GMPLS stands for Generalized Multi Protocol Label Switching. It is a network control and operational architecture specific for modern transport networks. The architecture is extended from the traditional Multi-Protocol Label Switching (MPLS) network to generally support wavelength lambda, time slot index, and regular packet labels.

GMPLS divides a transport network into two network planes, including a data plane and control plane. The data plane functions to transmit network data traffic to consist of different types of network switches such as MPLS switches, OXC, DXC, etc. Corresponding to the data plane, the control plane offers control functionalities to control the switches in the data plane. Three important control components are considered in the control plane, including routing component, signaling component, and Link Management Protocol (LMP).

Routing component functions to (1) keep alive between network controllers by exchanging "hello" message, (2) maintain a synchronized network state database, and (3) compute routes between node pairs based on the current network state database. Currently, OSPF-TE is the most popular routing protocol for this purpose.

Signaling component functions to establish, modify, and delete network service connections. For a new network service request, a connection needs to be established between a node pair. Sometimes, an existing connection may be modified in aspects such as bandwidth and traversing route. Also, an existing service may expire after some time. Then the signaling protocol should release the connection and free the resources of the connection. Currently, RSVP-TE protocol is the most popular signaling protocol for this purpose.

Link Management Protocol (LMP) is a new protocol specifically proposed for the GMPLS architecture. It functions to support the following four functions: (1) control link maintenance and initiation between controllers in the control plane, (2) abstraction of link properties in the data plane, (3) Data link verification, and (4) data link fault management and monitoring.