JP3246473B2 - Path switching control system and path switching control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a path switching control system and a path switching control method, and more particularly, to a path switching for switching two transmission routes serving as a working path and a protection path in response to a failure occurrence in a redundant network. The present invention relates to a control system and a path switching control method.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing a conventional example of a switching control system for a redundant network. In the figure, a signal from a transmitting end 701 is branched at a branch point 702 and passes through two routes, a transmission route A and a transmission route B. The relay node 703 exists in the transmission route A, and the transmission route B
Has a relay node 704.

On the receiving side, a failure detection unit 705 or 706 detects a route failure, and a switching control unit 708 controls switching of a selection unit 707 so as to select a normal one of the two routes.

[0004] Here, when a failure occurs upstream of the transmitting end 701, the failure spreads to route A and route B, and both systems fail. At this time, since the repair cannot be performed with the redundant configuration, the route switching by the selecting unit 707 is unnecessary.

[0005]

However, the conventional switching control system described above has the following problems. That is, if there is a distance difference between route A and route B, and route A is shorter, if route A is selected on the receiving side, even if both systems have failed, the failure is detected by failure detection unit 705. Therefore, the failure is detected before the failure detection unit 706. Therefore, the switching control unit determines that the route B is normal and the route A has a fault, and switches to the route B.

[0006] Referring to FIG. 10, a fault that has occurred at time point “a” propagates to route A and route B. Then, based on the transmission delay time difference between the routes, a failure of the route A is detected at the time point b, and a failure of the route B is detected at the time point c. In this case, time b
Focusing on the point, while the failure of the route A is detected, the failure of the route B is not detected, and the route B is normal until the time point c. Therefore, the transmission path is switched from the route A to the route B.

However, since both the routes A and B eventually become obstacles, it is unnecessary to switch the transmission path from the route A to the route B, and the unnecessary switching is notified to the network management system. This may cause a network manager to make an erroneous determination.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has as its object to provide a path switching control system and a path switching control capable of preventing unnecessary switching operations when a fault occurs in both systems. Is to provide a way.

[0009]

SUMMARY OF THE INVENTION A path switching control system according to the present invention has a first path which is branched and becomes a working and protection path.
A path switching control system that performs switching of a second transmission route in response to occurrence of a failure, and a failure detection unit that detects a failure in a path immediately before branching to the first and second transmission routes; A branching means for outputting the failure detection result to the path of the first and second transmission routes that are branched, and a failure detection result output to the path of the first and second transmission routes that are branched. A switch inhibiting means for inhibiting the switching of the first and second transmission routes when both indicate that there is a failure in the path. The branching unit includes an insertion unit that inserts the failure detection result into the path, and a branching unit that branches the first and second transmission routes after the insertion. The path is a path for transmitting an SDH signal, and the failure detection result is inserted into a specific part of an AU section of the SDH signal. Note that the specific portion of the AU section is H3 bytes or SS bits of H1 bytes.

[0010] A path switching control method according to the present invention is a path switching control method for switching a first and a second transmission route that is branched and becomes a working path and a protection path in response to occurrence of a failure. And a failure detection step of detecting a failure in the path immediately before branching to the second transmission route;
A branching step of outputting the failure detection result to a path based on the first and second transmission routes to be branched, respectively;
Switching suppression for suppressing the switching of the first and second transmission routes when the failure detection result output to the path by the branched first and second transmission routes indicates that the path has a failure. And a step. In the branching step, the failure detection result is inserted into the path, and after the insertion, the first and second transmission routes are branched. The path is a path for transmitting an SDH signal, and the failure detection result is inserted into a specific part of an AU section of the SDH signal. The specific part of the AU section is H3
Byte or SS bit of H1 byte.

In short, the present invention provides a digital transmission system in which a transmitting end branches and transmits signals to a plurality of routes, and a receiving end selects a signal to be received from the plurality of routes, thereby controlling switching of a route redundant system. Regarding the system, it is to prevent an unnecessary switching operation at the time of a failure in both systems due to a failure on the upstream side of the transmission end.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.

