JP5300955B2 - Client signal accommodating multiplexing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a circuit scale in an OTN apparatus that multiplexes and transfers a client signal, such as Ethernet(R). <P>SOLUTION: In an apparatus that stores and multiplexes an asynchronous client signal in which an idle signal is defined, a specific client signal is taken as a reference on a transmission side and an idle signal of another client signal of the same type is inserted or removed to synchronize the client signal before transmission. On a reception side, a clock is reproduced from a specific client and the clock is distributed for the another client signal and the clock is distributed for the another client signal, thus sharing a PLL section on the reception side. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a client signal accommodating and multiplexing apparatus and method, and more particularly, to a client signal accommodating and multiplexing apparatus and method for high-frequency transfer of various client signals including Ethernet (registered trademark) with high reliability.

  With the rapid increase in Internet traffic, the use of Ethernet (registered trademark) is spreading. Ethernet (registered trademark), which is internationally standardized by IEEE, has increased its communication speed from the original 10M to 100M, 1G, and 10G. Ethernet (registered trademark) has a maximum transmission distance of 40 km and cannot be transmitted over long distances. There is OTN (Optical Transport Network) defined by ITU-T as an international standardization technology for transferring a wide range of client signals including Ethernet (registered trademark) with high reliability. By accommodating Ethernet (registered trademark) in OTN, long-distance transmission exceeding 40 km can be performed.

  FIG. 6 shows a block diagram of the prior art when multiplexing a plurality of client signals to OTN. The client signal accommodating and multiplexing apparatus shown in the figure has an OTN transmission side (upper part of the figure) and an OTN reception side (lower part of the figure). The OTN transmission side includes a plurality of client signal reception units 11 and each client reception unit 11. Each of the receiving unit 12, the multiplexing unit 13, the framer unit 14, and the OTN signal transmission unit 15 is connected, and the OTN reception side includes an OTN signal reception unit 16, a framer unit 17, a separation unit 18, a plurality of restoration units 20, A PLL (Phase Locked Loop) unit 19 connected to each restoration unit 20 and a client signal transmission unit 21 connected to each restoration unit 20 are configured.

  The client signal such as Ethernet (registered trademark) is O / E converted by the client signal receiving unit 11, and then the client signal is mapped to the ODU suitable for each client signal by the accommodating unit 12, and further the ODU is mapped to the ODTU Is done. BMP (Bit-synchronous Mapping Procedure), AMP (Asynchronous Mapping Procedure), GMP (Generic Mapping Procedure), etc. are used as mapping of the client signal to ODU. AMP, GMP, etc. are used for mapping ODU to ODTU. Multiplexer 13 multiplexes a plurality of ODTUs to form an upper ODU, and framer unit 14 adds an overhead process and an error correction code to form an OTU signal. Finally, an optical transmission signal is generated and transmitted by the OTN signal transmission unit 15. On the receiving side of the OTN signal, the signal received by the OTN signal receiving unit 16 is O / E converted to obtain an OTU signal. The framer unit 17 performs overhead processing of the OTU signal and decoding of the error correction code, and sends the ODU signal to the separation unit 18. Subsequently, the separation unit 18 separates the ODU signal into a plurality of ODTU signals. The separated ODTU signal is demapped by the restoration unit 20 and is demapped to the ODU signal, and further from the ODU signal to the client signal. The client signal transmission unit 21 performs E / O conversion on the client signal and transmits it.

  In recent years, with the widespread use of Ethernet (registered trademark), the OTN standard has been greatly expanded to emphasize Ethernet (registered trademark) transfer (for example, see Non-Patent Document 2). Specifically, ODU0 that accommodates GbE and ODU2e that accommodates 10 GbE are defined as new ODUs (Optical Channel Data Units). By multiplexing these ODUs in higher-order ODUs (for example, ODU3 and ODU4), economical wide area transfer of Ethernet (registered trademark) becomes possible.

"Interfaces for the Optical Transport Network (OTN)", ITU-T Recommendation G.709 / Y.1331 (03/2003). "Interfaces for the Optical Transport Network (OTN)", ITU-T Recommendation G.709 / Y.1331 Amendment 3 (04/2009).

