JP2821221B2 - How to test network systems and duplicate addresses - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a communication network, and more particularly, to a duplicate address test method for preventing stations having the same address from overlapping in a network including a plurality of stations.

[Prior art]

In general, when a plurality of terminal stations (stations or nodes) having the same address exist in a network, a communication frame addressed to a specific terminal station is received by the plurality of terminal stations, and a communication frame is expected. There is a problem that the signal is received by an external terminal station. This problem is the same in a so-called local area network (LAN) that communicates via a common transmission line, and the addresses of the terminal stations connected to the transmission line must not overlap with each other. In other words, when communicating without connection, the addresses of the terminal stations must not be duplicated in the communication network and must be unique. As a conventional method for achieving the above condition in a ring LAN, there is a method described in the following document. “Token Ring Access Method and Physical Layer Sp
802.5-1985 (ISO / DP8802 / 5). According to the above literature, the operation of a terminal station (new terminal station) that newly joins (connects) to a ring LAN (hereinafter simply referred to as a ring) is as follows. Two operations are described: (1) A new terminal that joins the ring first (in a state where no other terminal is connected to the ring) does not need to be aware of address duplication, and Acti for centralized ring management
ve Monitor (AM). The active monitor generates a token for controlling the data transmission right, and manages the normal circulation of the token on the ring. (2) For a new terminal that joins the ring after the second (the state in which AM already exists in the ring), a terminal having the same address already exists in the ring before starting regular communication. Test (duplicate address test). This is performed by transmitting a Duplicated Address Test (DAT) frame in which the own station address is set as the transmission destination address onto the transmission line in accordance with the transmission control by the token, and making a round of the ring. If there is another terminal having the same address as the own station in the ring, when the DAT is received by the other terminal, an identifier indicating that fact is added by the other terminal. Will be returned. In the literature, this identifier is reflected in the Address Recognized indication bit (AR bit). Therefore, the new terminal station can check whether or not a duplicate address has occurred in the ring by checking the identifier in the frame that has gone round. When the addresses are duplicated, for example, by bypassing the own station (in a state of being separated from the ring), a plurality of terminal stations having the same address are prevented from being present in the same ring. This duplicate address test is performed as part of a procedure in the initial (initialized) state of the terminal station.

[Problems to be solved by the invention]

However, in the above conventional example, the following three points are not sufficiently considered, so that there is a problem that a plurality of terminal stations having the same address (duplicate address terminal stations) can continue to exist in the same ring. ing. (A) In the initial state, that is, when there is no active monitor on the ring, and a plurality of terminals having the same address join the same ring almost simultaneously, these terminals should establish an active monitor. Compete with each other. However, each terminal has a duplicate address
Since no test is performed, in this case, a duplicate address terminal station exists in the ring. (B) In a network in which a plurality of terminal stations are connected by a double ring composed of a first ring and a second ring having different signal transmission directions, for example, when a failure occurs, by ring back (loop back) on both sides of the failure point When a new closed ring is formed (ring degeneration), duplicate address terminals may exist in the closed ring. The reason for this is the first
Each terminal connected to the ring or the second ring performs a duplicate address test in the ring (for example, the first ring) to which the own terminal is connected, but performs another address (for example, the second ring). The test is not performed until the duplicate address test with the terminal connected to the terminal is completed. In the ring folding, a new closed ring bypassing the point of failure is formed by integrating the first ring and the second ring, so that an overlapping address test between these two rings is required. This is not done in the conventional method. (C) When a plurality of independent rings are combined to form one larger closed ring (ring expansion), for example, in the above-described double ring, a plurality of rings that have been separated due to a fault are re-established by repairing a fault location. In the case of coupling, the same problem as described above occurs. The point is that no duplicate address test is performed between rings, so that when multiple rings are combined into one, duplicate address terminals exist. The problem (a) is a disadvantage of the prior art described in the above-mentioned document, and the problems (b) and (c) are problems that occur when an attempt is made to realize a new function based on the conventional technology. An object of the present invention is to provide a duplicate address test method for confirming whether or not a plurality of stations having the same address exist in one ring. Another object of the present invention is to prevent the presence of a plurality of stations having the same address in the ring even when the number of terminal stations accommodated in one ring fluctuates due to ring degeneration or ring expansion. An object of the present invention is to provide a duplicate address test method. Another object of the present invention is to provide a network which can reliably prevent the presence of two or more stations having overlapping addresses.
