JPH08213996A - Synchronism establishing method for asynchronous transfer mode hub and asynchronous transfer mode intra-area network switching system - Google Patents

Abstract

PURPOSE: To establish the synchronism of plural ATM nuts to perform real-time transmission of multimedia by comparing discrimination information and determining a supply route based on the comparison result. CONSTITUTION: A comparison routine 25 which determines the priorities of ATM hubs and an internal comparison routine 26 which determines priorities of network interfaces of the ATM hub which is judged to have a high priority by the comparison routine 25 are provided. A wait cell routine 27 where the ATM hub which is judged to have a low priority by the comparison routine 25 transmits/receives cells to response information from ATM hubs having higher priorities and a clock master determining routine 28 which determines a clock master based on the execution result of the internal comparison routine 26 are provided. Thus, the comparison routine 25 is executed again and is switched to the internal comparison routine 26 with respect to network interfaces which are judged to have low priorities by execution of the internal comparison routine 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asynchronous transfer mode hub synchronization establishing method and an asynchronous transfer mode intra-area network switching system, and more particularly to a method for establishing synchronization of a plurality of asynchronous transfer mode hubs arranged on a communication network. And an asynchronous transfer mode intra-area network switching system for performing a desired switching operation by the asynchronous transfer mode hub.

[0002]

2. Description of the Related Art Conventionally, Ethernet (IEEE 802.3 compliant) etc. has been used as a technology for performing information communication in a relatively narrow limited area such as the same building or the same site. Local Area Net
work; hereinafter referred to as "LAN") is known and
Communication using the AN has already been performed.

Further, it is regarded as a favorite of the next-generation communication network technology, and as a technology capable of transferring multimedia data,
Asynchronous transfer mode (Simplified protocol for high quality transmission)
An exchange system called "M") is being actively developed and standardized. In the ATM switching system, transmission information is divided into fixed length blocks (53 bytes) to create asynchronous transfer mode cells (hereinafter referred to as "ATM cells"), and the ATM cells are sequentially sent out, which is a conventional method. It is possible to reduce the switching delay while inheriting the high transmission efficiency of the packet switching.

Recently, a plurality of ATM hubs are arranged on a network (communication network), and the ATM-LA is used as a multimedia-compatible LAN utilizing the ATM technology.
N has been actively developed, and attempts have been made to perform high-speed communication of information such as video, audio, and documents while accommodating a conventional LAN.

[0005]

However, the above-mentioned A
Since the TM-LAN has a high data transmission rate on the network (for example, 155.52 Mbps), in order to reliably receive the transmitted data, all A
It is necessary to make the clocks of the TM hub the same and keep the same state. That is, it is necessary to establish synchronization between the ATM hubs. For example, if an ATM hub that operates with a different clock of 1 ppm among the ATM hubs exists on the network, the clock “difference” during video transmission is accumulated and even if a buffer function such as a frame memory is interposed. There is a problem that one screen data is missed due to overflow or lack of data, and means for storing the previous screen data is inevitable.

The present invention has been made in view of the above problems, and an ATM hub synchronization establishing method and ATM-LAN exchange for establishing real time transmission of multimedia by establishing synchronization of a plurality of ATM hubs. The purpose is to provide a system.

[0007]

In order to achieve the above object, the method for establishing synchronization of an ATM hub according to the present invention comprises a plurality of A's.
After the identification information is given to each TM hub, the identification information is compared and one ATM hub that supplies a clock to all other ATM hubs and a clock supply route are determined based on the comparison result. It is characterized by that.

More preferably, after the identification information is given to each of the plurality of ATM hubs, the superiority or inferiority of the identification information is compared between the interface portions of different ATM hubs, and the interface portion of the ATM hub which has been superior is clocked. While setting to the transmittable state, the identification information of the interface section of the inferior ATM hub is set to the superior A
After rewriting to the identification information of the TM hub and setting the interface unit to the clock receivable state, the interface unit set to the receivable state until response information is received from the interface unit set to the transmittable state Is set to the communication standby state, and when the identification information between the interface portions of the ATM hub set to the transmission enabled state is not the same value, the identification information is rewritten to the most advantageous value and the transmission / reception information of the response information and the clock is possible. Are set to the initial state, and then the advantages and disadvantages of the identification information are again compared between the interface sections of different ATM hubs to execute the above-described series of operations, and the interface sections of the ATM hubs set to the transmittable state are If the identification information has the same value, one or more interface units that can receive the clock are At the same time, the response information is transmitted to the interface unit that has transmitted the response information transmission request to the interface unit, and further, the communication standby state of the ATM hub related to the interface unit that has received the response information is released and the transmission ready state is set. A series of operations similar to those of the set ATM hub is executed between the interface parts of the ATM hub, and then all the interface parts of the ATM hub are clocked to the ATM hub set to a state other than the receivable state. It is characterized in that the supply source is determined and the clock supply route is determined based on the transmittable / receivable information of each interface unit.

