JP2006166286A - Ring-shaped network system and ring-shaped network node - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein a period of time during which a clock master node does not exist, may occur until a node of the next node priority becomes the clock master node if any fault occurs in the clock master node since one node of the highest node priority is defined as the clock master node in a conventional ring-shaped network. <P>SOLUTION: In a ring-shaped network system, a plurality of nodes are provided to input an external clock, and a node of the highest node priority or including an external clock input is operated as a clock master node. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ring type network system and a ring type network node, and more particularly to multiple clock masters.

In a ring network in which a plurality of nodes are connected in a ring shape by a conventional duplex transmission line, one node operates with the clock of its own node and becomes a clock master node that sends its own clock to another node, The remaining nodes become clock slave nodes according to the clock sent from the clock master node. Each node transmits / receives information to / from each other via a transmission path.
In order to determine which node becomes the clock master node, each node has a node priority setting unit, a node priority extraction unit, a rank information generation unit, and a node priority determination unit. The node priority setting unit sets the node priority of the own node, and the node priority extraction unit extracts node priority data from information received from the transmission path. The rank information generation unit compares the node priority of its own node (referred to as its own node rank) and the node priority (transmission data rank) extracted from the information received from the transmission path, and determines whichever is greater. Is set as node priority data of information to be transmitted. Then, the node priority order determination unit compares the own node order with the transmission data order, and when both of the transmission paths have higher own node order, the own node becomes the clock master node, and in other cases, the own node becomes The clock slave node.
By setting the node priority in advance by the node priority setting unit, it is possible to easily set which node is the clock master node. It is shown that when a node operating as a clock master node fails, a node having the highest self node order among remaining healthy nodes operates as a clock master node (see, for example, Patent Document 1). ).

Japanese Patent Laying-Open No. 2001-35836 (FIG. 1)

In the device disclosed in Patent Document 1, when the node having the highest node priority leaves the ring network due to a failure or the like, the node having the next node priority changes to the clock master node. Since the node priority setting is not completed at the moment when the node having the highest node priority leaves, the node having the next node priority is not yet the clock master node, but the clock master in the ring network. A period in which there is no occurrence occurs.
For this reason, there is a problem that in the transition period, each other falls in a state of subordinate synchronization without a clock master, and the synchronization state becomes unstable, causing a temporary disruption of communication. In particular, the disruption of communication is not allowed even instantaneously. In such a system, the configuration disclosed in Patent Document 1 cannot be used.

  The present invention has been made in order to solve the above-described problem. Even when a failure occurs in one clock master node with a plurality of clock master nodes, a transient clock disturbance is generated. The purpose is to provide a highly reliable ring network system that does not cause any problems.

A ring network system according to the present invention includes a plurality of nodes that transmit and receive information to each other, and a duplex transmission path that connects the plurality of nodes in a ring shape and flows the information.
At least one of the plurality of nodes operates as a clock master node that operates according to the clock of the own node and transmits the clock of the own node to other nodes, and a clock other than the clock master node is transmitted from the clock master node Operates as a clock slave node according to
The information includes node priority data used to determine the clock master node,
A node priority setting unit for setting each node's own node order which is the node priority of the node; a node priority order extracting unit for extracting node priority data from the information received by each transmission path; A rank information generator for setting the node priority data of the information to be transmitted to each transmission path, the higher one of the transmission data rank, which is the node priority extracted from the information, and the own node rank; And the transmission data order and the own node order are determined, and both transmission paths are determined to operate as a clock master node when the own node order is higher in priority, otherwise the clock slave An operation mode determination unit that determines to operate as a node;
The plurality of nodes are divided into at least two first nodes capable of inputting an external clock input and a second node which is a node other than the first node, and the first node is an external clock. An external clock input determination unit that determines the presence or absence of input,
The frequency of the external clock input to all the first nodes is the same,
The node order of the first node is necessarily higher in priority than the node order of the second node;
The operation mode determination unit of the first node operates as a clock master node using the external clock as a clock of its own node even when the external clock input determination unit determines that there is an external clock input. To decide.

