[c-nsp] OSPF point-to-point vs dr/bdr

[Paul Cosgrove]

Peter Rathlev wrote:
> On Wed, 2008-08-20 at 07:41 -0700, Kelvin Goei wrote:
>> Want to ask, what is the benefit if we are using point-to-point for
>>  connection between each zones router to the core instead of using
>>  dr/bdr connection? 
> 
> Configuring a link as "point-to-point" means that OSPF skips the BR/BDR
> election, making the calculations a little simpler. Normally a
> multi-access media (like Ethernet) means the SPF algorithm has to use a
> "trick" to build a graph, since all graph links must exclusively be
> between two nodes. Electing a pseudo-node and treating the multi-access
> media like a star topology solves this, but makes the SPF graph more
> complex.
> 
> Regards,
> Peter
> 

Just to add, just in case it isn't obvious from Peters comments, that
the neighbor establishment can also be quicker since DR election does
not occur.  The wait timer, which is normally 40 seconds, does not need
to be used.

Paul.

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