JPS6313544A - Routing system - Google Patents

Abstract

PURPOSE:To accommodate a terminal equipment connected to a single communication medium without any change by changing an information frame into a format representing undesignation of route and transferring the result to a specific link only when a destination address terminal equipment is connected directly to a specific link other than the received link. CONSTITUTION:Network connection devices 1-5-1-9 select a channel according to an identifier when a communication route is designated in the route selection area of a received information frame. A link receiving the information frame is a component of a selected channel and a terminal equipment of a destination address recognizes it to be located at the side of the specific link being the component of the selected channel other than the received link, whether or not the terminal equipment of the destination address is connected to the communication media 1-1-1-4 connected directly to the specific link is checked. In case of the connection, the route selection area in the information frame is rewritten into a mark representing unselection and the area written with the identifier of the channel is transferred only to the specific erased link.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a routing system, and particularly to a routing system in a communication network in which a plurality of communication media having repeatability are connected by a plurality of network connection devices.

[, Prior Art] Many routing methods have been considered in the past for communication networks in which multiple communication media with repeatability are connected by multiple network connection devices, but there are two typical methods. . One is a first method in which the communication route from the source terminal to the destination terminal is known in advance, and all the address information of the network connection devices to be passed is included in the frame and transmitted.

This first method requires each terminal to hold route information to all destination terminals, and has the disadvantage that it is difficult to update the information to route 1 when the configuration is changed. However, since each terminal can select communication routes 1 through 1, it has the advantage that it is possible to specify the route I considered to be the best at that time. Such a method is generally called a source routing method. The other method does not require each terminal to hold any information regarding route links, but instead makes it appear as if all terminals are connected via the same communication medium. Therefore, this method imposes less burden on each terminal and is suitable for systems with a variable configuration (V).

To implement such a policy, one conceivable method would be to send all information frames received by each network connection device to all links other than the link from which it was received, regardless of the destination, but this method If there is a closed circuit, duplicate reception occurs, which places a heavy processing burden on each terminal. A possible way to avoid this duplicate reception is to configure a logical communication path with this structure that does not include a closed path on a communication path that physically has a closed path, and then perform the same procedure as this method on that logical communication path that does not include a closed path. It will be done. This is the second method, and is generally referred to as the hierarchical power routing method. This method will be explained using FIG. 2. FIG. 2 is an explanatory diagram for explaining the conventional method. In (a) and (b) of the same figure, 2-1. ~l-4 is a communication medium with broadcasting property, 2-5
．． 2-9 are network connection devices. FIG. 2(a) shows a communication network having a closed circuit as a whole. Figure 2(b)
The communication path shown in is an example of a logical communication path and does not include a closed path. In other words, the logical communication path in this case is network connection device 2-8.
By not using 2-9, the formation of a closed circuit is prevented. However, in such a system, for example, the communication medium 2
Although the information frame sent from the terminal connected to -3 to the terminal connected to the communication medium 2-4 is physically sent directly via the network connection device 2-9, , via the network connection devices 1-6, 2-5 and 2-8, and the communication media 2-1 and 2-2, so to speak, in a roundabout way. This is wasteful and also causes congestion in certain communication media, which is undesirable. In the above example, communication medium 2-3
It is preferable that the communication between the terminal -h and the terminal of the communication medium 2-41- is performed via the network connection device 2-9, and a routing method that uses the shortest route for communication between all terminals is desirable. As described above, both the conventional first and second methods have advantages and disadvantages.

An object of the present invention is to provide a communication network comprising a plurality of communication media having repeatability and a plurality of network connection devices, in accordance with the above-mentioned conventional method. A routing method that combines the advantages of the second method, that is, each terminal does not require any information regarding the location of the destination terminal, and moreover, it is possible to select a route that is considered to be better from among multiple routes. Moreover, it is an object of the present invention to provide a routing method that simultaneously allows terminals connected to a single communication medium to be accommodated without any changes.