It is to provide a system. It is another object of the present invention to provide a communication system in which each station can confirm that there is no other station having the same address on the same network and can join the network.

[Means for solving the problems]

In order to achieve the above object, according to the present invention, all the stations on the network are provided with means for identifying whether or not the duplicate address test has been normally completed, and the duplicate address test has been normally completed. Stations that have not done this normally start steady communication after completing this normally. However, exceptionally, 1 is determined as the active monitor.
For one station, the duplicate address test may be omitted. Because if all stations except the active monitor perform the duplicate address test,
This is because it is possible to prevent a station having the same address as the active monitor from joining the network. As means for identifying whether or not the duplicate address test has been completed, for example, a duplicate address check flag (Duplicat
ed Address Check flag (CAD).

[Action]

In the address test method of the present invention, for example,
In the station of [DAC = 0], the address test has not been completed.
In the case of "1", the process is terminated. When "DAC = 0", each station sends a DAT according to the token control and performs a duplicate address test as described above. When DAT ends normally, that is, when there is no duplicate address, the state is set to “DAC = 1”, and a mode in which steady communication is possible. On the other hand, DAT
Ends abnormally, that is, if there is a duplicate address, for example, the own station is bypassed from the ring. However, instead of completely disconnecting the station from the transmission path, the station may have only a function of relaying the received frame. In short, only stations that have successfully completed the duplicate address test are set to “DAC = 1”, and a ring is formed only by those stations. This solves the problem that there are a plurality of stations having overlapping addresses in a single ring. In a double ring network, the present invention ensures that each station included in a newly formed closed ring will perform a duplicate address test if a ring loopback occurs in a portion of the network. In other words, when the ring is looped back, all stations are set at one end,
The test is set to the unfinished state, the duplicate address test is performed again after a new closed ring is formed, and then the steady communication is started. Also in this case, the duplicate address test may be omitted for the station determined to be the active monitor in the new closed ring. Similarly, in the present invention, at the time of ring expansion, all the stations included in the expanded ring are set to the duplicate address unfinished state. By doing so, each station connecting to the newly formed closed ring will again perform the duplicate address test according to the modified single ring protocol, and will start regular communication. Here, considering the case of performing ring degeneration or ring expansion in a network having a dual ring configuration,
The duplicate address test is required again when the configuration of the ring is changed due to the degeneration or expansion of the ring. At this time, it is only necessary to obtain a trigger that sets each station to “DAC = 0”. For example, if a specific frame flows each time the ring configuration changes, the value of the DAC can be controlled using this frame. The specific frame is, for example, an abnormality notification frame that notifies that an abnormality has occurred in the ring (beacon: Beaco in the above document).
n), or may be a configuration control frame for performing contraction or expansion of the ring. Alternatively, the frame may be a dedicated frame provided for controlling the value of the DAC. In these cases, each station sets “DAC = 0” each time the specific frame is received, and then performs a duplicate address test (control may be performed so as to be in a steady communication mode. With the above method, According to the present invention, even when a new closed ring is formed by ring contraction or ring expansion,
The problem that duplicate address stations exist in the ring is eliminated.

【Example】

FIG. 1 shows an example of a network to which the present invention is applied. This network is constituted by a double ring 4 comprising first and second ring-shaped transmission lines 4A and 4B having signal transmission directions opposite to each other. A plurality of dual ring control stations or nodes (hereinafter, simply referred to as control stations) 1-1 to 1-3 are connected to each other. Each control station 1-n includes a pair of single ring stations (hereinafter simply referred to as terminal stations) 2-nA and 2-nB, and a transmission line switch 3-
n. The dual ring network may be considered to be a single ring network duplicated. In normal times, the main terminal station 2-nA is connected to the first transmission line 4A and the sub terminal station is connected to the second transmission line side. The switch 3-n is operated in such a state as to perform the operation. In each ring, a terminal station forming a control station and a terminal station not forming a control station may coexist. In the double ring network system, for example, when a failure occurs in a part of the first transmission path, the control station adjacent to the upstream side of the failure transmits the first transmission path from the first transmission path 4A to the second transmission path 4B.
