Re: [Ospf-manet] Simulation results for MPR adjacency reduction

Emmanuel Baccelli <Emmanuel.Baccelli@inria.fr> Mon, 08 January 2007 14:07 UTC

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Date: Mon, 08 Jan 2007 15:07:03 +0100
From: Emmanuel Baccelli <Emmanuel.Baccelli@inria.fr>
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Subject: Re: [Ospf-manet] Simulation results for MPR adjacency reduction
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Dear Richard, all,

Happy new year to you and yours. Thanks for your contribution to the 
MPR-OSPF code. We already knew that the MPR-OSPF draft is simple to 
understand and to implement, but you were really very fast. Congratulations.

However, we did not find exactly the same results as the ones you 
mentionned, we will release soon the results we got. In particular our 
simulation results show that MPR-based topology reduction and multicast 
outperforms MDR and OR performance reported by Boeing at the IETF.

Here is an update to the MPR-OSPF code that implements multicast 
transmissions http://ndquan.free.fr/GTNetS/gtnets-LSAreduc-Mcast.tar.bz2
The use of multicast is now implemented in addition to MPR topology 
reduction, which provides a simple and robust solution ensuring that 
while the overhead is drastically reduced, every advertized link is 
still symmetric and synchronized.

The available code for MPR-OSPF actually outperforms both OR and MDR
(full LSA) simulated with the same parameters, based on the reports of 
Boeing that were presented at the IETF. We will release
a report about these results soon. This confirms that topology reduction 
on its own is very efficient, apparently more than adjacency reduction.

We would nevertheless like to stress the fact that the simulation 
scenarios and parameters that are used in the Boeing reports are quite 
restrictive. In particular, we think the values of parameters such as 
Retransmit time and min LSA interval are not in tune at all with high 
mobility, and that the 2x2 scenario with almost mesh connectivity is too 
specific. We think that it is essential to simulate other scenarios and 
other parameters.

Concerning bugs in the code, we also found some of them that we want to 
share with you: for instance, it seems that an old Ack can somehow 
replace a newer Ack in the database and therefore create problems 
regarding retransmissions. Did you notice such a behaviour? We had to 
fix this. We have moreover fixed the bug you have mentionned concerning 
the conflicting flags OSPF6_MANET_MDR_FLOOD and 
OSPF6_MANET_MPR_TOPO_REDUC that can now be compiled together.

Regards,
Emmanuel




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