Companys who run their own private MPLS networks - Physical Topology ??

Hi guys,

I've always been interested in companies who run their own private MPLS networks - more of the physical topology if I'm honest and how they go about deploying it.

Looking at alot of conceptual documentation There are 3 'Network' components to the MPLS P routers, PE routers and CE routers.

Should the PE routers be deployed in the same DC as the P routers ? or should the PE routers be more localised to the branch sites as they provide aggregation?

Should all my P routers be linked via a ring or full mesh - generally how many P routers should you be going for in a deployment?

I appreciate that alot of this is down to how much $$ is at your disposal - but are there any guys who can share their experience with private MPLS networks and there physical typologies - just trying to fit the pieces together :)

Thanks!