[Means for solving problems]

The present invention provides a communication system in which a plurality of communication media having broadcasting properties are connected by a plurality of links of a plurality of network connection devices, in which each network connection device is connected to the communication medium to which it is directly connected. has a means for knowing the address of a terminal that has been accessed, and creates a communication path that does not include a plurality of closed circuits consisting of a specific communication medium in the communication system, a specific network connection device, and a link of the specific network connection device. However, a route selection area is provided in the information frame transmitted by the terminal to distinguish whether or not to specify a communication route, and if the sending terminal does not specify a communication route, the sending terminal specifies the communication route in the route selection area. If the transmitting terminal specifies a specific communication path among the plurality of communication paths, communication routes 1 to 1 are specified in the route selection area in the information frame. At the same time, an identifier indicating the specific communication channel among the plurality of communication channels is written in a specific area of the information frame and transmitted, and the network connection device stores the route selection area of the received information frame. look,
If there is a mark specifying a communication route, read the specific area where the identifier of the specified communication path is written, select the communication path shown there, and select the link that received the information frame. is a component of the selected communication path, and
If the terminal at the destination address is known to be on the side of a particular link that is a component of the selected communication path other than the receiving link, the terminal at the destination address is directly connected to the particular link. If it is connected, the route selection area in the information frame is rewritten to a non-selected mark, and if the communication path identifier is written, that area is deleted and the corresponding identification is performed. I am forwarding only the link.

"Operation" Next, the operation of the present invention will be explained in detail.Hereinafter, the connection between the network connection device and each communication medium will be referred to as a link.
For the sake of explanation, the upper link of each network connection device will be referred to as link 1 and the lower link will be referred to as link 2 in each country. In addition, here, the shortest path is used to mean the minimum number of hops compared to the number of network connection devices passed from the sending terminal to the destination terminal. In the present invention, it is necessary to construct a logical communication path that does not include a plurality of closed circuits. Basically, to configure a logical communication path that does not include closed circuits, one network communication device must be selected for each communication medium from among the multiple network connection devices connected to that communication medium. Bye. Such a network connection device will be referred to as a connection device responsible for each communication medium. To select the responsible connection device, for example, decide on the only central connection device in the communication system, and choose the network with the smallest number of hops to the central connection device from among the multiple network connection devices connected to each communication medium. The connecting device may be selected as the responsible connecting device for the communication medium. In order to configure a logical communication path that does not include a plurality of closed circuits, it is sufficient to select a plurality of central connection devices and determine the responsible connection device for each central connection device. Note that the central connection device can basically be selected in any way as long as it is uniquely determined; for example, it is sufficient to select the required number of logical communication paths from among all the network connection devices in descending order of address. Next, when a specific central connection device is selected, an example of how to select a responsible connection device corresponding to the central connection device will be described. The central connection device transmits a route determination frame in which its own address is written, using a specific group address determined among all network connection devices as the destination. The route determination frame is provided with a place to write the number of hops to the source central connection device, and the source central connection device writes '0°'' there. The network connection device that receives the route determination frame reads the number of hops written in the frame, and if that number of hops indicates that the route determination frame has been received from the central connection device on the received link. Only when the number of hops written in the received frame is smaller than the number of hops written in the received frame, the received frame is recorded along with the received link number, and the value of the number of pops in the frame is set to ±1 and sent to all links other than the received frame. do. In this way, each time the route determination frame passes through one network connection device, the number of hops written in the route determination frame increases by one, but it remains at a certain value predetermined depending on the size of the communication system. A network connection device that receives a frame with a hop count greater than or equal to the above value discards the received frame.

As a result of the above operations, after a certain period of time has elapsed, each network connection device determines its own number of hops to the central connection device from the recorded route determination frame. The number of hops for oneself to the central connection device is the smallest value of the number of hops written in the route determination frame received from the central connection device +
1.

There is a network connection device closer to the central connection device than the communication medium connected to the link that received the route determination frame with a hop number smaller than the own hop number, or there is a network connection device that is closer to the central connection device than itself, or Since it is directly connected, it cannot be the responsible connecting device for that communication medium. One of the links connected to such a communication medium will be referred to as a central connection device side link. If there are multiple such links, you may arbitrarily select one of them.