FIG. 1 is a block diagram showing an embodiment of a path switching control system according to the present invention. FIG. 1 shows a redundant configuration of the transmission system. In the figure, a signal is branched to transmission routes A and B by a branching unit 103 of a transmitting node 201, and a selecting unit 111 of a receiving node 204.
Use to select a route that receives a normal signal. The transmission route A passes through the relay node 202 having the upstream failure information transfer unit 104, and the transmission route B is the upstream failure information transfer unit 1
05 through the relay node 203 having

The normality of the signals on both routes is monitored by the fault detecting units 108 and 109, and when a fault is detected on the working route, a switching operation to the spare route is performed. In other words, the remedy section of the present redundant configuration is from the branching unit 103 to the selection unit 111, and a fault that occurs upstream of the end point Ta is not targeted for rescue. However, this upstream failure is caused by transmission routes A and B
And both routes do not transmit a normal signal. A feature of the present invention is that the selection unit 111 can determine whether a failure has occurred in the transmission route A or B or a two-system failure due to an upstream failure, and an unnecessary switching operation is performed when an upstream failure occurs. That is not to be.
Here, for the sake of explanation, a failure in a redundant transmission section (transmission route A or B from the branching unit 103 to the selection unit 111) is referred to as a “route failure”, and a failure upstream of the end point Ta is referred to as an “upstream failure”. Is defined.

As means for making the receiving node determine the upstream fault and the route fault, a mechanism for inserting the information (upstream fault information) into a specific time slot of the main signal before the branching unit 103 is provided. When the fault detecting unit 101 detects an upstream fault, the fault information inserting unit 102 inserts upstream fault information and sends it. Also, in order to transfer this information to the receiving end, the relay node 2 existing on the route
In 02 and 203, a mechanism for transferring upstream failure information is provided (upstream failure information transfer unit). On the receiving side, an upstream fault information detection unit 10 for detecting upstream fault information
6, 107 are provided. The switching control unit 110 determines whether the failure is a root failure or an upstream failure based on the upstream failure information and the failures detected by the failure detection units 108 and 109,
11 is controlled.

FIG. 2 shows an SDH (Synchronous Digital Hi
(Erarchy) This is an example of the configuration of a 4-node ring network system using transmission devices. This ring network system transmits a high-speed SDH frame in a ring, and each node has a function of demultiplexing a low-speed SDH frame into the high-speed transmission network in units of higher-order group paths VC. , Higher-order group paths can be transmitted over this network.

The transmission from the end point Ta to the end point Tb within the ring is performed by a transmission route A from the transmission node (A) 201 via the relay node (B) 202 and a transmission route B via the relay node (C) 203. Are used to form a redundant configuration. When a failure occurs in one of the routes, the selection unit of the receiving node (D) 204 performs one-way path switching, thereby relieving a failure in signal transmission from the end point Ta to the end point Tb.

As means for notifying the receiving end of the upstream failure,
H among H1 byte, H2 byte and H3 byte of AU (Administrative Unit) pointer of SDH multiplex frame
Uses 3 bytes. FIG. 3 shows an SDH signal (STM-
The frame configuration of N) is shown. The size of the SDH signal is N × 270 × 9 bytes. The 9 × 9 byte portion is SOH (Section Over Head).
) And the AU pointer section. The remaining 261 × 9 byte length is the payload section. In the payload, POH
(VC3, VC) with (Path Over Head) added
4) is mounted.

The AU section in FIG. 1 usually contains H1 to H3 bytes (not shown). B of the H1 byte
1 to b4 are new data flags indicating a change in pointer value, b5 and b6 of the H1 byte are AU type display, H1
The b7 and b8 and H2 bytes are defined as pointer values, and the H3 byte is defined as a negative stuff action byte for performing a stuff operation when the frequency of the reference clock and the frequency of the multiplexing clock of the apparatus are shifted. AIS (Alarm Indicati
on Signal) is a detection condition when the H1 byte and the H2 byte are all “1”, and the value of the H1 byte and the H2 byte is transmitted as all “1” when the AIS is transferred downstream. Since the H3 byte for negative stuff is used when the signal is normal, it can be used as an upstream failure information byte in the case of AIS transmission.

