JPH02290347A - Test method for network system and duplicated address - Google Patents

Abstract

PURPOSE:To prevent residence of a terminal station of the same address in duplicate in the same ring by writing 'No' into a flag information storage device when a duplicated address test frame sent from its own station is received and it is discriminated that no duplicate address exists in the frame. CONSTITUTION:A duplicate address test DAT frame sent from a 1st terminal station is returned to the 1st terminal station being a sender while an address recognition display AC field is rewritten logical '1' with a 2nd terminal station when the 2nd terminal station having the same address as the 1st terminal station exists on its way of circulation of a ring. When the AC of the received DAT frame is logical '1', the 1st terminal station erases the DAT frame circulated in the ring and reaches the bypass state. When the 2nd terminal station in the state of DAC '0' at the downstream of the 1st terminal station receives the DAT frame sent by the 1st terminal station, the 2nd terminal station applies the similar operation as the 1st terminal station. Thus, the 2nd terminal station receives the DAT frame of AC '0' and is resident in the network.

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a communication network, and more particularly to a duplicate address test method for preventing stations with the same address from existing redundantly in a network including a plurality of stations. [Prior art] In general, terminal stations (
If there are duplicate stations (or nodes), there is a problem in that a communication frame addressed to a certain terminal station is received by multiple terminal stations, and the communication frame is received by an unexpected terminal station. . This problem arises in so-called local area networks (local area networks) that communicate via a common transmission path.
The same applies to L A N ), and the addresses of terminal stations connected to the transmission path must not overlap with each other. In other words, when communicating in a connectionless manner, the address of each terminal station must not be duplicated within the communication network and must be unique. As a conventional method for achieving the above conditions in a ring LAN, there is a method described in the following literature. “Token Ring Access Met
hod and Physical Layer
Specifications” IEEEStd.8
02.5-1985 (ISO/DP8 8 0 2
/5). According to the above-mentioned document, the following two operations are described as operations of a terminal station (new terminal station) that newly joins (connects) to a ring LAN (hereinafter simply referred to as ring). (1) A new terminal station that joins a ring for the first time (in a state where no other terminal station is connected to the ring) is connected to an AC that centrally manages the ring without being concerned about address duplication.
Become a tive Monitor (AM). The active monitor generates a token for controlling data transmission rights and manages the normal circulation of the token on the ring. (2) A new terminal station that joins the ring from the second time onwards (in a state where an AM already exists in the ring), before starting regular communication, there is already a terminal station with the same address in the ring. (duplicate address test). This is a Duplicated Address Te with the own station address set as the destination address.
This is done by sending the st(DA'r) frame onto the transmission path in accordance with the transmission control using the token, and making one circuit around the ring. If there is another terminal station in the ring with the same address as the own station, when the DAT is received by the other terminal station, an identifier indicating that fact is added by the other terminal station. It will be returned to you. In said document, this identifier is reflected in the AddressRecognized indication bit (AR bit). Therefore, a new terminal station can know whether a duplicate address has occurred within the ring by checking the above-mentioned identifier in the frame that has passed through the ring. When addresses overlap, for example, by bypassing the own station (separated from the ring B), the presence of multiple terminal stations with the same address in the same ring is prevented. This duplicate address test is performed as part of the procedure in the initial state of the terminal station.

