JPH07226729A - Transmission line changeover control system - Google Patents

Abstract

PURPOSE:To realize selection logic by which a transmission is correctly selected when a fault takes place in an equipment of one system of a sender side 1 in the system switching the transmission line by sending/receiving transmission line changeover control information between the equipments located opposite to each other via the transmission lines comprising an active system and a standby system by using the transmission lines of both the systems. CONSTITUTION:An APS byte of system changeover control information is respectively inserted to a main signal SOH corresponding to an SDH at both system APS byte transmission sections 7, 8 of a sender side 1 and fault information representing the presence of a fault of each system is inserted to low-order 3-bits of APS K2 bytes by both system fault information transmission sections 5, 6. fault information reception sections 15, 16 of reception sections 13, 14 of each system at a receiver side 11 extract fault information to discriminate the presence of a fault. A selector 12 is changed over according to the changeover control information of APS byte of a system having no fault.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line switching control system, and more particularly to transmitting switching control information between the communication devices opposed to each other via a redundant transmission line constituted by an active system and a standby system. The present invention relates to a bidirectional transmission line switching control system that is performed by transmitting and receiving.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional bidirectional transmission line switching control system of this type. This example is a system corresponding to a new synchronous digital hierarchy (abbreviated as SDH), and SDH transmission apparatuses 1 and 2 that oppose each other via so-called 1 + 1 redundant transmission lines 10 and 20 of 0 system and 1 system. This is a case in which the transmission path is switched between 11 units. In this case, the APS (Autom) in the section overhead (SOH) inserted in the main signal to be transmitted.
The transmission path switching control information is transmitted by using the K1 and K2 bytes that make up the Attic Protection Switch byte.

In the figure, a system in which the devices 1 and 11 face each other is shown, and the 0-system transmission line 10 and the system transmission line 20 are bidirectional.
, But in the figure only the sender is shown in device 1,
In the device 11, only the receiving side is shown. That is, only the transmission / reception unit related to the one-way transmission path from the device 1 to the device 11 is shown. Since the same applies to the reverse direction, the description is omitted.

In the device 1, the main signal 100 branched by the signal branching unit 2 is supplied to the transmitting units 3 and 4 of the 0-system and the 1-system, respectively. In each of the transmitters 3 and 4, the APS byte transmitters 7 and 8 are used to store the APS in the SOH portion of each main signal.
The byte 101 is inserted, the switching control information given from the switching controller 9 is inserted and multiplexed, and the main signals of both systems are transmitted to the device 11.

In the apparatus 11, the 0-system and 1-system transmission signals are received by the 0-system and 1-system receiving sections 13 and 14, respectively. In each of the receiving units 13 and 14, the APS byte receiving unit 17 and 18 extracts the APS byte 201 and supplies the APS byte 201 to the switching control unit 19.

In the switching control unit 19, based on the switching control information contained in these APS bytes 201, the transmission line failure information from the respective system reception units 13 and 14 and the own device failure information 202, the selector is selected. Twelve switching controls are performed. Thus, the 0-system signal and the 1-system signal are alternatively the main signal 2
It is derived as 00.

On the transmitting side 1, the same switching control information is transmitted to both the 0 system and the 1 system.
The receiving side 11 normally extracts the switching control information transmitted from the transmitting side 1 from the standby system, and only when the standby system transmission line or the standby system device of the own device fails, the switching control information from the active system. To extract.

[0008]

In such a conventional transmission line switching control system, the receiving side normally extracts the switching control information transmitted from the transmitting side using both transmission lines from the standby system. Since the system extracts data from the active system only when the standby system transmission line fails or the standby system device on the local side fails, switching control information occurs when the standby system on the sending side fails. When it becomes a state where it cannot be normally transmitted (normally transmitted in the active system), the receiving side cannot recognize the failure of the transmitting side device, so that the switching control information is extracted from the standby system as usual.

Therefore, the receiving side cannot correctly recognize the information desired to be transmitted by the transmitting side device, and the switching control may not be normally performed.

FIG. 4 is a sequence example specifically showing the above case. It is assumed that a transmission line failure has occurred in the 0 system and the switching to the 1 system has been performed during operation of the 0 system as the active system and the 1 system as the standby system (step 41). After that, the transmission line failure of the 0-system is restored, and the 1-system is in the recovery standby (wait
o Restoration: WR).

