JP2006005506A - Transmission device, and transmission system and transmission method employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission device capable of detecting a link interruption signal in a Gigabit Ethernet (R) by using an opposite apparatus. <P>SOLUTION: On the occurrence of link interruption at a client side CH1, a link information control section 14 extracts a link interruption signal from flow information bits in a Gigabit Ethernet (R) frame in a Gigabit Ethernet (R) termination section 11 and transmits the link interruption signal to a format conversion section 12. The format conversion section 12 multiplexes Gigabit Ethernet (R) frames of CH1, CH2, converts the multiplexed frame into a payload of the Sonet/SDH, and transmits the payload to an SDH termination section 13. The SDH termination section 13 attaches the link interruption signal from the link information control section 14 to an SOH, attaches the SOH to the payload of the Sonet/SDH converted by the format conversion section 12 and transmits the resulting payload to a transmission block. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmission apparatus, a transmission system using the same, and a transmission method, and more particularly to a transmission apparatus that converts a Gigabit Ethernet (registered trademark) frame into a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame and transmits the frame. The present invention also relates to a transmission system and a transmission method using the same.

  FIG. 6 is a block diagram showing an example of a conventional transmission system of this type. Referring to the figure, an example of a conventional transmission system of this type includes a client-side transmission device 100 (hereinafter referred to as a transmission device 100), a remote-side transmission device 200 (hereinafter referred to as a transmission device 200), a transmission line, and the like. 300.

  A frame compliant with the Gigabit Ethernet (registered trademark) standard is input to the transmission apparatus 100, and a frame compliant with the Gigabit Ethernet (registered trademark) standard is output from the transmission apparatus 200.

  The transmission apparatus 100 includes a Gigabit Ethernet (registered trademark) termination unit 101, a format conversion unit 102, and an SDH termination unit 103.

  The Gigabit Ethernet (registered trademark) termination unit 101 has two interfaces of channel 1 (CH1) and channel 2 (CH2), and has a function of converting a data frame into 10 bits / 8 bits as an example.

  The format conversion unit 102 has a function of demultiplexing the CH1 and CH2 Gigabit Ethernet (registered trademark) frames and converting them into a SONET / SDH payload.

  The SDH termination unit 103 has a function of adding an SDH SOH (Section Over Head) to the SONET / SDH payload.

  The transmission apparatus 200 includes a Gigabit Ethernet (registered trademark) termination unit 201, a format conversion unit 202, and an SDH termination unit 203. Since the functions of these units 201 to 203 are the same as those in the transmission apparatus 100, the description thereof is omitted.

  Next, a configuration of an example of a conventional transmission system will be described. Referring to FIG. 6, the input light from the client side is optical / electrical signal (O / E) converted and then input to the gigabit Ethernet (registered trademark) termination unit 101 for 10-bit / 8-bit conversion.

  Now, when a link break occurs in the client side CH1, a link break signal is added to the Gigabit Ethernet (registered trademark) frame, but the Gigabit Ethernet (registered trademark) termination unit 101 converts 10 bits / 8 bits. The link disconnection signal, which is the flow information bit, is discarded, and the converted Gigabit Ethernet (registered trademark) frame is sent to the format conversion unit 102.

  The format conversion unit 102 multiplexes CH1 and CH2 Gigabit Ethernet (registered trademark) frame frames, converts them into SONET / SDH payloads, and sends the converted SONET / SDH payloads to the SDH termination unit 103.

  In the SDH termination unit 103, SOH is added to the SONET / SDH payload, and the SONET / SDH frame is sent to the opposite transmission apparatus 200 via the transmission line 300.

  In the SDH termination unit 203 of the transmission apparatus 200, the SOH of the SONET / SDH frame is discarded and the payload is sent to the format conversion unit 202.

  In the format conversion unit 202, the SONET / SDH payload is separated into CH1 and CH2, and the separated SONET / SDH payload is converted into a Gigabit Ethernet (registered trademark) frame and sent to the Gigabit Ethernet (registered trademark) termination unit 201. The

  In the Gigabit Ethernet (registered trademark) termination unit 201, the Gigabit Ethernet (registered trademark) frame is converted into 8 bits / 10 bits, further E / O converted, and then transmitted to the remote side.