Also, at the control station adjacent to the downstream side of the failure, a second return path from the second transmission path 4B to the first transmission path 4A is formed, whereby the first transmission path and the One closed ring consisting of two transmission lines is reconfigured and the communication function is restored. FIG. 1 shows that a failure 30 occurs on the first transmission line between the control stations 1-1 and 1-2, and the terminal stations 2-1A, 2-3B, 2-2A, and 2-3A are sequentially connected. The closed ring of the shape is shown in a reconstructed state. In the control stations 1-1 and 1-2 adjacent to the failure, the main terminal stations 2-1A and 2-2A are placed on the closed ring side where the communication function is restored, and the sub terminal stations 2-1-2A are placed on the transmission line on the failure 30 side. The switch is operating to connect 1B and 2-2B. In the above example, each control station 1-n is shown as a configuration including two terminals 2-nA and 2-nB.
For example, as described in Japanese Patent Application No. 61-100902 “Ring network configuration control method” proposed by the present inventors, an internal transmission line including a plurality of port switches is provided. A line concentrator structure in which a terminal station (terminal device) can be connected is also applicable. FIG. 2 shows an internal configuration of the terminal station 2-n. Reference numeral 10 denotes a physical layer communication mechanism (Physical Layer: PHY), and reference numeral 11 denotes a medium realized by executing a program by a microprocessor.
Medium Access Control / MA
C), and each function is also described in the prior art document. Although the actual terminal station 2-n has other mechanisms, other elements and communication functions not directly related to the present invention are omitted in the drawings. In the present invention, the MAC 11 has a memory 12 for storing a duplicate address test flag (DAC), and performs an address operation according to the state of the DAC flag as described later. The address test routine is started in response to the fact that the terminal station is changed from the idle state to the active state by turning on the power switch 13. FIG. 3 shows a frame 20 used by the MAC 11 of the terminal station 2 for communication.
Is shown. 21 is the Start Delimi
ter: SD), 22 is a function type (Functional Code: FC), 23 is a destination address (Destination Address: DA), 24 is a source address (Source Address: SA), and 25 is transfer information (Inf).
ormation: INFO), 26 is a frame check sequence (FCS), 27 is an end delimiter (ED), 28 is an address recognition display (Addr
This is a field for ess recognize and copy indicater (AC). The specification of the AC field 28 can be as follows, for example. The source terminal station sends out a frame with "AC =" 0 "", and the terminal station that has received the frame (the DA field 23 matches the own station address) rewrites the AC included in the received frame to "1". By doing so, the source terminal station can check whether the frame has been received by the transmitting end station by checking the AC field 28 in the received frame. FIG. 4 (A) is a program flowchart showing the operation of the terminal station embodying the present invention. This program routine is started, for example, by turning on the power of a terminal to be connected to the ring. First, the dual address test display (DAC) 12 is reset (DAC = "0") (step 10).
0), when you get the token, double address test
A frame (Duplicated Address Test frame: DAT) is transmitted to the transmission path (110). DAT frame is MAC frame 2
In the DA field 23 of 0, an address (My (This Stations) Address: MA) assigned to the own terminal is set, and A
The C field 28 is set to "0". The FC field 22 may include an identifier indicating that this frame is a DTA, and may be distinguished 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 continuously monitored, and if the DAT of “AC =“ 1 ”” is received by “DA = MA” (1
20) After releasing the token, the local terminal is bypassed from the ring transmission line by the switch 3-n (125). Within the dual ring control station 1-n, any single ring terminal station 2-
When nA or 2-nB is in the bypass state, the dual ring control station loses the dual ring configuration control function. On the other hand, when the DAT frame of “AC =“ 0 ”” is received in “DA = MA”, the token is released, the DAC flag 12 is set to “1” (135), and the state shifts to a steady communication state (135). 140). In this communication state, the terminal station 2 transmits and receives a communication frame according to, for example, a token control procedure. When the DAT frame transmitted in step 110 cannot be received within a predetermined time, the DAT frame permanent waiting state can be escaped, for example, by a timer interrupt. In FIG. 4A, this control is omitted. In the steady communication state 140, the terminal station repeats the following operation.
