JP2002354011A - Duplex switching system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To change an undefined length packet such as a PPP packet to SD
Even when mapping to an H frame, transmission path switching must be performed without causing loss or loss of synchronization of this undefined length packet. SOLUTION: An undefined length packet generated based on data from a predetermined device is inserted into a payload portion of the same SDH frame in accordance with a timing based on a phase of the SDH frame, and the SDH frame is used for transmission lines of a working system and a protection system. POS transmission device 9 and SDH transmission device 7 for transmitting the SDH frame transmitted through the working and protection transmission lines, and receiving means for reading an undefined length packet from the SDH frame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a duplex switching system, and more particularly to a duplex switching system in POS (Packet Over SONET) communication.

[0002]

2. Description of the Related Art Conventionally, broadband ISDN (B-ISD)
N: Broad band Integrated Services Digital Network)
SDH (Synchronous Digit)
al Hierarchy) based ATM (Asynchronous Tr
ansfer Mode (asynchronous transfer mode) has been proposed. In this communication method, ATM cells are mapped to SDH frames and transmitted. More specifically, ATM cells are sequentially inserted into a payload portion, which is an information carrying portion of an SDH frame, and transmitted (see Japanese Patent Application Laid-open No.
223129). FIG. 25 shows an example of the SDH frame into which the ATM cells are inserted. In FIG. 25, an SDH frame (STM (Synchronous Transport
A fixed length ATM cell is inserted into the payload portion of the (Module) -N frame).

[0003] As another communication method, SONE is used.
T (Synchronous Optical Network) / SDH
POS communication that realizes packet exchange by applying an int-to-point protocol has been proposed. In this POS, a PPP frame is stored in a payload portion of an SDH frame (or SONET frame) and transmitted. Strictly speaking, among the SDH networks, ITU-T
A network compliant with the specifications is called an SDH network, and a network compliant with the SONET specifications is a SON network.
The two are distinguished from each other by being referred to as ET, but the term “SDH” is used in common for both networks unless otherwise specified.

[0004] With respect to such a communication system, in order to maintain reliability at the time of occurrence of a failure, the active system / standby system (0
A dual switching system has been proposed in which a dual transmission line of (system / 1 system) is provided, and when the active system is in a failure state, instantaneous interruption switching to the standby system is performed. For example, with respect to the above-mentioned SDH-based ATM, APS (Automatic Protecti-Phone) using K1 (switch control byte) and K2 (section alarm indication byte) in the SOH byte in the SDH frame.
on Switching) has been proposed.

[0005]

On the other hand, with regard to the POS described above, a duplex switching system for switching between the active system and the standby system has not yet been proposed.
In this case, it can be considered that the above-mentioned switching system for SDH-based ATM may be applied as it is. However, while the ATM cell has a fixed length, the PPP frame has an undefined length. Cannot be applied as it is. That is, when an ATM cell is mapped to an SDH frame, the ATM cell is fixed in a certain area because the ATM cell has a fixed length. However, PPP in the SDH frame
When mapping a frame, the P
Since the PP frame area and the unused area are undefined, it is impossible to map an undefined length PPP frame. Further, even if mapping can be performed, a case may occur in which a PPP frame is mapped across two SDH frames.
There arises a problem that the P frame may be divided and lost, or the PPP frame may be out of synchronization.

[0006] The present invention has been made in view of the above,
It is an object of the present invention to provide a duplex switching system that can perform transmission path switching without causing loss or loss of synchronization of an undefined length packet such as a PPP packet when mapping the packet to an SDH frame. And

[0007]

In order to achieve the above object, a duplex switching system according to the present invention comprises: a duplex switching system for transmitting and receiving an SDH frame via a working system and a protection system; An undefined length packet generated based on data from a predetermined device is inserted into the payload of the same SDH frame in accordance with the timing based on the phase of the SDH frame, and the SDH frame is transmitted to the working and protection transmission lines. A transmission means, and a receiving means for receiving the SDH frame transmitted via the working and protection transmission lines and reading the undefined length packet from the SDH frame.

According to the present invention, the transmitting means converts the indefinite-length packet generated based on the data from the predetermined device into
The SDH frame is inserted into the payload of the same SDH frame in accordance with the timing based on the phase of the DH frame, and the SDH frame is transmitted to the working and protection transmission lines. The SDH frame transmitted as described above is received, and the undefined length packet is read from the SDH frame.

[0009] In the duplex switching system according to the next invention, in the above invention, the transmission means includes transmission-side packet processing means for writing a sequence number to the undefined length packet, and the reception means includes SDH frame storage means for storing the SDH frame transmitted via the transmission line of the system and the protection system, and transmitted through the transmission line of the working system when a predetermined transmission line failure or a switching request is issued. Sequence number of the SDH frame, and the SDH frame transmitted through the protection transmission line.
Switching means for switching between the active system and the standby system in units of SDH frames by detecting the sequence numbers of the respective frames and reading out the SDH frames from the SDH frame storage means when the sequence numbers match each other. And characterized in that:

According to the present invention, the transmitting side packet processing means writes the sequence number into the undefined length packet,
H frame storing means stores the SDH frame transmitted through the working and protection transmission lines, and the switching means, when a predetermined transmission path failure or a switching request is received, transmits the SDH frame. SD transmitted via the road
The sequence number of the H frame and the sequence number of the SDH frame transmitted through the protection transmission line are detected, respectively. When the sequence numbers match each other, the SDH frame storage means detects the sequence number.
By reading the DH frame, the working system and the standby system are switched over in SDH frame units.

[0011] In the duplex switching system according to the next invention, in the above invention, the transmission-side packet processing means of the transmission means rewrites a specific header included in the undefined-length packet to the sequence number. It is characterized by the following.

According to the present invention, the transmission-side packet processing means rewrites the specific header included in the undefined-length packet to the sequence number.

[0013] In the duplex switching system according to the next invention, in the above invention, the reception means rewrites the header rewritten by the transmission packet processing means to a predetermined normal header. Means are provided.

According to the present invention, the receiving-side packet processing means rewrites the header rewritten by the transmitting-side packet processing means to a predetermined normal header.

[0015] In the duplex switching system according to the next invention, in the above invention, the transmission-side packet processing means of the transmission means rewrites a predetermined area of the payload portion of the indefinite-length packet to the sequence number. In addition, an area after the predetermined area of the unfixed-length packet is shifted backward by the predetermined area.

According to this invention, the transmitting side packet processing means rewrites the predetermined area of the payload portion of the undefined length packet with the sequence number, and rewrites the area after the predetermined area of the undefined length packet to the predetermined area. It shifts backward by the area.

