A bridge node converts a MAC frame addressed to a station node into a RPR
MAC frame and thus transmits it, and encapsulates a MAC frame addressed a
station being located the outside of a ring and connected to other bridge
node into the RPR MAC frame, and transmits it. The bridge node thereby
receives a RPR MAC frame into which the MAC frame is encapsulated, and
the station node receives the RPR MAC frame that the MAC frame is not
encapsulated.