  FIG. 7 is an explanatory diagram showing a bitmap of flow information bits in a frame of Gigabit Ethernet (registered trademark). Referring to the figure, bits D0 to D4 are reserved bits, D5 is FD (Full Duplex), D6 is HD (Half Duplex), D7 is PS1 (Symmetric PAUS), D8 is PS2 (Asymmetric PAUSE), and D9 to D11 are Reserved, D12 and D13 indicate RF1, RF2 (Remote Fault 1, 2), and D14 indicates ACK (Acknowledge).

  Specifically, D5 indicates that the device supports full-duplex mode, and D6 indicates that the device supports half-duplex mode.

  D7 indicates that the device supports symmetric flow control. That is, the device supports both the reception and transmission functions of an optical output stop frame (optical stop signal) based on IEEE802.3x.

  D8 indicates that the device supports asymmetric flow control. D12 and 13 are link disconnection signals indicating that an error has been detected in the link. D14 indicates that the configuration register of the counterpart device has been correctly received.

  FIG. 8 is a diagram showing a detailed definition of a link disconnection signal in a flow bit. Referring to the figure, FR1 corresponds to D12, and RF2 corresponds to D13. When FR1 and FR2 are “0, 0”, the link is normal (default), when “0, 1” is offline, “1” , 0 ”indicates a link disconnection (link disconnection signal), and“ 1, 1 ”indicates an auto-negotiation error.

  FIG. 9 is a diagram showing an STM (Synchronous Transfer Mode) 1-frame configuration (SOH and payload portion) in SONET / SDH. Referring to the figure, the STM1 frame 400 is composed of SOH 401 and 402, an AU pointer (AUPTR) 403, and a payload 404.

  However, in the conventional transmission system of this type, since the link disconnection signal and auto-negotiation information in the frame of Gigabit Ethernet (registered trademark) are converted into 10 bits / 8 bits, the flow information bits are discarded. Flow control cannot be performed in a method for multiplexing Ethernet (registered trademark) over SONET / SDH signals (Gigabit Ethernet (registered trademark) over Sonet / SDH).

  On the other hand, in order to transmit the link disconnection signal in the frame to the opposite device, the method for multiplexing the Ethernet (registered trademark) over the SONET / SDH signal (Ethernet (registered trademark) over Sonet / SDH) in the Ethernet (registered trademark) frame A method of adding a link disconnection signal to a SONET / SDH frame is known. However, since the frame format is different from that of Gigabit Ethernet (registered trademark) and the standard itself is completely different, this is directly applied to Gigabit Ethernet ( (Registered Trademark) cannot be applied (see Patent Document 1).

  In addition, in the method of multiplexing to the SONET / SDH signal of Gigabit Ethernet (registered trademark) (Gigabit Ethernet (registered trademark) over Sonet / SDH), the link disconnection signal in Gigabit Ethernet (registered trademark) is transmitted to the opposite device. Therefore, there is a method of adding to the Sonet / SDH frame, but since a link disconnection signal is added to the payload of the Sonet / SDH frame, when a link disconnection occurs in CH1, the link disconnection signal of CH1 is Since it is added in the payload in the SDH frame, there is a drawback that the main signal area of CH2 is narrowed. Further, the link disconnection signal is added by providing a control bit to a specific bit of VC-4or (VC-3 + FS) * 3 (payload) 404 shown in FIG. 9 (see Patent Document 2).

Japanese Patent Laying-Open No. 2003-60603 (paragraphs 0022 to 0024, FIG. 3) JP 2001-308869 A (page 3, paragraph 4, lines 46 to 50)

  The first problem is that the link disconnection signal in Gigabit Ethernet (registered trademark) is opposite in the multiplexing method to Gigabit Ethernet (registered trademark) SONET / SDH signal (Gigabit Ethernet (registered trademark) over Sonet / SDH). It is not detected by the device.

  The reason is that when the Gigabit Ethernet (registered trademark) frame is converted to 10 bits / 8 bits at the end, the link disconnection signal (flow information bit) in the Gigabit Ethernet (registered trademark) frame is discarded, and the Sonet / SDH frame It is because it is not added to.

