Patent ID: 7978727

Claim:
An interface device, comprising: an Ethernet frame and a synchronous optical network frame convertible interface device, wherein a 1 st holding part with a VLAN identifier of said Ethernet frame and a path identifier of said synchronous optical network frame are placed opposite each other; and a plurality of multiplexers of the interface device, each of which can be established corresponding to a path identifier of said synchronous optical network respectively and each of which is operable to multiplex an Ethernet frame having said specific VLAN identifier corresponding to said specific path identifier that is held by said 1 st holding part among a plurality of input Ethernet frame VLAN identifiers; wherein said each multiplexer establishes a filtering part that passes through Ethernet frames having said specific VLAN identifier among a plurality of Ethernet frames and a 1 st encapsulating part that encapsulates information data contained in an Ethernet frame that passes through a filtering part, and said filtering part breaks down the frame when a VLAN identifier of the frame is different from any one of the VLAN identifiers that is held by said holding part.