If a communication medium connected to a link that only received a route determination frame with a hop number greater than the own hop number is connected to the communication medium that is closest to the communication medium, it is determined that the communication medium is responsible for the connecting device. Become.

If a link receives a route determination frame with the same number of hops as its own, there is another network connection device with the same number of hops as itself on the connected communication medium, so In that case, a conflict resolution rule is established and one network connection device is selected as the responsible connection device. As a rule for conflict resolution, for example, an address unique to each network connection device may be used, and the one with the smallest address may be selected as the responsible connection device. In the following manner, the only responsible connection device for each communication medium is selected for the central connection device, and each network connection device selects one link on the central connection device side among its own multiple links. You can see the link on the communication medium side for which you are the responsible connection device. These links will hereinafter be referred to as valid links. If each network connection device receives information only from its own valid link and transfers the received information frame only to valid links other than the received link, a logical communication path that does not include closed circuits can be constructed. In order to configure a logical communication path that does not include a plurality of closed circuits, the above procedure may be performed for each of a plurality of central connection devices. -4- Assign a number to the logical communication path that does not include a plurality of closed circuits and is configured by the procedure described above. For example, numbering may be done in the order of the addresses of the corresponding central connection devices, with the communication path corresponding to the central connection device with the smallest address being numbered 1, and the numbers may be numbered in order. Either each terminal sends data by specifying only the address/response without being aware of the routing, or
Or you can choose to send by selecting the communication route.

In the former case, it is the same as when the terminal is connected to the disputed communication medium, and there is no need to hold information regarding disconnection routing. Even in the latter case, it is basically only necessary to know the number of logical communication paths within the communication system, and it is not necessarily necessary to know what kind of logical communication path corresponds to that number. In the latter case, as shown in Figure 3 (1)), in addition to the destination address, the terminal also specifies a logical communication path number in the communication frame and at a predetermined location along with a mark indicating that the communication is Rou1-designated communication. Write and send. Each network connection device once receives all the information frames flowing on the communication medium to which it is connected, and then checks whether the communication is a route specified communication. If it is not a route specified communication, transfer processing is performed according to a predetermined specific communication path, for example, the communication path No. 1. If it is route 1~designated communication, the designated communication channel number is read and transfer processing is performed according to that communication channel. After the communication path is determined, the transfer process is performed as follows, for example.

If the link that received the information frame is not a valid link for that communication path, the received information frame is discarded. Also, if the received link is a valid link, read the destination address of the received information frame and discard the received information frame if you know that the terminal with the destination address is on the receiving link side, If the terminal at the destination address knows that it is on the side of a specific link that is a valid link of the selected communication path other than the receiving link, the terminal at the destination address connects directly to the specific link. Check whether the selected communication medium is connected, and if it is, rewrite the route selection area in the information frame to indicate that it is not selected, and if the communication path identifier is written, delete that area. If there is no direct connection, the received information frame will be forwarded to the specific link, and if none of the above cases exist, the received information frame will be forwarded only to the specific link. Transfer to all valid links of the selected communication path. An example of a method for knowing the positional relationship of destination terminals is to record the source address of the information frame received by each network connection device together with the logical communication path number used, It is possible to know the relative positional relationship of each terminal, that is, which link side it is located with respect to itself.

Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing logical communication paths in an embodiment of the present invention, 1-1. 1-4 are communication media, 1-5. ~
1-9 are network connection devices, and A to D are terminals. Figure 1 (a) shows a logical communication path in which the network connection bag N1-5 is used as the central connection device, (b) the network connection device 1-6 is used as the central connection device, and (C) the network connection device 1-7 is configured as the central connection device. <a> is called communication path 1. (b) is called communication path 2. (c) is called communication path 3. If no communication route is specified, communication path 1 is used.
We will use . FIG. 4 is a diagram showing the effective links of each network connection device in FIG. 1 and which link side the terminals connected to the communication medium directly connected to each link and the terminals not directly connected are located. It is. FIG. 3 shows information frame formats 1 to 1 in the embodiment of the present invention.
It is a figure which shows an example. In Figure 3 (a> and (b)), the route selection area is selected as the first bit of the source address.In a normal local area network, the first bit of the terminal address is determined to be 0. In many cases, the first bit is 1°.

