Hello,
As I see it, how you do the route reflection process is more your own business than the customers'. How well you are doing it will of course affect the customers, but this is more an internal issue of the core, rather than something to discuss with the customer. Anyway, in this case the customers might have a point.
The problem when you have 2 PE's as your RR's is that if you want to perform a maintenance procedure on those PE's, it might also affect customers not even connected to the particular PE's. If on the other hand the core routers are the RR's, if you perform maintenance on them, few things in the network will be operational anyway since they stand in the middle, so no more harm done than expected. One could argue that in both cases there are 2 RR's, so things cannot be that bad. If one goes down we do have the other. (In the case of the P's however, if one goes down you might have a split network, so route reflection is the last thing that would concern you.)
You have 122 PE's and expect more. My guess is that your routers can handle the process if in most cases only a couple of routes are exchanged between VPN sites. Whether you choose to make RR's the P's or the PE's is more of a matter of style. I would prefer the PE's, because I would rather keep the P's "clean", doing what they are supposed to do, that is label switching traffic. MPLS is supposed to relief the core from running BGP, and we do not want to take risks in the P's by running something not absolutely necessary for them. In addition, route reflection is supposed to relief the PE's from having to peer with each other directly, so it looks more their own business to handle the route reflection process, which is coming to remedy the necessity for them (that is the PE's) to peer with every other PE in the network.
The bottom line is: Your P's are more important to you than any other router. This is for the customers' best interest as well. Keep functions where they belong more naturally.
Kind Regards,
M.