Further, when the interface section of the ATM hub is refused the communication line connection with the interface section of the specific ATM hub, the interface section which can be connected with the interface section of the other ATM hub is set to the communication disabled state. It is also preferable that the clock transmission / reception information, the response information, and the identification information regarding the ATM hub for which the communication line connection is denied are set to the initial state.

Further, the ATM-LAN exchange system according to the present invention, the identification information giving means for giving the identification information to each of the plurality of ATM hubs, and the identification information given by the identification information giving means, the plurality of ATMs. Comparison means for comparing between hubs and all other ATMs from the comparison results of the comparison means
It is characterized by including one ATM hub for supplying a clock to the hub and a determining means for determining a clock supply route.

More preferably, a comparison is made between the plurality of ATM hubs and the identification information giving means for giving identification information to each of the plurality of ATM hubs, and the superiority or inferiority of the identification information given by the identification information giving means is compared between the plurality of ATM hubs. Means and the ATM hub that is predominant among the ATM hubs by the comparing means.
The first internal comparison means for performing internal comparison between the interface sections inside the TM hub, and the A means by the comparison means.
Between the ATM hub which is inferior among the TM hubs, the response information waiting means for waiting for the response information from the ATM hub which has been predominant, and when the response information from the response information waiting means is received, between the interface parts. Second internal comparison means for performing internal comparison, one ATM hub for supplying a clock to all other ATMs based on the comparison results of the first and second internal comparison means, and a clock supply route And a determining means for determining.

Specifically, the interface section is
A first flag that stores a first flag indicating whether communication is possible
Storage area and a second indicating whether or not the response information is in the standby state
Second storage area for storing a flag for the ATM hub, a third storage area for storing a third flag indicating the clock transmittable / receivable state, and a fourth storage area for storing first identification information unique to the ATM hub. And a second rewritable area according to the execution results of the comparison means and the first and second internal comparison means.
And a fifth storage area for storing identification information of the different ATM hubs, which is connected by a communication line when the first flag is set to the communicable state. The priority order determining means for comparing the second identification information with each other to determine the priority order, and the third interface section determined to be superior by the priority order determining means.
First flag of the clock is set to the transmittable state of the clock
Setting means and the second identification information of the interface section determined to be inferior by the priority determination section to the second identification information of the interface section determined to be superior, and the third flag can be received. And a second setting means for setting the first hub and the second internal comparison means, wherein the first and second internal comparison means have a second interface section included in the ATM hub.
The first determination means for determining whether or not all the identification information is the same value, and when the first determination means determines that they are not the same value, the second identification information is set to a value that is the most dominant. And third setting means for setting the second and third flags to initial values, and the second setting information is set to the most dominant value by the third setting means, and the second and third flags are set. When the flag is set to the initial value, the re-comparison execution means for executing the comparison means again, and when the first judgment means judges that they have the same value, the clock receivable interface section is set to 1 It is characterized in that it is provided with a receiving interface section determining means of not more than one.

The first connection requesting means for the interface section of the ATM hub to request the interface section of another ATM hub to establish a communication line connection, and whether or not a predetermined time has elapsed without a response to the request for the communication line connection. Second determining means for determining whether or not the second flag is set to the communication disabled state and the second flag of the interface section is set when the second determining means determines that the predetermined time has elapsed. And a third flag, and a fourth setting means for setting the second identification information to an initial value, and first to third flags and second flags of all the interface parts of the ATM hub that has requested the communication line connection. And a fifth setting means for setting the identification information of
When it is judged by the second judging means that the predetermined time has elapsed, it is judged whether or not the clock of the other interface section of the ATM hub which has requested the communication line connection is in a transmittable state. And a second connection requesting means for requesting a communication line connection to the other interface section when the clock of the other interface section is in a transmittable state. Is also preferable.

[0014]

The above-mentioned method for establishing synchronization of the ATM hub and ATM-LA
According to the N-switching system, first, by comparing the identification information of the interface section among a plurality of ATM hubs,
The superiority or inferiority of the ATM hub is determined, and then the superiority or inferiority is further determined among the interface sections of the superior ATM hub, and the number of interface sections that can be received by the ATM hub is set to one or less. On the other hand, in the inferior ATM hub, the response information is requested to the interface section of the superior ATM hub, and after receiving the response information from the superior ATM hub, the above-mentioned superiority comparison is performed between the internal interface sections. To do. And finally all ATMs
At least one receiving interface unit is determined in the hub, an ATM hub having no receiving interface unit is used as a clock supply source, and a clock supply route is determined based on the superiority or inferiority of the interface unit.