Problems to be Solved by the Invention 1 However, in the above conventional example, the following three points are not sufficiently considered, and as a result, multiple terminals with the same address (
The problem is that terminal stations with duplicate addresses can continue to exist in the same ring. (a) If multiple terminal stations with the same address join the same ring almost simultaneously in the initial state, that is, when there is no active monitor on the ring, these terminal stations will attempt to establish an active monitor. compete with each other. However, both terminal stations have duplicate addresses and
Since no test is performed, in this case there will be duplicate address terminals within the ring. (b) In a network in which multiple terminal stations are connected by a double ring consisting of a first ring and a second ring with different signal transmission directions, for example, when a fault occurs, ring loopback (loop pack) is performed on both sides of the fault point. When forming a new closed ring (ring degeneration), there may be terminal stations with duplicate addresses within the closed ring. The reason for this is that each terminal station connected to the first ring or the second ring is connected to the ring to which it is connected (for example,
Duplicate address test within the first ring) is performed, but
This is because a duplicate address test with terminal stations connected to other rings (for example, the second ring) is not performed. In ring return, a new closed ring that bypasses the failure point is formed by integrating the first ring and the second ring, so a duplicate address test is required between these two rings. This is not done in the conventional method. (C) When combining multiple independent rings to form one larger closed ring (ring expansion), for example, in the above double ring, multiple rings that have been separated due to a failure can be rebuilt by repairing the failure location. In the case of coupling, the same problem as described above occurs. The point is that there is no duplicate address test between rings, so if multiple rings are combined into one, duplicate address terminals will exist. The above problem (a) is a drawback of the prior art described in the above document, and the problems (b) and (C) are problems that arise when attempting to realize a new function based on the above prior art. SUMMARY OF THE INVENTION An object of the present invention is to provide a duplicate address test method for checking whether a plurality of stations having the same address exist within one ring. Another object of the present invention is to prevent the existence of multiple stations with the same address in the ring even if the number of terminal stations accommodated in one ring changes due to ring degeneration or ring expansion. The object of the present invention is to provide a method for testing duplicate addresses. Another object of the present invention is to provide a network system that can reliably prevent the existence of two or more stations having duplicate addresses. An object of the present invention is to provide a communication system that allows a station to join the network after confirming that no other station having the address exists. [Means for Solving the Problems] In order to achieve the above object, the present invention provides means for identifying whether or not the duplicate address test has been successfully completed in all stations on the network. , the stations that have not successfully completed the above-mentioned duplicate address test will start regular communication after successfully completing the duplicate address test. However, as an exception, the above duplicate address test may be omitted for one station determined as an active monitor. This is because if all stations other than the active monitor perform the duplicate address test, a station with the same address as the active monitor can be prevented from joining the network. As a means of identifying whether or not the duplicate address test has been completed, for example, a duplicate address check flag (Dupli
rated Address Check flag:
CAD). (Operation) In the address test method of the present invention, for example, (D
For stations with AC=O), the address test has not been completed. rDAc=
In the case of IJ, it will be terminated. When rDAc=OJ, each station sends a DAT under token control and performs a duplicate address test, as described above. When the DAT ends normally, that is, there is no duplicate address, the state is set to rDAc=IJ, and a mode in which regular communication is possible is established. On the other hand, D
If the AT terminates abnormally, that is, if there is a duplicate address, for example, the AT bypasses the own station from the ring. However, instead of completely separating the station from the transmission path, the station may be provided with only the function of relaying received frames. In short, only stations that successfully complete the duplicate address test will have rDAc=I
J, and the ring is made up of only those stations. This eliminates the problem of multiple stations with duplicate addresses in a single ring. In a dual ring network, the present invention ensures that each station included in the newly formed closed ring performs a duplicate address test whenever a ring return occurs in a portion of the network. In other words, when a ring return is performed, all stations are set to the state where the duplicate address test has not yet been completed, and after a new closed ring is formed, the duplicate address test is performed again, and then regular communication is resumed. Let it start. In this case as well, the duplicate address test may be omitted for stations determined to be active monitors in the new closed ring. Similarly, in the present invention, when a ring is expanded, all stations included in the expanded ring are set to the duplicate address unfinished state. By doing this, each station connected to the newly formed closed ring will re-perform the duplicate address test according to the modified single ring protocol and begin regular communication. If we consider the case of performing ring degeneration or ring expansion in a network with a dual ring configuration, the duplicate address test is required again when the ring configuration is changed due to ring degeneration or expansion. Therefore, at this time, it is only necessary to obtain an opportunity to set each station to rDAc=OJ. As a trigger for this, for example, if a specific frame is made to flow every time the ring configuration changes, this frame can be used to control the DAC value. The above specific frame is
For example, it may be an abnormality notification frame (beacon in the above-mentioned document) that notifies that an abnormality has occurred in the ring, or it may be a frame for configuration control to perform ring degeneration or expansion. Alternatively, it may be a dedicated frame provided for controlling the DAC value. In these cases, each station is sent to rDA each time the specific frame is received.