  However, in the above conventional technique, there is a problem that the apparatus scale becomes large when a large number of client signals such as Ethernet (registered trademark) are accommodated in the OTN and multiplexed and transferred. For example, when 10 GbE is accommodated in ODU2e and multiplexed and transferred to ODU4, ODU2e can be multiplexed to ODU4 up to 10 times. Further, when GbE is accommodated in ODU0 and is multiplexed and transferred to ODU4, ODU0 can be multiplexed to ODU4 up to 80. Thus, in order to multiplex a large number of client signals, each functional block corresponding to the number of multiplexing is required.

  Here, paying attention to the clock recovery on the receiving side in FIG. 6 in the above prior art, even if the same type of client signal is multiplexed and transmitted, the clocks of the individual client signals are independent. It is necessary to provide a PLL unit 19 that performs clock recovery adjacent to each restoration unit 20. When 80 GbEs (ODU0) are multiplexed, 80 PLL units need to be provided. When 10 GbE (ODU2e) is multiplexed 10, 10 PLL units need to be provided, resulting in a large circuit scale.

  The present invention has been made in view of the above points, and provides a client signal accommodation multiplexing apparatus and method capable of reducing the circuit scale in an OTN apparatus for multiplexing and transferring client signals such as Ethernet (registered trademark). The purpose is to do.

  FIG. 1 is a principle configuration diagram of the present invention.

The present invention (Claim 1) includes a plurality of client signal receiving means for receiving a plurality of client signals, and mapping each client signal received by the plurality of client signal receiving means to an ODU signal. A plurality of accommodating means for mapping to the ODTU signal, a multiplexing means for multiplexing each ODTU signal mapped by the plurality of accommodating means to generate an ODU signal, and a first for generating an OTU signal from the ODU signal generated by the multiplexing means A transmission-side OTN device comprising framer means and OTN signal transmission means for generating an OTN signal from the OTU signal generated by the first framer means and sending it to the transmission line;
OTN signal receiving means for receiving an OTN signal from a transmission line, second framer means for generating an ODU signal by terminating the OTN signal received by the OTN signal receiving means, and a plurality of ODU signals generated by the second framer means Separating means for separating the ODTU signal, a plurality of restoring means for demapping the ODU signal from the plurality of ODTU signals separated by the separating means, and then demapping the client signal from the ODU signal, and the plurality of restoring means Receiving OTN device comprising a plurality of client signal transmitting means for transmitting a plurality of demapped client signals respectively;
A client signal accommodating and multiplexing device comprising:
The reception-side OTN device includes PLL (Phase Locked Loop) means and idle insertion / extraction means connected immediately after each of the restoration means other than one restoration means A among the plurality of restoration means,
The PLL means reproduces the clock of the client signal based on the clock of the ODTU signal inputted by the restoration means A, the clock of the demapped ODU signal and the mapping information given to the ODTU signal, and restores the clock. Distribute to all A and idle insertion and removal means,
The idle insertion / extraction means synchronizes all of the plurality of client signals by inserting an idle signal into or removing an idle signal from the input client signal based on a clock.

According to the present invention (Claim 2), a plurality of client signal receiving means for receiving a plurality of client signals respectively, each client signal received by the plurality of client signal receiving means is mapped to an ODU signal, and then the ODU signal is mapped. A plurality of accommodating means for mapping to the ODTU signal, a multiplexing means for multiplexing each ODTU signal mapped by the plurality of accommodating means to generate an ODU signal, and a first for generating an OTU signal from the ODU signal generated by the multiplexing means A transmission-side OTN device comprising framer means and OTN signal transmission means for generating an OTN signal from the OTU signal generated by the first framer means and sending it to the transmission line;
OTN signal receiving means for receiving an OTN signal from a transmission line, second framer means for generating an ODU signal by terminating the OTN signal received by the OTN signal receiving means, and a plurality of ODU signals generated by the second framer means Separating means for separating the ODTU signal, a plurality of restoring means for demapping the ODU signal from the plurality of ODTU signals separated by the separating means, and then demapping the client signal from the ODU signal, and the plurality of restoring means Receiving OTN device comprising a plurality of client signal transmitting means for transmitting a plurality of demapped client signals respectively;
A method for accommodating and multiplexing client signals in a device comprising:
The reception-side OTN device includes PLL (Phase Locked Loop) means and idle insertion / extraction means connected immediately after each of the restoration means other than one restoration means A among the plurality of restoration means,
The PLL means regenerates the clock of the client signal based on the clock of the ODTU signal inputted by the restoration means A, the clock of the demapped ODU signal, and the mapping information given to the ODTU signal, and restores the clock. Distribute to all A and idle insertion and removal means,
The idle insertion / removal means synchronizes all of the plurality of client signals by inserting an idle signal into or removing an idle signal from the input client signal based on the clock.