  In the ring network system according to the present invention, a plurality of nodes are connected in a ring shape, and a plurality of nodes operating as clock masters by inputting an external clock are used. Therefore, even when one clock master node fails. There is an effect that a highly reliable ring network system that does not cause a transient clock disturbance can be obtained.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIGS.
FIG. 1 is a system configuration diagram showing a ring network system. FIG. 2 is a conceptual diagram showing a frame used for data transmission in the ring.
FIG. 3 is a block diagram showing the configuration of the Z4 byte reception comparison unit 32. As shown in FIG. FIG. 4 is a block diagram showing a node configuration in the ring network system. FIG. 5 is a flowchart showing a procedure for comparing node priority numbers in each node.

In FIG. 1, a plurality of nodes, in this case, four nodes 110, 111, 112, and 113 are connected by a 0-system transmission line 1 and a 1-system transmission line 2 in a ring shape. Of the nodes 110, 111, 112, and 113, the nodes 110 and 111 are connected to a network synchronous clock supply device, and are the first nodes to which an external clock can be input. On the other hand, the nodes 112 and 113 are second nodes that cannot input an external clock.
In the first embodiment, the number of nodes is four, but the present invention is not limited to this.

In FIG. 1, the terminal line IF (terminal line interface) 20 illustrated in the nodes 110 and 112 is compliant with standards such as the ITU-T (International Telecommunications Union) standard G-703. is there.
Each terminal line IF 20 is connected to a TDM 22 (Time Division Multiplexer) via a line transmission path 21. A Z4 byte reception comparison unit 32 that synchronizes the frame data transmitted in the ring is provided in each of the nodes 110, 111, 112, and 113. Although not shown in FIG. 1, the nodes 111 and 113 are also provided with the same terminal line IF 20, and are connected to the TDM 22 via the line transmission path 21.

FIG. 2 is a conceptual diagram showing a frame used for data transmission in the ring. Information is transmitted and received between nodes by this frame. 2 shows an STM-1 frame (Synchronized Trans Mode-1 frame), and this STM-1 frame is provided with one VC-4 frame capable of directly multiplexing data from the terminal line IF 20. . The STM-1 frame is composed of 270 bytes × 9 rows of time slots. SOH is a section overhead (SECTION OVER HEAD) consisting of 9 bytes × 9 rows of time slots, and is a channel in which fixed values for synchronization and control are set.
POH is a path overhead (PASS OVER HEAD) composed of 1 byte × 9 rows of time slots, and has a user channel that a user can freely use. In the first embodiment, a frame number corresponding to the reference is set in the Z4 byte which is the first user channel of this path overhead. For example, node priority numbers 1 to 127 are set in the Z4 byte of the VC-4 frame of the STM-1 frame. Here, 0 is not used as a node priority number.

Next, FIG. 3 shows a configuration of the Z4 byte reception comparison unit 32 provided in each of the nodes 110 to 113. The Z4 byte reception comparison unit 32 includes an STM-1 frame synchronization detection unit 50, an SOH termination unit 51 and a POH termination unit 52 that constitute a frame reception unit, a POH generation unit 59, an SOH addition unit 60, and a frame transmission unit. STM-1 frame synchronization pattern adding unit 61, Z4 byte extracting unit 62 for extracting and comparing Z4 bytes, node priority order setting unit 63, external clock input determining unit 69 and Z4 byte comparing unit 64 are transmitted. And a demultiplexing memory unit 56 for storing incoming frames and frames to be transmitted.
The STM-1 frame synchronization detection unit 50 synchronizes the STM-1 frame of the data received by the nodes 110-113. The reception clock extracted by the STM-1 frame synchronization detection unit 50 is sent to a clock recovery unit 67 (described later). The SOH termination unit 51 performs SOH analysis, and the POH termination unit 52 performs POH analysis.
It is checked whether the received frame is for this node in the demultiplexing memory 55, and the frame for this node is sent to the terminal line IF 20. Frames not directed to this node and frames sent from the terminal line IF 20 are stored in the demultiplexing memory unit 55 and processed by the POH generation unit 59 in order.

The POH generation unit 59 sets the node priority number determined by the Z4 comparison unit 64 to the Z4 byte of the POH for the frame sent from the demultiplexing memory unit 55. That is, the POH generation unit 59 is a rank information generation unit that generates rank information. The SOH adding unit 60 adds SOH, and the STM-1 frame synchronization pattern adding unit 61 transmits the STM-1 frame.
The Z4 byte extracting unit 62, which is a node priority extracting unit, extracts a node priority number from the Z4 byte of the received VC-4 frame. The node priority order setting unit 63 sets the node priority order number of its own node, and uses, for example, a dip switch.

