The two migration paths from legacy AR-based BPX networks into PNNI are
Deployment of SES controllers to enable PNNI on the BPXs At first, logically independent AR and PNNI networks exist on the same physical infrastructure. The AR connections can then be automatically migrated to standards-based PNNI SPVCs.
Deployment of an MGX-8850 or MGX-8950 PNNI core At first, hybrid connections (X-PVCs) can be created using AR-PNNI interworking. The PNNI core can then grow to eventually include the complete network. In this scenerio, the core either can be summarized as a logical group node (LGN) or can be exposed as individual core nodes. Exposing the core gives full visibility of the core and enables optimal routing accross peer groups.
A third migration path also exists if you combine the previous two paths into a mixed migration path.