[AusNOG] VPLS OSPF question

[Brad McGinn]

Hi AusNog list,
 
Long time listener, first or second time caller.
 
I know this list is pretty specific to Service Providers so I'm hoping any of you who not only know carrier networks, but also have an insight into enterprise networks maybe able to help me to get a view (or even help understanding) of the pros and cons of running OSPF or BGP across a VPLS network.  
 
I respectfully ask your advice.  
 
I am an enterprise network engineer, not a service provider however I hope you don't hold that against me.  We run OSPF in our Data Centre and BGP into a MPLS network that all of our sites connect into.
 
My fairly basic understanding of VPLS is kind of like EoMPLS or even one big broadcast domain.  I assume any IGP could potentially work across it but some factors must be taken into consideration:  eg flapping sites, latency, reference bandwidth, DR/BDR placement, multicast transmission and so on.
 
So, with that in mind, I'm wondering the following:
-    would it be wise to run an IGP across a VPLS backbone with over 200 sites? or would BGP be better? or even something else?
-    if an IGP is the go, would one use OSPF?
-    if OSPF, do you think it would be wiser to run a separate OSPF process for the VPLS connected sites and a separate OSPF process for the DC?  and then redistribute or just summarise right there? (so as to protect the DC from OSPF recalculations when sites go up and down)
-    if BGP would be the go I'm wondering how one might go about it..  I know that all iBGP neighbours must have a route to the peering IP of all other iBGP routers so I would assume an IGP must be run anyway???
-    cisco say that anything more than 50 routers on an area is a bad idea, so if I have over 200 sites potentially on the VPLS, will OSPF cut it?
 
I guess i'm just trying to get my head around the different technology.  I'd love to keep the stability that BGP brings, but also would like to be able to make use of the bandwidth that VPLS gives.
 
Any hints or tips will be gratefully received and thank you for any help.  If you would like to keep from cluttering up subscriber's inboxes, please reply offlist.
 
Again, thanks for any help.
 
Regards,
 
Brad David
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