In the duplex switching system according to the next invention, in the above invention, the reception means deletes the sequence number of the predetermined area rewritten by the transmission-side packet processing means and transmits the variable-length packet. And a receiving side packet processing means for shifting an area after the predetermined area forward by the predetermined area.

According to the present invention, the receiving-side packet processing means deletes the sequence number of the predetermined area rewritten by the transmitting-side packet processing means, and deletes the area of the indefinite-length packet after the predetermined area. It shifts forward by a predetermined area.

In the duplex switching system according to the next invention, a transmitting means and a receiving means are arranged in each node,
In a duplex switching system for transmitting and receiving H frames via working and protection transmission paths, the receiving means includes:
If a failure has occurred in the active transmission line on which the self side is the receiving side, a self-addressed transmission path alarm is output to the transmission means of the same node, or a transmission path alarm is transmitted from the transmission means of the opposite node. In the case, the opposite transmission path alarm is output to the transmission means of the same node, and the transmission means is notified of the self-addressed transmission path alarm from the reception means of the same node,
When a transmission path alarm is transmitted to the receiving means of the opposing node via the transmission path in the direction opposite to the transmission path in which the failure has occurred, or when the opposing transmission path alarm is notified from the receiving means of the same node. The present invention is characterized in that the active transmission line in which the failure has occurred is switched to the backup transmission line.

According to the present invention, when a failure has occurred in the active transmission line on which the receiving unit is the receiving side, the receiving unit outputs a transmission line alarm addressed to itself to the transmitting unit of the same node, or When receiving the transmission line alarm from the transmission unit of the node, the communication unit outputs an opposite transmission line alarm to the transmission unit of the same node, and the transmission unit notifies the transmission line alarm of the same node from the reception unit of the same node. In this case, the transmission path alarm is transmitted to the receiving means of the opposing node via the transmission path in the direction opposite to the transmission path in which the fault has occurred, or the opposing transmission path alarm is issued from the receiving means of the same node. When notified, the transmission line of the active system in which the failure has occurred is switched to the transmission line of the protection system.

[0021] In the duplex switching system according to the next invention, in the above invention, the transmission means includes an address search means for searching for an address from each indefinite-length packet generated based on data from a predetermined device; Switching means for selecting a transmission path for transmitting an indefinite-length packet based on the address searched by the address search means is provided.

According to the present invention, the address search means includes:
The transmitting means searches for an address from each of the undefined length packets generated based on data from the predetermined device, and the selector determines a transmission path for transmitting the undefined length packet based on the address searched by the address searching means. To choose.

[0023] In the duplex switching system according to the next invention, in the above invention, when the transmission means is notified of the transmission path alarm addressed to itself by the reception means of the same node, the transmission means is included in the undefined length packet. A specific header is rewritten to a predetermined control code, and the undefined-length packet rewritten to the control code is transmitted to the receiving means of the opposite node as the transmission path alarm.

According to the present invention, when the transmission means is notified of the transmission path alarm addressed to itself from the reception means of the same node, the transmission means rewrites a specific header included in the undefined length packet to a predetermined control code, and The variable length packet rewritten to the control code is transmitted to the receiving means of the opposite node as the transmission path alarm.

In the duplex switching system according to the next invention, in the above-mentioned invention, in the above-mentioned invention, the receiving means, when the control code is included in the indefinite-length packet transmitted from the transmitting means, A transmission path alarm is output to the transmission means of the same node, and the header rewritten by the transmission side packet processing means is rewritten to a predetermined normal header.

According to the present invention, when the control code is included in the undefined length packet transmitted from the transmitting means, the receiving means outputs the opposite transmission path alarm to the transmitting means of the same node. In addition, the header rewritten by the transmission side packet processing means is rewritten to a predetermined normal header.

[0027] In the duplex switching system according to the next invention, in the above invention, when the transmission means is notified of the self-addressed transmission path alarm from the reception means of the same node, the alarm included in the SDH frame is included. The transmission path alarm is transmitted using a transfer byte.

According to the present invention, when the transmission means is notified of the transmission line alarm addressed to itself by the reception means of the same node, the transmission means transmits the transmission line alarm using the alarm transfer byte included in the SDH frame. I am trying to do it.

[0029] In the duplex switching system according to the next invention, in the above invention, the receiving means performs an FCS check on the indefinite-length packet transmitted from the transmitting means, and an FCS based on the result of the FCS check. It is characterized in that an error alarm is output as the above-mentioned transmission line alarm addressed to itself.

According to the present invention, the receiving means transmits the FCS to the indefinite-length packet transmitted from the transmitting means.
Inspection is performed, and an FCS error alarm based on the result of the FCS inspection is output as the transmission line alarm addressed to the self.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a duplex switching system according to the present invention will be described below in detail with reference to the accompanying drawings.

Embodiment 1 First, the formats of an SDH frame (STM-N frame) and a PPP frame which is an undefined length packet used in the duplex switching system according to the first embodiment of the present invention will be described. The configuration and operation of the receiving device as the receiving means will be described.

FIG. 1 is a diagram showing a format of an SDH frame transmitted and received in the first embodiment. In FIG. 1, the SDH frame is roughly represented by SOH (Sec
and a payload section. Of these, SOH
Is an area mainly for transmitting a signal for frame synchronization and operation and maintenance of a transmission signal, and is a (9 × N) column (1 column = 1).
byte). This SOH has three rows of RSO
H (relay section overhead), one row of AU pointer, and five rows of MSOH (multiplex section overhead). POH is a status information signal area for operation and maintenance, and is composed of 9 rows and N columns. The payload section is a valid data area and is composed of 9 rows (260 × N) columns. This payload part is used as a PPP frame area to which one or a plurality of PPP frames are mapped.
Free area where no P frame exists Flag (0x7e in hexadecimal)
Filled with.

The PP to be mapped to this SDH frame
As the P frame, a frame having a control code different from a normal PPP frame is used. First, normal PPP
The frame will be described. FIG. 2 is a diagram showing a format of a normal PPP frame. In FIG. 2, the PPP frame includes a flag sequence 1, a header 2, an IP packet (or PPP information) 3, and a trailer 4.
(FCS: Frame Check Sequence) and a flag sequence 5 are sequentially provided. Of these, the flag sequences 1 and 5 are arranged at the beginning and end of the PPP frame as shown in the figure, and are a binary number 01111110 (0x7e in hexadecimal). The header 2 has an address 2-1,
It comprises a control code 2-2 and a protocol 2-3. Among them, the address 2-1 is a single octet and is 11111111 (0xff in hexadecimal) in binary.
The control code 2-2 is a single octet,
It is 00000011 in binary (0x03 in hexadecimal). The trailer 4 is a byte for error checking by the FCS.
The free space 6 other than the PPP frame configured as described above, that is, the portion other than the portion surrounded by the flag sequences 1 and 5 is filled with a flag (0x7e in hexadecimal).

