JPH06125354A - Network synchronization setting system in loop lan - Google Patents

Abstract

PURPOSE:To keep network synchronization at the time of occurrence of a multiple fault of a transmission line by allowing each node equipment to receive a network synchronization reference clock with high quality and recovering the synchronization in a short time for a transmission line fault. CONSTITUTION:In the network synchronization setting system of a loop LAN prepared by connecting a master node MN and a slave node SN in a ring with duplicate transmission lines R, L through which signals are sent in opposite directions to each other, the node MN outputs a network synchronization reference clock to both the duplicate transmission lines. Then the node SN selects transmission line with a small number of node relay stages till the node from the duplicate transmission lines and receives the reference clock set the synchronization in its own node. The node SN sends the number of relay stages to an adjacent node SN and the adjacent node SN adds 1 to the number of relay stages and sends result to a further adjacent node SN. The node SN recognizing the number of relay stages of each of the transmission lines L, R receives the network synchronization reference clock from the transmission line with the small number of relay stages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for setting synchronization common to all node devices connected to a loop type LAN, and in particular, it is possible to recover synchronization in a short time in response to a failure in a transmission line. It is configured as follows.

[0002]

2. Description of the Related Art Optical loop LANs (local area networks) for transmitting signals between node devices using optical fibers are widely used in facilities such as companies and universities.

This optical loop LAN, as shown in FIG. 5, has a master node device (MN) and a plurality of slave nodes.
It is composed of a node device (SN) and an optical fiber transmission line connecting these in a ring shape, and the transmission line is a dual system of a right system loop R and a left system loop L that transmit signals in mutually opposite directions. Made of loops. In addition, node devices (MN,
The terminal device is connected via (SN).

Each of the node devices forming the LAN is required to operate while synchronizing with the entire network. Therefore, in the conventional optical loop type LAN, the MN sends the network synchronization reference clock to each SN through the right loop R, and the SNs 1 to 5 which do not have a clock generator pass the filter F from the received signal and perform network synchronization. The reference clock is extracted, and the synchronization in its own node is set based on this clock.

As shown in FIG. 6, when a failure such as a disconnection occurs in a part of the transmission line (a), the MN that has detected the location of the failure from the information from the SN loops to the SN.
A back command is issued, and a network synchronization reference clock is sent to both the right loop R and the left loop L. As a result, a loop-shaped transmission line that avoids the faulty point is formed,
Also, network synchronization between the node devices is restored (b).

[0006]

However, in the conventional network synchronization setting method, when the transmission line is normal, the network synchronization reference clock is transmitted by one loop, and therefore, the node becomes closer to the downstream side. The number of relays by the device increases, and the quality of the network synchronization reference clock deteriorates. Therefore, there is a problem that a high quality reference clock cannot be obtained at SN4 and SN5 located downstream of the loop.

When a failure occurs in the transmission line, the MN
Since the network synchronization recovery measures are taken after the detection of the failure by the network, it takes a lot of time before the network becomes operable.

Further, as shown in FIG. 7, when a failure occurs at a plurality of locations, the transmission path between the MN and the S is disconnected.
Since N2, SN3, and SN4 do not have a clock generator inside their own devices, the clocks disappear and become inoperable.

The present invention solves the above-mentioned conventional problems, in which each node device can receive a high-quality network synchronization reference clock, and, in response to a transmission line failure, a short period of time is required. It is an object of the present invention to provide a network synchronization setting method capable of recovering network synchronization while maintaining network synchronization even when failures occur at a plurality of locations on a transmission line.

[0010]

Therefore, in the present invention, network synchronization of a loop type LAN in which a master node device and a slave node device are connected in a ring shape by a dual transmission line for transmitting signals in opposite directions to each other is provided. In the setting method, the master node device outputs the network synchronization reference clock to both of the dual transmission lines, and the slave node device determines the number of node relay stages from the dual transmission line to this node device. Select a small number of transmission paths to receive the network synchronization reference clock,
The synchronization within its own node is set based on this network synchronization reference clock.

Further, each node device transmits the number of node relay stages for each transmission line to the adjacent node device through each transmission line, and compares the number of node relay stages transmitted from both transmission lines, and the number of node relay stages is compared. The network synchronization reference clock is received from a transmission line with few traffic.

Further, the node device which has detected the failure of the transmission line notifies the adjacent node device of a number larger than the total number of node devices connected to the loop LAN as the number of node relay stages.

Further, the slave node device which is detecting the failure of one of the transmission lines outputs the clock signal itself when a number larger than the total number of the node devices is transmitted from the other transmission line.

