[Olsr-users] Scaling of olsr with reduced TTL

[Kim Hawtin]

Hi Jens,

Jens Nachtigall wrote:
> we all know that olsrd won't scale with, say 10'000 nodes (or more). Not only 
> due to CPU, but also due to the traffic that would cause. I wonder if one 
> could still have a working network of such size by simpling reducing the time 
> to live (TTL) to say 8 or something. So each node only knows its neighborhood 
> up to 8 hops away, but still one does not need to split the network up into 
> different wireless cells, that cannot talk to each other peer-to-peer. 
> 
> Of course, one could not talk to the nodes far away in the net anymore, but in 
> a scenario where a node only needs to communicate with nodes say at most 5 or 
> so hops away (because their is a gateway/HNA every few nodes), this might be 
> a simple approach to make this work. I do not know the Djikstra algorithm too 
> well, hence my question if this would work?

If you have a longer hop backbone network, eg; 802.11a BGP routed backbone network
and then you peer a lot of smaller OLSR 802.11b/g meshes attached to it. A comparable model
would be your suburban roads (meshes) that link together via highways(BGP), or alternatively
trams/metro light rail(Mesh) and interstate rail(BGP).

it does mean you have to manage two separate levels of networks(same with rail)
but the bonus is that you get the benefits of each network type, BGP gives you the
multi-homed access, other nicites like QoS and unicast/redundant services like DNS etc.
you keep the broadcast announce message volume to lower levels by summarising at the
boarder gateways between mesh and backbone.

you can peer from multiple points from within your mesh to the BGP backbone,
so redundancy with in the mesh is not such a big problem. if meshes grow you can add more
peers to the BGP net and add border gateways between the meshes. =)

the tech is there and its pretty easy to setup, all the real work is in the social networking ;)

cheers,

Kim
-- 
Community Wireless Miniconf Coordinator
  http://miniconf.mel8ourne.org/wiki/index.php?title=Community_Wireless
Linux.Conf.Au 2008
  http://linux.conf.au/