c=o'', and then performs a duplicate address test (control is performed so that the mode is in a steady communication mode.) By the above method, ``According to the present invention, new closure Even if a ring is formed,
The problem of duplicate address stations existing within the ring is eliminated. [Embodiment] Fig. 1 shows an example of a network to which the present invention is applied. A plurality of dual ring control stations or nodes (hereinafter simply referred to as control stations) 1-1 to 1-3 are interconnected by the ring 4. Each control station 1-n consists of a pair of single-ring stations (hereinafter simply referred to as terminal stations) 2 nA, 2 nB, and a transmission line changeover switch 3-n. A dual ring network can be thought of as a duplication of a single ring network.
Under normal conditions, the switch 3-n is connected to the main terminal station 2-nA to the first transmission line 4A side and the sub-terminal station to the second transmission line side.
n is working. Note that each ring may include a mixture of terminal stations that constitute a control field and terminal stations that do not constitute a control station. In a dual ring network system, for example, if a failure occurs in a part of the first transmission path, the control station adjacent to the upstream side of the failure will change the first return path from the first transmission path 4A to the second transmission path 4B. , In addition, in the control station adjacent to the downstream side of the failure, a second return path is formed from the second transmission path 4B to the first transmission path 4A. One closed ring is reconstructed. Communication functionality is restored. In FIG. 1, a failure 30 occurs on the first transmission path between control stations 1-1 and 1-2, and terminal stations 2-IA, 2-3B, 2-2A
, 2-3A are sequentially connected to each other in a reconfigured closed ring. Control stations 1-1 and 1 adjacent to the fault
-2, the main terminal station 2-
The switch is activated to connect IA, 2-2A and the sub-terminal station 2-IB, 2-2B to the transmission path on the faulty 30 side. In the above example, each control station 1-n is shown as having a configuration including two terminals 2-nA and 2-nB. -10
As described in No. 0902 "Ring network configuration control method", a line concentrator is equipped with an internal transmission path including multiple port switches, and further connects end stations (terminal devices) to these port switches. Device structures are also applicable. FIG. 2 shows the internal configuration of the terminal station 2-n. 10 is a physical calendar communication mechanism (Physical Layer: PH
Y ), 11 is a medium access control layer communication mechanism (Medium Access Control) realized by program execution by a microprocessor.
MAC), and each function is also described in the above-mentioned prior art document. Note that although the actual terminal station 2-n is equipped with other mechanisms than these, other elements and communication functions that are not directly related to the present invention are omitted from the drawings. In the present invention, MACII sets the Duplicated Address check flag.
k frag: Memory 12 for storing DAC)
and performs an address test operation as described later, depending on the state of the DAC flag. The address test routine is activated in response to turning on the power switch 13 to change the terminal station from a dormant state to an active state. FIG. 3 shows the structure of a frame 20 used by the MACII of the terminal station 2 for communication. 21 is the start delimiter (St
art Delimiter: S D). 2
2 is the functional type (Functional Code:
FC), 2 3 is the destination address (Destin
ation Address: DA). 24 is the source address (Source Address: SA
), 25 is transfer information (Information:
INFO), 26 is the frame check sequence (
Frame Check Sequence: F
C S ), 27 is the end decimeter ( End
D limitar: ED), 28 is an address recognition display (Address recognition and C
This is a field for opy indicator: AC). The specifications of the AC field 28 can be made as follows, for example. The source terminal station sends a frame with rAC="O",+,
The terminal station that received the frame (DA field 23 matches its own address) sets the AC included in the received frame as "
1'', the source terminal station can check the AC field 28 in the received frame to know whether or not the frame has been received by the destination station. A) is a program flowchart showing the operation of a terminal station implementing the present invention. This program routine is started, for example, by turning on the power of the terminal station to be connected to the ring.・Reset test display (DAC) 12 (DAC= “O”) L (
Step 100), when the token is acquired, a Duplicated Address Test Frame (Duplicated Add
(res Test frame: DAT) is sent to the transmission path (110). The DAT frame is. The DA field 23 of the MAC frame 20 contains the address (My (This Station)
ns) Address: Set MA>. AC field 28="Q++" is set. FC