Further, the number of relay stages is transmitted to the adjacent node device by using the overhead area of SDH (Synchronous Digital Hierarchy).

[0015]

Therefore, the slave node device uses the network synchronization reference clock from the transmission line with the smaller number of node devices interposed between itself and the master node device, that is, the network synchronization reference clock sent from the slave node device. It receives from the transmission line whose clock quality has not deteriorated and establishes synchronization within its own node.

In order to inform the adjacent node device of the number of the intervening node devices, each node device notifies the adjacent node device of the number of relay stages indicating which node device the own node is in each transmission line. The adjacent node device to which this number of relay stages is transmitted adds 1 to the number and transmits it to the adjacent node device, and by taking over such operations, all the node devices can know the number of relay stages in each transmission line. You can Then, each node device that has learned the number of relay stages compares the number of relay stages in both transmission lines, selects the transmission line with the smaller number, and receives the network synchronization reference clock.

When the node device detects a failure in the transmission line, it notifies the adjacent node device of a number larger than the total number of nodes as the number of relay stages. As a result, each node device eliminates the risk of selecting a faulty transmission line when selecting a transmission line.

A slave detecting a failure on one transmission line
When the node device receives the number of relay stages indicating a failure from the other transmission line, this slave node device belongs to a block isolated from the master node device due to the occurrence of a plurality of failures. At this time, this slave node device outputs the clock generated by the built-in clock generator and operates as a pseudo center node device to maintain the network synchronization within the isolated block.

When the signal transmission of the LAN is carried out by using the SDH frame, the information of the number of relay stages can be placed in the overhead area of the SDH and transmitted between the node devices.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A slave node device SN which implements the network synchronization setting system of the present invention has a clock generator inside the device, and when it receives a network synchronization reference clock sent from a center node device MN, it slaves to it. To maintain the internal synchronization of the device (this is called "dependent synchronization").
That). Also, each SN can execute a necessary loop back based on autonomous judgment when a failure occurs in the transmission line (for this function, Japanese Patent Application No.
No. 92337, Japanese Patent Application No. 4-92338, “Transmission path control system for double-loop communication device”).

The MN also sends a network synchronization reference clock to both the right loop R and the left loop L. Therefore, each SN receives the network synchronization reference clock from both the right system loop R and the left system loop L, but one of the systems is selected and received from the selected system by the method described below. Dependent synchronization is performed based on the network synchronization reference clock.

In order to select this system, each node device firstly provides information (relay stage number information) indicating the number of stages in which the node itself relays the network synchronization reference clock.
Is sent to both adjacent nodes. Therefore, as shown in FIG. 1, the MN that generates the network synchronization reference clock receives the information of the relay stage number of 0 in SN1 through the right loop R, and simultaneously, the information of the relay stage number of 0 in SN6 through the left loop L. In addition, each SN sends the information obtained by adding 1 to the number of relay stages received through each loop to the adjacent node device through each loop.

Therefore, in the case of the right loop R, SN1 adds 1 to 0 to obtain the information of the number of relay stages 1 as S.
The SN2 which has transmitted this to N2 and which has received this adds 1 to 1 and transmits the information of the number of relay stages of 2 to SN3. These operations are successively taken over, and the SN3 transmits information about the number of relay stages 3 to S
N4 sends information of 4 relay stages, SN5 sends information of 5 relay stages, and SN6 sends information of 6 relay stages.

On the other hand, in the left loop L, SN6 transmits information of the number of relay stages of 1 to SN5, and SN5 which received this information,
1 is added to 1 to transmit the information of the relay stage number 2 to SN4, and SN4 sequentially transmits the information of the relay stage number 3 and SN3 is the relay stage number 4
Information of SN2, and information of SN2
1 transmits information of the number of relay stages 6.

Each SN that has received this relay stage number information from both the right loop L and the left loop L selects the system with the smaller relay stage number as the system to perform slave synchronization. However, when these values are equal, the right loop R is selected.

Therefore, SN1 compares the value of the relay stage number 0 received from the right system loop R with the value of the relay stage number 5 received from the left system loop L, and selects the right system loop R having the smaller value. To perform subordinate synchronization. Similarly, right loop R
1 to 1 and SN2 that receives the relay stage number information of 4 from the left loop L, and SN3 that receives the relay stage number information of 2 from the right loop R and 3 from the left loop L to the right loop R
Select. Further, since the SN 4 receives the relay stage number information of 3 from the right system loop R and 2 from the left system loop L, the SN 4 selects the left system loop L, and similarly, from the right system loop R to 4, the left system loop L. SN5 that receives the relay stage number information of 1 and SN6 that receives the relay stage number information of 5 from the right loop R and 0 from the left loop L selects the left loop L and performs slave synchronization.

