Transmission system

A transmission method implemented by a transmission system including a first communication device and a second communication device, the first communication device and the second communication device being connected with each other via a first line to be used for transmitting frames of traffic from the first communication device to the second communication device while performing error-correction coding on the frames, a second line to be used when the first line is in failure, and a third line to be used for transmission from the second communication device to the first communication device, the second communication device including a first buffer which stores the frames received from the first line, and a second buffer which stores the frames received from the second line, the method comprising:

• by the second communication device, when determines that it is necessary to perform line switching from the first line to the second line based on a status of error correction with respect to the frames received from the first line, transmitting a predetermined message to the first communication device via the third line,
• by the first communication device, when receiving the predetermined message via the third line, transmitting a frame of a post-switching message to the first line after switching the line used for transmission from the first line to the second line, and
• by the second communication device, when receiving the post-switching message from the first line, starting reading of the frames from the second buffer after reading all of the frames stored in the first buffer.

A communication device connected with another communication device via a first line to be used for transmitting frames of traffic while performing error-correction coding on the frames, a second line to be used when the first line is in failure, a third line to be used for transmitting frames of traffic while performing error-correction coding on the frames, and a fourth line to be used when the third line is in failure, wherein

• the communication device includes a first buffer which stores the frames received from the first line, and a second buffer which stores the frames received from the second line, and
• the communication device is adapted to
• when determining that it is necessary to perform line switching from the first line to the second line based on a status of error correction with respect to the frames received from the first line in a normal operation state, after switching the line used for transmission from the third line to the fourth line, transmit a frame of a post-switching message to the third line and allow the state of the communication device to be changed to a post-switching event message reception waiting state, and when receiving the post-switching message from the first line in the post-switching event message reception waiting state, perform reception section switching in which the communication device starts reading of the frames from the second buffer after reading all of the frames stored in the first buffer, and then allow the state of the communication device to be changed to the normal operation state, and
• when receiving the post-switching message from the first line in the normal operation state, perform reception section switching in which the communication device starts reading of the frames from the second buffer after reading all of the frames stored in the first buffer, and after switching the line used for transmission from the third line to the fourth line, transmit a frame of the post-switching message to the third line and allow the state of the communication device to be changed to the normal operation state.