JPH0227841A - Composite local area network - Google Patents

Abstract

PURPOSE:To prevent a branch network connecting to a connection node from being isolated even if the connection node is faulty by using communication nodes and a transmission medium connecting them so as to couple two branch networks. CONSTITUTION:Communication nodes 7c, 7d and transmission media 12a, 12b are added newly. When a connection node 4c of a 3rd branch network is faulty, the communication nodes 7c, 7d are operated and the 3rd branch network and the 4th branch network are connected by the transmission media 12a, 12b. Then the communication with other branch networks caused in the 3rd branch network is realized via a connection node 4d of the 4th branch network. Thus, the 3rd branch network is connected to a node 5d of a trunk network via the connection node 4d even if the connection node 4c is faulty, then the node is not isolated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a local area network that allows a plurality of nodes to communicate with each other using a single transmission medium, and more specifically: The present invention relates to a composite local area network configured by dividing the local area network into a branch network and a trunk network, and connecting each of the plurality of branch networks to the trunk network via a connection node.

[Conventional technology]

Although a large number of examples of local area network configurations have been known in the past, the prior art will be explained here using the configuration example closest to the present invention.

FIG. 4 shows a composite local area network configured using the conventional technology, in which 1axle is the master node of the branch network, 2a-1, 2a-2,
2a-3, 2b-1, 2b-2, 2b-3, 2cm1,
2cm2.2cm3゜2d-1, 2d-2, 2d-3,
2e-1, 2e-2, 26-3 are all general nodes of the branch network, 3a-1, 3a-2, 3a-3, 3
a-4, 3b-1, 3b-2, 3b-3, 3b-4゜3
cm1, 3cm2, 3cm3, 3cm4.3d1.3d
-2,3d-3,3d-4,3e-1゜3e-2,3e
-3 and 3e-4 are transmission media that connect the nodes of the branch network, 4a to 4e are connection nodes, 5a to 5e are nodes of the trunk network, and 6a to 6e are transmission media of the trunk network *1a, 2a 1 ,2a 2
．． 2a 3゜3a-1, 3a-2, 3a-3, 3a-
4 constitutes a first branch network.

Similarly, lb, 2b-1, 2b-2, 2b-3, 3b-
1, 3b-2, 3b-3, and 3b-4 constitute a second branch network. Also, 3rd. 4th. The fifth branch network is configured similarly*5
a, 5 b, 5 c, 5 d, 5 e.

6a, 6b, 6c, 6d, and 6e constitute a trunk network. A plurality of branch networks and a trunk network are connected to connection nodes 4a and 4b.

They are connected by 4c, 4d, and 4e.

FIG. 5 is a diagram schematically showing a transmission frame format used in the composite local area network of FIG. 4. A transmission frame has a structure in which a destination address (DA) and a source address (SA) are added to transmission information (INFO).

First, a communication method in the branch network will be explained by taking the first branch network as an example.

As an example of a medium access method, a token passing method will be taken as an example. When the system is initialized, master node 1a
generates free tokens. The free token is sent to the general node 2a-1 via the transmission medium 3a-1. Then, the free tokens sequentially visit the nodes.

Now, assume that a packet addressed to the general node 2a-3 is generated at the general node 2a-1. The general node 2a-1 converts the received fleet token into a busy token, attaches the busy token to the beginning of a transmission packet (frame structure shown in FIG. 5), and transmits it to the subsequent node. The frame of the transmitted packet includes the destination address and the source address, as shown in Figure 5, so each node can determine whether it is addressed to its own node by reading the destination address. .

Since the packet of interest is a packet addressed to the -a node 2a-3, the general node 2a-2 directly transmits the transmission packet with the busy token attached to the beginning toward the general node 2a-3. The general node 2a-3 is
By reading the destination address, it learns that the sent packet is addressed to its own node, copies the packet, and sends the outgoing packet with a busy token prefixed to the subsequent node. This packet is collected by the general nodes 2a-1. - The touch node 2a-1 converts the busy token into a free token and transmits it to the subsequent node.

In this way, a node having a transmission packet can acquire the transmission right by capturing a free token, and can perform communication by attaching a busy token to the beginning of the transmission packet and transmitting it. Communication can be performed using similar operations in either branch network. However, the communication described above is confined within a single branch network.