Here, the node priority number will be described. The node priority order number determines the priority order of the nodes, and is different for each node. Assume that a node with a low node priority number has a high priority. For the nodes 110 and 111 that are the first nodes, numbers that are smaller than the nodes 112 and 113 that are the second nodes, that is, in a higher priority order, are set. When the node priority number is the same, it is possible to determine the node priority in combination with other data, such as determining that the smaller node number is the higher priority. Further, a node having a higher node priority number may have a higher priority.
The Z4 byte comparison unit 64 that is an operation mode determination unit compares the node priority number extracted from the Z4 byte with the node priority number set by the node priority setting unit 63, and determines the comparison result and external clock input determination. Based on the input from the unit 69, the operation mode is determined. The determined operation mode is used by the clock selection unit 65, and the node priority number with the higher priority is used by the POH generation unit 59.

  The external clock input determination unit 69 is provided in the first node capable of inputting an external clock, and sets whether to use the external clock input 68. For example, a dip switch is used. The second node that cannot input the external clock does not have the external clock input determination unit 69, and the Z4 byte comparison unit 64 always operates assuming that there is no external clock input. The external clock input determining unit 69 may be configured by software that automatically determines the presence or absence of an external clock input, or all nodes may have the external clock input determining unit 69.

The configuration of the clock selector 65 will be described with reference to FIG. The clock selection unit 65 includes a clock recovery unit 67 that recovers the reception clock extracted by the STM-1 frame synchronization detection unit 50, and a master clock generation unit 66 that generates a clock of its own node. In the first node, there is an external clock input unit 68 to which an external clock from the network synchronous clock control device 4 is input. When there is an external clock input unit 68 and the external clock input determination unit 69 determines that there is an external clock, the master clock generation unit 66 generates an external clock from the external clock input unit 68 as a clock of its own node.
The clock selection unit 65 regenerates the clock from the master clock generation unit 66 when it is determined that both the 0-system and the 1-system Z4 byte comparison unit 64 should operate as a clock master node. The clock reproduced by the unit 67 is supplied to the 0-system and 1-system Z4 byte reception comparison section 32.

Next, the operation will be described. In FIG. 1, the digital data time-division multiplexed by the TDM 22 passes through the line transmission path 21 and is terminated at the terminal line IF 20. Among the nodes 110 to 113, the nodes 110 and 111 operate as clock master nodes, and the rest operate as clock slave nodes, but immediately after startup, all the nodes 110 to 113 operate with their own clocks. To do.
Each of the nodes 110 to 113 sets the priority number set by the node priority setting unit 63 at its own timing in the Z4 byte (see FIG. 2) of the POH. Here, the smaller node priority number is the node with the higher priority. In each node, a Z4 byte node priority number (referred to as transmission data rank) in a frame received from an adjacent node, and a node priority number of the node set in advance by the node priority setting unit 63 (own node rank) Is called).

The comparison procedure will be described with reference to the block diagram of FIG. 3 and the flowchart of FIG. In step S1, the Z4 byte extracting unit 62, which is a node priority extracting unit, extracts the transmission data order M from the Z4 byte of the POH. In step S2, the Z4 byte comparison unit (operation mode determination unit) 64 compares the transmission data rank M with the own node rank N.
In step S2, if the transmission data rank M extracted from the Z4 byte is larger, the own node rank N is set to Z4 byte in the POH generation unit 59 in step S3, and the count value n of the counter is set to 1 in step S4. And go to step S5.

In step S5, if the count value n of the counter is larger than a predetermined value, that is, if the transmission data rank M is a value larger than the own node rank N for a predetermined number of times, that node is set as a temporary master node in step S6. The process proceeds to step S8. Here, the specified number of times is set to a value obtained by adding a slight margin for noise or the like to the total number of nodes. For example, if the total number of nodes is 127, it is set to 140 times, 1.1 times.
If the transmission data rank M is smaller than or equal to the own node rank N in step S2, the transmission data rank M is set to Z4 bytes in the POH generation unit 59 in step S7, transmitted to the next node, and the process proceeds to step S8. go. In step S8, it is determined whether both the 0-system and the 1-system are temporary master nodes. If they are temporary master nodes, the process goes to step S10. In step S8, if neither the 0 system nor the 1 system are both temporary master nodes, the process goes to S9.