Next, the PPP frame to be mapped will be described. FIG. 3 is a diagram showing a format of a PPP frame to be mapped. In FIG. 3, P
The PP frame is the control code 2 of the PPP frame in FIG.
-2 with control code 2-4 (00000100 (16
The configuration is replaced with 0x04)), and the other configurations are the same.

The use of such a PPP frame is as follows.
For the following reasons. That is, the control code 2-2,
The area 2-4 is originally used in the protocol area before the POS transmission processing, and is not used in the POS processing and the SDH processing. Therefore, in the first embodiment, by using the control code 2-4 as the sequence area of the PPP frame, it is possible to perform the frame phase collation at the time of reception, thereby constructing a duplex switching system.

Next, the transmitting device will be described. FIG.
FIG. 3 is a block diagram showing a configuration of a transmitting apparatus according to the first embodiment. In FIG. 4, the transmission device is configured to include a system 0 SDH transmission device 7, a system 1 SDH transmission device 8, and a POS transmission device 9. The generated PPP frames are mapped to SDH frames in the SDH transmitting devices 7 and 8, and transmitted to the 0-system and 1-system transmission paths.

The configuration of the POS transmission device 9 will be described in more detail. FIG. 5 is a block diagram showing the configuration of the POS transmission device 9 of FIG. 4 in detail. In FIG. 5, a POS transmission device 9 includes a control code detection rewriting unit 10 as a transmission side packet processing unit, an FCS generation unit 11,
It comprises a buffer memory 12, a write control unit 13, a write counter 14, a read counter 15, a phase comparison unit 16, a read control unit 17, a byte stuff 18, and a scrambler 19.

The POS transmission device 9 configured as described above
Works as follows. First, a protocol processing unit (third layer processing unit) (not shown) on the upstream side of the POS transmission device 9
And the control code enable pulse are input to the control code detection rewriting unit 10 of the POS transmission device 9. Then, the control code detection rewriting unit 10 detects the control code 2-2 from the input data based on the control code enable pulse. Then, the control code 2-2 is changed to the control code 2-
Rewrite to 4. Specifically, the sequence numbers of the PPP frames from 0x00 to 0xff are written in the area of the control code 2-2.

Then, the FCS generation unit 11 calculates the FCS of the PPP frame, and
After insertion into the S byte, the PPP frame is stored in the buffer memory 12. Then, the SDH transmission devices 7 and 8
From the buffer memory 12 based on the clock from
Read the PP frame. And the byte staff 18
, The flag sequence 1 is detected, and if the flag sequence 1 is found, the PPP frame following the flag sequence 1 is converted into a 2-byte numerical code. Output to the transmission devices 7 and 8. This is PPP
Transmission of the frame is completed.

Here, when transmitting the PPP frame, the control of the timing of transmitting the PPP frame to the SDH transmitters 7 and 8 is performed as follows. That is,
Conceptually, when the maximum length of the PPP frame after byte stuffing is L, when the remaining area of the payload section when mapping the PPP frame to the payload section of the SDH frame becomes L or less, the following is performed. To suspend the transmission of the PPP frame and map the next PPP frame from the beginning of the next SDH frame,
What is necessary is just to restart transmission of a P frame.

The specific control of the transmission timing is performed by the read control unit 17 of the buffer memory 12 shown in FIG.
This can be performed by constantly monitoring the phase of the SDH frame. FIG. 6 is a block diagram showing the configuration of the read control unit 17 of FIG. 5 in detail. 6, the read control unit 17 includes a frame counter 20 and a packet enable generation unit 21. In such a configuration, the frame counter 20
Monitors the SDH frame pulse, counts the SDH frame pulse, and performs timing control in the packet enable generation unit 21 based on the value. That is, the area length of the payload portion of the SDH frame is set to Ls
Then, when the value of the frame counter 20 is (Ls-L) to Ls, the frame counter 20 cannot map the next PPP frame in the remaining area of the payload section (the PPP frame is divided). ), The reading of the PPP frame is temporarily stopped, and when the value returns to 0, the reading of the PPP frame is restarted. In this control, the packet enable generation unit 21 generates a signal that is disabled when the value of the frame counter 20 is (Ls-L) to Ls, and outputs this signal to the read counter 15 in FIG. This can be performed by controlling the read counter 15.

Next, the receiving apparatus will be described. FIG.
FIG. 3 is a block diagram illustrating a configuration of a receiving device. This FIG.
, The receiving devices are the 0-system SDH receiving devices 22, 1
SDH receiver 23, buffer memories 24, 25,
Control code detection units 26 and 27, control code collation unit 28,
It is provided with a selector 29 as a switching means and a POS receiving device 30. The data and frame pulses transmitted from the 0-system and 1-system transmission lines are roughly transmitted to the SDH receiving devices 22 and 23. And sends one of them to the POS receiver 30.

The configuration of the POS receiver 30 will be described in more detail. FIG. 8 shows the POS receiver 3 of FIG.
FIG. 3 is a block diagram showing a configuration of a 0. In FIG. 8,
The POS receiver 30 includes a descrambler 31, a byte destuffer 32, an FCS inspection unit 33, a buffer memory 34 as an SDH frame storage unit, and a write counter 3
5. Read counter 36, phase comparing section 37, and control code rewriting section 38 as a receiving-side packet processing means
It is provided with.

The receiving apparatus thus configured operates as follows. First, the SDH frame transmitted through the 0-system and 1-system transmission paths is transmitted to the SDH receiver 22,
After termination of SDH reception at 23, respectively, the data is temporarily stored in buffer memories 24 and 25. Then, in the control code detection units 26 and 27, the control code 2-4 in the PPP frame existing in the payload of the received SDH frame is used.
Is detected. Then, in the control code collating unit 28,
The control code 2-4 is checked, and the control code 2-4 in the PPP frame transmitted through the system 0 and the control code 2-4 in the PPP frame transmitted through the system 1 are checked.
Are matched with each other, the buffer memories 24, 2
5 are simultaneously read and transmitted to the selector 29.

The selector 29 receiving this transmission performs selective switching between the 0 system and the 1 system based on the switching command. Specifically, when the control code matching unit 28 detects a match of the sequence numbers as described above, the SDH receiving device 2
In steps 2 and 23, it is determined whether or not there is a switching command. This determination can be made based on the contents of the K1 and K2 bytes of the SOH included in the SDH frame. When the switching command is indicated, the PPP frame read from the switching destination buffer memory (for example, the first system buffer memory 25) indicated by the switching instruction is selected, and the PPP frame is read. Output to the POS receiver 30.