Next, communication between different branch networks will be explained. Assume now that a packet addressed to the general node 2b-2 belonging to the second branch network is generated at the general node 2a-1 belonging to the first branch network.

The general node 2a-1 acquires a transmission right by capturing a fleet token in the first branch network, and transmits a transmission packet by attaching a busy token to the beginning of the transmission packet.

When this packet reaches master node 1a, master node la determines that the packet is addressed to a node in the second branch network by reading the destination address, and copies the packet. At the same time, the transmission packet with the busy token attached at the beginning is transmitted to the subsequent node (2a-1). This packet is collected by the general node 2a-1 which is the transmission source. The master node 1a sends the copied packet to the connection node 4a. The connecting node 4a transmits the received packet to a node 5a included in the trunk network.

At this time, the connecting node 4a converts the media access control protocol of the branch network to the media access control protocol of the trunk network. The connection node 4a then sends the packet to the trunk network. In the trunk network, the packet is sent from node 5a to node 5b. The packet is captured by the node 5b and transmitted to the connecting node 4b,
Here, the media access control protocol of the trunk network is converted to the media access control protocol of the branch network, and the master node 1b
sent to. By performing the same operation as described above in the second branch network to which the master node 1b belongs, the packet to be transmitted is transmitted to the general node 2b-2, and communication is successful.

As described above, in a composite local area network that includes multiple branch networks and one trunk network, communication can be performed by connecting the networks through connection nodes and converting communication protocols.

[Problem to be solved by the invention]

However, conventional hybrid local area networks have the following problems. That is, since the branch network and the trunk network are connected by one connection node, there is a problem that if the connection node fails, the branch network in question will not be able to communicate with other branch networks. In other words, the branch network in question becomes isolated within the complex local area network. In order to solve this problem, it is possible to connect one branch network and the main network using multiple connection nodes, but this would not only make the equipment heavy but also make the communication protocol complicated because there are multiple connection nodes. It's not practical.

The present invention provides a complex local area network that can provide a simple and effective solution to the problems of conventional complex local area networks, namely isolation of branch networks mainly due to failures of connecting nodes. The purpose is to

[Means to solve the problem]

To achieve the above object, the present invention provides a composite local area network consisting of a plurality of branch networks and a trunk network connected to each of the branch networks via a connection node, in which one of the plurality of branch networks is At least one pair of branch networks were each provided with a communication node including a transmission line changeover switch, and the two communication nodes were coupled by a transmission medium.

[Effect]

The communication node receives and regenerates and relays the signal sent via the prefix node in the branch network to which it belongs, and also refers to the network management information included in the signal to determine the branch network to which it belongs. The presence or absence of a failure in the connection node that connects the network and the main network network is determined, and if there is a failure, the transmission line changeover switch included in the self-communication node and the transmission line of the other party communication node connected by the transmission medium are checked. By switching the route changeover switch, the two branch networks are connected in a signal route manner.

The main feature of the present invention is that at least two branch networks are equipped with a communication node including a transmission line changeover switch, and the communication nodes are interconnected by a transmission medium, and the main line and This method differs from the prior art in that even if a connection node connecting the branch lines fails, the branch lines will not become isolated.

〔Example〕

FIG. 1 is a schematic explanatory diagram of an embodiment of the present invention. 7c
, 7d are contact nodes, and 12a and 12b are transmission media. Fig. 4 explained as the prior art has a new 7c,
The difference is that 7 d, 12 a, and 12 b are added.

As shown in Figure 1, lc, 3cm1, 2cm1.3c
m2,2cm2.3cm3.2cm3゜3cm41,7
A third branch network consisting of c, 3 cm 43 etc. and l
d, 3d-11, 7d, 3d-13,, 2d-1, 3d
-2, 2d-2, 3d-3, 2d-3, 3d-4, etc., is the transmission medium 12a, 12
connected by b. Under normal conditions, communications between different branch networks occur via their respective connection nodes in the same manner as described in FIG. 4. At this time, the transmission media 12a, 12b are not operating.

Assume now that the connection node 4c of the third branch network has failed. Contact node 7c in FIG.

7d to connect the third branch network and the fourth branch network via transmission media 12a and 12b, and connect the fourth branch network to communicate with other branch networks occurring in the third branch network. node 4d
Realized through.

