[Olsr-users] Functionality of HNA when no OLSR link is established

Henning Rogge (spam-protected)
Tue Dec 1 10:35:26 CET 2009

On Tue December 1 2009 10:02:34 (spam-protected) wrote:
> We are using OLSR in a wireless network with nodes having both an air
>  interface and a LAN interface. The OLSR routing is used for the air
>  interfaces.
> In order to inform the other nodes of the relation between each node's air
>  interface IP address and LAN IP address, we use the HNA function.
That's exactly what HNAs should be used for.
> What we experience is that a node will transmit UDP/IP unicast packets with
>  a LAN IP address as long as the validity time of the HNA message from that
>  particular node is not exceeded even when the OLSR link is broken. Our
>  assumption was that packets addressed to such HNA given addresses would
>  not be transmitted unless there exists a valid link between the related
>  air interface IP addresses established by the HELLO and TC messages.
I think the OLSR.org implementation only sets HNA routes if there is a route 
to the target host.

OLSR.org remembers all HNA settings, but does not use them for routes 
> As it functions there are two drawbacks;
> 1. The air interface capacity is wasted with packet transmissions getting
>  nowhere - and not stopped before the HNA validity time is past after a
>  link is broken. 2. After the HNA validity time is past, it takes a long
>  time to reestablish the link to the HNA given address (depending on the
>  HNA interval time) after the air interface link is reestablished by the
>  HELLO and TC messages. Short HNA interval times is not a solution due to
>  more OLSR overhead traffic.

> Have we implemented OLSR correctly or is this how OLSR functions?
Are you using the olsr.org implementation (if yes, which version of it ?) or 
do you have implemented OLSR yourself ?

Henning Rogge

Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für
Kommunikation, Informationsverarbeitung und Ergonomie FKIE
Kommunikationssysteme (KOM)
Neuenahrer Straße 20, 53343 Wachtberg, Germany
Telefon +49 228 9435-263,   Fax +49 228 9435 685
mailto:(spam-protected) http://www.fkie.fraunhofer.de
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