In the POS receiving apparatus 30 receiving this output, the descrambler 31 in FIG. 8 descrambles the PPP frame, and in the byte destuff 32, the byte-stuffed data in the byte stuff 18 of the POS transmitting apparatus 9 Is byte destuffed to return to the original data. Then, in the FCS inspection unit 33,
The FCS inserted is checked by the POS transmission device, and the PPP frame is temporarily stored in the buffer memory 34. Further, the control code rewriting unit 38 rewrites the control code 2-4 in the PPP frame read from the buffer memory 34 into a normal control code 2-2. Then, this PPP frame is output to a protocol processing unit (not shown) at the subsequent stage of the receiving device. This completes the receiving operation. Alternatively, when a match between sequence numbers is detected by the control code collating unit 28, when an external switching signal is given to the selector 29 or the like, at the timing of the K1 and K2 bytes detected by the SDH receiving devices 22 and 23, That is, switching between the 0 system and the 1 system is performed in units of SDH frames.

In the first embodiment, since the receiving apparatus can synchronize based on the control code 2-4 in the PPP frame, the transmission path switching between the 0-system and the 1-system is performed in SDH frame units. In this case, P
Loss of the PP frame and loss of synchronization can be prevented.

Embodiment 2 Next, a second embodiment of the present invention will be described. The second embodiment relates to a duplex switching system that switches between the 0-system and the 1-system by inserting a sequence number without rewriting the control code. That is, in Embodiment 1 described above, after the POS transmission device 9 rewrites the control code 2-2 in the PPP frame to the control code 2-4,
In the POS receiving apparatus 30, the control code 2-4 is returned to the original control code 2-2, whereas in the second embodiment, the control code 2-
2 is inserted without rewriting, and the sequence number is deleted upon reception. Configurations and operations not particularly described are the same as those in the first embodiment.

First, the format of the PPP frame to be mapped will be described, and then the configurations and operations of the transmitting device and the receiving device will be described. FIG. 9 is a diagram showing a format of a PPP frame according to the second embodiment. In FIG. 9, the PPP frame is configured by adding a sequence number (0x00 to 0xff in hexadecimal) 39 to the first byte in the information area following the header 2; Is the same as Since the PPP frame is a flag sequence, the sequence number 39 is used for the headers 1 and 2.
It consists of codes other than 01111110 (hexadecimal 0x7e).

Next, the POS transmission device 9 will be described. FIG. 10 is a block diagram illustrating a configuration of the POS transmission device 9. In FIG. 10, the POS transmitting device 9
The control code detection rewriting unit 10 of the POS transmission device 9 in FIG.
In place of the byte stuff 18, a control code detection unit 40 and a byte stuff (SN generation unit) 41 as a packet processing unit on the transmission side are provided.

The POS transmission device 9 configured as described above
Works as follows. First, the operation until the input data is read from the buffer memory 12 is almost the same as in the first embodiment. However, the control code detection unit 4
At 0, the control code 2-2 is not detected and rewritten. After that, the byte stuff (SN generation unit) 41 detects the flag sequence 1, and when the flag sequence 1 exists, the PPP frame following the flag sequence 1 is converted into a 2-byte numerical code.
At this time, the byte stuff (SN generation unit) 41
The sequence number 39 is inserted at the head of the information area of the PPP frame, and the subsequent bytes are shifted backward by the insertion area of the sequence number 39 (here, one byte). Thereafter, the same operation as in the first embodiment is performed.

Next, the receiving device will be described. FIG.
FIG. 9 is a block diagram showing a configuration of a receiving apparatus according to the second embodiment. 11, the receiving apparatus is configured to include SN detecting sections 42 and 43 and an SN checking section 44 instead of the control code detecting sections 26 and 27 and the control code checking section 28 of the receiving apparatus in FIG. .

The configuration of the POS receiver 30 of this receiver will be described in more detail. FIG.
FIG. 2 is a block diagram showing a configuration of an OS receiving device 30 in detail. In FIG. 12, the POS receiver 30 is
Instead of the byte destuff 32 and the control code rewriting unit 38 of the POS receiving device 30, a byte destuff (SN removing unit) 45 and a control code insertion unit 46 as packet processing means on the receiving side are provided.

The receiving apparatus thus configured operates as follows. First, the SDH frames transmitted via the transmission lines of the 0-system and the 1-system are stored in the buffer memories 24 and 2.
5 is the same as that of the first embodiment. After that, the SN detectors 42 and 43 detect the sequence number 39 in the PPP frame existing in the payload of the received SDH frame. Thereafter, the SN collating unit 44 checks the sequence number 39 in the PPP frame stored in the buffer memories 24 and 25, and checks the sequence number 39 in the PPP frame transmitted through the system 0 and the sequence number 39 in the PPP system. If the sequence number 39 in the sent PPP frame matches each other, reading from the buffer memories 24 and 25 is performed simultaneously, and the result is transmitted to the selector 29. And the selector 29
In the above, when the matching of the sequence number 39 is detected by the SN collation unit 44 as described above, a PPP frame is selected as in the first embodiment, and one of the PPP frames is output to the POS receiver 30.

In the POS receiving device receiving this output, the descrambler 31 in FIG. 12 descrambles the PPP frame. And byte destuff (S
N remover) 45, the sequence number 39 is
If it is located at the beginning of the information area of the frame, the sequence number 39 is deleted and the sequence number 3 is deleted.
The 9th and subsequent bytes are shifted forward by the deletion area of the sequence number 39 (here, 1 byte). On the other hand, if the sequence number 39 is located at a position other than the head of the information area, the data stuffed by the byte stuff (SN generation unit) 41 of the POS transmission device 9 is byte-destuffed to the original data. return. After that, in the FCS inspection unit 33, the FCS inserted by the POS
Is checked, and this PPP frame is stored in the buffer memory 34. In the control code insertion unit 46, the control code 2 used in the protocol processing unit is added to the PPP frame read from the buffer memory 34.
Insert -2. Alternatively, in the SN matching unit 44, 0
When a match between the sequence numbers 39 of the system and the system 1 is detected,
When a switching signal from the outside is given, switching between the 0 system and the 1 system is performed at the timing of the K1 and K2 bytes detected by the SDH receiving devices 22 and 23, that is, in SDH frame units.

In the second embodiment, at the time of memory reading in the receiving apparatus, synchronization can be established based on the sequence number 39, so that the transmission path can be switched between the working system and the protection system in SDH frame units. In this case, P
Loss of the PP frame and loss of synchronization can be prevented.

Embodiment 3 FIG. Next, a third embodiment of the present invention will be described. The third embodiment is different from the system in which switching is performed in units of SDH frames as in the first and second embodiments, and relates to a duplex switching system in which switching is performed in units of POS frames. Configurations and operations not particularly described are the same as those in the first embodiment.

