Link-state pass through (LPT) transparently transmits the local link status to the opposite end so that the opposite end can perform operations accordingly.
Ethernet LPT can detect and report a link fault on the Ethernet user side or a fault on an intermediate point-to-point network.
After detecting a fault on the local link, the local user equipment automatically enables a backup link and uses the backup link to communicate with the opposite user equipment. The opposite user equipment, however, cannot obtain information about the local link fault. Therefore, it still uses the original link to communicate with the local user equipment. As a result, services are interrupted.
If Ethernet LPT is enabled, the local user equipment can send information about the local link fault to the opposite network edge equipment using Ethernet LPT packets. The opposite network edge equipment disables the UNI-side port so that the opposite user equipment starts to use the backup link. In this manner, services are transmitted over the backup link between the user equipment at both ends.