Here, it is assumed that a failure occurs in the 1-system interface section on the transmitting side 1 (step 42). On the transmission side transmission line, an A having this NB information is sent in order to send a command (NB) for switching the selector 12 back to the 0 system to the reception side 11.
The PS byte is inserted and multiplexed into the main signal by the APS byte transmitting units 7 and 8 of both systems (step 43).

However, the NB information cannot be set because the transmitting unit of the 1st system is out of order, and therefore the APS byte transmitted from the transmitting side 1 is "NB" for the 0th system and "W" for the 1st system.
R "(step 44).

Since the receiving side 11 is extracting the APS bytes from the spare system, the NB information cannot be received from the 0 system and the WR is still being received, and the switchback to the 0 system is not executed. (Step 45). This means that the service cannot be performed using the 0-system whose failure has already been recovered, and the service cannot be relieved.

Note that "RR" in FIG. 4 indicates a switching response (Reverse Request) from the receiving side 11.

Therefore, the present invention has been made to solve the above-mentioned drawbacks of the prior art, and its object is to solve this problem even if one of the two systems of the transmission side device has a failure. It is to provide a transmission line switching control system that enables service relief by correctly recognizing the above.

[0016]

According to the present invention, the transmission path switching control information is used between the communication apparatuses facing each other via the redundant transmission path constituted by the active system and the standby system by using the transmission lines of both systems. In this transmission line switching control system, the transmission lines of these two systems are switched by transmitting and receiving, and failure information indicating the presence / absence of a failure in each transmission unit of both systems is sent to the main system of both systems. Means for inserting into the signal respectively are provided in the transmitting section of the communication device, means for extracting the failure information inserted into the main signals of both systems, and failure of the opposite device based on the extracted failure information. A transmission line switching control system is provided, in which a receiving unit of the communication device is provided with a selecting unit that determines a non-existent system and selectively extracts the switching control information from the system having no failure. .

[0017]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and the same portions as those in FIG. 3 are designated by the same reference numerals. Also in this example, for simplification, the opposite devices are the transmission side 1 and the reception side 11.
And only a transmitting / receiving unit related to the one-way transmission path from the device 1 to the device 11 is shown. The same applies to the reverse direction and is omitted.

Explaining only the parts different from those of FIG. 3, in the transmitting side 1, in addition to the APS byte transmitting parts 7 and 8 in the transmitting parts 3 and 4 of the 0-system and the 1-system, a failure information transmitting part 5 and 6 is added.

The failure information transmitters 5 and 6 each insert failure information indicating that a failure has occurred at the time of failure of their own device into the undefined portion (see FIG. 2) in the K2 byte of the APS byte and send it. Have a function.

Therefore, the switching control device 9 receives the failure information 102 from the transmission units 3 and 4 of each system and receives the failure information from the AP.
In addition to S-byte switching control information, failure information for each system is generated and passed to the transmission units 3 and 4 of each system.

FIG. 2 shows SOH (section overhead)
3 shows the definition state of the lower 3 bits of the K2 byte that constitutes the APS byte in the above. (000), (11
1) and (110) are bit patterns already defined by CCITT, and therefore other bit patterns are undefined and can be used. Therefore, in the present embodiment, two bit patterns of (101) and (100) are used as failure information, the former (101) is a "system 1 failure" and the latter (011) is a system 0 failure. , Respectively, but it is clear that other undefined bit patterns may be used.

On the receiving side 11, failure information receiving units 15 and 16 are added to the receiving units 13 and 14 of the 0-system and 1-system, respectively, and in addition to extracting the APS byte of each system (in this example, the other device). The failure information of the opposing device 1) is also extracted and sent as information 201 to the switching control unit 19.

The operation of the embodiment of the present invention will be described below.
Description will be given based on the same conditions as the example shown in FIG. In other words, when the 0 system is operating as the active system, after the failure is further recovered, the operating state of the 1 system is in recovery standby (WR).
It is assumed that

Further, at this point, a failure occurs in the 1-system transmitting section 4 of the device 1 and it is necessary to switch the 1-system operating state back to the 0-system. Due to this, the APS byte transmitting section of the 1-system transmitting section 4 is affected. 8
The AP that requests the opposite device 11 to switch back to system 0
Consider a case where the S byte cannot be set.

