The GMPLS UNI assumed a flat addressing scheme between the UNI-C nodes and the optical network. In this model, a common addressing scheme is used between the UNI-C (IP router) and UNI-N (optical edge). The UNI-C and UNI-N must be in the same subnet. Also, none of the UNI-C addresses can overlap or clash with any of the GMPLS-aware nodes in the optical network. This does not mandate that the whole IP network share a common address space with the optical network, as a separate loopback address can be used for the GMPLS UNI on the UNI-C.
The ERO Expansion (RFC 5151) model is assumed for the GMPLS LSPs. The UNI-C is not exposed to the full ERO between the UNI-N nodes. Instead, the full ERO is inserted at the UNI-N. This model limits the sharing of topology information between the UNI-N and UNI-C.