JPH02206254A - Time slot acquisition method - Google Patents

Abstract

PURPOSE:To secure equality of communication right by providing a time slot release system area so as to cause an idle time slot to be reached after one circulation without fail. CONSTITUTION:A time slot release system display area is added in an access field. When a time slot is occupied for a long period by the communication from a communication node 1 to a communication node 3, since no idle slot reaches in excess of a predetermined timer setting, a communication node 2 revises the display of the time slot release system into the sender side release type. Since the time slot revised into the sender side release type is released by the communication node 1, the arrival of an idle time slot to the communication node 2 is warranted.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a slot-type media access control method in a ring-type transmission path. Concerning possible time slot acquisition methods.

[Conventional technology]

Local area networks (LANs) are steadily expanding their field of use. For example, LANs using optical fibers are increasingly being introduced into new intelligent buildings. It is generally used to connect a host computer and a terminal. High speed L
The AN transmission method uses time division multiplexing or token passing (for example, see "Nikkei Electronics" 1985, 4-22 pp, 185-238).

One of the LANs described in the above magazine has a transmission speed of 32 Mbit/sec, uses optical fiber as the transmission medium, has a dual transmission path, and controls the network with a single control device. Sixty-five nodes are connected to this network. The transmission frame is divided into slots with a transmission rate of 1.5 Mbit/sec, and the slots are divided into circuit switching and packet switching.

FIG. 2 is a configuration diagram of a conventional ring-type transmission line LAN.

In FIG. 2, 1, 2, 3.4 are communication nodes, and 5 is a ring type transmission line.

Each of the communication nodes 1 to 4 is cascade-connected via a transmission path 5 . The frames to be transmitted are transmitted on the ring-shaped transmission line 5 in the direction of the arrow.

FIG. 3 is a diagram of a time slot structure within a conventional transmission frame.

The transmission frame consists of fixed length time slots (#1 to #N
), and each time slot is divided into an access field and an information area. Of these, the access field is composed of an indication bit for identifying whether the time slot is vacant or in use, a destination address, a local station address, and the like.

In FIG. 2, for example, when communicating from communication node 1 to communication node 3, when a time slot in which the blockage indication is empty arrives in communication node 1, that time slot 1- is captured and the blockage indication is displayed. At the same time, it writes the address of the communication node 3 in the destination address area, the address of the communication node 1 in the local address area, and the communication content in the information area, and sends them to the transmission path. When the communication node 3 receives the incoming time slot, it confirms that the destination address is its own address, and then copies the contents of the time slot 1- and imports it into its own node. At the same time, the empty indication of the time slots 1 to 1 is changed to empty, and the slots are released to the transmission line.

[Problem to be solved by the invention]

In FIGS. 2 and 3 above, when communication node 1 has a lot of information to send to communication node 3, communication from communication node 1 to communication node 3 takes a long time, and therefore communication node 3 Communication node 1 will reuse the released time slot. The problem here is that the communication node sandwiched between the source and destination communication nodes, in the example above, communication node 2, wants to start communication but no free slots arrive at its own station, so it cannot communicate. It is impossible.

Alternatively, in order to ensure equality of communication rights, time slots may be released on the transmitting side, and one communication node may be prohibited from continuously using the same time slot. However, in the above method, there is a period in which the time slot is not released even after the purpose of communication is achieved, resulting in a problem that the transmission efficiency is reduced.

The purpose of the present invention is to solve such conventional problems and to provide a time slot acquisition method that can create a receiving-side open network without reducing transmission efficiency and guarantee equality of communication rights. It is about providing.

[Means to solve the problem]

In order to achieve the above object, the time slot acquisition method of the present invention provides a method for acquiring time slots 1-1 in a local area network in which a plurality of communication nodes are connected to a ring-shaped transmission path that is time-division multiplexed using fixed-length time slots. A display area is provided to identify whether the time slot is in use or free, and a display area is provided to identify whether the time slot is released by the transmitting communication node or by the receiving communication node. is a receiver-side open type, and when a communication note requesting communication arrives at its own communication node within a predetermined free time slot,
Capture the timeslot.

The sending side displays the message "In use" and writes the communication contents to the above transmission path, and when an empty time slot does not arrive within a predetermined time, the time slot release method display area of the blocked time slot is displayed on the sending side. The feature is that by displaying the release type, the time slot release method is changed to ensure that an empty time slot arrives at the own communication node.

[For production]

In the present invention, by newly providing a time slot release method display area in the time slot access field, it is possible to ensure that a free time slot will arrive for a communication node that wants to start communication but no free time slot has arrived. This makes it possible to guarantee equal communication rights between communication nodes.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a format diagram of time slots of a transmission frame showing an embodiment of the present invention.