First, the configuration of the inter-node transmission line according to the third embodiment of the present invention will be described, and then the configuration and operation of a transmitting device as a transmitting device and a receiving device as a receiving device will be described. FIG. 13 is a diagram showing an example of a mode of an inter-node transmission line according to the third embodiment. In FIG. 13, the transmitting device 47 is provided to the node # 1.
The receiving device 50 and the receiving device 48 and the transmitting device 49 are arranged in the node # 2. And the transmitting device 4
Transmission path from 7 to receiving device 48 and transmitting device 4
The transmission paths from 9 to the receiving device 50 are duplicated in 0 system and 1 system, respectively.

Here, basically, the POS transmission system is a one-to-one protocol, and takes a bidirectional form between nodes. In this POS transmission method, similarly to communication in a higher-order packet layer, it is possible to refer to an IP address by address search, select a transmission path to be transmitted for each of the IP addresses, and transmit. That is, in a normal state, it is possible to transmit a PPP frame via a desired transmission path regardless of the working system and the protection system. Therefore, if the transmission side can grasp that the transmission path has deteriorated, the transmission side can select a transmission path that has not deteriorated and transmit the PPP frame by the control of the transmission side. Can be switched. In other words, in order to perform switching on a PPP frame basis, it is necessary for the transmission side to grasp that the transmission path has deteriorated.

The switching operation necessary for the transmission side to know that the deterioration has occurred will be described. Here, as shown in FIG. 13, an example of a switching operation when a failure such as deterioration occurs in the transmission line of system 0 from node # 1 to node # 2. In this case, first, the receiving device of the fault occurrence system, that is, the receiving device 48 of the node # 2 detects the transmission line fault of the zero system. Then, the receiving device 48 notifies the transmitting device of the same node as itself, that is, the transmitting device 49 of the node # 2, of the transmission path failure of the system 0 by a predetermined alarm (transmission line alarm addressed to itself). The transmitting device 49 that has received this notification notifies the receiving device of the opposite node, that is, the receiving device 50 of the node # 1, of the transmission path failure of the system 0. Then, the receiving device 50 issues a predetermined alarm (0) to the transmitting device of the same node as itself, that is, the transmitting device 47 of the node # 1 for the transmission line failure of the 0 system.
System's opposite transmission path alarm). The transmitting device 47 of the node # 1 sends the 0
It is possible to recognize the occurrence of a failure in the transmission line of the system and switch the transmission line to the first system. By such an operation, switching between the 0 system and the 1 system can be performed on the transmission side, and it is possible to perform switching on a PPP frame basis.

In practice, in many cases, the bidirectional transmission lines of the same system are the same, so that not only the one-way transmission line of system 0 as described above but also, for example, as shown in FIG. , 0 in both directions.
In such a case, the transmission device 49 of the node # 2 notifies the reception device 50 of the node # 1 of the transmission path failure of the system 0 using the transmission path of the system 1 instead of the system 0. Just do it.

Next, a system configuration and operation for performing such a switching operation will be described in more detail.
First, the configurations of the transmission devices 47 and 49 will be described in more detail. FIG. 15 is a block diagram illustrating a configuration of the transmission devices 47 and 49. In FIG. 15, the transmitting device 47,
Reference numeral 49 denotes a POS transmission device 51, an address search unit 52 as an address search unit, a transmission system selection control unit 53, a selector 54 as a switching unit, and a 0-system SDH transmission device 5.
5 and a first-system SDH transmission device 56.

Next, the operation of the transmitting devices 47 and 49 will be described. First, the POS transmission device 51 converts the data input from the protocol processing unit into a PPP frame and transmits the PPP frame to the selector 54. At the same time, this PPP
The frame is transmitted to the address search unit 52. The address search unit 52 searches for an IP address in a PPP frame and stores the IP address in a storage area (not shown). Thereafter, the transmission system selection control unit 53 selects a transmission path of the PPP frame for each IP address. When selecting this transmission path, in normal times (when there is no deterioration),
As shown in FIG. 16A, either the system 0 or the system 1 is selected according to the IP address, and the selector 54 is selected so that transmission is performed via a transmission path according to the selection result.
Control.

Here, consider a case where a failure such as deterioration occurs in the transmission path. For example, as shown in FIG. 13, when the transmission line of system 0 from the transmission device 47 to the reception device 48 is deteriorated, the reception device 48 detects the deterioration of the transmission line of system 0, and the same node # 2 as its own. And outputs a transmission line alarm for the system 0 to the transmission device 49. This self-addressed transmission line alarm is shown in FIG.
5, the POS data is input to the POS transmission device 51 and the transmission system selection control unit 53 of the transmission device 49. Upon receiving this input, the transmitting device 49 generates a 0-system degradation packet for notifying the opposing node of the 0-system degradation, and sends this to the opposing receiving device via the 0-system or 1-system transmission path. Send to 50. Here, the degraded packet of system 0 is shown in FIG.
As shown in (5), the control code detection rewriting unit 10 (see FIG. 5) of the POS transmission device 51 generates the control code 2-2 of the PPP frame by rewriting the control code 2-2 of the PPP frame to a predetermined 0-system degradation control code 57.

On the other hand, the receiving apparatus 50 receiving the 0-system deteriorated packet determines that the packet is a 0-system deteriorated packet based on the fact that the 0-system deterioration control code 57 is included in the packet. , And transmits an opposing transmission path alarm to the transmission device 47 of the same node # 1 as the self. The opposite transmission path alarm is input to the transmission system selection control unit 53 of the transmission device 47. Transmitter 4 receiving this input
The transmission system selection control unit 53 changes transmission path selection. Here, since the 0 system is deteriorated, all 1 systems are selected as shown in FIG. Then, the transmission system selection control unit 53 controls the selector 54 so that transmission is performed via the transmission path according to the selection result. By such an operation, the system 0 can be switched to the system 1.

When the system 1 is deteriorated instead of the system 0, in the above description of the operation, the word "system 0" is replaced with the word "system 1".
Can be switched from system 1 to system 0. In this case, the control code detection rewriting unit 10 rewrites the control code 2-2 of the PPP frame into a predetermined one-system deterioration control code 58 as shown in FIG. Generate a packet. In the case of 1-system degradation, the transmission system selection control unit 53
As shown in (c), all 0 systems are selected.

Next, the configuration and operation of the receivers 48 and 50 will be described in more detail. FIG. 18 is a block diagram showing a configuration of receiving apparatuses 48 and 50 according to the third embodiment. In FIG. 18, receiving devices 48 and 50
Are the 0-system SDH receiver 59, the 0-system POS receiver 60, the 0-system IP forwarding 61, and the 1-system SD
H receiver 62, 1-system POS receiver 63, 1-system I
It comprises a P forwarding 64 and an IP switching 65.