  As described above, according to the present invention, an idle signal of a client signal such as Ethernet (registered trademark) is inserted or removed to synchronize clocks between a plurality of client signals, thereby sharing a PLL and suppressing an increase in device scale. It becomes possible.

  A bit rate is defined for a client signal such as Ethernet (registered trademark). For example, GbE is 1.25 Gb / s ± 100 ppm, and 10 GbE is 10.3125 Gb / s ± 100 ppm. However, the clock of the signal sent from each client device to the OTN device is independent even if it is the same type of client signal, and it is usually different within the range of the above bit rate regulations. It is. Also, the bit rate of a client signal from the same device varies from moment to moment. By inserting or removing an idle signal with respect to such a client signal, it is possible to synchronize the clocks of a plurality of client signals and share the PLL.

It is a principle block diagram of this invention. It is a block diagram of the client signal accommodation multiplexing apparatus in the 1st Embodiment of this invention. It is a block diagram of the client signal accommodation multiplexing apparatus in the 2nd Embodiment of this invention. It is a block diagram of the client signal accommodation multiplexing apparatus in the 3rd Embodiment of this invention. It is a block diagram of the client signal accommodation multiplexing apparatus in the 4th Embodiment of this invention. It is a block diagram of the conventional client signal accommodation multiplexer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 2 shows the configuration of the client signal accommodating and multiplexing apparatus in the first embodiment of the present invention. In the figure, one clock domain is shown for each shaded area (that area is operating based on a reference oscillator).

  The client signal accommodating and multiplexing apparatus shown in the figure is composed of an OTN transmitting side (upper part of the figure) and an OTN receiving side (lower part of the figure). The OTN transmitting side includes a client signal receiving unit 101, an idle insertion / extraction unit 102, and an accommodating unit. 103, a multiplexing unit 104, a framer unit 105, and an OTN signal transmission unit 106. On the OTN reception side, an OTN signal reception unit 107, a framer unit 108, a separation unit 109, a PLL unit 110, a restoration unit 111, and a client signal transmission unit 114 Consists of.

The client signal receiving units 101 _{1 to} 101 ₃ receive client signals and perform O / E conversion. In the configuration of FIG. 2, the client signal receiving unit 101 ₁ receives the first client signal, the client signal receiving unit 101 ₂ receives the second client signal, the client signal receiving unit 101 _3, 3 It is assumed that the client signal is received. Among them, the client signal receiving unit 101 ₁ reproduces a clock, and outputs the idle insertion unit ₁₀₂ 1, 102 _2.

In the idle insertion / extraction units 102 ₁ and 102 ₂ , idle signals of other client signals (client signal reception units 101 ₂ and 101 ₃ ) are inserted or extracted by a clock regenerated from the first client signal of the client signal reception unit 101 ₁ . To synchronize client signals.

The accommodating units 103 _{1 to} 103 ₃ map a plurality of synchronized client signals to the ODU, and subsequently map the ODU to the ODTU. As a specific example of mapping, BMP, AMP, GMP, or the like is used for mapping a client signal to an ODU, and AMP, GMP, or the like is used for mapping an ODU to an ODTU, as in the prior art.

The multiplexing unit 104 multiplexes a plurality of ODTUs from the accommodation units 103 _{1 to} 103 ₃ , generates an ODU, and outputs the ODU to the framer unit 105.

  The framer unit 105 generates an OTU signal by adding overhead processing and an error correction code to the ODU input from the multiplexing unit 104.

  The OTN signal transmission unit 106 generates an optical transmission signal from the OTU signal and sends it to the transmission path.

  The receiving-side OTN signal receiving unit 107 receives an optical transmission signal and converts it into an electrical signal.

  Framer section 108 terminates the OTN signal and decodes the error correction code, and sends the ODU signal to demultiplexing section 109.

