[Ospf-manet] Regarding OSPF MDR

Philippe Jacquet <philippe.jacquet@inria.fr> Fri, 09 February 2007 15:52 UTC

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Date: Fri, 09 Feb 2007 16:52:17 +0100
From: Philippe Jacquet <philippe.jacquet@inria.fr>
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To: Richard Ogier <rich.ogier@earthlink.net>
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Subject: [Ospf-manet] Regarding OSPF MDR
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Dear Richard,

We have studied the MDR code and draft.

1. The algorithm described in the MDR draft does not provide the feature 
it claims: minimum cost paths in the routing table. Links are not 
guaranteed to be symmetrically advertized and, consequently, part of the 
LSAs will systematically be killed by backlink check.

2. Making a nodes LSA dependent of other nodes LSA is a source of 
circular dependancy.

3. The code for minCost LSA in the GTNet MDR-implementation does not 
implement the algorithm which is described in the MDR draft: For the 
option used in the simulations which you presented lately 
(LSAFullness=1), the code has three embedded loops that in the end make 
a node i to advertize a link to a node j if and only if i is the closest 
node to j. But this does not result in shortest path advertizements.

4. The GTNet MDR implementation artificially distorts link metrics as a 
way of expressing both the actual cost and the property (synchronized or 
not) of the link as one. This approach is, not specified in the MDR 
draft, so also on this point the GTNet MDR implementation and the MDR 
draft exhibit a significant discrepency.

The preliminary conclusions are, therefore:

   - that the algorithms and the claims of the MDR draft do not
     correspond with each other;

   - that the MDR draft and the GTNet MDR implementation do not
     correspond with each other;

and so:

   - that the simulation results presented from GTNet for the MDR-OSPF
     proposal correspond NEITHER to the MDR draft algorithms NOR to the
     properties claimed by the MDR draft.

Sincerely,

Philippe

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