This Recommendation describes the methods, procedures and transport plane mechanisms fo discovering layer adjacency for ASON according to the requirements of ITU-T Rec. G.7714/Y.1705 and architecture of ITU-T Rec. G.8080/Y.1304. Layer Adjacency Discovery describes the process of discovering the link connection end-point relationships and verifying their connectivity. The term "discovery" is used throughout the Recommendation to refer to both "discovery" and verification. Two alternative methods are described: one using a test set in the client layer, the other using in-band overhead in the server layer. Additional actions that may be required for obtaining Physical Media Adjacency Discovery and Transport Entity Capability Exchange, etc., will be addressed in future Recommendations. Equipment developed prior to this Recommendation might not interwork with some of the features developed within this Recommendation. Care should be taken where old and new equipments are to interwork.