Separating section 109 separates the ODU signal into a plurality of ODTU signals and outputs them to restoring sections 111 _{1 to} 111 ₃ .

The restoration units 111 _{1 to} 111 ₃ demap the ODU signal from the ODTU signal, and further demap the client signal from the ODU signal. Here, PLL unit 110 reproduces the clock of the client signal based on clock and mapping information of the first ODTU signal and ODU signal in restoring unit 111 _1, distributes the clock to the restoring unit 111 ₁ to 111 ₃ . Mapping information refers to the contents of JC (Justification Control) bytes defined in the OPU overhead when using AMP for mapping, for example, and the contents of C _m and C _n bytes when using GMP. Yes. Since a plurality of client signals are synchronized between the client signal in the OTN apparatus (transmission side), it becomes possible to use the clock of the thus first ODTU signal and ODU signal in restoring unit 111 _1.

The client signal transmission units 114 _{1 to} 114 ₃ transmit the client signals acquired from the restoration units 111 _{1 to} 111 ₃ .

  With the configuration described above, the PLL unit 110 can be shared by the OTN device (reception side), and the number of PLL units can be greatly reduced as compared with the related art.

  For example, when 80 GbEs are accommodated in ODU0 and 80 × ODU0 is multiplexed and transferred to ODU4, the number of PLLs required on the receiving side can be reduced to one.

  As another example, when 10 10GbE are accommodated in ODU2e and 10 × ODU2e is multiplexed and transferred to ODU4, the number of PLLs required on the receiving side is reduced to one. Can do.

  Even if multiple client signals are mixed, if there is a relationship such that one clock is shared for each type, or the ratio of both can be expressed in a simple fraction between the bit rates of mixed client signals, It is possible to reduce the number of PLLs by dividing and multiplying a single clock for conversion. For example, when 8 GbEs are accommodated in ODU0 and 9 10GbE are accommodated in ODU2e, and all of them are multiplexed and transferred to ODU4, the clock is shared between the 8 GbEs in the OTN device (receiving side). In addition, by sharing the clock among the nine 10 GbEs, it is possible to reduce the number of PLLs that were required from 17 to two. Alternatively, the GbE bit rate is 1.25 Gb / s, the 10 GbE bit rate is 10.3125 Gb / s, and the relational expression 10.3125 = 33/4 × 1.25 holds between them, so either one of the clocks can be used. If the clock is converted and used for the other client signal, the OTN device (reception side) can be realized with only one PLL.

  The above describes the case of a client signal multiplexed on a single ODU signal (GbE or 10GbE multiplexed on a single ODU4 in the above example), but the PLL between clients accommodated in multiple ODUs Can also be shared. For example, when a plurality of ODU4 signals are received by wavelength multiplexing transmission, the PLL reduction effect is further enhanced by sharing the PLL among a plurality of GbEs or 10 GbEs multiplexed in each ODU4.

  The client signal that can use this method is not limited to Ethernet (registered trademark), but other client signals (for example, fiber channel) and encoding formats that use the same encoding format as Ethernet (registered trademark). Can be applied to a client signal in which an idle signal is defined for the purpose of absorbing a clock deviation or the like, and the above-described method can be used even when the client signals are mixedly accommodated.

[Second Embodiment]
FIG. 3 shows the configuration of the client signal accommodating and multiplexing apparatus in the second embodiment of the present invention. In the figure, the same components as those in FIG.

The configuration shown in FIG. 3 includes idle insertion / removal units 102 _{1 to} 102 ₃ between the client signal reception units 101 _{1 to} 101 ₃ and the accommodation units 103 _{1 to} 103 ₃ in the OTN device (transmission side). A local clock is input to each of the insertion / extraction units 102 _{1 to} 102 ₃ .

The difference from the first embodiment is that the local clock is used instead of the clock from the first client signal in the OTN device (transmission side). Each of the idle insertion / extraction units 102 _{1 to} 102 ₃ inserts / removes an idle signal of the client signal based on the clock to synchronize the client signals. In the first embodiment, the clock is lost when the first client signal is cut off, but such a situation can be avoided by using the local clock.

[Third Embodiment]
FIG. 4 shows the configuration of a client signal accommodating and multiplexing apparatus according to the third embodiment of the present invention. In the figure, the same components as those in FIG.