Field 22 may include an identifier indicating that this frame is a DAT to distinguish it from frames used for other functions. This identifier may be included in the INFO field 25 instead of the FC field 22. Next, the reception of the transmitted DAT frame is continued to be monitored, and if a DAT with rDA=MAJ and rAC="1" is received (120). After releasing the token, switch 3-n bypasses the own terminal station from the ring transmission path (
1 2 5). If any of the single ring terminal stations 2-nA or 2-nB in the dual ring control station 1-n enters a bypass state, the dual ring control station loses the dual ring configuration control function. Now. On the other hand, rDA=MAJ and rAC
= "When a DAT frame of O'J is received, the token is released and the DAC flag 12 is set to II II II (135). The state shifts to a normal communication state (140). In this communication state, the terminal station 2 transmits and receives communication frames according to, for example, a token control procedure.If the DAT frame sent out in step 110 cannot be received within a predetermined time, for example, due to a timer interrupt,
It is possible to escape from the DAT frame permanent waiting state. In FIG. 4(A), this control is shown in an omitted form. In the steady communication state 140, the terminal station repeats the following operations. If a token is received when the DAC flag 12 is "0" (150). Return to the initialization state and perform the double address test again. DAC="0" means that it is necessary to perform a double address test for some reason in a steady communication state. In this example, the double address test is performed in response to reception of a token, but this does not necessarily have to be a token as long as it indicates that the ring is normal. For example, it may be a purge MAC frame or an active monitor present (AMP) MAC frame as shown in the above-mentioned document. When a failure occurs in a part of the network during normal communication and ring configuration control operation is performed (160), the DAC7 lag 12 is set to "'0" (
170). This ensures that the next time a token is received,
Dual address test is rerun. As a method of knowing whether or not configuration control has been implemented in a network, for example, the frame described in the following document can be used. I E E E E 8 0 2 Local Area
a Networks, 802. 5 (To
ken Ring), ” Recommend
dPractice for Dual Ping O
peration with Wrapback Rec
configuration", 802.5c/Dl5,
Sept. 9, 1988. According to the above literature, when configuration control, that is, transmission path loopback, is implemented in a dual ring network, a reconfiguration beacon (BeaconReconfigura) is used.
tion: BNR) is sent. Each terminal station, for example, by receiving the above BNR, can know that configuration control is to be performed and can reset the DAC 12. Note that when performing ring expansion as configuration control, the BNR may not flow on the ring in the above-mentioned document. In order to prevent the problem of duplicate addresses with the same control during ring expansion and ring degeneration, B
What is necessary is to allow NR to flow on the ring. In other words, the dual ring terminal station adjacent to the recovered failure point and which should cancel the loopback of the transmission path and perform ring expansion will send out the BNR. Furthermore, within the dual ring control station, 2
There is no need for both single ring terminals 2-nA and 2-nB to send out BNR; only one ring terminal
R may also be sent. In short, it is sufficient if the DAC flags 12 of all single ring terminal stations included in the newly formed ring can be reset (set to "O'"). The operation flow in FIG. 4(A) can be roughly divided into an initial state (initialization state s) up to step 135 and a steady operation state after step 140. The steady operating state is the state of the terminal station that has successfully completed the dual address test. In the present invention, when a dual address test becomes necessary due to implementation of configuration control, each configuration control station or ring terminal station transitions from the normal operating state to the initial state again. FIG. 4(B) is a flowchart showing the operation of a terminal station when it receives a DAT frame having the same destination address as its own address sent by another terminal station. If the own station receives a DAT frame addressed to itself even though it has not sent out a DAT frame, the AC field 28 included in the received DAT frame is rewritten to "1" (
Step 180), and sends the DAT frame to the transmission path (Step 190). When the above DAT frame is received by the source terminal station, as described above, the DAT frame is
), the source terminal station performs a bypass operation. Figures 5A to 5H illustrate the dual address test procedure described above on a network consisting of dual rings. Figure 5A: DAC in newly activated control station ↓-2