If the token is received when the DAC flag 12 is "0" (150), the process returns to the initialization state and performs the double address test again. DAC = "0" means that the need for performing a double address test arises for some reason in the steady communication state. In this example, the double address test is performed when the token is received. However, this is not necessarily a token as long as it indicates that the ring is normal. For example, purging (Purg
e) It may be a MAC frame or an active monitor present (AMP) MAC frame. When a failure occurs in a part of the network in the normal communication state and the ring configuration control operation is performed (160), the DAC flag 12 is set to "0" (170). This causes the duplicate address test to be re-performed the next time a token is received. As a method of knowing whether or not the configuration control has been performed in the network, for example, a frame described in the following document can be used. IEEE 802 Local Area Networks, 802.5 (Token Rin
g), “Recommended Practice for Dual Ping Operatio
n with Wrapback Reconfiguration ", 802.5c / D15, Sept.
According to the above-mentioned document, when a configuration control, that is, a transmission path return is performed in a dual ring network, a beacon reconfiguration (BNR) is transmitted. For example, by receiving the above BNR, each terminal station can know the execution of the configuration control and reset the DAC 12. Note that when ring expansion is performed as configuration control, the BNR may not flow on the ring in the above document. In order to cope with the problem of the double address by the same control at the time of ring expansion and ring degeneration, the BNR may be made to flow on the ring even in ring expansion. In other words, the double ring terminal that is adjacent to the restored point of failure and needs to cancel the transmission path return and perform ring expansion is the BN
Send R. Note that in the dual ring control station, it is not necessary for both the ring terminal stations 2-nA and 2-nB to transmit the BNR, and only one single ring terminal station needs to transmit the BNR.
May be transmitted. In short, the DAC flags 12 of all the single ring terminals included in the newly formed ring
Can be reset (limited to “0”). The operation flow of FIG. 4A can be roughly divided into an initial state (initialization state) up to step 135 and a steady operation state after step 140. The normal operation state is a state of the terminal station which has successfully completed the dual address test. In the present invention, when the necessity of the dual address test arises due to the execution of the configuration control, each configuration control station or ring terminal station returns from the normal operation normal state to the initial state again. FIG. 4 (B) is a flowchart showing the operation of the terminal station when it receives a DAT frame having the same destination address as its own address transmitted by another terminal station. Even though your station has not sent a DAT frame,
When an AT frame is received, the AC field 28 included in the received DAT frame is rewritten to "1" (step 18).
0), and sends the DAT frame to the transmission path (step 19).
0). When the DAT frame is received by the source terminal station, the source terminal station performs the bypass operation in step 125 of FIG. 4A as described above. 5A to 5H show the procedure of the above-described dual address test on a network composed of dual rings. FIG. 5A: DAC in newly activated control station 1-2 =
Terminal stations 2-2A and 2-2B of "0" are DATs indicated by broken lines, respectively.
Transmit frame (Tx-DAT) and perform double address test. Fig. 5B: Both terminal stations 2-2A and 2-2B are DAs
-Receive DAT of MA and AC = "0" (Rv-DAT (DA = MA, A
C = 0)), thereby ending the double address test normally and setting the DAC flag 12 to “1”. FIG. 5C shows a state in which a failure 30 has occurred in the first transmission path 4A between the control stations 1-1 and 1-2, and these control stations have formed a return path for bypassing the failure 30. When an abnormality occurs in the network, the terminal station that has noticed it transmits a BNR frame. If the network abnormality is caused by, for example, a physical failure in the transmission path, the terminal station located immediately downstream of the failure (for the failure 30, the terminal station 2-2A in FIG. 5C) First detect this. When each terminal station receives the BNR frame from the upstream (Rv-BNR), it relays this to the downstream side and resets the DAC flag to "0".
