station is
using the medium to transmit messages via the wireless medium.
Enabling RTS/CTS medium reservation on the Base Station would require
the Base Station 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 Base Station, you
will notice that the configuration of this option for Base Stations is slightly
different from that of stations.
The Base Stations 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 Base Station should
apply the RTS/CTS mechanism. For example:
NOTE:
In most networking environments it is very unlikely that you will need to enable RTS/CTS
medium reservation on the Base Station to prevent collisions.