The terminal stations 2-2 and 22-2B with = "0" each send a DAT frame indicated by a broken line (Tx-DAT). Perform a double address test. FIG. 5B 2 The above two terminal stations 2-2A and 2-2B both receive DAT with DA=MA and AC=“0” (
Rv-DAT (DA=MA, AC=O)), the dual address test is successfully completed. DAC flag 1
Let 2 be "1". Figure 5C: First transmission line 4 between control stations 1-1 and 1-2
A failure 30 has occurred at A, and these control stations have formed a return route to bypass the failure 30. When an abnormality occurs in the network, the terminal station that notices it becomes the BN
Send R frame. If the abnormality in the network is caused by, for example, a physical failure in the transmission path, the terminal station located immediately downstream of this failure (for failure 30, the terminal station 2-2A in FIG. 5C)
) detects this first. Each terminal station has BN from the upstream
When an R frame is received (Rv-BNR). Along with relaying this to the downstream side. Reset the DAC flag to “0”. At this time, if it is sending out a BNR frame, it stops sending out the BNR frame. As a result, the control station closest to the fault point on the downstream side of the fault point
Only the terminal station 2-2A located at -2 continues to send out BNR frames (Tx-BNR), and this becomes the active monitor AM. The formation of the first and second turnaround routes for detouring around the obstacle point was, for example, disclosed by the inventors in Japanese Patent Application No. 170953/1983.
This can be achieved by adopting the control procedure proposed in the issue of ``Data Communication System''. Figure 5D: Through the above network reconfiguration control operation, a new closed ring (active ring) consisting of both the first and second transmission paths is formed, and when the network communication function is restored, the DAC flag is reset. Each end station has a DAT for duplicate address testing.
Transmit the frame (Tx-DAT). In this case, the terminal station 2-2A that became the active monitor first sends out a DAT frame, and when the duplicate address test is completed, it releases a token, and the next terminal station 2-3A that receives this starts the address test. The DAT frame transmission operation is performed sequentially in this manner. Note that, as mentioned above, if the active
The terminal station 2-2A serving as a monitor may omit the duplicate address test (steps 110 to 170) and immediately send the token. Figure 5E: Each terminal station that sent the DAT frame
When a DAT frame containing the terminal station address in the field and an AC field of II O II is received, it means that the duplicate address test has been successfully completed, and the DAC flag is set to l! I Set to I+ to return to normal communication status. As a result, each terminal station other than the active monitor sequentially becomes a standby monitor. FIG. 5F: shows one state in the ring expansion process to unify two independent closed rings after the fault 30 has been recovered. When the local ring including the fault 3o becomes independent from the active ring as shown in FIG. 5C, each terminal station included in the local ring
Each beacon frame (BN
N), and when it receives the BNN sent by another terminal station, it relays this and operates to stop sending out the BNN from its own station. In the example of FIG. 5C, the terminal station 2-IB is a BNN
The transmission of the beacon BNN is stopped, and only the terminal station 2-2B continues to transmit the beacon BNN. When the fault 30 is recovered, the BNN goes around the local ring and returns to the source terminal station 2-2B, so the terminal station 2-2B can detect that the fault in the local ring has been recovered. At this time, the terminal station 2-2B sends a token to the local ring, and checks whether the token can go around the local ring twice. The terminal station 2-IB can detect recovery from the failure 30 by receiving the token. When the terminal station 2-2B confirms that the local ring has become the active ring by receiving the token, the control station 1-2 integrates the two active rings to become the state shown in FIG. 5F. Switch 3-2 is activated. Then, one of the two terminal stations 2-2A and 2-2B becomes an active monitor and sends out a BNR frame (Tx-BNR). The BNR goes around the integrated active ring once, and the DAC flag of each terminal station that receives this BNR is reset to "O". Each terminal station whose DAC flag has been reset sequentially transmits DAT frames in the same manner as described in FIGS. 5D to 5E, and after successfully completing the duplicate address test, returns to the normal communication state. FIG. 5G: The operation of integrating the active rings described above is also executed in the control station 1-1, and if there is no address overlap, the first
Duplicate address test completed on transmission line 4A (DAC=
"1") A sub-terminal station 2- that includes only the main terminal stations 2-IA to 2-3A and that has also undergone the duplicate address test on the second transmission path 4B.