The difference between the format of FIG. 1 and the conventional format of FIG. 3 is that a time slot release method display area is added to the access field.

Normally, this time slot release method display area indicates that the time slot release method is used. In other words.

The communication node displaying the destination receives this time slot, copies the information, and then releases the time slot by changing the display from blocked to free.

As described above, when a time slot is occupied for a long time by communication from communication node 1 to communication node 3, only the blocked time slot always arrives at communication node 5. In this case, when a predetermined timer value is exceeded and no free slot arrives, the communication node that requested communication changes the display of the time slot release method to the sender release method.

Since time-over 1-, which has been changed to the transmitter release type, will be released by communication node 1, it is guaranteed that an empty time slot will arrive at communication node 2. The communication node 2 captures an empty time slot, writes the destination address, the transmitting source's own address, and communication information, and then sends it to the transmission path. Then, after this time slot has made one circuit around the transmission path, the area display of the time slot release method is returned to its original state so that the transmitter side is released and the time slot release method is set to the receiver side release again.

In this way, a specific communication node can use all the network resources when there is no communication request from other communication nodes, and can allocate communication rights when a communication request occurs from another communication node. Can be done.

FIG. 4 is a flowchart of the transmission and reception processing of the communication node according to the present invention.

In the case of reception, the destination address of the received frame is checked to determine whether it is the local station (step 411). If it is addressed to the local station, the contents of the information area are copied and imported (step 412), and the time Determine the slot release method area and
If it is the receiving side release type (step 413), the time slot is changed from a blocked indication to an empty indication and the time slot is released (step 414). Also, if the receiving side is not open type.

Since it is released on the transmitting side, it is directly relayed to the transmission path (step 415).

In the case of transmission, it is determined whether or not an empty time slot has arrived (step 401), and if it has arrived, the time slot is immediately captured, the empty display is changed to a blocked display, and then transmitted to the transmission path. (Step 404).

Also, if no free time slot arrives (step 401), a timer is set and when the time is over (
Step 402), determine the area of the time slot release method of the incoming blocked time slot and confirm that this is the receiver release type (step 403);
Change the time slot release method area to sender release type and relay transmission as is. (Step 405). Then, because that time slot is not released on the receiving side but is released on the transmitting side, the time slot arrives in the transmitting side released form, but since it is not the time slot for own station transmission, the process returns to step 401 (step 406 ). Here, since an empty time slot always arrives (step 401), it is captured, the destination address, the source's own address and communication information are written, and the time slot is sent to the transmission path (step 404). When the time slot that has completed one rotation arrives, it is confirmed that the time slot is an open time slot on the transmitting side for transmission by the own station (step 406), and the time slot is changed from a blocked indication to an empty indication. After releasing the data (step 407), the data is changed to the receiving side release type again and relayed to the transmission path (step 408). Note that if the communication content is repeatedly present in the local station, the communication content is written again without being displayed as empty, and then sent to the transmission path. This completes the series of processing.

In this way, when the time slot release method is set to the transmitter release type, the time slot release method is released on the transmitter side. On the other hand, in the case of a normal receiving side release type time slot, the receiving side changes the blocked indication to an empty indication and releases it.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a time slot release method area in a receiving side release type network, an empty time slot always arrives after one round, thereby ensuring equality of communication rights. It becomes possible to guarantee.

[Brief explanation of the drawing]

FIG. 1 is a time slot format diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a conventional LAN, FIG. 3 is a conventional time slot format diagram, and FIG. 4 is a diagram of the conventional time slot format. Flowchart 1 of communication node transmission/reception processing
It is. 1 to 4: communication node, 5: ring type transmission path. Diagram

Claims (1)

[Claims] (1) In a local area network in which multiple communication nodes are connected to a ring-shaped transmission path that is time-division multiplexed using fixed-length time slots, the time slots have a display area that identifies whether they are in use or vacant. As a method of releasing the time slot, a display area is provided to identify whether the time slot is released by the sending communication node or the receiving communication node.Usually, the receiving side is released, and the communication node requesting communication When an empty time slot arrives at its own communication node within a predetermined time, it captures the time slot, displays that it is in use, writes the communication content, and sends it to the above transmission path. When an empty time slot does not arrive within the specified time, the transmitting side release type is displayed in the time slot release method display area of the blocked time slot to change the time slot release method and release the time slot to the own communication node. A time slot acquisition method characterized by ensuring that an empty time slot arrives.