Ad-hoc Networking

[John Watlington]

On Apr 23, 2008, at 5:26 PM, Benjamin M. Schwartz wrote:

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> John Gilmore wrote:
> | The presence implementation only works on access points and on  
> meshes --
> | but not on non-meshed, ad-hoc 802.11.  The vast majority of  
> computers
> | with 802.11 don't have mesh, but they would benefit from being  
> able to
> | "see" nearby laptops and share applications with them (whether or  
> not
> | a local access point, or global Internet access, is working).   
> For full
> | integration, this probably requires some driver work, but most of  
> the work
> | is probably at a daemon and library level.
>
> There is explicitly support for this idea in 802.11s.  It is called a
> "Mesh Access Point", or MAP, and it is the inverse of a "Mesh Portal"
> (MPP).  A Mesh Portal is a 802.11s device (e.g. an XO) that is  
> acting as a
> client to 802.11b/g Access Point and is then sharing that connection
> (perhaps an internet connection) into the 802.11s mesh.  A Mesh Access
> Point is connected to an 802.11s network, and also acts as an 802.11b
> Access Point whose clients can essentially join the mesh.  With  
> both of
> these things it is possible to have:
>
> Satellite internet <--> Standard 802.11b access point <--> XO  
> acting as
> MPP <--> XO <--> XO <--> XO acting as MAP <--> Standard 802.11b laptop
> and thus provide a relatively distant internet connection to a  
> standard
> laptop, which also sees all the XOs on its local network.
>
> MPP support is in place, but it does not play well with the School  
> Server
> (and possibly DHCP), so it has been disabled.  MAP support has not  
> been a
> high priority, and I do not know anything about its current status.

The laptop as an MPP is an interesting idea, but the problem is the  
havoc
it can wreck when a number of XOs are together in a school.

Satellite Internet <-> XS <-> 802.11b AP <-> XO
can support around 50 laptops per channel.
But all it takes is one kid running in MPP mode near the AP
to eat up the spectrum with mesh routing packets.   This is
why it no longer enters MPP mode by default when connected
to an AP.

> I would certainly love if the XOs and Active Antennas could be made  
> to run
> in MPP and MAP mode.  I do not know to what degree the Marvell  
> device is
> capable of this

The hardware is capable of being both.  We are working with Cozybit
to get soft AP code for the hardware that will support both.

wad