When the connection of the communication line with the specific ATM hub becomes impossible, the AT requesting the line connection
The clock transmittable / receivable information, the response information, and the identification information in the interface section of the M hub are set to the initial state.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment (first embodiment) of an asynchronous transfer mode intra-area network (ATM-LAN) switching system according to the present invention.

This ATM-LAN exchange system is composed of
The fourth ATM hubs 1 to 4 are arranged on the network,
These first to fourth ATM hubs 1 to 4 are connected to each other by network lines 5 to 8. Further, these first to fourth ATM hubs 1 to 4 are connected to various terminal devices (not shown) directly or via an ATM terminal adapter to perform data direction selection, ATM cell switching operation, and the like.

The first ATM hub 1 is equipped with two network interface devices 9 and 10, and
The TM hub 2 is provided with two network interface devices 11 and 12. Also, the third ATM hub 3 has three network interface 1
3, 14, 15 are provided, and the fourth ATM hub 4 is provided with a network interface 16.
The network interface 9 is connected to the network interface 11 of the second ATM hub 2 via the network line 5, and the network interface 10 is connected to the third interface via the network line 6.
ATM hub 3 network interface 15
It is connected to the. The network interface 13 of the third ATM hub 3 is connected to the network interface 12 of the second ATM hub 2 via the network line 7, and the network interface 14 of the third ATM hub 3 is connected to the network line 8. Via the network interface 16 of the fourth ATM hub 4.

Storage devices 17 to 24 are provided in the respective network interfaces 9 to 16, and the storage devices 17 to 24 have first to fifth storage areas 17 (n) to 24. (N) (n = 1 to 5) are provided.

Further, in each of the network interfaces 9 to 16, each first storage area 17 is provided.
The first flag is stored in (1) to 24 (1), the second flag is stored in each of the second storage areas 17 (2) to 24 (2), and each of the third storage areas 17 is stored. (3) to 24 (3)
A third flag is stored in. The first ID number is stored in each of the fourth storage areas 17 (4) to 24 (4), and the second ID is stored in each of the fifth storage areas 17 (5) to 24 (5).
ID number of is stored.

Here, each of the first flags is a flag indicating whether or not the network interface is communicable, and is set to "0" when the network interface is in an incommunicable state, and is in a communicable state. It is set to "1" at some time, and is set to "0" in the initial state as shown in FIG.

Each second flag is a flag indicating whether or not the network interface is waiting for a response from a partner connected by a network line, and is set to "1" in the response waiting state. It is set, and is set to "0" when not waiting for a response, and in the initial state, as shown in FIG.
It is set to "0" as shown in.

Each of the third flags is a flag which indicates a transmission / reception direction of a supply clock (hereinafter referred to as "master clock") from a clock supply source which will be described later, and is "0" in the initial state as shown in FIG. Is set to 1, and is set to "1" in a mode in which master clock transmission / reception is not performed.
Further, it is set to "2" in the master clock transmission mode, and is set to "3" in the master clock reception mode.

Each first ID number is set to an invariable value unique to each of the first to fourth ATM hubs 1 to 4 by, for example, a DIP switch. That is, the first ID number is given as identification information for identifying each of the first to fourth ATM hubs 1 to 4, and in the present embodiment, as shown in FIG. Is set to "1" and the second ATM hub 2 is set to "2". Further, the third ATM hub 3 is set to "3", and the fourth ATM hub 4 is set to "4".

In the initial state, each second ID number is set to the same value as each first ID number and is appropriately rewritten as will be described later, and finally, an ATM hub which is a clock supply source, that is, a clock. It is rewritten to the same value as the first ID number of the master.

FIG. 2 is a block diagram showing a schematic configuration of a synchronization establishing method of the ATM hub according to the present invention. The first to fourth ATM hubs 1 to 4 are compared to determine a clock master. A comparison routine 25 (comparing means) for determining the priority order of the ATM hub and an internal comparison routine 26 (first comparison routine for determining the priority order between the network interfaces in the ATM hub determined to have a high priority by the comparison routine 25). And second internal comparison means)
Then, the ATM hub, which has been determined by the comparison routine 25 to have a lower priority, transmits / receives cells and is superior to the ATM hub.
It has a waiting cell routine 27 (response information waiting means) for waiting for response information from the hub and a clock master determination routine (determination means) 28 for determining a clock master based on the execution result of the internal comparison routine 26. The network interface judged to be inferior by the execution of the comparison routine is configured to execute the comparison routine again and shift to the internal comparison routine 26.

The ATM hub synchronization establishment method of the present invention will be described in detail below.

FIG. 3 is a flowchart of the comparison routine. In the comparison routine, each ATM hub 1 to 4 is used.
The second ID numbers are compared with each other, and the ATM hub having the smaller second ID number is determined as the ATM hub having the higher priority.