Next, as shown in FIG. 2, when a failure occurs in a part of the transmission path (between SN2 and SN3), each S
How N selects the system to be slave-synchronized will be described.

In this case, the SN that has detected the failure informs the adjacent node device of a value larger than the number of nodes connected to the LAN as information on the number of relay stages. The values used at this time are different between the right loop R and the left loop L. For example, the right loop R uses hexadecimal 80 and the left loop L uses hexadecimal FF.

The SN which has received this 80 or FF as the relay stage number information transmits the value of 80 or FF to the next node device as it is without adding 1 to it.

Therefore, in the case of FIG. 2, in the right loop R, the MN sends the information of the number of relay stages 0 to SN1, and SN1
Sends the information of the relay stage number 1 to SN2, and SN2 sends the information of the relay stage number 2 to SN3. However, this information does not reach SN3 because of the failure.

When SN3 detects a failure, it sends the value of 80 to SN4 as relay stage number information. SN4 sends this value to SN5 as it is, SN5 sends SN6, and SN6 sends the value of 80 to MN.

On the other hand, in the left loop L, the MN sends the information of the relay stage number 0 to SN6, the SN6 sends the information of the relay stage number 1 to SN5, and the SN5 sends the information of the relay stage number 2 to SN4.
, SN4 sends the information of the relay stage number 3 to SN3, and SN3 sends the information of the relay stage number 4 to SN2. However, because of the failure, this information does not reach SN2.

Upon detecting a failure, SN2 sends the value of FF as relay stage number information to SN1, and SN1 transmits this value to MN as it is.

Each SN that has received these relay stage number information
Selects the system for subordinate synchronization as follows.

Since SN1 receives the value of 0 from the right loop R and the value of FF from the left loop L, the right loop R having a smaller value is selected as the system to be subordinately synchronized. SN2
Detects a failure in the left loop L, and selects the right loop R. Since SN3 has detected a failure in the right loop R, it selects the left loop L.

Since SN4 receives the value of 80 from the right loop R and the value of 2 from the left loop L, the left loop L having a smaller value is selected as the system to be slave-synchronized. Similarly, SN5 that receives 80 from the right loop R and 1 from the left loop L, and SN6 that receives 80 from the right loop R and 0 from the left loop L respectively have the left loop. Select L to perform slave synchronization.

In this way, subordinate synchronization is performed in each SN, and network synchronization of the faulty LAN is maintained, thereby enabling data transmission between SNs. In SN2 and SN3 which detected the failure, based on autonomous judgment,
Performs a loopback of data transmission.

Next, as shown in FIG. 3, SN4 and SN5
An operation will be described in the case where a second transmission line fault newly occurs during the period and there are two transmission line faults.

In the right loop R, the MN sends the information of the relay stage number 0 to the SN1, and the SN1 sends the information of the relay stage number 1 to the SN.
2 and SN2 sends the information of the number of relay stages of 2 to SN3. However, because of the failure, this information is
It does not reach SN3.

SN3 detects the failure and sends the value of 80 to SN4 as relay stage number information, and SN4 sends this value as it is to SN5. However, this information does not reach SN5 because of the second failure. SN
5 detects a failure and sends the value of 80 to SN6 as relay stage number information, and SN6 transmits the value of 80 to MN as it is.

On the other hand, in the left loop L, the MN sends information of 0 relay stages to SN6, SN6 sends information of 1 relay stages to SN5, and SN5 sends information of 2 relay stages to SN4.
Send to.

However, due to the second obstacle, this information does not reach SN4. On the other hand, SN4 that detected the failure
Sends the value of FF to SN3 as relay stage number information.

Upon receiving this value, SN3 receives the right loop R
Then, the failure is being detected. In this way, when the SN that is detecting a failure in one loop receives a number larger than the total number of nodes in the other loop, that SN becomes a pseudo MN and self-runs, and is generated by the internal clock generator. It outputs a clock and also outputs information of the number of relay stages 0. However, due to the failure, this information of SN3 does not reach SN2.

SN2 detects a failure and sends the value of FF as relay stage number information to SN1, and SN1 transmits this value as it is to MN.

Each SN that has received the relay stage number information
Selects the system to be slave-synchronized as follows (FIG. 4).

