Method and apparatus for automatic discovery in optical transport networks

In order to improve the link adjacency discovery in an Optical Transport Network, a method and related network nodes are provided. A first network node (21) has a first discovery agent (216) and a second network node (22) has a second discovery agent (226). A discovery message (210) is transmitted from a first interface of the first network node (21) over one or more subsequent network links (25, 26, 27) to a second interface of the second network node (22). The discovery message (210) contains information indicative of on discovery agent identifier associated with the first discovery agent (216) and of a termination connection point identifier associated with the first interface. In order to transmit the discovery message (210), the first interface is configured to perform a tandem connection source functions (217) using a reserved field in an overhead portion of signal frames to be transmitted. The second interface is configured to perform a Tandem Connection Monitoring function (227) on the same reserved field of received signal frames. The discovery message is sent using a Trail Trace Identifier (TTI) byte available in the reserved field.