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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