The above is an outline of the configuration of the present invention. The present invention will be described in more detail below, focusing on the configuration and operation of the communication nodes 7c and 7d. Note that although an example in which an optical fiber is used as a transmission medium will be described here, the present invention can be similarly applied to a case in which a normal metal wire is used as a transmission medium.

FIG. 2 is a diagram showing in detail the main parts of FIG. 1, including communication nodes 7c and 7d and transmission medium 12a.

12b is a diagram illustrating an example of the main part configuration of the present invention, focusing on 12b. FIG. 8c and 8d are optical/electrical converters; 9c;

9d is a control unit, 10c and 10d are electrical/optical converters, 11
c, lid is optical switch circuit, 3cm41°3cm42
, 3cm43, 3d-11, 3d-12, and 3d-13 are transmission media (optical fibers).

In FIG. 2, thick arrows indicate the flow of optical signals, double arrows indicate the flow of electrical signals, and thin arrows indicate the flow of control signals.

The normal operation in FIG. 2 will be explained first.

The optical signal sent from the front node via the transmission medium 3cm41 is converted into an electrical signal by the optical/electrical converter 8C, and is taken into the control section 9C. The control unit 9C monitors network management information addressed to its own node. If the network management information does not include failure information, the signal is simply regenerated and relayed.

The regenerated and relayed signal is converted into an optical signal by an electrical/optical converter 10c and sent to a transmission medium 3 cm 42. The optical switch circuit 11c is set so that the light from the transmission medium 3C-42 is guided to the transmission medium 3cm43. Therefore,
The optical signal is transmitted to the subsequent node via the transmission medium 3 cm 43. A similar operation is performed at the contact node 7d opposite to the contact node 7C.

Assume now that the connection node 4C of the third branch network has failed. When network management information indicating that the connection node 4C has failed is sent from the master node 1C to the control unit 9C via the optical/electrical converter 8C, the control unit 9C
switches the optical switch circuits 11C and 11d. That is,
In the optical switch circuit 11c, 3 c-42-12a,
12 b-+3 c-43 path, optical switch circuit li
At d, the routes are 3d-12-+12b and 12a-+3d-13.

Therefore, the signal is 3 c-41-+8 c-+9 c-+
10 c-+3 c-42-+11 c-+12 a-
+11 d-+3 d-13→...3d-1
1→8d→9d→10d→3d-12→lld→12b
The flow is →llc→3cm43→... That is, the third branch network and the fourth branch network are connected by 11C911d, 12a, and 12b.

As a result, the third branch network connects the connecting node 4c
Even if the master node IC fails, it will be connected to the trunk network via the connection node 4d, so it will not become isolated.The network management information can be transmitted from the master node IC to the contact node 7C as follows. Since the third branch network itself is functioning normally, when the master node 1c transmits a packet containing network management information to the contact node 7C, the control unit 9c can obtain the network management information.

FIG. 3 is a diagram showing another example of the main part configuration of the present invention*
13c and 13d are electrical/optical converters; 14c;

14d is an optical switch circuit, 15c and 15d are optical/electrical converters, 3cm44, 3cm45, 3cm46, . 3d-
14, 3d-15, and 3d-16 are transmission media (optical fibers). In Fig. 3, thick arrows indicate the flow of optical signals, double arrows indicate the flow of electrical signals, and thin arrows indicate the flow of electrical signals. Arrows indicate the flow of control signals. The normal operation in FIG. 3 is the same as the operation described in FIG. 2.

The optical switch circuit 14c is set so that the light from the transmission medium 3c-4'4 is guided to 3cm46, and the light from the transmission medium 12a is guided to 3cm45. Further, the optical switch circuit 14d is set so that the light from the transmission medium 12b is guided to 3d-15, and the light from the transmission medium 3d-14 is guided to 3d-16. Therefore, the control section 9c and the control section 9d can communicate with each other.

From the control unit 9c, 13c, 3cm44, 14c.

3cm46. llc, 12b, 14d, 3d-15,1
5d to the control unit 9d, and conversely from the control unit 9d to 13
d,,3d-14,14d,3d-16,lid,12
Information can be transmitted to the control unit 9c via the a, 14c, and 3cm 45, 150.

