User`s guide

Aironet Wireless Communications, Inc. 7-55 Confidential and Proprietary
Payload types
The PC4500/4800 may be configured to transmit and receive packet payloads as is (LLC host) or
as ethernet payloads. Ethernet payloads have an ethertype field as the first word of the payload.
These payloads must be modified for transmission on the 802.11 network. Details of this are
discussed under encapsulation.
The receive payload type is selected with the PayloadType bit of the OperatingMode field of the
General Configuration. The transmit payload type is selected with the PayloadType bit of the
TxControl field of the transmit FID.
Aironet Extensions
Aironet provides some proprietary extensions to 802.11. The primary extension is the Aironet
Information Element that is transmitted in some management packets. This element contains
additional information about the access point and stations.
The Aironet extensions are enabled automatically by stations if the access point is transmitting the
Aironet Information Element. The Aironet extensions are enabled on an access point by setting
the AironetExtensions bit in the OperatingMode field of the General Configuration.
Access Point Interface
The access point interface is described in more detail in a separate section.
Receive Mode
This field should only be used in station mode. The receive mode field may be used to limit the
traffic passed to the host by the station. It may be used to discard broadcast and multicast traffic
rather than pass them to the host. This field is mainly intended for slower serial (RS232) hosts
where broadcast and multicast traffic could significantly delay real traffic destined to the host.
Device Type
The device type field should be left as a zero for normal operation. The device type field is
provided to allow an override of the default device type in the Aironet information element
(Aironet extension) to distinguish different products within the Aironet product line.
802.11 Configuration Parameters
Several 802.11 configuration parameters are provided. Please see the 802.11 specification for
additional details.
Fragment Threshold
Decreasing/shortening the fragment threshold will cause long packets to be sent as many shorter
fragments. The shorter packets will be reassembled at the receiving station. Shortening the
fragments increases the chance of delivering the packet to the destination since shorter packets
have less chance of a bit error. However shortening the fragments also increases the bandwidth
consumed. Under ideal conditions, the throughput will decrease with shorter fragments.
RTS Threshold
This value defines the packet length above which all larger packets will be transferred using the
RTS/CTS reservation protocol.