A dual ring network containing only IB~2-3B is reconfigured. FIG. 5H: Shows a state in which one terminal station 2-2B having an address that overlaps with any other terminal station is bypassed from the ring transmission path. FIG. 6 is a diagram showing an improved duplicate address test method that employs the method described in the above-mentioned document as a prior art and has been additionally modified to apply the present invention.
Statements marked 'x x x x' are prior art. In the present invention, deficiencies in the single ring protocol in the prior art are addressed by SQL, S22, and S4X, and deficiencies due to ring degeneracy can be addressed by further adding S4Y and S62. In ring expansion, for example, one of the dual ring control stations (
In the above document, the above problem can be solved by forcibly shifting only the single ring terminal station (on the MACI side) to the S6 state (BNR transmission: 'rx-BNR). This migration has the advantage of having a single active monitor. Since a terminal station that has already become an active monitor relinquishes the active monitor right upon receiving the BNR sent by another terminal station, the only active monitor is quickly determined. If a plurality of dual ring terminal stations cancel ring loopback at the same time and perform ring expansion, BNR will be sent from the plurality of terminal stations (single ring terminal stations). According to the control described in the above document,
BNR contention control makes it possible to uniquely identify the station that continues to send BNR, but in some cases, terminal stations that are sending BNR may mutually receive BNR sent by other terminals, causing BNR to be transmitted from the ring. There may be cases where there is no terminal station that continues to send out signals. According to the present invention, even in this case, there is no problem because an active monitor can be established in the end. Also, for implementing the present invention, a dual address test,
Even if the and prevention functions are added, the existing functions are not limited. Furthermore, the problem of dual addresses can be solved while maintaining equal distribution between each dual ring control station or between each single ring terminal station. In the embodiment described above, each terminal station that sent out a communication frame such as a DAT frame transmits the communication frame after the communication frame returns after going around the ring. Communication was carried out in the form of releasing tokens. However, the duplicate address testing method according to the present invention uses an early token release method in which each terminal station releases a token immediately after transmitting a communication frame, allowing multiple terminal stations to transmit data one after another. The method can also be applied to ring networks. In this case, if the DAT frame sent by the first terminal station goes around the ring and returns, if the second terminal station with the same address sends out another DAT frame, these two A of each other's DAT frame
There is a possibility that the C field will be rewritten to "1" and both terminal stations will fall into a bypass state. In an early token release ring network, two nodes with the same address
To put only one of the two terminal stations into bypass status,
The DAT frame sent by the first terminal station
After the DAT frame has been circulated, the DAT frame transmission control may be performed so that the other terminal station transmits the next DAT frame onto the transmission path. For the above-mentioned DAT frame transmission control, for example, the active monitor includes one group address in the DA field 23 that is to be received by all stations whose DAC flag is "0", and in the information field 25, this frame address is included in the information field 25. DAT S for controlling the transmission of DAT frames
(Duplicated address T e
st Start) A control frame containing a code indicating that it is a frame and containing "0" in the AC field 28 is sent, and each terminal station transmits a DA with rAc=OJ.
The right to transmit a DAT frame may be obtained when a TS frame is received. closest to the active monitor,
When the first terminal station whose DAC flag is in the "O" state receives the DATS frame, it rewrites the AC field in the DATS frame to "1", and upon receiving the token, sends out the DAT frame. . AC=1 D
The ATS frame goes around the ring once and is erased by the active monitor that is the source. The DAT frame sent by the first terminal station is on its way around the ring, and if there is a second terminal station with the same address as the first terminal station, the AC field is changed to u 1 by the second terminal station. The data is rewritten as u and returns to the first terminal station as the source. The first terminal station is D
When the AT frame returns, the new DAT of rAc=OJ
S frame is transmitted, and if the AC of the received DAT frame is LL I I+, the DA that has gone around the ring
After erasing the TS frame, it enters a bypass state. 1st
The next terminal station downstream of the terminal station with DAC=0 is
When receiving the DATS frame sent by the first terminal station, it performs the same operation as the first terminal station. In this way, by controlling the transmission of DAT frames, the second terminal station can
At the time the AT frame is sent, the first terminal station with the same address has already been bypassed, so the second terminal station can receive the DAT frame with AC=O.