The receiving devices 48 and 50 thus configured
Works as follows. First, the receiving devices 48 and 50
SDH receiving apparatuses 59 and 62 receive and terminate SDH frames, respectively. Then, the SDH receiving devices 59 and 62
Determines whether there is a failure such as deterioration of the transmission path based on the received SDH frame. Here, when a failure has occurred, the SDH receivers 59 and 62 send the transmission path alarm addressed to themselves to the POS transmitter 51 and the transmission system selection controller 53 of the transmitters 47 and 49 of the own node for each system. Send.

On the other hand, when no failure has occurred, the POS receiving devices 60 and 63 of the 0-system or 1-system terminate the POS reception of the SDH frame. This POS receiver 6
0 and 63 determine whether or not a degraded packet is included in the received packet. Then, when the degraded packet is included, the opposite-side transmission path alarm of each system is transmitted to the transmission system selection control unit 53 of the transmission devices 47 and 49 of the own node. The POS reception-terminated packet is output to the IP forwarding 61 and 64, so that the IP forwarding process is performed. Further, the IP switching 65 performs the IP switching. This IP switching is performed irrespective of whether or not deterioration has occurred in the 0-system or 1-system transmission path. In a general packet receiving device, when transmission line degradation does not occur, the 0-system and 1-system packet multiplexing is performed with reference to the routing table of the packet receiving device.
The routing table is changed to select the first system due to system degradation, and redundancy switching is performed in the packet layer. Therefore, reception switching processing in the SDH layer and the POS layer is unnecessary.

Next, the configuration and operation of the POS receivers 60 and 63 will be described in more detail. FIG. 19 shows FIG.
8 is a block diagram showing a configuration of an POS receiving device 60, 63 of FIG. In FIG. 19, the POS receiving devices 60 and 6
3 is provided with a control code collating and rewriting unit 66 instead of the control code rewriting unit 38 of the POS receiving device 30 in FIG.

The POS receiver 6 configured as described above
0 and 63 operate as follows. First, the operation up to temporarily storing the SDH frame transmitted via the transmission lines of the 0-system and the 1-system in the buffer memories 24 and 25 is the same as in the first embodiment. Then, the read PPP
It is determined whether or not the frames include the deterioration control codes 57 and 58 shown in FIGS. And
When the deterioration control codes 57 and 58 are included, the opposite channel warning is output to the transmission system selection control unit 53 of the transmission devices 47 and 49 of the own node. Thereafter, the control code collation rewriting unit 66 rewrites the deterioration control codes 57 and 58 into the normal control code 2-2 used in the protocol processing unit.

The detection of a transmission line failure in the receiving devices 48 and 50 can also be performed by using FCS inspection. Hereinafter, the configuration and operation in this case will be described. First, the receiving devices 48 and 50 will be described. FIG. 20 is a block diagram illustrating a configuration of the receiving devices 48 and 50. In FIG. 20, receiving apparatuses 48 and 50 have substantially the same configuration as receiving apparatuses 48 and 50 shown in FIG.
The difference is that the data is output from the POS receiving devices 60 and 63 instead of the POS data.

The POS receiver 6 for performing such output
0 and 63 will be described. FIG. 21 shows the POS of FIG.
FIG. 3 is a block diagram illustrating a configuration of receiving apparatuses 60 and 63. In FIG. 21, the POS receivers 60 and 63 are
9 is substantially the same as the POS receivers 60 and 63 shown in FIG. 9 except that the FCS inspection unit 33 outputs a transmission line alarm addressed to itself. In such a configuration,
The FCS inspection unit 33 conforms to the POS transmission standard (RFC16
FCS inspection is performed according to 62). In this FCS inspection, a flag and a trailer (FC
Since bit error detection is performed based on all bits except S), a transmission path failure is detected as a bit error, and the FCS is detected.
An error alarm can be output as a transmission line alarm addressed to itself.

In the third embodiment, a failure such as deterioration of a transmission line can be transmitted to the transmission device, and the transmission line can be selected on the transmission device side. And loss of PPP frames and loss of synchronization can be prevented.

Embodiment 4 Next, a fourth embodiment of the present invention will be described. In the third embodiment, the opposite transmission path alarm is transmitted using the degraded packet. On the other hand, in the fourth embodiment, the opposite transmission path alarm is transmitted using the K2 byte of the SDH frame. It is about. However, configurations and operations that are not particularly described are the same as those in the third embodiment.

FIG. 22 is a block diagram showing a configuration of transmitting apparatuses 47 and 49 according to the fourth embodiment. In FIG. 22, the transmission devices 47 and 49 are configured in substantially the same manner as the transmission devices 47 and 49 in FIG. 15, but do not notify the POS transmission device of the transmission path alarm addressed to the own device, but use the 0 system or 1 system. It is configured to notify the SDH transmission device of the system. FIG. 23 is a block diagram showing a configuration of receiving apparatuses 48 and 50 according to the fourth embodiment. In FIG. 23, the receiving devices 48 and 50 are configured in substantially the same manner as the receiving devices 48 and 50 in FIG. 18 except that the opposite transmission line alarm is sent not from the POS receiving devices 60 and 63 but to the SDH receiving devices 59 and 62. It is configured to notify from.

The transmitting devices 47 and 49 configured as described above
The receiving devices 48 and 50 operate as follows. That is, when a transmission line failure is detected in the receiving device 48 of the node # 2, the transmission line alarm addressed to the own device is transmitted to the SD of the receiving device 48.
The signals are output from the H receiving devices 59 and 62. This self-addressed transmission path alarm is sent to the SDH transmitter 5 of the transmitter 49 of the node # 2.
5 and 56 are input. These SDH transmitting devices 55, 5
6 uses the alarm transfer byte 67 (K2 byte or unused SOH byte) in the SDH frame shown in FIG.
1 to the receiving device 50. In this receiving device 50,
The SDH receivers 59 and 62 detect a transmission line alarm from the alarm transfer byte 67 and notify the transmission system selection control unit 53 of the transmission device 47 of the opposite transmission line alarm. Then, the transmission path switching is performed by the transmission system selection control unit 53 in the same manner as in the third embodiment.

In the fourth embodiment, a fault such as deterioration of a transmission path can be transmitted using an alarm transfer byte in an SDH frame, and switching between system 0 and system 1 is performed in PPP frame units. This can prevent the loss of the PPP frame and the loss of synchronization.

