JPH02206251A - Time slot acquisition method - Google Patents

Abstract

PURPOSE:To warrant the equality of communication right by providing a time slot security reservation area so as to reserve an area for the succeeding use. CONSTITUTION:A time slot security reservation area is added in an access field. A communication node 2 sets a reservation bit to the time slot security reservation area when no idle slot arrives in excess of a predetermined timer content. Even when a time slot whose reservation bit is set becomes an idle time slot while being passed through a communication node 1 after the slot is released from a communication node 3, because the slot is reserved, the communication node 1 does not acquire the slot. Since the time slot reserved by a communication node 2 is circulated as above and becomes an idle time slot surely, the communication node 2 uses the slot to start the communication.

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 line, and more specifically, a slot acquisition method for making time slots equally used among nodes. Regarding.

[Conventional technology]

The field of use of local area networks (LANs) is expanding to 1M. 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 J1985 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 with an empty blockage indication arrives in communication node 1, that time slot is captured and the blockage indication is blocked. At the same time, the address of the communication node 3 is written in the destination address area, the address of the communication node 1 in the local address area, and the communication content is written in the information area, and then sent to the transmission path. When the communication node 3 receives the incoming time slot 1-, it confirms that the destination address is its own address, and then copies the contents of the time slot and takes it into its own node. At the same time, the empty indication of that time slot is changed to empty, and the time slot is released to the transmission path.

[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.

Another method is to release time slots in the transmission image to ensure equality of communication rights.

It is also possible to prohibit one communication node 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 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. has a display area for identifying whether it is in use or free, and a time slot reservation area for reserving the start of communication, and a communication node requesting communication can wait for an empty time slot to arrive at its own communication node within a certain period of time. When this occurs, the time slot is captured, the time slot is displayed as being in use, and the communication content is written and sent to the transmission path, and when an empty time slot does not arrive within a certain period of time,
When a reserved time slot is set in the time slot reserved area of a blocked time slot and transmitted, the time slot is released to an empty state at the destination communication node, and the time slot reserved bit is set, so that the reserved time slot is not reserved. Since it is not captured by nodes other than the communication node that communicated with
When the time slot arrives again after going around the transmission path, the communication node captures the time slot, turns off the time slot reservation reservation bit, indicates that it is in use, and writes the communication content to the transmission path. It is characterized by sending out.

[For production]

In the present invention, a time slot reserved area is newly provided in the access field of a time slot, and when a communication node wants to start communication but no free time slot arrives, the communication node registers its own address in this time slot reserved area. By doing so, it is possible to reserve the use of time slots for communication nodes that have completed transmission preparations.

This allows each communication node to acquire communication rights equally, eliminating the conventional inequality in which a specific communication node is unable to communicate while other nodes are unable to communicate. Can be done.

〔Example〕

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

FIG. 1 is a diagram illustrating a format 1 of time slots of a transmission frame according to 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 reserved area is added to the access field.

When a time slot is occupied for a long time by communication from the communication node 1 to the communication node 3, only the blocked time slot always arrives at the communication node 2. In this case, when an empty slot does not arrive after a predetermined timer value, a reservation bit is set in the time slot reservation reservation area. The time slots for which the reserved bit is set are
Even if the time slot is free when passing through the communication node 1 after being released by the communication node 3, the communication node 1 will not capture it because it is reserved. In the communication node 2, after the time slot reserved by the own station has gone around once as described above, the communication node 2 will definitely arrive as an empty time slot, so it can use this slot to start communication. Writes the communication information of the communication node 2 into the time slot captured by the communication node 2, changes the empty display to a blocked display, and turns off the reservation bit, writes the destination address and the source's own address, Send it to the transmission path. In this way, slots are released on the receiving side, but reserved bits are released on the transmitting side, thereby ensuring equality of communication rights. Note that a communication node that has turned on the reservation bit of a time slot must wait for this time slot to complete one rotation, but if an empty time slot arrives while it is waiting, it can use it to transmit data. You may. just,
In that case, it is necessary to turn off the reservation bit of the time slot that has returned after one round.

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), and if it is addressed to the local station, the content of the information area is copied and imported (step 412); The empty bit of the time slot is turned off and released (step 413).

In the case of transmission, it is determined whether or not free time over 1~ has arrived (step 4o1), and if it has arrived, the time slot is immediately captured, the empty bits are blocked, and then transmitted to the transmission path. (Step 4o4).

Also, if no free time slot arrives (step 401), a timer is set and when the time is over (
Step 402), after confirming that the reservation bit of the slot reservation area is not turned on for the incoming blocked time slot (step 403), the reservation bit of the slot reservation area is turned on (step 405). ).

Then, it waits until that time slot returns after making one circuit around the transmission path (step 406). When the time slot that has completed one cycle arrives (step 407), capture that time slot, turn off the reserved bit, and change the empty bit to next time, and then write the destination address and the source's own station address. The information is stored in the information area and transmitted to the transmission path (step 408). This completes the series of processing.

In this way, reserved bits are released at the sender. Further, processing for changing a time slot from a occupied time slot to an empty time slot and releasing the time slot is performed on the receiving side.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a time slot reserved area in a receiving side open type network, it is possible to reserve the next use, thereby guaranteeing equality of one communication right. becomes possible.

[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 an axis tree j)L A N, and FIG. 3 is a conventional time slot format diagram.
FIG. 4 is a flowchart of the transmission/reception processing of the communication node according to the present invention. 1 to 4: communication node, 5: ring type transmission path. Figure Figure

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 of transmission frames, the time slots are displayed to identify whether they are in use or vacant. A communication node that requests communication captures an empty time slot when it arrives at its own communication node within a predetermined time. and sends it to the above transmission path by displaying that it is in use and writing the communication contents, and when an empty time slot does not arrive within a predetermined time, it is sent to the time slot reserved area of the blocked time slot. When the time slot is transmitted with the reservation bit set, the time slot will be released to a vacant state at the destination communication node, and since the time slot reservation reservation bit is set, it will not be captured by any node other than the communication node that reserved the reservation. When the time slot arrives again after going around the transmission path, the communication node captures the time slot, turns off the time slot reservation reservation bit, indicates that it is in use, and writes the communication content to the transmission path. A time slot acquisition method characterized by sending.