  The second problem is that a link disconnection signal in Gigabit Ethernet (registered trademark) occurred in the method of multiplexing to the SONET / SDH signal of Gigabit Ethernet (registered trademark) (Gigabit Ethernet (registered trademark) over Sonet / SDH). In this case, the client side transmission apparatus cannot perform flow control of the opposite apparatus by auto-negotiation.

  The reason is that since the link disconnection signal mentioned as the first problem is not detected by the opposite device, the opposite device cannot know the timing of the flow control.

  The third problem is that, as shown in the technique described in Patent Document 2, when a link disconnection signal (flow information bit) in a Gigabit Ethernet (registered trademark) frame is added to the payload of a Sonet / SDH frame, the channel on the client side When the number is plural, the main signal band of the other channel is narrowed when a link disconnection signal is generated in one channel.

  The reason is that when a link break occurs in one channel on the client side, the link break signal in the Gigabit Ethernet (registered trademark) frame is always added to the payload portion of the Sonet / SDH frame. This is because the signal area of other channels is inevitably reduced.

  Therefore, an object of the present invention is to detect a link disconnection signal in the Gigabit Ethernet (registered trademark) by the opposite device, thereby enabling flow control of the opposite device and the signal area of the payload portion of the Sonet / SDH frame. It is an object of the present invention to provide a transmission apparatus, a transmission system using the transmission apparatus, and a transmission method using the same.

  In order to solve the above problems, a transmission apparatus according to the present invention is a transmission apparatus that converts a Gigabit Ethernet (registered trademark) frame into a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame and transmits the frame. Link disconnection signal transmission means for extracting a link disconnection signal from a flow information bit in a Gigabit Ethernet (registered trademark) frame, adding the link disconnection signal to the SOH (Section Over Head) of the SONET / SDH frame, and transmitting the link disconnection signal. It is characterized by including.

  Another transmission apparatus according to the present invention is a transmission apparatus that converts a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame into a Gigabit Ethernet (registered trademark) frame and transmits the frame. A link disconnection signal receiving means for extracting a link disconnection signal added to a SOH (Section Over Head) of a frame and adding the link disconnection signal as an optical stop signal to a flow information bit in the Gigabit Ethernet (registered trademark) frame It is characterized by including.

  In addition, a transmission system according to the present invention includes the two transmission devices and a transmission path connected between the transmission devices.

  The transmission method according to the present invention is a transmission method for converting a Gigabit Ethernet (registered trademark) frame into a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame and transmitting the frame. A link disconnection signal transmission step of extracting a link disconnection signal from a flow information bit in a trademark frame, adding the link disconnection signal to a SOH (Section Over Head) of the SONET / SDH frame, and transmitting the link disconnection signal. To do.

  According to another aspect of the present invention, there is provided a transmission method for converting a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame into a Gigabit Ethernet (registered trademark) frame and transmitting the frame. A link disconnection signal receiving step of extracting a link disconnection signal added to the SOH (Section Over Head) of the frame and adding the link disconnection signal as an optical stop signal to the flow information bits in the Gigabit Ethernet (registered trademark) frame It is characterized by including.

  According to the present invention, the link disconnection signal included in the flow information bit in the Gigabit Ethernet (registered trademark) frame is added to the SOH (Section Over Head) of the SONET / SDH frame and transmitted.

  According to the present invention, by having the above-described configuration, the link disconnection signal in Gigabit Ethernet (registered trademark) can be detected by the opposite device, thereby enabling flow control of the opposite device and the Sonet / SDH frame. This has the effect of not reducing the signal area of the payload portion.

  Specifically, since it becomes possible to transmit a link disconnection signal to the opposite device in the multiplexing method (Gigabit Ethernet (registered trademark) over Sonet / SDH) to the SONET / SDH signal of Gigabit Ethernet (registered trademark), Auto-negotiation link disconnection flow control is possible.

  In addition, when a link break occurs in channel 1, the link break signal is transferred using the SOH area without generating a monitoring packet for the link break signal in the main signal, so the payload area of the Sonet / SDH Since the main signal of channel 2 can be fully used, the main signal band can be effectively used.

  Furthermore, since link disconnection detection is realized in hardware without using a monitoring system terminal, it is possible to deal with it immediately and to reduce costs.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an example of a transmission system according to the present invention.