can remain on the network. Further, a method other than the above-described procedure may also be considered. The DAT may also include information specific to the sending station, such as the physical location address of the station or information on neighboring stations. This unique information makes it possible to distinguish between the DAT transmitted by the own station and the DAT transmitted by the overlapping address station, and to determine the priority between the two stations. Another way to deal with the dual address problem. For example, (a) each end station in the network transmits a specific frame addressed to all other end stations, such as the AM P shown in the conventional example above.
(Active Monitor Present) or S M P (Standby Monit
orPresent), and the terminal station that receives the frame checks the source address (SA) to know the occurrence of duplicate addresses and take countermeasures. (b) A method for a specific terminal station that centrally manages the network. For example, a method can be considered in which a server is provided and the station takes measures against problems such as address duplication. However, in the former case, there is a problem in that it is difficult to know when to start and end the duplicate address test, and the test is always performed, resulting in a large load. In the latter case, there is a problem that the problem cannot be solved without the server. In addition, in both methods, address abnormalities are detected after each terminal station in the network reaches a steady operating state, so the performance and reliability of the communication function of the terminal station (MAC upper layer: user) is affected. There are problems that have a large impact. [Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to prevent terminal stations having the same address from duplicating in the same ring. Moreover, even when the terminal stations connected to the ring change due to ring degeneration or ring expansion configuration control, the effect of preventing the above-mentioned duplicate addresses can be obtained. One of the basic ideas of the present invention is to perform a duplicate address test every time a plurality of networks are connected, and it does not depend on the topology of the networks, ie, the configuration of rings, buses, meshes, etc.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of a dual ring network to which the present invention is applied, Fig. 2 is a block diagram showing the main components of a terminal station, and Fig. 3 is a diagram showing the format of a duplicate address test frame. Figure 4 (A) is a flowchart of control operations executed by each terminal station to implement the duplicate address test according to the present invention, and Figure 4 (B) is a flowchart of control operations executed by other terminal stations. A flowchart showing the operation of each terminal station when receiving a duplicate address test frame,
5A to 5H are diagrams for explaining the procedure of the duplicate address test according to the present invention according to network conditions, and FIG. 6 is a diagram for explaining the procedure of the duplicate address test according to the present invention.
It is a diagram shown on a state transition diagram of each terminal station. Explanation of codes 1 (1-1 to 1-3)...control station, 2 (2-IA
~2-3B)...terminal station, 3 (3-1~3-3)...
- Switch, 10... Physical layer communication mechanism, 11... Media access control calendar communication mechanism, 12... Duplicate address test (DAC) flag memory, 13... Power switch - Figure 1A (A)

Claims (1)

[Claims] 1. In a network system consisting of a plurality of stations connected to at least one ring-shaped transmission line and each having one address, each station has access to other stations in the network having the same address as the local station. a first means for storing flag information indicating whether or not a duplicate address test is necessary for detecting whether or not a station exists; and a second means for setting the flag information to a test required state at a predetermined timing. and a third means for sending a signal frame for a duplicate address test to the transmission path when the flag information is in a test required state; When a duplicate address test frame is received, information indicating the existence of a duplicate address is added to the test frame and relayed to the next station,
When a duplicate address test frame transmitted by the own station is received, it is checked whether the frame contains information indicating the presence of a duplicate address, and when it is determined that there is no duplicate address, the test frame is stored in the flag information storage means. 4. A network system comprising: fourth means for writing flag information indicating whether or not the network system is disable. 2. The network system according to item 1, wherein each of the second means resets the flag information when the station changes from a dormant state to an active state. 3. The network system according to item 1 or 2, wherein each of the second means resets the flag information when receiving a specific control frame transmitted by one of the plurality of stations. . 4. first and second ring-shaped transmission paths having mutually opposite signal transmission directions, and connected to at least one of these transmission paths, some of which constitute a control node that performs network configuration control; In a network system consisting of multiple stations, each station stores flag information indicating whether a duplicate address test is performed to detect whether or not there is another station with the same address as the local station in the network. a first means for resetting the flag information to a state indicating that the address test has not been performed; and a second means for resetting the flag information to a state indicating that the address test has not been performed; A third means of transmitting a signal frame for the duplicate address test to the transmission path of No. 2, and when receiving a signal frame for the duplicate address test sent by another station, if the source address of the frame is the same as that of the local station. If it matches, information indicating that there is a duplicate address is added to the received frame and relayed to the next station. and a fourth means for checking whether information indicating the presence of an address is included, and if not included, writing flag information indicating completion of the duplicate address test into the first means. A network system featuring: 5. If the duplicate address test frame sent by the local station includes information indicating the presence of a duplicate address, the fourth means bypasses the station from the first or second transmission path. 5. The network system according to item 4. 6. The network system according to item 4 or 5, wherein each of the second means resets the flag information when the station changes from a dormant state to an active state. 7. Items 4 to 6, wherein each of the second means resets the flag information when receiving a control frame for implementing network configuration control sent by any other station. The network system described in any of the paragraphs. 8. Each of the control node means connects the first transmission line to the second transmission line.