Configuration shown in FIG. 4, the transmission side is the same as that of the conventional art shown in FIG. 6, the receiving side, the second restoring unit 111 ₂ and the second between the client signal transmitting unit 114 _2, third idle insertion unit ₁₁₅ 1 between the restoring unit 111 ₃ and the third client signal transmitting unit 114 _3, 115 ₂ are provided, these idle insertion unit ₁₁₅ 1, 115 _2, the PLL unit 110 When the clock is input, the client signal idle signal is inserted or removed to synchronize the client signals.

Each client signal receiving unit 101 _{1 to} 101 ₃ on the transmitting side receives the client signal and performs O / E conversion.

Each of the accommodating units 103 _{1 to} 103 ₃ maps a plurality of client signals to ODU and ODU to ODTU.

The multiplexing unit 104 multiplexes a plurality of ODTUs output from the accommodating units 103 _{1 to} 103 ₃ to generate an ODU, and then transmits the ODU to the framer unit 105.

  The framer unit 105 generates an OTU signal by adding overhead processing and an error correction code to the ODU acquired from the multiplexing unit 104.

  The OTN signal transmission unit 106 generates an optical transmission signal from the OTU signal acquired from the framer unit 105 and sends it to the transmission path.

  The OTN signal receiving unit 107 on the receiving side receives the optical transmission signal and converts it into an electrical signal.

  The framer unit 108 terminates the OTN signal and decodes the error correction code, and sends the ODU signal to the separation unit 109.

Separating section 109 separates the ODU signal into a plurality of ODTU signals and outputs them to restoring sections 111 _{1 to} 111 ₃ .

Each restoration unit 111 _{1 to} 111 ₃ demaps the ODU signal from the ODTU signal and further demaps the client signal from the ODU signal. Here, PLL 110 ODTU signal and the clock and mapping information of the ODU signals to reproduce the clock of the client signal based on a first restoration unit 111 ₁ and the other recovery unit in the first restoration unit 111 ₁ 111 _2, 111 ₃ idle insertion unit ₁₁₅ 1 positioned downstream, 115 ₂ to distribute clock.

The idle insertion / extraction units 115 ₁ and 115 ₂ use the clock regenerated by the PLL unit 110 to insert / extract individual client signals to synchronize the client signals.

Thereafter, each client signal transmitting unit ₁₁₄ 1 to 114 ₃ transmits the client signals.

  With this configuration, the number of PLLs in the OTN device (reception side) can be greatly reduced.

[Fourth Embodiment]
FIG. 5 shows the configuration of a client signal accommodating and multiplexing apparatus in the fourth embodiment of the present invention. In the figure, the same components as those in FIG.

The configuration of the OTN device (reception side) shown in FIG. 5 includes idle insertion / extraction units 115 _{1 to} 115 ₃ provided between the restoration units 111 _{1 to} 111 ₃ and the client signal transmission units 114 _{1 to} 114 ₃ , respectively. This is different from the configuration shown in FIG.

The difference between the third embodiment, to use a clock generated by the PLL unit 110 to the clock and mapping information of the first ODTU signal and ODU signal in restoring unit 111 ₁ based on the OTN apparatus (receiving side) Instead, a local clock is used. Based on the clock, the idle insertion / extraction units 115 _{1 to} 115 ₃ insert / extract the idle signals of the client signals input from the restoration units 111 _{1 to} 111 ₃ to synchronize the client signals.

  In the third embodiment, the clock is lost when the first ODU signal is disconnected, but such a situation can be avoided by using the local clock.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims.

  The present invention provides a client signal such as a fiber channel adopting the same encoding format as that of Ethernet (registered trademark) as a client signal, or an idle signal for use in absorbing a clock deviation even if the encoding format is different. Can also be applied to client signals defined by the above-mentioned method, and it is possible to cope with the mixed accommodation of these client signals by the above-described method.