Here, the H3 byte value is defined. When the signal is normal (when the H1 byte and H2 byte are not all "1"), the H3 byte is a negative stuff action byte (as before). In the case of AIS (H1 byte and H2 byte are all “1”), H3 = “01010101”
("55h") indicates upstream failure information. The AIS that is not an upstream failure sets the H3 byte to all “1” as in the past. Note that "h" indicates a hexadecimal number.

FIG. 4 is a block diagram showing an upstream failure transmission function in the transmission node. As shown in the figure,
The transmitting node includes an SOH processing unit 301 that terminates the SOH of the low-speed SDH frame signal from the end point Ta, an AU pointer processing unit 302 that terminates the AU pointer, an AIS monitoring unit 303 that monitors AIS information of the AU pointer, H3 byte insertion unit 304 for inserting upstream failure information, branch unit 305 for branching a signal in two directions, and SOH processing units 306 and 3 for generating SOH of a high-speed SDH frame signal
07 is included.

FIG. 5 is a block diagram showing an upstream failure transfer function in the relay node. As shown in the figure,
The relay node monitors the SOH processing units 401 and 404 for terminating and generating the high-speed SDH frame signal, the AU pointer processing unit 402 for terminating the AU pointer, the AIS monitoring unit 405 for detecting the AIS, and monitors the H3 byte value. An H3 byte monitoring unit 406 that detects an upstream fault, an upstream fault detection unit 407 that detects an upstream fault, and an H3 byte insertion unit 403 that inserts upstream fault information are configured.

FIG. 6 is a block diagram showing an upstream failure judgment function at the receiving node. As shown in the figure,
The receiving node performs termination S of the high-speed SDH frame signal.
OH processing units 501 and 502, AU pointer processing units 503 and 504 for terminating the AU pointer, POH monitoring units 505 and 506 for monitoring the error monitoring byte (B3 byte) of the path signal, and H for monitoring the H3 byte value.
3-byte monitoring units 507 and 508 and AU pointer A
AIS monitoring units 511 and 512 for monitoring IS information,
Upstream fault detectors 509 and 510 for detecting an upstream fault
And path switching trigger monitoring units 513 and 514 for detecting a path switching trigger, a path switching control unit 515 for controlling path switching, and a selecting unit 516 for selecting a route A or route B signal. It is configured.

The operation of the present system having such a configuration will be described. In FIG. 4, the low speed SD from the end point Ta
When the node A 201 receives the H frame signal, the SOH processing unit 301 in the node A terminates the SOH and separates the AU unit. At this time, the AU pointer terminated by the AU pointer processing unit 302 is monitored by the AIS monitoring unit 303.
If the U pointer is all "1", it is determined to be AIS.
When it is determined to be AIS, the H3 byte value “55h” defined as the upstream failure information is inserted by the H3 byte insertion unit 404. The signal branched at the branch point 305 is S
The OH processing units 306 and 307 multiplex the signal with a high-speed SDH frame signal and transmit the multiplexed signal to a route A or route B.

In the node B or the node C, the high-speed SDH frame is terminated and the AU pointer is terminated.
Processing for transferring the upstream failure information to the receiving node is required. The upstream failure information transfer function can be realized by inserting an upstream failure definition value after normal AU pointer generation processing is performed when an upstream failure is detected. The operation will be described with reference to FIG.
The signal terminated by the AU pointer processing unit 402
The pointer is terminated. In the upstream failure detection unit 407, the AI
AIS information from S monitor 405 and H3 byte monitor 4
It is determined based on the H3 byte information from 06 whether an upstream fault has occurred, and if it is an upstream fault, the H3 byte insertion unit 403 inserts an upstream fault definition value “55h”. Upstream failure detector 407
Is determined when the AIS (the H1 and H2 bytes of the AU pointer are all “1”) and the H3 byte is “55h”. Then, the SOH processing unit 4
At S04, the data is subjected to SOH processing and transmitted to the transmission path.

