[Olsr-users] max packet size

[Henning Rogge]

On Sun September 5 2010 13:24:55 Mitar wrote:
> Hi!
> 
> On Sun, Sep 5, 2010 at 9:39 AM, Henning Rogge <(spam-protected)> wrote:
> > Even with IPv6 you should have enough space inside a Hello/TC for nearly
> > 100 neighbors. How dense is your network ?
> 
> Uh. What about VPN servers? Those could get easily more than 100 neighbors.
Do we have a network like this at the moment ?

The problem is that the 0.5.x codebase does not handle the difference between 
maximum message size and maximum packet size well. Messages must be small 
enough that they fit through all interfaces, even those with a smaller MTU. 
Packets are "link only" and could be assembled to the full interface MTU.

Maybe the maximum message size should be reduced, so that every OLSR message 
can be transmitted with a single IPv6 datagram without fragmentation. That 
would mean the maximum message size would be 1280 (minimal ipv6 mtu) - 40 
(ipv6 header size) - 8 (udp header size) - 4 (olsr packet header size). 1200 
bytes could be a good value, so we have still some space left for ip header 
extensions.

But the size of the link buffers should increase to the full MTU size of the 
interface.

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 9435-961,   Fax +49 228 9435 685
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