At this time, if you are sending a BNR frame,
Stop sending NR. As a result, finally, only the terminal station 2-2A in the control station 1-2 closest to the failure point on the downstream side of the failure point continues to transmit the BNR frame (Tx-BNR), and this is the case. Active monitor AM. The formation of the first and second return paths for bypassing the obstacle point can be realized by adopting, for example, a control procedure proposed by the present inventors in Japanese Patent Application No. 62-177093 "Data Communication System". . Fig. 5D: By the above network reconfiguration control operation,
When a new closed ring (active ring) consisting of the second transmission line is formed and the communication function of the network is restored, each terminal whose DAC flag is reset is used to perform the duplicate address test. Transmit a DAT frame (Tx-DAT). This is because the terminal station 2-2A, which has become the active monitor, first sends a DAT frame, releases a token when the duplicate address test is completed, and the next terminal station 2-3A that receives the token starts the address test. In this manner, the DAT frame transmission operation is sequentially performed. As described above, the terminal station 2-2A, which is already the active monitor, may skip the duplicate address test (steps 110 to 170) and immediately transmit the token. FIG.5E: Each terminal that has transmitted a DAT frame includes its own terminal address in the DA field, and upon receiving a DAT frame in which the AC field is “0”, the terminal has successfully completed the duplicate address test, and The flag is set to “1” and the state returns to the normal communication state. As a result, each terminal station other than the active monitor sequentially enters the standby monitor state. FIG. 5F: Shows one state in the ring expansion process performed to unify the two independent closed rings after the fault 30 is recovered. The local ring containing the obstacle 30
As shown in FIG. 5C, when the terminal becomes independent from the active ring, each terminal station included in the local ring transmits a beacon frame (BNN) different from the aforementioned BNR,
When a BNN sent by another terminal is received, it is relayed to it,
It operates to stop sending BNN from its own station. In the example of FIG. 5C, the terminal station 2-1B stops transmitting the BNN, and the terminal station 2-2B
Only the beacon BNN continues to transmit. When the failure 30 recovers, the BNN makes a round of the local ring and the originating terminal station 2
Since the terminal station 2-2B returns to −2B, the terminal station 2-2B can detect that the failure 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 make a round around the local ring. The terminal station 2-1B receives the token,
Recovery of failure 30 can be detected. 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 form the active ring.
The switch 3-2 operates so as to be in the state shown in FIG. 5F. Then, one of the two terminal stations 2-2A and 2-2B becomes an active monitor and transmits a BNR frame (Tx-B
NR). The BNR makes one round of the integrated active ring, and the DAC flag of each terminal that has received this BNR is reset to “0”. Each terminal whose DAC flag has been reset sequentially receives DAs in the same manner as described in FIGS. 5D to 5E.
After transmitting the T frame and completing the duplicate address test normally, the communication mode returns to the normal communication state. Figure 5G: The operation of the active ring integration described above
This is also executed in the control station 1-1, and if there is no address duplication, finally, as shown in FIG. 5G, the duplicate address retest is completed on the first transmission line 4A (DAC = “1”). )
A double ring network including only the main terminal stations 2-1A to 2-3-3A and also including only the sub terminal stations 2-1B to 2-3B that have received the duplicate address test on the second transmission path 4B is reconfigured. . FIG. 5H: A state where one terminal 2-2B having an address overlapping with any other terminal is bypassed from the ring transmission line. FIG. 6 is a diagram showing an improved duplicate address test method in which the method described in the above-mentioned document is adopted as the prior art and an additional modification for applying the present invention is made. The statements indicated by are prior art. In the present invention, the deficiency of the single ring protocol in the prior art is dealt with in S01, S22, and S4X, and the deficiency due to ring degeneration can be dealt with by adding S4Y and S62. In ring expansion,
For example, one of the dual ring control stations (MAC1
Only) the single ring terminal is forced to S6 state (BNR transmission:
Tx-BNR) can solve the above problem. This transition has advantages in terms of uniquely unifying active monitors. The terminal station that has already been the active monitor relinquishes the active monitor right upon receiving the BNR transmitted by the other station, so that the only active monitor is quickly determined. If a plurality of double ring terminals simultaneously release the ring return and extend the ring, a plurality of terminals (single ring terminals) will transmit BNR. According to the control described in the above-mentioned document, it is possible to uniquely identify the station that continues to transmit BNR by the BNR contention control, but in some cases, the terminal stations in the BNR transmission state transmit the BNR transmitted from the other station to each other. , And there may be no terminal station that continues to transmit BNR from the ring. According to the present invention, even in this case, there is no problem since the active monitor can be finally established. Also, a dual address test to implement the invention,
