JPH0683237B2 - Termination delimiter control method in loop network - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method of a signal frame end delimiter for reducing the influence of a code error on a transmission line in a loop network, even if it occurs. .

(Prior Art) As a communication method for realizing the integration of broadband services such as video communication and high-definition images in addition to the integration of voice communication and data communication, for example, 1983 IEICE Exchange Study Group Material SE83-107 There is a loop network described in "Study on high-speed synchronous packet loop" described above.

This loop network constitutes the network as shown in FIG. In the figure, the trigger station TS20 sends a polling signal onto the transmission line 24 to perform polling control on the node stations NS21, NS22, NS23. Also, node stations NS21, NS22, NS23
Performs packet transmission / reception via the transmission line 24 in accordance with the polling control. Each of these stations is a transmission line
By 24, they are connected in a loop as shown. (In the present specification, the trigger station is
S, the node station is abbreviated as NS, and TS and N
S is generically called a station. ) In this loop-shaped network, as shown in FIG. 6, TS20 sends a polling signal (p1 or p2), and each NS monitors the polling signal passing through the transmission path 24 and sends a packet. After preparing and acquiring the transmission right, the packet is transmitted. For example, in the example of FIG. 6, the NS21 receives the polling signal p1 transmitted by the TS20, acquires the transmission right after passing the signal, and transmits the hacket a1. NS22 receives packet a1 after receiving polling signal p1.
After that, the transmission right is acquired and the packet b1 is transmitted. Similarly, NS23 also transmits packet c1.

When the polling signal p1 transmitted by the TS20 makes one round in the transmission line 24 and returns, the TS20 transmits the polling signal p1 to the transmission line 24.
After removing from 24 (signals removed at each station in the figure are indicated by *), the packets a1, b1 and c1 transmitted by NS21, NS22 and NS23 are passed, and then the transmission right is acquired. The polling signal p2 is transmitted, and the transmission of the packet a2 is started to NS21. Also, each NS also removes from the transmission line 24 when the packet transmitted by itself returns around the transmission line 24. In this way, the transmitted signal is removed at the transmission source station after passing through the transmission path 24 once.

(Problems of Prior Art) Each station in the loop network is
When the transmission of a signal is started, the transmission line 24 is temporarily disconnected, the signal in its own station is transmitted, the signal waits for one round in the transmission line 24, the signal is removed from the transmission line 24, and then transmitted again. Connect line 24. In this way, each station controls the opening / closing of the transmission path 24 during transmission. Therefore, the transmission line 24
If a station mistakenly opens or closes the transmission line 24 due to a code error in the above, the transmitted packet may be removed at the station before it reaches the receiving station, or the packet may be transmitted. Despite going through 24 cycles, a failure occurs such as not being removed at the transmission source station, causing an abnormality in the access method of each station. For example, in the example of FIG. 7, when the end delimiter indicating the end of the packet appears due to a code error in the middle of the packet a1 transmitted by the NS21, the NS21 that transmitted the packet a1 is the same packet. When the packet has returned through the transmission path 24 and returned, the removal of the packet a1 ends when the end delimiter caused by the code error is detected. Therefore, as shown by the diagonal lines in FIG. 7, a part of the latter half of the packet a1 is not removed and remains.

On the other hand, NS22 sends the remaining signal to the packet
The transmission line 24 is cut and removed until it is identified as b1 and the end delimiter of the signal indicated by the diagonal lines is detected, and the transmission line 24 is returned to the passing state when the end delimiter is detected. Therefore, even if the packet b1 transmitted by the NS22 goes around the transmission path 24 and returns to the transmission source station NS22, it remains without being removed at the same station and is removed at NS23. In the same way
The packet c1 sent by NS23 is removed at TS20, and TS
The polling signal p2 transmitted by 20 is removed in NS21, and thereafter, an abnormal state in which each source station removes a signal different from the packet transmitted by itself, continues.

(Object of the Invention) An object of the present invention is to provide an end delimiter control method for a signal frame that can promptly return to a normal state even if a signal that is not removed remains on the transmission line due to a code error on the transmission line. To do.

(Structure of the Invention) According to the end delimiter control method of the present invention, the end delimiter given to the last signal frame of the signal frames transmitted by the trigger station is added to the last of the signal frames transmitted by each node station. It is possible to obtain a form different from the end delimiter given to the signal frame to be sent.

(Detailed Description of Configuration) The addition of the end delimiter of the loop network and the access control based on it in the present invention will be described in detail with reference to the drawings. TS20 is shown in Fig. 2 (a) and (b).
Frame structure of polling signal transmitted by
The structure of the packet signal transmitted by the NS is shown respectively. These signals consist of a header part (HDR) indicating the source station address, destination station address, frame control information, etc., and a message part (INFO) indicating the communication content. Before and after this, there are delimiters indicating the start and end of the signal. Has been added. However, although the start delimiter (SD) is common, the delimiter indicating the end is different, and the end delimiter TED is given to the signal frame transmitted by TS20, and the end delimiter NED is given to the signal frame transmitted by NS. give.

The signal first received from the upstream side of the transmission line 24 by all stations including the TS20 and each NS after the transmission is the signal of its own which normally makes one round in the transmission line 24 in the normal time. As shown in the figure, TS20 receives polling signals p1, NS21, 22 and 23 packets a1, b1 and c1, respectively. Therefore, the TS 20 recognizes one cycle of the packet transmitted by itself by detecting the end delimiter TED and each NS detecting the end delimiter NED, and ends the transmission packet removal control as in the prior art.

