Optical Network Control: Architecture, Protocols, and Standards

6.2. Types of Adjacencies and Discovery Procedures

ITU-T recommendation G.7714 [ITU-T02a] defines three types of adjacencies. These are described below.

6.2.1. Layer Adjacency

Consider Figure 6-1a, which illustrates a network segment with IP routers, OEO (e.g., SONET) optical cross-connects (OXCs), WDM devices, and amplifiers. The figure depicts physical links between network elements, for example, between the OXCs and the WDM devices. The transmission system, consisting of the WDM devices and optical amplifiers, is referred to as the optical line system. Figure 6-1b depicts connectivity at various SONET layers—path, line, and section (see also Figure 5-5). Two network elements are said to be neighbors at a certain layer if each terminates the ...