In one general embodiment, a method for setting a value of waiting time
for switching is provided. At a node in a sonet ring, it is determined
which path to the node is an actual path and which path is a preliminary
path. Additionally, it is determined whether a one way fiber transmission
delay of the actual path is less than a one way fiber transmission delay
of the preliminary path. If the one way fiber transmission delay of the
actual path is greater than the one way fiber transmission delay of the
preliminary path, a switching time is set to zero and normal switching is
performed. If the one way fiber transmission delay of the actual path is
less than the one way fiber transmission delay of the preliminary path, a
switching time is set equal to the one way fiber transmission delay of
the preliminary path minus the one way fiber transmission delay of the
actual path and it is determined whether a path alarm indication signal
(AIS) occurred in the actual path. If the path alarm indication signal
occurred in the actual path, path switching of the actual path is stopped
within the switching time and it is determined whether a path alarm
indication signal occurred in the preliminary path. If the path alarm
indication signal did not occur in the preliminary path, normal path
switching is performed for the actual path.