Re: [Ospf-wireless-design] Design team outbrief (draft slides) posted

[Richard Ogier <rich.ogier at earthlink.net>]

> Emmanuel Baccelli stated that MPR flooding offers better properties 
> than CDS flooding, with at least as good topology reduction 
> capabilities, and better routing stretch performance

After further consideration, I partly agree with the above statement
depending on how it is interpreted.
The part about "better route stretch performance" is true if we are
talking only about *flooding* and not *routing* (since routing can
occur along non-adjacencies).  Min-hop routing can be achieved either
with MPRs or with the min-cost LSAs described in the MDR draft.

The part about "good topology reduction capabilities" depends on how
adjacencies are defined. (By topology reduction I am talking about
adjacencies, keeping in mind that LSAs can also include non-adjacent
neighbors.) In our simulations, Phil and I showed that this
is certainly not true if each node forms an adjacency with each of
its MPRs and MPR selectors, and Emmanuel has agreed with this:

> On the other hand using
> MPR/MPRselector adjacencies does yield more adjacencies,
> but no route stretching whatsoever.


If adjacencies are defined in another way, then the method needs
to be specified. One possible way (which I plan to investigate by
modifying OSPF-MDR) is to select the CDS/MDRs by pruning MPRs
and then defining adjacencies as in the MDR draft, but Emmanuel
did not specify such a method.

Richard




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