Even if the prevention function is added, the conventional function is not limited. In addition, the dual address problem can be solved while maintaining equal dispersibility between each dual ring control station or each single ring terminal station. In the above-described embodiment, each terminal station that has transmitted a communication frame such as a DAT frame performs communication in such a form that a token is released after the communication frame has returned after making a round of the ring. However, the method for testing duplicate addresses according to the present invention uses an early token release in which each terminal releases a token immediately after transmitting a communication frame so that a plurality of terminals can transmit data one after another. It can also be applied to a ring network of the system. In this case, if the second terminal station having the same address transmits another DAT frame before the DAT frame transmitted by the first terminal station returns after making a round of the ring,
These two terminal stations may rewrite the AC field of the other DAT frame to “1”, and both ends may fall into a bypass state. In the ring network of the early token release system, in order to make only one of the two terminals having the same address into the bypass state, the DAT frame transmitted by the first terminal must make a round of the ring. The transmission control of the DAT frame may be performed so that the other terminal station transmits the next DAT frame on the transmission path. For the DAT frame transmission control, for example, the active monitor includes, in the DA field 23, one group address to which all the stations with the DAC flag “0” are to be received, and stores the frame address in the information field 25. To control the transmission of DAT frames.
est Start) Contains a code indicating that this is a frame, AC
A control frame including "0" in the field 28 may be transmitted, and each terminal station may obtain a DAT frame transmission right when receiving a DATS frame of "AC = 0". When receiving the DATS frame, the first terminal closest to the active monitor and having the DAC flag “0” receives the DATS frame.
The AC field in the TS frame is rewritten to “1”, and the DAT frame is transmitted when the token is received. AC = 1
DATS frame makes one round of the ring and is erased from the active monitor which is the transmission source. Sent by the first terminal
In the course of one round of the ring, if a second terminal having the same address as the first terminal exists, the DAT frame is transmitted to the second terminal.
With the AC field rewritten to “1” by the terminal,
Return to the source first terminal. When the DAT frame returns, the first terminal station transmits a new DATS frame of “AC = 0”,
If the AC of the received DAT frame is “1”, the DATS frame that has made one round of the ring is deleted, and then the bypass state is set. After receiving the DATS frame transmitted by the first terminal station, the next terminal station downstream of the first terminal station with DAC = 0 performs the same operation as the first terminal station described above. As described above, if the transmission of the DAT frame is controlled, when the second terminal transmits the DAT frame, the first terminal having the same address as that of the second terminal has already been bypassed.
The terminal station can receive the AC = 0 DAT frame and can remain on the network. Further, a method different from the above-described procedure is also conceivable. DAT
May include information unique to the source station, for example, the physical location address of the station or information on adjacent stations. The unique information makes it possible to distinguish between the DAT transmitted from the own station and the DAT transmitted from the duplicate address station, and to determine the priority between the two stations. As another method for solving the problem of the double address, for example, (a) each terminal station in the network sends a specific frame addressed to all other terminal stations, for example, AMP (Activate
e Monitor Present) or SMP (Standby Monitor Pr)
esent), and the terminal station that has received the frame checks the source address (SA) to know the occurrence of a duplicate address and takes measures against it. (b) A specific terminal station that centrally manages the network For example, a method is conceivable in which a server is provided and the station takes measures against problems such as address duplication. However, in the former case, the duplicate address
The start and end of the test cannot be grasped and the test is always performed. In the latter case, there is a problem that the problem cannot be solved without the server. Also, in both methods, after each terminal station in the network enters a steady operation state, an address error is detected. Therefore, the performance and reliability of the communication function of the terminal station (MAC upper level: user) are reduced. There is a problem that has a significant effect.

