t recognize packet/cell boundaries and can forward data based on the content of the packet/cell header Examples of these include interfaces on routers that forward data based on the content of the shim header and that are interfaces on Asynchronous Transfer Mode (ATM) LSRs that forward data based on the ATM Virtual Path Identifier/Virtual Channel Identifier (VPI/VCI). Such interfaces are referred to as packet-switch capable (PSC). Interfaces that forward data based on the data's time slot in a repeating cycle An example of such an interface is an interface on a Synchronous Optical Network (SONET) crossconnect. Such interfaces are referred to as time-division multiplex capable (TDMC). Interfaces that forward data based on the wavelength on which the data is received An example of such an interface is an GMPLS in Optical Networks interface on an optical crossconnect (OXC) that can operate at the level of an individual wavelength. Such interfaces are referred to as lambda- switch capable (LSC). Interfaces that forward data based on a position of the data in real-world physical spaces An example of such an interface is an interface on an OXC that can operate at the level of single or multiple fibers. Such interfaces are referred to as fiber-switch capable (FSC). Using the concept of a nested LSP enables the system to scale by building a forwarding hierarchy. At the top of this hierarchy are FSC interfaces, fol- lowed by LSC interfaces, followed by TDMC interfaces, followed by PSC inter- faces. This way an LSP that starts and ends on a PSC interface can be nested (together with other LSPs) into an LSP that starts and ends on a TDM inter- face. This LSP, in turn, can be nested (together with other LSPs) into an LSP that starts and ends on an LSC interface, which can be nested (together with other LSPs) into an LSP that starts and ends on an FSC interface. The establishment of LSPs that span only the first class of interfaces is defined in the Label Distribution Protocol (LDP), constraint-based routing LDP (CR-LDP), and