Next, a description will be given with reference to FIG. Node D
Receives the SDH signals from route A and route B, these signals are sent to SOH processing units 501 and 502.
Terminated by Next, the AU pointer processing units 503 and 50
4, the AU pointer is terminated, the H3 byte is sent to the H3 byte monitoring units 507 and 508, and the H1 byte and H2 byte are sent to the A
The information is passed to IS monitoring units 511 and 512. The values of the H1 and H2 bytes (AIS information) and the value of the H3 byte are passed to the upstream failure detection units 509 and 510,
If the AIS (H1 byte and H2 byte are all "1") and the H3 byte value is "55h", there is an upstream fault, and AIS
When the H1 byte and the H2 byte are all “1” and the H3 byte value is also all “1”, it is determined that there is no upstream failure. That is, when the signal is not AIS (the signal is normal), H
The 3 bytes are bytes for negative stuff, and the H3 byte is “5”.
5h "does not mean an upstream failure.

The VC (Virtua after the AU pointer processing)
l Container) signal is monitored by the POH monitor
The B3 byte indicating the code error information of the signal is passed to the path switching trigger monitoring units 513 and 514. The path switching trigger is
AIS or B3 byte error is detected. Switching control unit 5
Reference numeral 15 controls the switching of the selection unit 516 by the path switching trigger. However, when the upstream failure detecting units 509 and 510 detect the upstream failure information, the switching control is not performed even if the path switching trigger is present.

Next, another embodiment of the path switching control system according to the present invention will be described with reference to FIG. In the above-described embodiment, the H3 byte is used as the upstream fault information notifying means.
Bits (the fifth and sixth bits of the H1 byte) are used. This SS bit is a bit used to indicate the type of AU.

All "1" s are substituted into the H1 byte and H2 byte of the AU pointer at the time of AIS. The SS bit is defined as a notification bit of upstream fault information.

The configuration and operation of the system according to this embodiment are almost the same as those of the above-described embodiment, and therefore, different parts will be described with reference to FIG. Specifically, the functions of inserting, transferring, and determining the SS bit will be described.

First, the SS bit of the upstream failure information is defined. Normally, H1 byte and H2 byte are AIS
In the ring network, all bits except the SS bit are all "1". When SS = “00”, it indicates upstream failure information, and otherwise, it is “11”. That is, when the receiving end receives the AIS, the H1 byte serving as a switching trigger is "1
The H1 byte that does not become a switching trigger in “1110011” is “11111111”. This definition is closed to the ring network system, and the AIS reception at the transmission node and the AIS to the low-speed side at the reception node are performed.
For transmission, AIS is transmitted and received based on a normal definition.

When the AIS is detected by the AIS monitoring unit 601, the SS bit insertion unit 602 inserts “00” into the SS bit, and then transfers it via the branch unit 603. At the relay node, AIS monitoring by the AIS monitoring unit 604 and S
The S bit monitoring unit 605 monitors the SS bit. If the AIS and the SS bit are “00”, the SS bit insertion unit 606 inserts “00” into the SS bit and transfers the SS bit. In the receiving node, when the AIS monitoring unit 607 and the SS bit monitoring unit 608 detect AIS and SS bit = “00”, the switching control unit 610 determines whether the switching trigger is detected by the switching trigger monitoring unit 609 or not. Do not switch.

In the two embodiments described above, the following path switching control method is realized. In other words, this is a path switching control method that switches between two transmission routes that are branched and becomes a working path and a protection path in response to the occurrence of a failure. The control method includes a failure in a path immediately before branching into two transmission routes. And a branching step of outputting the result of the fault detection to each of the paths of the two branched transmission routes, and a fault detection result output of the path of the two branched transmission routes. A switching inhibition step of inhibiting the switching of two transmission routes when it is indicated that there is a failure in the transmission route.

This control method will be further described with reference to FIG. As shown in the figure, first, a failure in a path immediately before branching into two transmission routes is detected (step S701). Then, the failure detection result is output to each of the paths based on the two branched transmission routes (step S702).

