I have a fairly flat ISP network that I am upgrading to use MPLS (dont ask why, that decision is above my position) but clients/CPE are authenticated using PPPoE. Each POP uses a router configured as an LAC with a L2TP-tunnel to a LNS stack. Client information is stored in a Radius server.
I have these requirements: 1)Must use PPPoE to authenticate clients/CPE 2)avoid adding more traffic to the network as much as possible 3)Maintain IS-IS as the IGP (if IS-IS needs to go, provide valid reasons that I can use) 4)try not to use additional vendors equipment, Currently Cisco is the default with some Linksys (Cisco) equipment.
What I am planning is to just use an AToM tunnel to the LNS stack and adding MPLS to each router.
Any other ideas?