If it is determined in step 9 that the external clock input determination unit 69 determines that there is an external clock input, the process proceeds to S10. If the external clock input determining unit 69 does not determine that there is an external clock input, this node is not a clock master node, and the process proceeds to S12.
In step S10, the node is set as a clock master node, and in step S11, the clock selection unit 65 uses the clock of the reclock generation unit 66. In step S12, the node is set as a clock slave node. In the clock slave node, the reception clock extracted by the STM-1 frame synchronization detection unit 50 is used.

Thus, the node set with the highest node priority or the node determined to have an external clock input operates as the clock master node. The same applies when a new node is added. In addition, when it is desired to change the node that operates as the clock master node, the node priority setting and the presence / absence of external clock input are changed.
Therefore, both the node 110 and the node 111, which are determined to have an external clock input and whose node priority is set to the highest and next node, operate as clock master nodes. Even if one of the nodes 110 and 111 fails, a period in which no clock master node exists does not occur, and a transient clock disturbance does not occur. Although two nodes are determined by the external clock input determination unit 69 as having an external clock input, the number of nodes may be more than two. Further, although the external clock is input to the plurality of nodes from the same network synchronous clock input device 4, the external clock may be input from a different device for each node as long as the clocks have the same frequency.

Embodiment 2. FIG.
In the first embodiment, the case where the external clock input to the external clock input unit 68 is not stopped has been described. However, as shown in FIG. When the external clock input is interrupted due to the failure of the input unit 68, that is, when the external clock is not normally input, if the external clock input determination unit 69 determines that there is an external clock input, it is set as the clock master node. The signal output from the node to the ring is forcibly stopped to leave the ring network. Since the external clock input disconnection detection circuit 70 is provided in this manner, it is possible to prevent the clock slave node from erroneously continuing the slave synchronization to the external clock input disconnection node and to perform the slave synchronization to the other clock master node. it can.

Embodiment 3 FIG.
In the second embodiment, when the external clock input determining unit 69 detects the external clock input disconnection at the node determined to have the external clock input, the signal output from the node to the ring is forcibly stopped. As described above with reference to FIG. 7, the external clock input disconnection detection circuit 70 detects the external clock input at the node where the external clock input determination unit 69 determines that there is an external clock input. When an input disconnection is detected, the node shifts from the clock master node to the clock slave node and is subordinately synchronized with the other clock master nodes, and the node priority order extracted from the received frame in the Z4 byte of the frame transmitted to both transmission paths And a signal that prevents other nodes from subordinate to its own node. Set to a predetermined position of the frame.

In the third embodiment, a signal equivalent to the upstream failure signal in the fifth embodiment in Patent Document 1 is used as a signal that prevents other nodes from subordinate to the own node. The operation of each node that has received the upstream failure signal is the same as in the case of Patent Document 1.
Further, the upstream failure notification output in FIG. 7 means that a signal equivalent to the upstream failure notification output in the fifth embodiment of Patent Document 1 is output. In this way, the clock slave node is subordinately synchronized with the other clock master node, and all clock slave nodes that have been subordinately synchronized with the clock master node that has been disconnected from the external clock are disconnected from the external clock input. There is no need to leave the connected node off the network, and there is an effect that the communication of the terminal connected to the own node can be continued.
Note that another signal may be used as a signal that prevents other nodes from being subordinate to the own node.

  The first to third embodiments of the present invention as described above can be used for a ring network system that requires high reliability.

1 is a system configuration diagram showing a ring network system according to a first embodiment of the present invention. It is a conceptual diagram which shows the flame | frame used for the data transmission in the ring of Embodiment 1 of this invention. It is a block diagram which shows the structure of the Z4 byte reception comparison part of Embodiment 1 of this invention. It is a block block diagram which shows the structure of the node in the ring type network system of Embodiment 1 of this invention. It is a flowchart which shows the comparison procedure of the node priority number number in each node of Embodiment 1 of this invention. It is a system block diagram which shows the ring type network system of Embodiment 2 of this invention. It is a system block diagram which shows the ring type network system of Embodiment 3 of this invention.

