Re: virtual wireless interfaces / WDS

In discussions I have had with people that know more about this subject
than myself, we had concluded that having a virtual interface for each
connection (such as sta0, sta1, etc...) might also prove usefull when one
is trying to run link state routing protocols (such as ospf) over wireless
interfaces.

-Ken


Ken Caruso
[email protected]
http://ken.ipl31.net

"when in doubt tell the truth" -Mark Twain

On Mon, 14 Apr 2003, David Young wrote:

> The other night I sketched out some benefits of adding two kinds of
> virtual wireless interface to *BSD.
>
> The first virtual interface type is probably familiar, since Linux has
> it. Call it wds(4). It represents a link from AP to AP. A property of
> a wds(4) is the RA field of the 4-address 802.11 header. You can bind a
> bunch of wds(4) to a bridge(4) and run STP on it. Maybe you're familiar
> with this notion in Linux.
>
> The second virtual interface type I call a sta(4). Each host associated
> with a host access point may get its own sta(4). Also, each host in
> an Independent BSS may get its own sta(4). Reasons for sta(4): it is
> useful to keep per-destination statistics, WEP keys, Tx power, and 802.11
> parameters such as fragmentation threshold, RTS/CTS threshold, etc. I
> think that this is all justified (necessitated, really) by the fact that
> conditions on a wireless subnet are not ordinarily uniform, as they are
> on a wired network, but some STAs may be more distant or they may have
> weaker transmitters/receivers, they may or may not be mobile, etc.
>
> Sta(4) lets one use an existing abstraction in BSD, the interface, to
> get link-layer information into a routing daemon. Just for instance,
> as soon as a STA disassociates, you may delete its sta(4), which will
> provoke an RTM_IFANNOUNCE on a routing socket and also take some ARP
> entries out of the routing table (I think). An RTM_IFINFO can indicate
> severe packet loss. These sorts of indications are important for routing
> in mobile wireless networks.
>
> A sta(4) lets you track and control a station's data rate and media
> (DSSS/OFDM).  I think that it will also let you set per-STA queueing
> disciplines using, e.g., ALTQ (hmmm---may or may not be useful).
>
> Like a wds(4), you will ordinarily put all the sta(4) into a bridge(4),
> which will take the IP number.
>
> Is the usefulness of sta(4) clear?
>
> I imagine that the device attachment will look something like this,
>
>   sta0 at wi0 ...
>   sta1 at wi0 ...
>   wds0 at wi0 ...
>
> Your thoughts?
>
> Dave
>
> --
> David Young             OJC Technologies
> [email protected]      Urbana, IL * (217) 278-3933
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>

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