Now, the first to fourth embodiments of the present invention have been described.
Has been described, but the present invention is not limited to these embodiments, and may be embodied in other different forms within the scope of the technical idea described in the claims. For example, in each of the above embodiments, P
Although the description has been made assuming that the PP frame is mapped to the SDH frame, the present invention is not limited to the PPP frame, and the present invention can be applied to a case where a packet of an arbitrary indefinite length is mapped to the SDH frame to perform transmission path switching.

[0081]

As described above, according to the present invention, the transmitting means converts the undefined length packet generated based on the data from the predetermined device into the payload of the same SDH frame in accordance with the timing based on the phase of the SDH frame. The SDH frame is transmitted to the working and protection transmission lines, and the receiving means receives the SDH frame transmitted through the working and protection transmission lines, and receives the SDH frame. Is read from the same SDH frame according to the timing based on the phase of the SDH frame.
It can be inserted into the payload portion of the frame to prevent the mapping of an undefined length packet to a different SDH frame, thereby preventing the loss or loss of synchronization of the undefined length packet.

According to the next invention, the transmitting side packet processing means writes the sequence number into the undefined length packet,
DH frame storage means stores the SDH frame transmitted through the working and protection transmission lines, and the switching means, when a predetermined transmission path failure or a switching request is received, causes the transmission of the working system to fail. S transmitted via the road
The sequence number of the DH frame and the sequence number of the SDH frame transmitted through the backup transmission path are detected, respectively. When the sequence numbers match each other, the SDH frame storage means detects the SDH frame. , The working system and the protection system are switched between each other in units of SDH frames. Therefore, synchronization can be established at the time of transmission line switching based on the sequence number, and the working system and the protection system can be synchronized in units of SDH frames. In this case, there is an effect that loss of an undefined-length packet and loss of synchronization can be prevented from occurring.

According to the next invention, the transmission-side packet processing means rewrites the specific header included in the undefined-length packet to the sequence number. This has the effect that synchronization can be achieved.

According to the next invention, the receiving-side packet processing means rewrites the header rewritten by the transmitting-side packet processing means into a predetermined normal header. This brings about an effect that the processing can be performed without any trouble as usual.

According to the next invention, the transmitting side packet processing means rewrites the predetermined area of the payload portion of the undefined length packet with the sequence number, and rewrites the area after the predetermined area of the undefined length packet to the sequence number. Since the data is shifted backward by a predetermined area, synchronization at the time of transmission line switching can be achieved based on this sequence number.

According to the next invention, the receiving-side packet processing means deletes the sequence number of the predetermined area rewritten by the transmitting-side packet processing means, and deletes the area after the predetermined area of the variable-length packet. Since the data is shifted forward by the predetermined area, there is an effect that data processing after packet reception can be performed without any trouble as usual.

According to the next invention, when a failure has occurred in the active transmission line on which the receiving unit is the receiving side, the receiving unit outputs a transmission line alarm addressed to itself to the transmitting unit of the same node, or When receiving a transmission path alarm from the transmitting means of the opposing node, the transmission means outputs an opposing transmission path alarm to the transmitting means of the same node, and the transmitting means receives the transmission path alarm from the receiving means of the same node. When notified, the transmission path alarm is transmitted to the receiving means of the opposite node via the transmission path in the direction opposite to the transmission path in which the failure has occurred, or the opposite transmission path alarm is transmitted from the reception means of the same node. Is notified, the transmission line of the active system in which the failure has occurred is switched to the transmission line of the standby system, so that a failure such as deterioration of the transmission line can be transmitted to the transmission device side. Switching of transmission path on the side It is possible to perform, it is possible to switch between the 0-system and 1-system in the PPP frame, P
This has the effect of preventing the loss of the PP frame and the occurrence of loss of synchronization.

According to the next invention, in the address search means, the transmission means searches for an address from each undefined length packet generated based on data from a predetermined device, and the selector transmits the undefined length packet. Since the transmission path is selected based on the address searched by the address searching means, efficient packet transmission can be performed using the given redundant transmission path without distinguishing between the working system and the protection system. This has the effect that it becomes possible.

According to the next invention, when the transmitting unit is notified of the self-addressed transmission line alarm from the receiving unit of the same node, the transmitting unit rewrites a specific header included in the undefined length packet to a predetermined control code, Since the undefined length packet rewritten to the control code is transmitted to the receiving means of the opposite node as the transmission path alarm, the transmission path alarm generated on the receiving side can be transferred to the transmitting side. This has the effect that the transmission path can be switched on the transmission side.

According to the next invention, when the control code is included in the undefined length packet transmitted from the transmitting means, the receiving means sends the opposite transmission path alarm to the transmitting means of the same node. In addition to the output, the header rewritten by the transmission-side packet processing means is rewritten to a predetermined normal header, so that control code processing after packet reception can be performed without any trouble as usual. It has the effect of becoming.

According to the next invention, when the transmission means is notified of the transmission path alarm addressed to itself by the reception means of the same node, the transmission means issues the transmission path alarm using the alarm transfer byte included in the SDH frame. Because we are transmitting
The transmission path alarm generated on the reception side can be transferred to the transmission side, and the transmission path can be switched on the transmission side.

[0092] According to the next invention, the receiving means transmits the FC to the indefinite-length packet transmitted from the transmitting means.
Since the SCS inspection is performed and the FCS error alarm based on the result of the FCS inspection is output as the above-mentioned transmission line alarm addressed to itself, transmission line monitoring other than the SDH layer becomes possible, and a more detailed transmission line There is an effect that redundancy switching by quality monitoring becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a format of an SDH frame used in a duplex switching system according to Embodiments 1 and 2 of the present invention.

FIG. 2 is a diagram showing a format of a normal PPP frame.

FIG. 3 is a diagram showing a format of a PPP frame used in the duplex switching system according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a transmission device according to Embodiment 1 of the present invention.

FIG. 5 is a block diagram illustrating a configuration of the POS transmission device in FIG. 4;

FIG. 6 is a block diagram illustrating a configuration of a read control unit in FIG. 5;

FIG. 7 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 1 of the present invention.

FIG. 8 is a block diagram illustrating a configuration of the POS receiving device of FIG. 7;

FIG. 9 is a diagram showing a format of a PPP frame used in a duplex switching system according to Embodiment 2 of the present invention.

FIG. 10 is a block diagram illustrating a configuration of a POS transmitting apparatus according to Embodiment 2 of the present invention.

FIG. 11 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 2 of the present invention.

FIG. 12 is a block diagram illustrating a configuration of the POS receiving apparatus in FIG. 11;

FIG. 13 is a diagram showing an example of a form of an inter-node transmission line according to the third embodiment.

FIG. 14 is a diagram showing an example of another mode of the inter-node transmission line according to the third embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration of a transmitting apparatus according to Embodiment 3 of the present invention.

