in light of the trend to migrate the enterprise WAN from layer-2 based circuits to layer-3 MPLS VPN. Is there a
need to match such change when designing WAN routing. As example, in a WAN of 1,000 router, we mostly used to consider OSPF with some area xs for the regions and then summerize the routes advertized into each area. This is not the case in IP/MPLS based WAN, since it is
any-to-any technology, and all the routes for the same VRF will show up in every router.
I just wonder if any one is aware of a URL talk about selecting the IGP for IP/MPLS based enterprise network.
I think so. What you can structure is a WAN that becomes your own private Internet. Each site routes within it however you chose but communcates its address block using eBGP to the WAN. (Somewhat similar to doing the same on the Internet if you eBGP peer with your ISP and pass route information both ways.)