An Internet protocol network alternate routing system comprises: a traffic control
unit for detecting the state of congestion of an LAN, which is an Internet protocol
network; a call control unit for establishing a link between an extension telephone
and the LAN based on the detection results of the traffic control unit; a central
processing unit for designating the signal path of voice signals that are transmitted
from the extension telephone based on the results of establishing a link in the
call control unit; and a switch control unit for switching the signal path that
connects a path to the extension telephone. In a case in which the call control
unit does not establish a link, voice signals that are transmitted from the extension
telephone are rerouted by switching performed by the switch control unit to a leased
line network by way of a leased line trunk.
