[Xorp-hackers] XORP enhancement for wireless mesh network routing

Jiangxin Hu jiangxin.hu at crc.gc.ca
Fri Jun 8 11:12:28 PDT 2012


The restriction for subnetwork still there even you use add_interface_route
function. 

The protocol should specify which interface a route go for. The current
XORP-OLSR does not do this.

By the way, I found to delete a wireless route also has problem. 

Jiangxin

-----Original Message-----
From: Igor Maravic [mailto:igorm at etf.rs] 
Sent: Friday, June 08, 2012 9:51 AM
To: Ben Greear
Cc: Jiangxin Hu; xorp-hackers at icir.org
Subject: Re: [Xorp-hackers] XORP enhancement for wireless mesh network
routing

Going through the code I found function:

add_interface_route in RIB's xrl. With that function, route is directly
added to the specified interface, no questions asked.

If the OLSR would use that function it could add route as directly connected
without any problem. Because I don't know any thing much about OLSR, I have
to ask this - Does the route should be added to the interface from which it
received advertisement?

If that is the case, interface name could be propagated through the code,
and instead of calling send_add_route, OLSR could call
send_add_interface_route, with appropriate vif name.
BR
Igor

2012/6/1 Ben Greear <greearb at candelatech.com>:
> On 06/01/2012 02:09 PM, Igor Maravic wrote:
>>>
>>> Igor:  Why should we ever restrict adding the connected routes?
>>>
>>> It seems to me that if the routing protocol wants it added, fea 
>>> should just do so.  But maybe I'm missing something?
>>>
>>
>> When the route comes to the RIB, if it isn't recognized as direct 
>> route, RIB assumes that this route is external one.
>> This happens with BGP routes, because their nexthop is external.
>>
>> Because of that it will try to resolve the nexthop for that route 
>> with existing IGP routes.
>>
>> The BGP routes can't be resolved, if this behavior is overridden.
>>
>> Thus I think that the best solution would be if the OLSR would tell 
>> the RIB to add directly connected route.
>> This will resolve the problem of RIB recognizing OLSR routes as external.
>> My proposition is to add function add_direct_route, that would be 
>> called via xrl from OLSR, the same way as add_route is called now. 
>> But that function would be in any doubt if it should resolve route as 
>> external or not.
>>
>> Maybe it is possible to check if route is resolved for wireless link, 
>> or not, from the add_route function, without braking the BGP route 
>> resolution, but I think that would stress out a performance 
>> dramatically. This is due the fact that before resolving any BGP 
>> route it would pass through all vifs to check if they are wireless or 
>> not (according to Jiangxin
>> patch)
>
>
> Ok, I haven't looked at this stuff in a while (and perhaps never in 
> great detail), so a new method: add_direct_route seems good to me.
>
> Better than changing behaviour based on an interface flag I think.
>
> Thanks,
> Ben
>
>>
>> BR
>> Igor
>
>
>
> --
> Ben Greear <greearb at candelatech.com>
> Candela Technologies Inc  http://www.candelatech.com
>




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