  An example of a transmission system according to the present invention includes a client-side transmission device 10 (hereinafter referred to as a transmission device 10), a remote-side transmission device 20 (hereinafter referred to as a transmission device 20), a transmission device 30, a transmission line 300, and 301. The transmission apparatus 10 and the transmission apparatus 20 are opposed to each other via the transmission path 300, and the transmission apparatus 20 and the transmission apparatus 30 are opposed to each other via the transmission path 301.

  In the figure, the gigabit Ethernet (registered trademark) termination unit 11 of the transmission apparatus 10 has two interfaces of channel 1 (CH1) and channel 2 (CH2), and has a function of converting a data frame to 10 bits / 8 bits. Have.

  The format conversion unit 12 has a function of demultiplexing CH1 and CH2 Gigabit Ethernet (registered trademark) frames and converting them into a Sonet / SDH payload.

  The SDH termination unit 13 has a function of adding an SDH SOH (Section Over Head) to the Sonet / SDH payload.

  The link information control unit 14 extracts the link disconnection signal when the client side link disconnection signal is generated from the Gigabit Ethernet (registered trademark) termination unit 11 and adds the link disconnection signal to the SOH of the SDH termination unit 13. When the link disconnection signal is added to the SOH of the Sonet / SDH frame by the SDH termination unit 13, the flow information bits of the Gigabit Ethernet (registered trademark) frame of the Gigabit Ethernet (registered trademark) termination unit 11 Has a function of adding a light stop signal.

  The in-device clock counter 15 has a function of synchronizing the link information control unit 14 and the Gigabit Ethernet (registered trademark) termination unit 11 and a function of synchronizing the link information control unit 14 and the SDH termination unit 13. Have.

  In the transmission apparatus 10, input light from the client side is O / E converted and sent to the Gigabit Ethernet (registered trademark) termination unit 11. When the link break occurs in the client side CH1, the link information control unit 14 extracts the link break signal from the flow information bits in the Gigabit Ethernet (registered trademark) frame in the Gigabit Ethernet (registered trademark) termination unit 11. The 10-bit / 8-bit conversion is performed, and the converted Gigabit Ethernet (registered trademark) frame is sent to the format conversion unit 12.

  The format conversion unit 12 multiplexes CH1 and CH2 Gigabit Ethernet (registered trademark) frames, converts them into a Sonet / SDH payload, and sends them to the SDH termination unit 13.

  The SDH termination unit 13 adds a link disconnection signal to the SOH from the link information control unit 14 while synchronizing with the link information control unit 14 from the in-device clock counter 15, and converts the SOH by the format conversion unit 12. It is added to the SDH payload and sent to the transmission section.

  In the opposite device (transmission device 20), the link disconnection signal added to the SOH by the SDH termination unit 23 is sent to the link information control unit 24, the SOH is discarded, and the signal after the SOH discard is the format conversion unit. 22 is sent out.

  The format conversion unit 22 converts the Sonet / SDH payload into a Gigabit Ethernet (registered trademark) frame, and the converted Gigabit Ethernet (registered trademark) frame is separated into CH1 and CH2 Gigabit Ethernet (registered trademark) frames. The data is sent to the Gigabit Ethernet (registered trademark) terminal unit 21.

  In the Gigabit Ethernet (registered trademark) termination unit 21, when the data frame is converted to 8 bits / 10 bits, the in-device clock counter 25 synchronizes with the link information control unit 24, and the link information control unit 24 sends a link disconnection signal. Is added to the flow information bits of the Gigabit Ethernet (registered trademark) frame as an optical stop signal, E / O converted, sent to the remote side, and transmitted to the transmission device 30 which is the opposite device of CH1 of the transmission device 20 Send out an Ethernet (registered trademark) frame.

  The transmission device 30 receives the light stop signal in the flow information bit of the Gigabit Ethernet (registered trademark) frame, and stops the transmission light output of the transmission device 30 by the auto-negotiation function.

  As described above, the link disconnection signal can be transmitted to the transmission apparatus 20 by adding the link disconnection signal in the flow information bits of the Gigabit Ethernet (registered trademark) of the transmission apparatus 10 to the SOH of the Sonet / SDH. Thus, flow control is also possible by the auto-negotiation function.

