The link management protocol (LMP, [2]), an important component of GMPLS, allows a GMPLS application to associate labels with non-packet switched links between adjacent nodes. For example, labels may be associated with time-slots, wave-lengths, or physical ports of a switch. This helps integrate optical networking equipment with the GMPLS control plane applications.

The LMP protocol, handles dynamic link provisioning and fault management. According to [2], "LMP will be used to maintain control channel connectivity, verify the physical connectivity of data-bearing channels, correlate the link property information, and manage link failures". The LMP decouples the link information (of local significance to a pair of adjoining nodes) from the logical traffic engineering (TE) links used to build label switched paths. It enables greater reliability by separating the control and data channels (links), including an option for physical diversity between control and data hannels.

Consider an OXC supporting OC-48 interfaces. interface is multiplex capable, say, it can de-multiplex an OC-48 stream into four OC-12 streams; using the capabilities of LMP, TE links can be formed out of one or more individual OC-12 streams. The OC-12 streams are treated as data links, identified by the component id (of the OC-48 interface), and the individ-ual time slot. For instance, a logical TE link at OC-24 rate may be formed, with two of these OC-12 streams. The LMP functionality correlates the logical TE link with the constituent data links, transparent to the application.

Extending the example, with two multiplex capable OC-48 interfaces, LMP enables an application to form TE links from speeds of OC-12 to OC-96 equivalent, in steps of OC-12 rates. The logical TE links configured by LMP are available for data transportation applications.

Apart from offering dynamic TE link provisioning, the LMP handles data link connectivity, control channel maintenance and fault localization, thereby reducing the administrative burden on the application.

MindTree’s LMP component enables the equipment management software to rapidly incorporate optical terminations into a GMPLS framework. By using the LMP component, the applica-tion can treat the optical termination systems through the abstraction of a TE link; the application is shielded from issues of optical transmission, such as transmission format (SDH or SONET), speed (for example, upgrade from OC-48 to OC-192), or technology (WDM or TDM).

The application API of the LMP component presents a logical view of the optical transmission system as dynam-ically configurable TE links. The hardware abstraction API helps integrate different optical transmission sys-tems, irrespective of speed or transmission format, and the command language used to control the hardware (e.g., TL/1, through NMS commands, or assembly language code). The optional API to the MIB agent helps integrate the LMP component into a SNMP-based management system. The API to the OS enables portability to different OS platforms.

The reference documents [1,2,3] are still work-in-progress at the IETF. MindTree’s implementation reflects the latest publicly available version. In case the references get updated by the IETF, MindTree reserves the right to make appropriate changes.