Since SN1 receives the value of 0 from the right loop R and the value of FF from the left loop L, the right loop R having a smaller value is selected as the system to be subordinately synchronized. SN2
Detects a failure in the left loop L, and selects the right loop R.

SN3 has a value FF larger than the number of nodes in the left loop L while detecting a failure in the right loop R.
Since it received the message, it becomes a pseudo MN and runs on its own.

Since SN4 has detected a failure in the left loop L, the SN4 selects the right loop R as the system to be subordinately synchronized. Since SN5 has detected a failure in the right loop L, it selects the left loop L. Further, since the SN 6 receives 80 from the right loop R and 0 from the left loop L, the SN 6 selects the left loop L having a smaller value and performs slave synchronization.

Thus, SN2, SN1, MN, SN6
And SN5, network synchronization based on the network synchronization reference clock output from MN is maintained, and between SN3 and SN4 separated from MN by a failure,
Network synchronization is maintained by the clock output from SN3 operating as a pseudo MN. As a result, data can be transmitted between the nodes in each of the two divided blocks. The SN2, SN5 and SN3, SN4 that have detected the failure execute loop back of data transmission based on autonomous judgment.

Signal transmission of the optical loop type LAN is SD
When using the H (Synchronous Digital Hierarchy) method (the above-mentioned Japanese Patent Application Nos. 4-92337 and 4-92)
No. 337), the relay stage number information can be transmitted and received between the node devices using a location where the unique specification is recognized in the overhead area of SDH.

Further, the network synchronization setting method of the present invention can be applied to a loop type LAN for transmitting electric signals.

[0052]

As is apparent from the above description of the embodiments, in the network synchronization setting method of the present invention, each SN uses the network synchronization reference clock with a small number of node relays and good quality to perform network synchronization. Can be set.

Also, network synchronization can be restored in a short time in response to the occurrence of a failure in the transmission path.

Further, even if a plurality of failures occur in the transmission line and the network is divided into a plurality of blocks, the network synchronization can be maintained in each block.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an operation of a node device according to a network synchronization setting method of the present invention,

FIG. 2 is a diagram showing an operation when a failure occurs in a node device according to the method of the present invention;

FIG. 3 is a diagram showing an operation when multiple failures occur in a node device according to the method of the present invention;

FIG. 4 is a diagram showing a state of a LAN when coping with multiple failures according to the method of the present invention;

FIG. 5 is a diagram showing a conventional network synchronization setting method,

FIG. 6 is a diagram showing an operation in a conventional network synchronization setting method when a failure occurs,

FIG. 7 is a diagram showing an operation in a conventional network synchronization setting method when multiple failures occur.

[Explanation of symbols]

 MN master node device SN1 to 6 slave node device F filter L left loop R right loop

Front page continued (72) Inventor Hiroyuki Nishi 3-3-1 Tsunashima-higashi, Kohoku-ku, Yokohama-shi, Kanagawa Matsushita Communication Industrial Co., Ltd. (72) Inventor Akira Sakai 4-chome Tsunashima-higashi, Kohoku-ku, Yokohama-shi, Kanagawa No. 1 Matsushita Communication Industrial Co., Ltd.

Claims (5)

[Claims] 1. A loop-type LAN network synchronization setting system in which a master node device and a slave node device are connected in a ring shape by a dual transmission line that transmits signals in mutually opposite directions, wherein the master node device comprises: A network synchronization reference clock is output to both of the dual transmission lines, and the slave node device selects a transmission line having a small number of node relay stages from the dual transmission line to the node device. And receiving the network synchronization reference clock and setting synchronization within the own node based on the network synchronization reference clock. 2. Each node device transmits the number of node relay stages for each transmission line to an adjacent node device through each transmission line, compares the number of node relay stages transmitted from both transmission lines, and determines the number. 2. The network synchronization setting method according to claim 1, wherein the lesser transmission path is selected to receive the network synchronization reference clock. 3. The node device which has detected a failure of a transmission line,
3. The network synchronization setting method according to claim 2, wherein a number larger than the total number of node devices connected to the loop LAN is transmitted to the adjacent node device as the number of node relay stages. 4. A slave node device which is detecting a failure of one transmission line outputs a clock signal by itself when a number larger than the total number of node devices is transmitted from the other transmission line. The network synchronization setting method according to claim 3. 5. The number of relay stages is SDH (synchronous digital
5. The network synchronization setting method according to claim 2, wherein the information is transmitted to the adjacent node device by using an overhead area of the hierarchy.