At this time, the switching control unit 9 has an APS byte (N
B) is set in the 0-system APS byte transmission unit 7 (assuming that it could not be set in the 1-system APS byte transmission unit 8).
At the same time, the switching control unit 9 sets a code indicating “normal 0 system transmitter / abnormal 1 system transmitter” in the 0 system failure information transmitter 5 (cannot be set in the 1 system failure information transmitter 6). Suppose).

In the device 11, as the received APS byte,
The APS byte (WR: recovery standby request) before the failure occurs in the 1-system transmitting section of the device 1 is still received from the 1-system receiving section, but the 0-system receiving section transmits the APS byte to the 0-system. An APS byte indicating a switchback request is received. Further, as the failure information of the apparatus 1, the failure information receiving section 16 of the 1-system receiving section 14 could not set the apparatus failure information on the apparatus 1 side, and therefore "0 system transmitting section normal / 1 system transmitting section normal" is displayed. Received (information before the failure occurred is retained)
However, the failure information receiving section 15 of the 0 system receiving section 13 receives "0 system transmitting section normal / 1 system transmitting section abnormal".

The switching control unit 19 determines whether the failure information received by the failure information receiving units 15 and 16 is correct (whether the information is reliable or not) based on the transmission line failure condition and the device failure condition detected on the device side. Or)) is determined. That is, in this case, since there is no device failure on the transmission lines of both systems and the device 11 side, failure information of both systems is taken in.

Here, the failure information (0
System transmission unit normal: System 1 transmission unit abnormal) and failure information extracted from system 1 (System 0 transmission unit normal: System 1 transmission unit normal) are both checked to determine which system 0 transmission unit has a failure state. The information extracted from the system is normal, and the failure state of the transmission unit of the system 1 is that the information extracted from the system 1 is normal, but the information extracted from the system 0 is abnormal.

As a result, it is determined that the 1-system transmitter is abnormal and the 0-system transmitter is normal, and the APS bytes extracted from the 0-system are taken. Therefore, since the APS byte extracted from the 0-system is a request for switching back to the 0-system, the selector 12 is controlled to switch to the 0-system.

[0031]

As described above, according to the present invention,
The transmitter has means for inserting the device failure information of both systems into the main signal of both systems, and the receiver has means for extracting the device failure information of both systems. By providing a selection means for determining a system without any error and extracting the switching control information from the system without a failure, the receiving side can improve the APS byte extraction selection logic, and the transmitting side cannot transmit the ASP byte to one system. Even if a failure occurs, the switching control can be normally executed.

[Brief description of drawings]

FIG. 1 is a system block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a usage example of lower 3 bits of a K2 byte in an APS byte of an SOH unit used in an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional transmission line switching control system.

FIG. 4 is a sequence diagram for explaining problems in the conventional system.

[Explanation of symbols]

 1 transmission side transmission device 2 branching unit 3,40 system and 1 system transmission unit 5,60 system and 1 system failure information transmission unit 7,80 system and 1 system APS byte transmission unit 9,19 switching control unit 10, 20 0 system and 1 system transmission path 11 Receiving side transmission device 12 Selector 13, 14 0 system and 1 system receiving section 15, 160 0 system and 1 system failure information receiving section 17, 180 0 system and 1 system APS byte receiving section

Claims (5)

[Claims] 1. A transmission line switching control information is transmitted and received between communication devices opposed to each other via a redundant transmission line constituted by an active system and a standby system by using transmission lines of both systems to thereby transmit and receive both of them. A transmission line switching control system for switching between transmission lines of a system, wherein the communication means includes means for inserting failure information indicating the presence / absence of a failure in each of the transmitters of both systems into the main signal of each system. A means for extracting the failure information provided in the main signal of both systems, which is provided in the transmission section of the device, and the switching control information for judging the system having no failure in the opposite device based on the extracted failure information. And a selection means for selectively extracting from this fault-free system,
A transmission line switching control system, which is provided in a receiving unit of the communication device. 2. The selecting means extracts the switching control information inserted into the main signals of both systems, and the extracted switching control information is selectively extracted from the failure-free system. The transmission line switching control system according to claim 1, further comprising means for selecting one of both systems according to the switching control information. 3. The transmission line switching control system according to claim 1, wherein the communication device is an SDH transmission device compatible with Synchronous Digital Hierarchy (SDH). 4. The transmission line switching control system according to claim 3, wherein the failure information and the switching control information are inserted in a part of the section overhead inserted in the main signal. 5. The transmission line switching control system according to claim 4, wherein the failure information is inserted in an undefined bit portion of the section overhead.