This is because an address is used to identify a group of multiple terminals. However, in general, an address that identifies a group appears only as a destination address, and therefore, the first bit of the source address field is usually set to "0°" and is considered to contain no information. If the route selection area is set in the first bit of the source address field and no communication path is specified, “
0°', and 1''' when specified, information frame formats 1 to 1 are used for communication that does not specify a communication path
is exactly the same as the format of the information frame when there is only one communication medium, and has the advantage that the sending terminal can transmit without any changes compared to when it is connected to a single communication medium. Regarding reception, according to this embodiment, the information frame received by the destination terminal is always in a format that does not specify a communication path, so there is no change at all when both transmission and reception are connected to a single communication medium. I can do it. Next, with reference to FIG. 4, a case will be described in which terminal A in FIG. 1 specifies communication path 1 to send data to the terminal. The information frame transmitted from terminal A is received by link 1 of network connection device 1-5 and link 1 of network connection device 1-6. Network connection device 1-6 looks at the channel number 1 column in Figure 4 and learns that both links 1 and 2 are valid links, and then looks at the destination address and finds out that the terminal is on the side of link 1 that received it. Discard. On the other hand, the network connection device 1-5 similarly looks at the channel number 1 column and knows that links 1 and 2 are valid links, and then looks at the destination address and identifies links other than link 1 that the terminal received. Knowing that it is located on the link 2 side, it sends it directly to the link 2 side. Next, network connection device 1-7 receives the information frame sent by network connection device 1-5 via link 1, looks at the channel number 1 column, learns that both links 1 and 2 are valid links, and then Looking at the destination address, the terminal learns that it is a terminal directly connected to link 2, changes the received information frame to a format without specifying a route, and transmits it via link 2. The terminal receives the information frame transmitted by the network connection device 1-7,
This has a format as shown in FIG. 3 (a>), so there is no need for a terminal to distinguish between receiving information frames from other terminals using the same communication medium.

〔Effect of the invention〕

As explained above, the routing method of the present invention requires almost no information regarding routing at the terminal;
This has the effect of making it possible to designate different routes, as well as allowing terminals to be accommodated without any changes compared to when connecting to a different communication medium.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a logical communication path in an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining a conventional method, and FIG.
The figure shows formats 1 to 1 of information frames in the embodiment of the present invention, and FIG. 4 shows the effective links of each network connection device in FIG. 1 and the terminals connected to the communication medium directly connected to each link. FIG. 4 is a diagram showing which link side terminals that are not directly connected are located. 1-1. ~1. -4.2'-1. ~2-4... Communication medium, 1-5. ~ll-9.1-5. ~2-9...Network connection device, A~D...Terminal.

Claims (1)

[Claims] In a communication system in which a plurality of communication media having broadcasting properties are connected by a plurality of links of a plurality of network connection devices,
Each network connection device has means for knowing the address of a terminal connected to a communication medium to which it is directly connected, and has means for knowing the address of a terminal connected to a communication medium to which it is directly connected. A communication path that does not include a plurality of closed circuits is configured by links of connecting devices, and a route selection area is provided in the information frame transmitted by the terminal to distinguish whether or not to specify a communication route, and the transmitting terminal If a communication route is not specified, a mark indicating that no communication route is specified is sent in the route selection area, and if the sending terminal specifies a specific communication path among the plurality of communication paths, sends a mark specifying a communication route in the route selection area in the information frame, and writes an identifier indicating the specific communication path among the plurality of communication paths in a specific area in the information frame. The network connection device looks at the route selection area of the received information frame, and if there is a mark specifying a communication route, reads the specific area in which the identifier of the specified communication path is written. Select the communication path shown there, and the link that received the information frame is a component of the selected communication path, and the terminal at the destination address is a component of the selected communication path other than the receiving link. If you know that you are on the side of a particular link, check whether the terminal with that destination address is connected to a communication medium that is directly connected to that particular link, and if so, A routing method characterized in that a route selection area in an information frame is rewritten with a non-selection mark, and if a communication path identifier is written, that area is deleted and transfer is made only to the specific link.