【The invention's effect】

As is apparent from the above description, according to the present invention, it is possible to prevent terminal stations having the same address from overlapping in the same ring. Further, even when the terminal stations connected to the ring fluctuate due to the configuration control of the ring degeneration or the ring expansion, the effect of preventing the above-mentioned duplicate address is obtained. One of the basic concepts of the present invention is that a duplicate address test is performed each time a plurality of networks are connected, and does not depend on the topology of the network, that is, the configuration of a ring, a bus or a mesh.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a double ring network to which the present invention is applied, FIG. 2 is a block diagram showing main components of a terminal station, and FIG. 3 is a diagram showing a format of a duplicate address test frame. FIG. 4 (A) is a flowchart of a control operation executed by each terminal for realizing a duplicate address test according to the present invention, and FIG. 4 (B) is a duplicate address transmitted by another terminal. A flowchart showing the operation of each terminal performed when a test frame is received,
5A to 5H are diagrams for explaining a procedure of a duplicate address test according to the present invention according to the state of a network,
FIG. 6 is a diagram showing a duplicate address test according to the present invention on a state transition diagram of each terminal station. Description of reference numerals 1 (1-1 to 1-3) ... control station, 2 (2-1A to 2-3B) ... terminal station, 3 (3-1 to 3-3) ... switch, 10 ... Physical layer communication mechanism, 11 ... Media access control layer communication mechanism, 12 ...
... Duplicate address test (DAC) flag memory, 13 ... Power switch.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jiro Kashio 1099 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture Inside the Hitachi, Ltd.System Development Laboratory Co., Ltd. (72) Inventor Hiroyuki Wada 1st Horiyamashita, Hadano-shi, Kanagawa Prefecture Inside Kanagawa Factory, Hitachi, Ltd. (72) Inventor Yoshito Saco 1st-Horiyamashita, Hadano-shi, Kanagawa Prefecture Kanagawa Factory, Hitachi, Ltd. 72) Inventor Fumiaki Matsuura 6-81 Onoe-cho, Naka-ku, Yokohama-shi, Kanagawa Prefecture Within Hitachi Software Engineering Co., Ltd. (72) Inventor Ihei 6-81 Onoe-cho, Naka-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-63-1 09625 (JP, A) JP-A-62-86943 (JP, A) JP-A-61-248638 (JP, A) JP-A-61-59938 (JP, A) JP-A-60-25345 (JP, A) JP-A-58-33340 (JP, A) JP-A-57-168555 (JP, A) JP-B-59-43862 (JP, B2) The 39th (late 1989) Information Processing Society of Japan national conference paper (III) p p. 1980-1981 (5T-3) Susumu Nakayashiki et al. "Method for Preventing Duplicate Addresses in Token Ring LAN Automatic Configuration Control" IEEE Staudards for Local Area Networking Token Access Medicine and Physics Physics and Physical Trading (Approved June 2, 1989) IEEE Std 802.5-1984 (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 12/42-12/437 JICST file (JOIS) WPI (DIALOG) PCI ( DIALOG)

Claims (13)

(57) [Claims] 1. A network system comprising a plurality of stations connected to at least one ring transmission line and each having one address, wherein each station has another station having the same address as its own station in the network. First means for storing flag information indicating whether or not to execute a duplicate address test for detecting whether or not to execute the second address test; second means for setting the flag information to a test required state at a predetermined timing; A third means for transmitting a signal frame for a duplicate address test to the transmission line when the flag information indicates that a test is required; and a duplicate address test transmitted by another station having the same address as the own station. When a frame is received, the test frame is added with information indicating the presence of a duplicate address and relayed to the next station,
When receiving the duplicate address test frame transmitted by the own station, it checks whether or not the frame includes information indicating that there is a duplicate address, and when it is determined that there is no duplicate address, a test is performed in the flag information storage means. And a fourth means for writing flag information indicating no. 2. The network system according to claim 1, wherein said second means resets said flag information when said station changes from a dormant state to an active state. 3. The apparatus according to claim 1, wherein the second means resets the flag information when a specific control frame transmitted by one of the plurality of stations is received. Network system. 4. A first and a second ring-shaped transmission line having signal transmission directions opposite to each other and connected to at least one of these transmission lines, and some of them constitute a control node for controlling network configuration. Flag information indicating whether or not a duplicate address test is performed to detect whether or not another station having the same address as the own station exists in the network in the network system including a plurality of stations. A second means for resetting the flag information to a state indicating that the address test has not been performed, and a first means connected to the station when the flag information has been reset. A third means for transmitting a signal frame for the duplicate address test to the second transmission line, and a signal frame for the duplicate address test transmitted by another station. If the transmission source address of the frame matches the own station, the information indicating that a duplicate address is present is added to the received frame, and the received frame is relayed to the next station. When a signal frame for a test is received, it is checked whether or not the received frame contains information indicating the presence of a duplicate address. If not, the first means notifies the first means of completion of the duplicate address test. And a fourth means for writing flag information to indicate. 