[OLSR-users] Default routing question

Andreas T√łnnesen (spam-protected)
Sat Mar 27 07:47:08 CET 2004

John Gorkos wrote:

>>>>John Gorkos wrote:
>>>>>I have a project involving a large number of WRT54G routers running
>>>>>linux w/ OLSR.  Perhaps 1 in 10 of the routers will have a backhaul to
>>>>>the internet, the rest will use these internet connected routers as
>>>>>gateways. The kicker is this:  I want to have a single configuration
>>>>>that works on all routers, regardless of whether they are
>>>>>internet-connected or not. Is this possible with the current OLSR
>>>>>imlpementation?  From what I've been able to decipher, the OLSR daemon
>>>>>finds out from the configuration file whether or not it is a "default"
>>>>>router.  I need to determine this dynamically, because I don't know yet
>>>>>which routers get an internet connection and which ones don't.
>>>>IMO you should create a startupscript that checks wether the node has a
>>>>internet route avalible. This check could easily be done inside the olsr
>>>>daemon - but IMO this is not olsrs job. Modularity! :)
>>>But what if a route becomes available while olsrd is running.  For
>>>example, I plug a DSL modem into the WAN jack of my WRT54G.  It detects
>>>the insertion as a hotplug event, runs the DHCP client and receives an IP
>>>address and a default route.  In my perfect world, olsr would "see" this
>>>and reconfigure itself as a gateway node.  Am I pipe-dreaming?
>>Ok - yout want a completley "plug and play" interface to the Internet
>>gateway configuration...
>>Well - a plugin could do this. Plugins will be supported from the next
>>release(0.4.1) - and if you are interested I could write a plugin that
>>dynamically checks for Internet routes and sets the node up as a gateway.
> Well, that would be darn near perfect for me.  It would be easy to power-cycle 
> the router when I plug in a new internet connection, but then there is the 
> possibility of a race:  dhcpc usually forks, and what if olsrd is started 
> before the dhcp configuration is complete?  the default route could be 
> assigned mere milliseconds after olsrd runs, but by then it's too late.

Well - you should time olsrd to start after all initialization. But then 
again - such a plugin would regulary poll for a default route so if it 
is not set up at startup it would be discovered at the next poll. So if 
one polls every 10 seconds it would be discovered 10 seconds later - you 
could probably accept that?

>>I would say so. If mobility is low the control traffic emission
>>intervals could be set up(longer intervals). This greatly reduces
>>overhead - expecially for flooded traffic.
> I'll experiment with values and report on the best that I find.

That's good. I think this kind of real-life experiment would be much 
appreciated by the MANET community.

- Andreas

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