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 From:  Jim Thompson <jim at netgate dot com>
 To:  Alex M <radiussupport at lrcommunications dot net>
 Cc:  "Monowall Support List" <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] Wireless WDS
 Date:  Fri, 14 Mar 2008 12:06:02 -1000
On Mar 14, 2008, at 7:18 AM, Alex M wrote:

> WDS is the way of bridging between APs so CP will work if you  
> connect your
> primary (Master) AP to CP Interface and all the rest Slave Repeaters  
> will
> use master as the source of Inet connection.
> However if you want to use mono's wireless interface and connect  
> your AP to
> that interface in WDM mode, then it may work or not it just depends  
> on your
> APs. For us we never even considering trying that because majority  
> of AP
> makes use proprietary bridging (and WDM)  things, they all similar  
> but some
> of them just refuse to tallk to other makes, so its better to do WDM  
> in same
> brand ewuipment.
> If you still need to do WDM on multi make APs that just set up one  
> or 2 APs
> as repeaters, that gona do the same as some cheap APs call WDM ex:  
> Senao WDM
> is just plain repeater


Nothing you said makes any sense to me.

Technical issue that WDS solves is that with the 'normal' 3-address  
format there isn't enough address space.

In the normal single AP case, you have this:
Source MAC's address
Destination MAC's address
BSSID (also the MAC address of the AP or WDS station)

The BSSID MAC is ACKed by an associated STAtion when it receives a  
valid (non-group addressed, CRC checks, etc) frame.
The AP ACKs the association STAtion when it receives a valid frame.

A ---- B ---- C

Here 'B' is the AP, and both 'A' and 'C' could be associated to the AP  
(over the wireless medium), or one of them could be on a "distribution  
medium", typically Ethernet, but it could be a WDS link as well.

When you're bridging across a wireless link, two of the nodes must be  
transmitting over the wireless medium.

A ----- B ----- C ------ D

Here 'B' and 'C' are the bridges (they could be APs as well) the AP,  
and both 'A' and 'D' could be associated to the APs (over the wireless  
medium), or one or both of them could be on a "distribution medium",  
again typically Ethernet.

here you have the situation that 'B' and 'C' *must* be able to ACK  
frames sent by the other.   B must ACK C's valid frames, and C must  
ACK B's.   This ACKing is a fundamental requirement of the 802.11 MAC.

So we have, assuming that 'A' wishes to send a frame to 'D':

A Source MAC address (A)
A Destination MAC address (D)
A transmitter MAC address (B)
A receiver MAC address (C)

Using 4 addresses, you have the ability to directly address any two  
nodes on the (layer 2) network, and the frames between the bridge  
nodes can be ACKed.

the bridge nodes also set 'FromDS' and 'ToDS' bits in the 802.11  
header for frames that cross the 'B'-'C' link.

The WDS mode isn't supported in FreeBSD 6.2.   I don't think that Sam  
Leffler has checked the WDS code in his p4 tree in for 7.0, but I  
could be wrong.  Until he does,
it is unlikely that WDS will work in m0n0wall.   I wish it were