5. When the duplicate address test frame transmitted by the own station includes information indicating presence of a duplicate address, the fourth means causes the station to bypass the first or second transmission line. 5. The network system according to claim 4, wherein: 6. The network system according to claim 4, wherein said second means resets said flag information when said station changes from a dormant state to an active state. 7. The apparatus according to claim 4, wherein said second means resets said flag information when receiving a control frame transmitted from any other station for performing network configuration control. 7. The network system according to claim 6. 8. A switch for establishing each of the control node means from the first transmission path to the second transmission path or a signal return path in a direction opposite to the first transmission path and canceling the signal return path already established. Means for transmitting a predetermined control frame to the first or second transmission line when a network configuration control operation performed by using the switch means is performed by at least one station included in each of the control nodes. The network system according to any one of claims 4 to 6, wherein the second means resets flag information stored in the first means when receiving the control frame. 9. In a network in which a plurality of stations each having one address are interconnected by a ring transmission line, a station which has shifted from a dormant state to an operating state has another station having the same address as its own station. Resetting flag information indicating whether or not a duplicate address test is performed to detect whether the address exists on the network; and a station in which the flag information is in a reset state obtains a right to transmit data to the transmission path. Sending a signal frame for a duplicate address test to the transmission path when the other station has received the test frame, checks the address of the own station with the check target address included in the received frame, If they match, add the information indicating that there is a duplicate address and relay to the next station, and receive the test frame sent by the own station. Check whether or not information indicating the presence of a duplicate address is added to the frame, and if not, change the flag information to a test-executed state and shift to a passable operation mode. And a duplicate address test method, comprising: 10. The ninth aspect of the present invention is characterized in that, when receiving the test frame transmitted by the own station, if information indicating that there is a duplicate address is added to the frame, the station is bypassed from the transmission line. The duplicate address test method described in the section. 11. A step in which any one of the plurality of stations transmits a control frame for resetting the flag information of another station included in the network to the transmission path, and wherein the other station receives the control frame. 11. The duplicate address test method according to claim 9, wherein each station resets the flag information stored in the station. 12. A first and a second signal transmission directions opposite to each other.
Address test in a network consisting of a ring-shaped transmission path and a plurality of stations connected to at least one of these transmission paths, some of which constitute a plurality of control node means for controlling the configuration of the network A method wherein any one of the control node means transmits a control frame to the first or second transmission line when performing a network configuration control operation; A second step in which each station resets flag information for indicating whether or not a duplicate address test is performed; and each station in which the flag information is in a reset state executes a duplicate address test, and additionally, assigns the same address as its own station. A third step of setting the flag information to a tested state after confirming that there is no station having the A plurality of stations whose flag information has been tested are allowed to communicate. 13. The duplication address test of the third step is such that when each station obtains a data transmission right in the network, the duplication address test is performed on the first or second transmission line to which the station is connected. When the frame returns after making a round of the network, it is performed by checking whether or not the received frame contains information indicating the presence of a duplicate address. 13. The double address test method according to claim 12, wherein the information indicating is added by another station having the same address as the station while the test frame makes a round of the network.