Establishing a transmission path or a signal return path in the opposite direction,
switch means for canceling an already established signal loop path, and at least one station included in each of the control nodes performs the network configuration control operation using the switch means. a predetermined control frame is sent to the first or second transmission path, and each of the second means transmits a predetermined control frame to the first or second transmission path when receiving the control frame.
The network system according to any one of items 4 to 6, characterized in that the network system performs an operation of resetting flag information stored in the means. 9. In a network in which multiple stations, each with one address, are interconnected by a ring-shaped transmission path, a station that has transitioned from a dormant state to an active state is able to connect other stations with the same address as itself on the network. a step of resetting flag information indicating whether or not a duplicate address test has been performed to detect whether or not a duplicate address test exists; A step of transmitting a signal frame for a duplicate address test to a transmission path, and another station receiving the test frame checks the check target address included in the received frame and its own address to see if they match. If so, a step of adding information indicating that there is a duplicate address and relaying it to the next station; and when receiving the above test frame sent by the own station, determining whether or not information indicating that there is a duplicate address is added to the frame. A duplicate address test method comprising the steps of: checking the flag information, and if the flag information is not included, changing the flag information to a state in which the test has been performed, and shifting to a communicable operation mode. 10. When receiving the test frame sent by the local station, if information indicating the existence of a duplicate address is added to the frame, the station is bypassed from the transmission path, according to item 9. Duplicate address test method. 11. One of the plurality of stations transmits a control frame to the transmission path for resetting the flag information of another station included in the network, and each other station that has received the control frame , a step of resetting the flag information stored in the local station, and the duplicate address test method according to item 9 or 10. 12. First and second ring-shaped transmission paths having mutually opposite signal transmission directions, and a plurality of control node means connected to at least one of these transmission paths, some of which control the configuration of the network. A duplicate address test method in a network consisting of a plurality of stations configuring a network, wherein one of the control node means sends a control frame to the first or second transmission path when executing a network configuration control operation. A second step in which each other station that has received the control frame resets flag information indicating whether or not a duplicate address test is to be performed, and each station whose flag information is in a reset state. a third step in which the station executes a duplicate address test and confirms that there is no other station with the same address as its own station, and then sets the flag information to a tested state; A duplicate address test method characterized in that a plurality of stations in a tested state are allowed to communicate. 13. In the third step of the duplicate address test, when each station obtains the right to transmit data on the network, a signal for the duplicate address test is sent to the first or second transmission path to which the station is connected. This is done by sending a frame, and when the frame goes around the network and returns, it is checked whether the received frame contains information indicating the presence of a duplicate address, and the information indicating the presence of a duplicate address is checked. 13. The duplicate address test method according to claim 12, wherein the test frame is added by another station having the same address as the station while the test frame goes around the network. 14. In a communication network including multiple stations, each station must have the same address in the communication network as its own station when it joins the communication network and when the configuration of the communication network changes. 1. A duplicate address test method, characterized in that a duplicate address test operation is executed to check whether or not another station exists.