  FIG. 2 is a flowchart showing a series of processes until a data frame received on the client side is transmitted to the remote side. FIG. 3 is a series of processes until a data frame received on the remote side is transmitted to the client side. It is a flowchart which shows the flow.

  FIG. 4 is a diagram showing an example of the SOH bitmap in the SDH frame, and the hatched portion in FIG. 4 shows bytes writable from the outside. In the figure, A1 and A2 are frame synchronization bytes, C1 is a frame identification byte, B1 is a relay section error monitoring byte, E1 is a relay section voice meeting byte, F1 is a relay section failure specifying byte, B2 is a section error monitoring byte, K1 , K2 are section switching control bytes, D1 to D3 are relay section data communication bytes, D4 to D12 are section data communication bytes, Z1 and Z2 are reserved bytes, and NU1 to NU38 are reserved bytes (Bytes reserved for National Use).

  FIG. 5 is a time chart when a link disconnection signal is added to the SOH in the Sonet / SDH frame. The link information control unit 14 in FIG. 1 generates a frame pulse by the 19.44 MHz clock in the apparatus in FIG. 5 (the clock counted by the in-apparatus clock counter 15 in FIG. 1), integrates the SOH start bit, and performs Sonet / A link disconnection signal is added to the link disconnection signal bit of the SDH and sent to the SDH termination unit 13 in FIG.

  Next, the operation of the transmission system according to the present invention will be described in detail with reference to FIGS.

  When the Gigabit Ethernet (registered trademark) frame from the client side reaches the Gigabit Ethernet (registered trademark) termination unit 11 (step S1 in FIG. 2), it is linked to the flow control bit in the Gigabit Ethernet (registered trademark) frame. The presence / absence of a disconnection signal is checked (step S2 in FIG. 2). If there is, a link disconnection signal is extracted to the link information control unit 14 (step S6 in FIG. 2), and the gigabit Ethernet (registered trademark) termination unit 11 is included. 10bit / 8bit conversion (step S3 in FIG. 2), and the format conversion unit 12 multiplexes Gigabit Ethernet (registered trademark) for each CH and converts it into a Sonet / SDH payload (step 2 in FIG. 2). S4), the SDH termination unit 13 adds SOH of Sonet / SDH (step S5 in FIG. 6).

  Thereafter, the SDH termination unit 13 and the link information control unit 14 are synchronized, a link disconnection signal is added to the Sonet / SDH SOH, and transmitted to the remote side (step S7 in FIG. 2).

  On the other hand, if there is no link disconnection signal in step S2 in FIG. 2, only steps S3, S4, and S5 are executed, and then step S7 is executed.

  Further, when a link disconnection signal is added to the SOH of Sonet / SDH in step S7 of FIG. 2, C1 (frame identification byte), E1 (relay section voice meeting byte), F1 (relay) in the SOH bitmap of FIG. Section failure specific byte), D1 to D3 (relay section data communication byte), D4 to D12 (section data communication byte), Z1, Z2 (reserved byte), NU1 to NU38 (Byte reserved for National Use) A link break signal bit is provided and added to the used byte.

  As for the addition timing when adding to the SOH of Sonet / SDH, as shown in the time chart of FIG. 5, a link disconnection signal is added while referring to the clock in the apparatus and synchronizing.

  On the other hand, when the Sonet / SDH frame from the remote side reaches the SDH termination unit 13 (step S11 in FIG. 3), the presence / absence of a signal in the link disconnection signal bit in the SOH frame of the Sonet / SDH is checked (step in FIG. 3). S12) If there is, the link information control unit 14 extracts the link disconnection signal (step S15 in FIG. 3), terminates the Sonet / SDH frame, and sends the Sonet / SDH payload to gigabit at the format conversion unit 12. Convert to Ethernet (registered trademark) frame, separate the Gigabit Ethernet (registered trademark) frame for each CH (step S13 in FIG. 3), and 8 bits / 10 bits at the Gigabit Ethernet (registered trademark) termination unit 11 Conversion is performed (step S14 in FIG. 3).

  Thereafter, the Gigabit Ethernet (registered trademark) termination unit 11 and the link information control unit 14 are synchronized, and an optical stop signal is added to the Gigabit Ethernet (registered trademark) flow information bit and transmitted to the client side (FIG. 3 step S16).

