Patent ID: 7590147

Claim:
A LAN signal transmission method of transmitting and receiving a LAN signal between a first LAN apparatus and a second LAN apparatus each for transmitting and receiving the LAN signal through a first transmission apparatus and a second transmission apparatus that are arranged between the first LAN apparatus and the second LAN apparatus, wherein the first transmission apparatus converts the LAN signal transmitted from the first LAN apparatus into a digital wrapper signal, and transmits the digital wrapper signal to the second transmission apparatus; and wherein the second transmission apparatus converts the digital wrapper signal into the LAN signal, and transmits the LAN signal to the second LAN apparatus, the LAN signal transmission method comprising: a step of the first transmission apparatus extracting only a data section of the LAN signal that is received, accommodating the data section in the digital wrapper signal, accommodating link information between the first transmission apparatus and the first LAN apparatus in an overhead of the digital wrapper signal, and transmitting the digital wrapper signal to the second transmission apparatus; a step of the second transmission apparatus extracting the data section of the digital wrapper signal of the LAN signal, extracting the link information from the overhead of the digital wrapper signal, generating a LAN signal constituted by the extracted data section and the link information, and transmitting the LAN signal to the second LAN apparatus; and a step of shutting down the LAN signal to the second LAN apparatus if the extracted link information indicates “link down”, and masking link information to be transmitted to the first LAN apparatus, the link information indicating “link down” between the second transmission apparatus and the second LAN apparatus.