[OLSR-users] Re: routing if hna (0.0.0.0) is < 3 hops and host is > 5 hops

[Andreas Tønnesen]

Hi Andrew,

While your idea is interesting, there are multiple problems:

- We have no way of knowing if a gateway is implementing NAT. That
   means that we have no way of knowing if it supports "real" routing
   into the manet even if the addresses used are global. Therefore host3s
   gateway might not support "reverse routing".
- We have no way of knowing what router incoming traffic will be routed
   by into the manet. The traffic to host3 might very well be routed back
   via the GW host1 sent it, or even worse, by a gateway further away.
- To make sure we can control routing back into the manet we must do
   something along the lines of subnetting within the manet. This means
   nodes must configure/reconfigure IPs based on the nearest GW. Not very
   easy - it would cause much more damage then good IMO.

However, in IPv6 nodes might configure themselves with one IPv6 address
pr. gateway. This way a sender can in a way control by which GW packets
are supposed to be routed back into the manet. Still this assumes that
a connections dest address is dynamically changed when the topology
changes which would probably cause TCP issues AFAIK. Also this change
would have to be transparent to applications...

Anyways, my reaction is that such a solution is very difficult to
design if you would want a generic solution and not a very
special-purpose solution for a spesific scenario/network.

At least that's my 0.02$ :)

- Andreas

Andrew Hodel wrote:
> Also should note that the implementation should check for a routable
> IP, i.e. not RFC1918.
> 
> 
> 
> Andrew
> 
> On 7/12/05, Andrew Hodel <(spam-protected)> wrote:
> 
>>I have a suggestion that seems would be best in my scenario.
>>
>>Consider a network with multiple hna nodes to the internet (0.0.0.0).
>>I want to ping host3 which 6 hops away from me.  I am 2 hops from an
>>HNA node and host3 is 1 hop away from another HNA node.  Perhaps we
>>could configure nodes to route these packets over the internet (or
>>whatever hna to hna is) instead of taking a 6 hop route directly over
>>the mesh.
>>
>>This would of course be a parameter you configure on the hna nodes.
>>It seems this would effectively erase all routes greater then X number
>>of hops if other nodes were closer to another HNA node?
>>
>>On each HNA node you could have a link cost parameter which is
>>relative to the cost of using a 6+ hop path on the mesh, or going
>>directly over the internet...
>>
>>This would sure help routing table sizes in mesh networks...
>>
>>Please comment, improvise :)
>>
>>
>>
>>Regards,
>>Andrew
>>
> 
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-- 
Andreas Tønnesen
http://www.olsr.org