FIG. 1 is a diagram showing an embodiment of a trigger station TS20 and each node station NS according to the present invention. The trigger station TS20 shown in FIG. 3A comprises a switch 1, a TED detection unit 2, a transmission right acquisition unit 3, an access control unit 4, and a transmission register 5. The transmission right acquisition unit 3 detects the end delimiter (TEDorNED) of the signal frame passing through the transmission path 24, and notifies the access control unit 4 of acquisition of the transmission right if the end delimiter (TEDorNED) is detected immediately thereafter. Based on this, the access control unit 4 switches the switch 1 from the transmission line 24 side to the transmission register 5 side.
The transmission register 5 stores the HDR of the polling signal to be transmitted,
INFO, start delimiter SO, and end delimiter TED are supplied, and this polling signal is sent to the transmission line 24 via the switch 1. On the other hand, the TED detection unit 2 monitors the signal supplied from the upstream side of the transmission line 24, and when the termination delimiter TED is detected, notifies the access control unit 4 to that effect. Based on this, the access control unit 4 connects the switch 1 to the transmission path 24 side and returns it to the passing state. By this control, the polling signal that makes a round in the transmission path 24 is removed, and the packet signal following it is bypassed and supplied to the downstream node station.

Each node station NS in FIG.
1, NED detection unit 32, transmission right acquisition unit 33, access control unit 34,
It consists of a transmitting reservoir 35. In this configuration, the NED detector is the end delimiter NE of the signal frame received from the transmission line 24.
It is the same as TS20 except that it detects D and the transmit register 35 sends out the packet signal of the end delimiter NED.

The operation of this embodiment will be described with reference to FIG. The TS20 sends the polling signal p1 with the end delimiter TED added. The NSs 21, 22, 23 detect the idle state of the transmission line 24 after passing p1, and send the packets a1, b1, c1 to which the end delimiter NED is added, respectively. The polling signal is removed by TS20 after passing through the transmission path 24 (indicated by *).
When the TS20 detects the termination delimiter TED, the TS20 terminates the removal control and allows the signals of the packet a1 and the subsequent packets that are continuously received to pass. And in a normal state, packets a1, b1, c1
Are removed from the transmission line 24 by NS 21, 22 and 23, respectively. However, it is now assumed that a pseudo end delimiter NED indicated by a black mark x occurs due to a transmission error in the middle of the packet b1. Packet b1
The NS22 that has sent the error message erroneously recognizes this pseudo end delimiter NED as the NED of the packet b1 and ends the removal control. Therefore,
The rest of the packet b1 shown in the shaded area is not removed and is supplied to NS23. Since the NS23 ends the removal control based on the termination delimiter NED that is detected first, it partially removes the packet b1 but allows its own transmission packet c1 to pass downstream. Unlike each NS, TS20 ends the removal control by detecting TED, so packet c1 that NS23 could not remove
The removal control is not stopped by passing the delimiter NED.
It ends when the end delimiter TED of the polling signal p2 is detected. Therefore, in TS20, the polling signal p2 transmitted by itself is removed from c1, which NS23 could not remove, and returns to the normal state.

On the contrary, a case where the pseudo end delimiter TED occurs due to a transmission error in the middle of the packet signal will be described. Now, it is assumed that the pseudo delimiter TED indicated by the black mark Y occurs in the packet a1. NS21 does not finish the removal control based on TED.
Even if such an error occurs, it does not affect access control.

As described above, even if a transmission error occurs in a packet on the transmission line, it does not affect the next polling control.

Although the case where each station sends only one signal frame has been described, the present invention can be applied to the case where a plurality of signal frames are sent. In this case, the patent application number Sho
As described in 59-084581 "Transmission control method in loop network", the end delimiter IED indicating an intermediate packet is added to the end delimiter of a packet other than the last packet to be transmitted. Figure 4 (a),
(B) shows how to give the end delimiter of each signal frame when the trigger station TS20 and the node station NS connect and transmit three packets.

(Effects of the Invention) By using the termination delimiter control method of the present invention, even if a pseudo termination delimiter occurs in a packet on a transmission line due to a code error and an abnormal state occurs, the trigger station recovers to a normal state, and Abnormal condition does not continue for time.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a trigger station and a node station, FIG. 2 is a diagram showing a configuration of a signal frame, FIG. 3 is a diagram showing a flow of a signal frame on a loop transmission line, and FIG. FIG. 5 is a diagram showing how to give an end delimiter when transmitting a plurality of signal frames, FIG. 5 is a diagram showing a configuration of a loop network, and FIGS. 6 and 7 are flow diagrams of signal frames on a transmission line in a conventional example. FIG. In the figure, 1 and 31 are switches, 2 and 32 are end delimiter detection units, 3 and 33 are transmission right acquisition units, 4 and 34 are access control units, and 5 and 35
Is a transmission register, 20 is a trigger station, and 22,23,24 are node stations.

Claims (1)

[Claims] 1. A trigger station and a plurality of node stations, each station being connected to a loop transmission line, said trigger station sending a polling signal, each node station sending a polling signal or another node station. Control the transmission of its own packet signal after the passage of the packet signal from the trigger station and each node station starts the polling signal or the removal control from the loop of the packet signal from the loop at the same time as the transmission of these signal frames, An end delimiter control in a loop network in which an end delimiter different from other signal frames is added to the last transmitted signal frame, and the removal control from the loop of the signal frame is ended by detecting the end delimiter indicating this end In the method, the end delimiter of the first format is given to the last signal frame transmitted from the trigger station, and the second signal frame is transmitted to the last signal frame transmitted from each node station. The end delimiter of the form
The termination control of the outgoing signal frame from the loop is terminated by the detection of the ending delimiter of the form, and the node station terminates the elimination control of the outgoing signal frame of the loop by the detection of the ending delimiter of the second type. Termination Delimiter Control Method for Active Loop Networks.