Explanation of symbols

1 0 transmission line, 2 1 transmission line, 4 network synchronous clock supply device,
32 Z4 byte reception comparison unit, 59 POH generation unit (rank information generation unit),
62 Z4 byte extracting unit (node priority extracting unit), 63 node priority setting unit,
64 Z4 byte comparison unit (operation mode determination unit), 69 external clock input determination unit,
70 External clock input disconnection detection circuit, 110 to 113 nodes.

Claims (6)

A plurality of nodes that transmit and receive information to each other, and a duplex transmission path that connects the plurality of nodes in a ring shape and flows the information,
At least one of the plurality of nodes operates as a clock master node that operates according to the clock of the own node and transmits the clock of the own node to other nodes, and a clock other than the clock master node is transmitted from the clock master node Operates as a clock slave node according to
The information includes node priority data used to determine the clock master node,
A node priority setting unit for setting each node's own node order which is the node priority of the node; a node priority order extracting unit for extracting node priority data from the information received by each transmission path; A rank information generation unit that sets the node priority order data of the information to be sent to each transmission path, whichever is higher among the transmission data rank that is the node priority order extracted from the information and the own node rank The transmission data order and the own node order are compared, and both transmission paths are determined to operate as a clock master node when the own node order has a higher priority, otherwise the clock slave An operation mode determination unit that determines to operate as a node;
The plurality of nodes are divided into at least two first nodes capable of inputting an external clock input and a second node which is a node other than the first node, and the first node is an external clock. An external clock input determination unit that determines the presence or absence of input,
The frequency of the external clock input to all the first nodes is the same,
The node order of the first node is necessarily higher in priority than the node order of the second node,
The operation mode determination unit of the first node operates as a clock master node using the external clock as a clock of its own node even when the external clock input determination unit determines that there is an external clock input. A ring network system characterized by deciding. The first node has an external clock input break detection unit that detects whether or not an external clock is normally input;
The external clock input determination unit determines that there is an external clock input, and the node detected by the external clock input disconnection detection unit if the external clock is not normally input is transmitted by the node to the transmission path. The ring network system according to claim 1, wherein the ring network system is stopped. The first node has an external clock input break detection unit that detects whether or not an external clock is normally input;
In the node where the external clock input determining unit determines that there is an external clock input, and the external clock input disconnection detecting unit detects that the external clock is not normally input, the operation mode of the node 2. The ring according to claim 1, wherein the decision unit decides to operate as a clock slave node, and the node sends a signal for preventing other nodes from subordinate to the own node to each transmission line. Type network system. From a clock master node or a clock master node that is connected in a ring form by a duplex transmission path to form a ring network, send / receive information to / from each other, operate with the clock of its own node, and send its own clock to another node A node that operates as one of the clock slave nodes according to the clock being sent,
An external clock input determination unit for determining the presence or absence of an external clock input;
A node priority order setting unit for setting the own node order that is the node priority order of the own node;
A node priority extraction unit that extracts node priority data from the information received by each transmission path;
A rank information generation unit for setting the node priority order data of the information to be transmitted to each transmission path, the transmission data rank that is the node priority order extracted from the information and the higher priority among the own node ranks; ,
The transmission data order and the own node order are compared, and either of the cases where the priority of the own node order is higher in both transmission paths or the case where the external clock input determination unit determines that there is an external clock input And an operation mode determination unit that determines to operate as a clock slave node in other cases.
A ring network node characterized in that, when the external clock input determination unit determines that there is an external clock input, the external clock is used as a clock of its own node. It has an external clock input disconnection detection unit that detects whether the external clock is normally input,
When the external clock input determination unit determines that there is an external clock input, and the external clock input disconnection detection unit detects that the external clock is not normally input, information from the own node to the transmission path The ring network node according to claim 4, wherein the transmission of the ring network is stopped. It has an external clock input disconnection detection unit that detects whether the external clock is normally input,
When the external clock input determination unit determines that there is an external clock input, and the external clock input disconnection detection unit detects that the external clock is not normally input, the operation mode determination unit determines that the clock slave 5. The ring network node according to claim 4, wherein the ring network node is determined to operate as a node, and sends a signal that prevents other nodes from subordinate to the own node to each transmission path.

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