DESCRIPTION OF SYMBOLS 101 Client signal receiving means, client signal receiving part 101 ₁ 1st client signal receiving means 101 ₂ 2nd client signal receiving means 101 ₃ 3rd client signal receiving means 102 ₁ 1st idle insertion / extraction means, idle insertion / extraction part 102 ₂ Second idle insertion / removal means, idle insertion / removal part 102 ₃ Third idle insertion / removal means, idle insertion / removal part 103 accommodation means, accommodation part 103 _1st accommodation means 103 ₂ 2nd accommodation means 103 ₃ 3rd accommodation means 104 multiplexing means, multiplexing section 105 first framer means, framer section 106 OTN signal transmission means, OTN signal transmission section 107 OTN signal reception means, OTN signal reception section 108 second framer means, framer section 109 separation means, separation section 110 PLL unit, PLL unit 111 restoring means, the restoring unit 111 ₁ first restoring means 111 ₂ second Restoration means 111 ₃ third restoration means 114 client signal transmitting means, the client transmitting unit 114 ₁ first client signal transmitting unit 114 ₂ second client signal transmitter 114 ₃ third client signal transmitting unit 115 ₁ idle insertion unit 115 ₂ Idle insertion / removal part 115 ₃ Idle insertion / removal part

Claims (2)

A plurality of client signal receiving means for respectively receiving a plurality of client signals, and a plurality of accommodating means for mapping each client signal received by the plurality of client signal receiving means to an ODU signal and subsequently mapping the ODU signal to an ODTU signal Multiplex means for multiplexing each ODTU signal mapped by the plurality of accommodating means to generate an ODU signal, first framer means for generating an OTU signal from the ODU signal generated by the multiplex means, and the first framer A transmission-side OTN device comprising OTN signal transmission means for generating an OTN signal from the OTU signal generated by the means and sending it to the transmission line;
OTN signal receiving means for receiving the OTN signal from the transmission path, second framer means for generating an ODU signal by terminating the OTN signal received by the OTN signal receiving means, and an ODU signal generated by the second framer means Separating means for separating the ODU signal from the plurality of ODTU signals separated by the separating means, and subsequently demapping the client signal from the ODU signal, and the plurality of restoring means, A receiving-side OTN device comprising a plurality of client signal transmitting means for sending a plurality of client signals demapped by the restoring means, and
A client signal accommodating and multiplexing device comprising:
The reception-side OTN device includes PLL (Phase Locked Loop) means and idle insertion / extraction means connected immediately after each of the restoration means other than one restoration means A of the plurality of restoration means,
The PLL means regenerates the clock of the client signal based on the clock of the ODTU signal inputted by the restoration means A, the clock of the demapped ODU signal and the mapping information given to the ODTU signal, Distributing to all of the restoration means A and the idle insertion / extraction means,
The idle insertion / extraction means synchronizes all of the plurality of client signals by inserting an idle signal into or removing an idle signal from the client signal based on the clock. Client signal accommodating multiplexer. A plurality of client signal receiving means for respectively receiving a plurality of client signals, and a plurality of accommodating means for mapping each client signal received by the plurality of client signal receiving means to an ODU signal and subsequently mapping the ODU signal to an ODTU signal Multiplex means for multiplexing each ODTU signal mapped by the plurality of accommodating means to generate an ODU signal, first framer means for generating an OTU signal from the ODU signal generated by the multiplex means, and the first framer A transmission-side OTN device comprising OTN signal transmission means for generating an OTN signal from the OTU signal generated by the means and sending it to the transmission line;
OTN signal receiving means for receiving the OTN signal from the transmission path, second framer means for generating an ODU signal by terminating the OTN signal received by the OTN signal receiving means, and an ODU signal generated by the second framer means Separating means for separating the ODU signal from the plurality of ODTU signals separated by the separating means, and subsequently demapping the client signal from the ODU signal, and the plurality of restoring means, A receiving-side OTN device comprising a plurality of client signal transmitting means for sending a plurality of client signals demapped by the restoring means, and
A method for accommodating and multiplexing client signals in a device comprising:
The reception-side OTN device includes PLL (Phase Locked Loop) means and idle insertion / extraction means connected immediately after each of the restoration means other than one restoration means A of the plurality of restoration means,
The PLL means regenerates the clock of the client signal based on the clock of the ODTU signal inputted by the restoration means A, the clock of the demapped ODU signal, and the mapping information given to the ODTU signal. Distributing to all of the restoration means A and the idle insertion / extraction means,
The idle insertion / extraction means synchronizes all of the plurality of client signals by inserting an idle signal into or removing an idle signal from the input client signal based on the clock. Client signal accommodation multiplexing method.

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