  On the other hand, if there is no signal in the link disconnection signal bit in step S12 in FIG. 3, only steps S13 and S14 are executed, and then step S16 is executed.

It is a block diagram of an example of the transmission system which concerns on this invention. It is a flowchart which shows a series of processes until the data frame received on the client side is transmitted to the remote side. It is a flowchart which shows a series of flows until the data frame received by the remote side is transmitted to the client side. It is a figure which shows an example of the bit map of SOH in an SDH frame. It is a time chart at the time of adding a link disconnection signal to SOH in a Sonet / SDH frame. It is a block diagram of an example of this kind of conventional transmission system. It is explanatory drawing which shows the bit map of the flow information bit in the flame | frame of Gigabit Ethernet (trademark). It is a figure which shows the detailed definition of the link disconnection signal in a flow bit. It is a figure which shows STM (Synchronous Transfer Mode) 1 frame structure (SOH and payload part) in SONET / SDH.

Explanation of symbols

10 Client-side transmission device 11, 21 Gigabit Ethernet (registered trademark) termination unit 12, 22 Format conversion unit 13, 23 SDH termination unit 14, 24 Link information control unit 15, 25 In-device clock counter
20 Remote transmission equipment
30 Transmission device 300, 301 Transmission path

Claims (9)

A transmission device that converts a Gigabit Ethernet (registered trademark) frame into a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame and transmits the frame.
Link disconnection signal transmitting means for extracting a link disconnection signal from the flow information bits in the Gigabit Ethernet (registered trademark) frame, adding the link disconnection signal to the SOH (Section Over Head) of the SONET / SDH frame, and transmitting it. A transmission apparatus comprising: A transmission apparatus that converts a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame into a Gigabit Ethernet (registered trademark) frame and transmits the frame.
A link that extracts a link disconnection signal added to SOH (Section Over Head) of the SONET / SDH frame and adds the link disconnection signal as an optical stop signal to the flow information bits in the Gigabit Ethernet (registered trademark) frame A transmission apparatus comprising a disconnection signal receiving means. The link disconnection signal transmission means synchronizes the timing of adding the link disconnection signal to the SOH and the timing of converting the Gigabit Ethernet (registered trademark) frame into the SONET / SDH frame. Item 2. The transmission device according to Item 1. The link disconnection signal receiving means extracts the link disconnection signal from the SOH, adds the link disconnection signal as an optical stop signal to the flow information bits in the Gigabit Ethernet (registered trademark) frame, and the SONET The transmission apparatus according to claim 2, wherein the transmission apparatus synchronizes the timing for converting the / SDH frame into the Gigabit Ethernet (registered trademark) frame. A transmission system comprising the transmission device according to claim 1 or 3, the transmission device according to claim 2 or 4, and a transmission path connected between the two transmission devices. A transmission method that converts a Gigabit Ethernet (registered trademark) frame into a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame and transmits the frame.
A link disconnection signal transmission step of extracting a link disconnection signal from a flow information bit in the Gigabit Ethernet (registered trademark) frame, adding the link disconnection signal to a SOH (Section Over Head) of the SONET / SDH frame, and transmitting it. The transmission method characterized by including. A transmission method for converting a SONET (Synchronous Optical Network) / SDH (Synchronous Digital Hierarchy) frame into a Gigabit Ethernet (registered trademark) frame and transmitting the frame.
A link that extracts a link break signal added to the SOH (Section Over Head) of the SONET / SDH frame and adds the link break signal as an optical stop signal to a flow information bit in the Gigabit Ethernet (registered trademark) frame A transmission method comprising a disconnection signal receiving step. The link disconnection signal transmission step synchronizes the timing of adding the link disconnection signal to the SOH and the timing of converting the Gigabit Ethernet (registered trademark) frame into the SONET / SDH frame. Item 7. The transmission method according to Item 6. The link disconnection signal receiving step extracts the link disconnection signal from the SOH and adds the link disconnection signal as an optical stop signal to the flow information bit in the Gigabit Ethernet (registered trademark) frame, and the SONET The transmission method according to claim 7, wherein a timing for converting an / SDH frame into the Gigabit Ethernet (registered trademark) frame is synchronized.

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