Next, it is determined whether or not the failure detection results output to the path by the two branched transmission routes both indicate that the path has a failure (step S).
703). If the result of this determination indicates that both paths have a failure, the switching of the two transmission routes is suppressed (step S703 → S70).
4), the process ends (step S706). Also,
If the result of the determination in step S703 indicates that at least one of the two paths has no failure, the switching is not suppressed, and the path switching is performed as usual to select a normal path ( The process ends (step S705) (step S706).

[0036]

As described above, according to the present invention, by transferring upstream fault information when a fault occurs at a transmission point, it is possible to determine whether the fault is a two-way route fault that has spread from the upstream fault or a route fault that requires switching. Therefore, it is possible to prevent an unnecessary switching operation that occurs when a route failure occurs in both directions, and to suppress an erroneous determination by a network administrator due to an unnecessary switching notification.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a path switching control system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a four-node ring network system using an SDH transmission device.

FIG. 3 is a diagram showing a frame of an SDH signal.

FIG. 4 is a block diagram illustrating an upstream failure transmission function in a transmission node.

FIG. 5 is a block diagram showing an upstream failure transfer function in a relay node.

FIG. 6 is a block diagram illustrating an upstream failure determination function in a receiving node.

FIG. 7 is a block diagram showing a configuration of a path switching control system according to another embodiment of the present invention.

FIG. 8 is a flowchart showing a path switching operation of the path switching control system according to the present invention.

FIG. 9 is a block diagram illustrating a configuration of a conventional path switching control system.

FIG. 10 is a time chart showing a path switching operation in a conventional path switching control system.

[Explanation of symbols]

 Reference Signs List 101 failure detection unit 102 failure information insertion unit 103 branch unit 104, 105 upstream failure information transfer unit 106, 107 upstream failure information detection unit 108, 109 failure detection unit 110 switching control unit 111 selection unit 201 transmission node 202, 203 relay node 204 Receiving node

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 1/22 H04J 3/00 H04L 12/00

Claims (10)

(57) [Claims] 1. A first branch which is branched and becomes a working and protection path.
A path switching control system that performs switching of a second transmission route in response to occurrence of a failure, and a failure detection unit that detects a failure in a path immediately before branching to the first and second transmission routes; A branching means for outputting the failure detection result to the path of the first and second transmission routes that are branched, and a failure detection result output to the path of the first and second transmission routes that are branched. A path switching control system comprising: a switching inhibiting unit that inhibits switching of the first and second transmission routes when both indicate that a path has a failure. 2. The method according to claim 1, wherein the branching unit includes an insertion unit that inserts the failure detection result into the path, and a branching unit that branches the first and second transmission routes after the insertion. The path switching control system according to claim 1. 3. The path switching control system according to claim 2, wherein the path is a path for transmitting an SDH signal, and the failure detection result is inserted into a specific part of an AU section of the SDH signal. 4. The path switching control system according to claim 3, wherein the specific part of the AU unit is an H3 byte. 5. The path switching control system according to claim 3, wherein the specific part of the AU section is an SS bit of an H1 byte. 6. A first path that is branched and becomes a working path and a protection path.
And a path switching control method for switching the second transmission route in response to the occurrence of a failure, comprising: a failure detection step of detecting a failure in a path immediately before branching to the first and second transmission routes; A branching step of outputting the fault detection result to a path based on the first and second transmission routes to be branched, respectively; and the first and second branches.
When the failure detection result output to the path by the transmission route indicates that the path has a failure, the first and the second
And a switching inhibition step of inhibiting the switching of the transmission route. 7. The path switching according to claim 6, wherein in the branching step, the fault detection result is inserted into the path, and after the insertion, the first and second transmission routes are branched. Control method. 8. The path switching control method according to claim 7, wherein the path is a path for transmitting an SDH signal, and the failure detection result is inserted into a specific part of an AU section of the SDH signal. 9. The path switching control method according to claim 8, wherein the specific part of the AU section is an H3 byte. 10. The path switching control method according to claim 8, wherein the specific portion of the AU section is an SS bit of an H1 byte.