WDS links & P2P mode?

Mike Saywell ms at ecs.soton.ac.uk
Thu Mar 27 11:57:36 EST 2003

On Thu, Mar 27, 2003 at 07:03:21AM -0800, Jon Loeliger wrote:
> > For the routing etc we're just running OSPF, each access point is assigned
> > a /26 half of which is currently used for clients, the other half for
> > links and any hosts connected via ethernet.  Automating that side of
> > things is a something we're about to start on...
> Interesting.  How well does that work?  I mean using OSPF?
> How well does it recover from a network drop-out?  Or are
> you using a small enough set of links it converges very
> quickly again?  Are you placing all your APs into the
> backbone area?  And does the route flooding cause any blips
> in the perceived service?

The routing only changes when you add/remove a node from the mesh, so
there might be a slight blip then - I've not really tested too much.
I don't expect it should be too much of an issue.

The mobility itself doesn't rely on routing updates though, to try and
clarify it works roughly like this:

Each client has its own /30 network, this is taken out of the address
space of the home node (where the client first connected).

When the client migrates to a different access point (which has a
different subnet) this is detected and the new access point will act as
the clients gateway, it sends a few arp "is-at" messages to update the
clients arp table.

An IP in IP tunnel is also setup from the new access point to the original
one.  Outgoing packets are routed as normally but the routing on the
mesh means that reply packets will go back to the original access point.
This knows the client has migrated and so routes these packets to the
current AP via the tunnel.

So whilst it's not exactly a clean solution what with asymmetric routing
etc we think it's the best way whilst avoiding other nasties such as
NAT and without any form of client side support.

I hope that made some sense... :)



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