JPH02206252A - Time slot acquisition method - Google Patents

Abstract

PURPOSE:To warrant the equality of communication right by providing an emergency time slot in addition to a normal operating time slot so as to cause a time slot circulated among nodes while being in idle state in an emergency. CONSTITUTION:The attribute of a time slot is divided into two groups as normal use and emergency use and allocated in a transmission frame separately. When a normal operating time slot is monopolied for a long period by the communication from a communication node 1 to a communication node 3, a communication node 2 acquires an emergency use time slot when a normal use idle time slot does not arrive in excess of a predetermined timer setting writes, a destination address and a sender's own station address to the slot, changes an idle display into a busy display and sends the frame to a transmission line.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an access control method for slotted media in a ring-type LAN (local area network) transmission path, and more specifically, the present invention relates to a method for controlling access to slotted media in a ring-type LAN (local area network) transmission path. Regarding how to get slots to play.

[Conventional technology]

Local area networks (LAN) 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. Time division multiplexing or token passing is used as the transmission method for high-speed LAN (for example, "Nikkei Electronics" 1985, 4-22 pp, 185-238).
reference).

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 path.

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, 1. 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 is written in the own 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 and confirms that the destination address is its own address, the communication node 3 copies the contents of the time slot and takes them 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 The communication node 1 will reuse the released time slot. The problem here is that
A communication node sandwiched between the source and destination communication nodes,
In the above example, even if the communication node 2 wants to start communication, it cannot communicate because no free slots arrive at its own station.

Another method is to release time slots on the transmitting side 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 the above method 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 of transmission frames. The time slots of the transmission frame are divided into two types, a normal use group and an emergency use group, and a communication node requesting communication must find a time slot that is displayed as vacant in the normal use time slot group within a predetermined time. When the time slot arrives at its own communication node, it captures the time slot, indicates that it is in use, writes the communication content, and sends it to the above transmission path, and returns to the normal use time slot that is displayed as vacant within a predetermined time. If the time slot of the emergency use group is not arrived, the time slot of the emergency use group is captured and communication is started, while other communicating nodes that detect that the time slot of the emergency use group has been used arrive at their own communication node. The feature is that the capture rate of time slots that are displayed as empty is reduced by a predetermined amount.

[For production]

In the present invention, the time slots of a transmission frame are divided into two types: normally used time slots and emergency use time slots, and when an empty time slot does not arrive within a certain period of time after a transmission request is made, an emergency Capture and transmit time slots of use. in this way,
A communication node that has captured a time slot for emergency use can avoid a monopolized state of network resources by notifying a communication node monopolizing the network resources of a request for equalization of communication rights.

〔Example〕

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

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

The difference from the conventional arrangement of timeovers 1 to 1 shown in Figure 3 is that the time slot attributes are divided into two groups, normal use and emergency use, and are arranged separately in the transmission frame. . Generally, each communication node captures one normally used time slot and uses it to communicate. In that case,
Leave the emergency use time slot free.

As in the past, when a normally used time slot is occupied for a long time by communication from the communication node 1 to the communication node 3, only the blocked normally used time slot always arrives at the communication node 2. At this time, in the communication node 2, if a predetermined timer value is exceeded and a free time slot for normal use does not arrive, one communication node 2 captures an emergency use time slot, and sends the destination address and Write the original own station address, change the empty display to a blocked display, and send it to the transmission line.

By sending an emergency use time over 1-.

All communication nodes of the network can be informed that the emergency use time slot is being used. This emergency use time slot is sender-released and
After the communication node that has captured this signal makes one circuit around the transmission path, the time slot is released by changing the empty display to the blocked display.

Which communicating nodes detect that the emergency use timeslot has been used and are currently communicating.

Thereafter, the acquisition rate of normally used time slots is reduced for a certain period of time. For example, if a communication node that has information to be communicated has always captured the information when an empty time slot arrives in a normally used time slot, it will not be able to detect that an emergency use time slot has been used. After detection, even if an empty time slot arrives in a normally used time slot, it will be allowed to pass through in an empty state once every few times.

By doing this, whenever an emergency use time slot is used, there will be a normal use time slot that circulates unoccupied, so that a specific communication node will not monopolize the time slot. .

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, check the destination address of the received frame to determine whether it is your own station (step 411), and if it is addressed to your own station, copy and import the contents of the information area (step 4.12). , the empty bit of the time slot is turned off and released (step 413).

Also, even if the destination address of the received frame is not addressed to the local station (step 411), if the time slot is an emergency use time slot and is displayed as blocked (step 414), the local station It is determined whether or not communication is currently in progress (step 415). If communication is in progress, the acquisition rate of the normally used time slot is decreased (step 416).
).

In the case of transmission, it is determined whether an empty time slot has arrived (step 401), and if it has arrived, the time slot is immediately captured, the empty bits are filled, and then transmitted to the transmission path (step 401). 404). If the emergency use time slot does not arrive, set a timer, and when the time expires (step 4o2), confirm that the empty bit is not turned on for the emergency use time slot that has arrived (step 403), and then set the emergency use time slot. After changing the empty display to a blocked display and writing the destination address, local address, and information, it is sent to the transmission path (step 405). Then, it waits until that time slot returns after making one circuit around the transmission path (step 406). When an emergency use time slot that has completed one cycle arrives (step 407), the blocked indication of that time slot is changed to a blocked indication and released, and the empty bit is changed to blocked, and then sent to the transmission path. (Step 408), thereby ending the series of processing.

In this way, emergency use time slots are released at the sending side. On the other hand, processing for changing one normally used time slot from a blocked display to an empty display and releasing it is performed on the receiving side.

〔Effect of the invention〕

As explained above, according to the present invention, by providing an emergency use time slot in addition to the normally used time slot in a receiving side open type network, in an emergency state, a time slot that remains vacant and repeats the same cycle is created. This makes it possible to guarantee equality of communication rights.

[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. It is a flowchart of the transmission/reception process of a communication node. 1 to 4: communication node, 5: ring type transmission line. 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 of the transmission frame, the time slots of the transmission frame are used for normal use and emergency use. Communication nodes that request communication are divided into two types of usage groups:
When a time slot that is displayed as vacant in a group of normally used time slots arrives at its own communication node within a predetermined time, the time slot is captured, displayed as being in use, and the communication content is written. When the normal use time slot that is displayed as vacant does not arrive within a predetermined time, the time slot of the emergency use group is captured and communication is started; 1. A time slot acquisition method, characterized in that another communication node in communication which detects that a time slot has been used reduces the acquisition rate of empty time slots arriving at the own communication node by a predetermined amount.