Optical Network Control: Architecture, Protocols, and Standards

6.3. Protocol Mechanisms

The basic neighbor discovery protocol mechanism consists of periodic keep-alive or “Hello” message exchanges by neighboring NEs. These messages are sent over each logical link whose end point identifiers need to be associated. In SONET/SDH networks, logical links are bidirectional, that is, the transmit and the receive links are paired in an OXC and their end points are identified by a single identifier (e.g., a bidirectional port ID). With PXCs, there may or may not be an association between transmit and receive links. Hence, in the neighbor discovery procedures, the transmit and receive end points may be separately identified (e.g., a unidirectional port ID). The protocol, in its simplest form, can be described as follows ...