When normal traffic cannot be transmitted from a port, for example, when a received signal is in a failed state or when a port is administratively disabled and traffic is disrupted, the BTI7800 Series will usually forward a maintenance signal from the transmit port to indicate to the downstream node that a local outage exists. For all interface protocols, the default maintenance signal (Table 1) enables the receiving node to conclude that the link to the adjacent upstream node is intact.
Table 1: Default Maintenance Signals - Interface Protocols
Default Maintenance Signal
OC192, WAN PHY over OC192
STM64, WAN PHY over STM64