Assume now that the connection node 4c of the third branch network has failed. Network management information indicating that the connection node 4c has failed is transmitted from the master node IC to the control unit 9c via the optical/electrical converter 8c. The control unit 9c transmits a transmission path switching request addressed to the control unit 9d to the control unit 9d using the means described above. The control unit 9d uses the above-described means to respond to the transmission path switching request.
tell to.

In this way, after both parties have agreed to switch the transmission path,
Optical switch circuit 11c, lid, 14c.

By switching 14d, the third branch network and the second branch network are coupled. The signal flow after being combined is 3cm41→8 c-+9 c-
+10 c-+3 c-42→llc→3C-45-+
l 4 C-+l 2B→11 d-+3 d-13-
+・・・3d-11→8d→9d→10d→3d
-12→lid→3d-16→14d→12b→11C
→3cm43→... As a result, even if the connection node 4c fails, the third branch network is connected to the trunk network via the connection node 4d, so it will not become isolated.

After the third branch network and the fourth branch network are combined, 13c, 3cm44°14c, 3cm
46. llc, 12b, 14d.

3d-15, 15d transmission line, and 13d, 3d-1
4, 14d, 3d-16, lid, 12a.

Although the transmission paths 14c and 3cm45.15c become unusable, they can communicate on the combined network, so negotiations for network separation can be performed without any problem after the connected node 4C is repaired. .

If the transmission loss of the transmission line connecting the two branch networks is large due to reasons such as the distance between the third branch network and the fourth branch network being large,
Or, if the waveform distortion is large, the transmission media 12a, 12
A repeater may be inserted in the middle of b. The operation and effects in this case are similar to those described in FIGS. 1 to 3.

〔Effect of the invention〕

As explained above, two branch networks can be connected using a contact node and a transmission medium that connects it, so even if a connection node fails,
The branch network connected to the connection node is never isolated. Note that one possible way to avoid isolation of the branch network is to duplicate the connection nodes, but this method requires the cost of having duplicate connection nodes responsible for protocol conversion, and is not suitable for network simplicity or economy. It's not a good idea from a gender perspective. In comparison, the present invention connects networks at the transmission medium level, so there is no need for protocol conversion and a simple and economical configuration can be realized.

The above explained the effect of preventing isolation of the branch network in response to a failure of a connected node. However, if a trunk node fails and the trunk goes into bypass mode or loopback mode, or if the branch master node fails. This is effective because isolation of the branch line network can be avoided even when the branch line goes into bypass mode or loopback mode.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of one embodiment of the present invention, and FIGS. 2 and 3 are configuration diagrams showing details of the main parts of FIG. 1, respectively. Fourth
This figure is a schematic diagram showing a composite local area network configured using a conventional technique, and FIG. 5 is a schematic explanatory diagram of a frame format used in the composite local area network of FIG. 4. Explanation of symbols 1a to 1e: master node of branch network, 2
a-1, 2a-2, 2a-3, 2b-1, 2b-2, 2
b-3,2c-1,2c-2,2c-3゜2d-1,2
d-2, 2d-3, 2e-1, 2e-2, 2e-3...
General nodes of the branch network, 4a to 4e... Connection nodes, 5a to 5e... Nodes of the trunk network, 6a to 6e... Transmission medium of the trunk network, 7
c, 7d... contact node, 8c. 8d... Optical/electrical converter, 9c, 9d... Control unit,
10c, 10d--electrical/optical converter, llc, lld
...Optical switch circuit, 12a, 12b...Transmission medium, 13c, 13d...Electrical/optical converter, 14c, 14
d... Optical switch circuit, 15c, 15d... Optical/electrical converter. Agent Patent Attorney Akio Namiki

Claims (1)

[Scope of Claims] 1) In a composite local area network comprising a plurality of branch networks and a trunk network connected to each of the branch networks via a connection node, at least one pair of the plurality of branch networks Each of the branch networks is equipped with a contact node including a transmission line changeover switch, and the two contact nodes are connected by a transmission medium, and each of the contact nodes transmits data via a prefix node in the branch network to which it belongs. In addition to receiving the incoming signal and reproducing and relaying it, it also refers to the network management information included in the signal to know whether there is a failure in the connection node that connects the branch network to which it belongs and the main network, and to detect the presence of a failure. In this case, the network consists of a node that connects both branch networks in terms of signal paths by switching the transmission line changeover switch included in the own communication node and the transmission line changeover switch of the other communication node connected by the transmission medium. A complex local area network characterized by: