User's Manual

Appendix
BreezeNET PRO.11 Series 8-35 User’s Guide
This bit indicates that this frame is being sent using the Strictly-Ordered
service class.2
Duration/ID
This field has two meanings depending on the frame type:
• In Power-Save Poll messages this is the Station ID
• In all other frames this is the duration value used for the NAV
Calculation.
Address Fields
A frame may contain up to 4 Addresses depending on the ToDS and
FromDS bits defined in the Control Field, as follows:
• Address-1 is always the Recipient Address (i.e. the BSS station that is
the immediate recipient of the packet). If ToDS is set, this is the AP
Address; if ToDS is not set, then this is the address of the end-station.
• Address-2 is always the Transmitter Address (i.e. the station which is
physically transmitting the packet). If FromDS is set, this is the AP
address; if it is not set, then it is the Station address.
• Address-3 is in most cases the remaining, missing address. On a frame
with FromDS set to 1, Address-3 is the original Source Address; if the
frame has the ToDS set, then Address 3 is the destination Address.
• Address-4 is used in special cases where a Wireless Distribution System
is used, and the frame is being transmitted from one Access Point to
another. In such cases, both the ToDS and FromDS bits are set, so both
the original Destination and the original Source Addresses are missing.
The following Table summarizes the usage of the different Addresses
according to ToDS and FromDS bits setting:
To DS From
DS
Address
1
Address
2
Address
3
Address
4
0 0 DA SA BSSID N/A
2
The Strictly-Ordered Service Class is defined for users that cannot accept change of ordering between Uni-
cast Frames and Multicast Frames (ordering of Unicast frames to a specific address is always maintained).
The only known protocol that would need this service class is DEC’s LAT.