FIG. 16 is a diagram illustrating a system selection state before and after a redundant switch of a transmission device used in a duplex switching system according to a third embodiment of the present invention;

FIG. 17 is a diagram showing a format of a PPP frame used for transfer of a transmission path alarm transfer in Embodiment 3 of the present invention.

FIG. 18 is a block diagram showing a configuration of a receiving device according to Embodiment 3 of the present invention.

FIG. 19 is a block diagram showing a configuration of the POS receiving device of FIG.

FIG. 20 is a block diagram showing a configuration of a receiving apparatus of another embodiment according to Embodiment 3 of the present invention.

FIG. 21 is a block diagram showing a configuration of the POS receiving device of FIG.

FIG. 22 is a block diagram showing a configuration of a transmitting apparatus according to Embodiment 4 of the present invention.

FIG. 23 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 4 of the present invention.

FIG. 24 is a diagram showing a format of an SDH frame used for transfer of a transmission path alarm transfer in Embodiment 4 of the present invention.

FIG. 25 shows an SDH used in a conventional duplex switching system.
It is a figure showing the format of a frame.

[Explanation of symbols]

1,5 flag sequence, 2 header, 2-1 address, 2-2,2-4 control code, 2-3 protocol, 3 IP packet, 4 trailer, 7,8 SDH transmitter, 9 POS transmitter, 10 control code Rewriting unit, 16, 37 phase comparing unit, 22, 23 SDH receiving device, 24, 25 buffer memory, 26, 27 control code detecting unit, 28 control code collating unit, 29 selector, 30 POS receiving device, 33 FCS checking unit, 34
Buffer memory, 38 control code rewriting unit, 39
Sequence number, 40 control code detection unit, 41 byte stuff (SN generation unit), 42, 43 SN detection unit,
44 SN collation unit, 45 byte destuff (SN removal unit), 46 control code insertion unit, 47 transmitting device, 48
Receiving device, 49 transmitting device, 50 receiving device, 51
POS transmission device, 52 address search unit, 53 transmission system selection control unit, 54 selector, 55, 56 SDH transmission device, 59, 62 SDH reception device, 60, 63 POS
Receiving device, 66 Control code collation rewriting unit.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiro Ichigase 2-3-2 Marunouchi 2-chome, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation F-term (reference) 5K014 AA01 BA01 CA06 FA01 FA09 HA10 5K028 AA15 BB08 CC05 KK32 MM05 MM12 MM14 QQ01 RR04 5K030 GA11 HA10 LB11 MA04 MB01 MD02 5K035 AA03 BB01 CC08 DD01 LL18

Claims (12)

[Claims] 1. A duplex switching system for transmitting and receiving an SDH frame via a working system and a protection system transmission line, wherein an undefined length packet generated based on data from a predetermined device is transmitted at a timing based on the phase of the SDH frame. Transmission means for inserting the SDH frame into the working and protection transmission lines according to the above, and the SDH frame transmitted through the working and protection transmission lines. And a receiving means for reading the undefined length packet from the SDH frame. 2. The transmission means comprises transmission-side packet processing means for writing a sequence number to the undefined length packet, and the reception means comprises: the SDH transmitted through the working and protection transmission lines. SDH frame storage means for storing a frame; a sequence number of the SDH frame transmitted via the working transmission line when a predetermined transmission line failure or a switching request occurs; And by detecting the sequence numbers of the SDH frames transmitted through the SDH frame and reading out the SDH frames from the SDH frame storage means when the sequence numbers match each other, the working system and the standby system are connected to the SDH frame. 2. A duplexer according to claim 1, further comprising: switching means for switching between frames. Exchange system. 3. The duplexer according to claim 2, wherein the transmission side packet processing unit of the transmission unit rewrites a specific header included in the undefined length packet to the sequence number. Switching system. 4. The receiving means according to claim 3, wherein said receiving means comprises receiving packet processing means for rewriting said header rewritten by said transmitting packet processing means to a predetermined normal header. Dual switching system. 5. The transmitting-side packet processing means of the transmitting means rewrites a predetermined area of the payload portion of the unfixed-length packet with the sequence number, and rewrites an area after the predetermined area of the unfixed-length packet with the sequence number. The duplex switching system according to claim 2, wherein the shift is performed by a predetermined area backward. 6. The receiving means deletes the sequence number of the predetermined area rewritten by the transmission-side packet processing means, and moves an area after the predetermined area of the undefined-length packet forward by the predetermined area. The duplex switching system according to claim 5, further comprising: a receiving-side packet processing unit that shifts. 7. A duplex switching system in which a transmitting means and a receiving means are arranged at each node and an SDH frame is transmitted / received via working and protection transmission lines. When a failure occurs in the transmission line of the active system, a transmission line alarm addressed to the own node is output to the transmission means of the same node, or when a transmission line alarm is transmitted from the transmission means of the opposite node, the opposite transmission is performed. A path alarm is output to the transmitting means of the same node, and the transmitting means, when notified of the transmission path alarm addressed to itself by the receiving means of the same node, transmits the transmission path alarm to the transmission path in which the failure has occurred. When the transmission is transmitted to the receiving means of the opposing node via the transmission path in the reverse direction, or when the opposing transmission path alarm is notified from the receiving means of the same node, the transmission path of the working system in which the fault has occurred is set aside. system Switching to the transmission path of (1). 8. The address search means, comprising: an address search means for searching for an address from each variable-length packet generated based on data from a predetermined device; and a transmission path for transmitting the variable-length packet to the address search means. The switching system according to claim 7, further comprising: switching means for selecting based on the searched address. 9. The transmission means, when notified of the transmission path alarm addressed to itself by the reception means of the same node, rewrites a specific header included in the undefined length packet to a predetermined control code, and The rewritten indefinite length packet is
9. The duplex switching system according to claim 7, wherein the transmission path alarm is transmitted to the receiving unit of the opposite node. 10. 10. The receiving means outputs the opposite transmission path alarm to the transmitting means of the same node when the undefined length packet transmitted from the transmitting means includes the control code, The duplex switching system according to claim 9, wherein the header rewritten by the transmission-side packet processing means is rewritten to a predetermined normal header. 11. The transmission means, when notified of the transmission path alarm addressed to itself from the reception means of the same node, transmits the transmission path alarm using an alarm transfer byte included in an SDH frame. The duplex switching system according to claim 7 or 8, wherein: 12. The receiving means performs an FCS check on the undefined length packet transmitted from the transmitting means, and issues an FCS error alarm based on the result of the FCS check.
12. Output as the self-addressed transmission line alarm, according to any one of claims 7 to 11, wherein
Redundancy switching system.