Specifically, first, in order to perform priority comparison between the first ATM hub 1 and the second ATM hub 2,
The comparison routine uses the first ATM hub 1 and the second ATM.
Implemented on both hubs 2.

That is, in step S1, whether or not the first flag is "1", that is, the first ATM hub 1
Communication is possible and waits until the first flag is set to "1". Specifically, from the network interface 9 of the first ATM hub 1 to the second AT
The first storage area 17 (1) of the network interface 9 is transmitted by transmitting the first predetermined cell to the network interface 11 of the M hub 2 via the network line 5 and receiving the first response cell to the first predetermined cell.
The first flag stored in is rewritten from "0" to "1", and the network interface 11 of the second ATM hub 2 to the network interface 17 of the first ATM hub 1 via the network line 5. The first flag stored in the first storage area 19 (1) of the network interface 11 is changed from "0" to " It is rewritten to "1" so that they can communicate with each other. When the first flag is set to "1", in the subsequent step S2, the first ATM hub 1 transfers to the second ATM hub 2 and the second ATM hub 2 transfers to the first ATM hub 1, respectively. Send comparison cells, each 5th
The second ID number of its own and the second ID number of the other party stored in the storage areas 17 (5) and 19 (5) are compared. Then, in the first ATM hub 1, the second ID number of itself is set to "1", and the second A
Since the second ID number of the TM hub 2 is set to "2", the answer in step S3 becomes affirmative (Yes), and the second
The ID number is maintained as it is and the third flag is rewritten to "2" indicating that the master clock can be transmitted (step S4), and the process proceeds to the internal comparison routine (step S5).
That is, it is determined that the first ATM hub 1 has a higher priority than the second ATM hub 2, and the process proceeds to the internal comparison routine.

On the other hand, in the second ATM hub 2, the second ID number of itself is set to "2", and the second ID number of the first ATM hub 1 as the other party is set to "1". Therefore, the answer in step S3 is negative (No),
Rewriting the second ID number to "1" which is the second ID number of the other party (step S6), and then rewriting the third flag to "3" indicating that the master clock can be received (step S7) Waiting cell Proceed to the transmission routine (step S8).

Similarly, the first ATM hub 1 and the third AT
The comparison routine is also executed with the M hub 3.

That is, the first predetermined cell is transmitted from the network interface 10 of the first ATM hub 1 to the network interface 15 of the third ATM hub 3 via the network line 6, and a first response to this is sent. By receiving the cell, the first flag stored in the first storage area 18 (1) of the network interface 10 is rewritten from “0” to “1”,
Also, the first predetermined cell is transmitted from the network interface 15 of the third ATM hub 3 to the network interface 11 of the first ATM hub 1 via the network line 6, and the first response cell to the cell is received. As a result, the first flag stored in the first storage area 23 (1) of the network interface 15 is rewritten from "0" to "1", making them mutually communicable. In this way, when the first flag is rewritten to "1", the answer to step S1 becomes affirmative (Yes), and in the following step S2, the first ATM hub 1 to the third ATM hub 3 and the third ATM hub 3 ATM hub 3 to 1st
To the ATM hub 1 of each other, and the own second ID number and the other party's second ID number stored in the respective fifth storage areas 18 (5) and 23 (5) are transmitted. Compare. Then, in the first ATM hub 1, the second ID number of its own is set to "1", and the third A that is the other party.
Since the second ID number of the TM hub 3 is set to "3", the answer in step S3 becomes affirmative (Yes), and the second
The ID number is maintained as it is and the third flag is rewritten to "2" indicating that the master clock can be transmitted (step S4), and the process proceeds to the internal comparison routine (step S5).
That is, it is determined that the first ATM hub 1 has a higher priority than the third ATM hub 3, and the process proceeds to the internal comparison routine.

On the other hand, in the third ATM hub 3, the second ID number of its own is set to "3", and the second ID number of the other first ATM hub 1 is set to "1". Therefore, the answer in step S3 is negative (No),
Rewrite the second ID number to "1" (step S6),
Next, the third flag is rewritten to "3" indicating that the master clock can be received (step S7), and the process proceeds to the waiting cell transmission routine (step S8).

Similarly, the second ATM hub 2 and the third AT
The comparison routine is also executed with the M hub 3.

That is, the first predetermined cell is transmitted from the network interface 12 of the second ATM hub 2 to the network interface 13 of the third ATM hub 3 via the network line 7, and a first response to this is sent. By receiving the cell, the first flag stored in the first storage area 20 (1) of the network interface 12 is rewritten from "0" to "1",
Also, the first predetermined cell is transmitted from the network interface 13 of the third ATM hub 3 to the network interface 12 of the second ATM hub 2 via the network line 7, and the first response cell to this is received. As a result, the first flag stored in the first storage area 21 (1) of the network interface 13 is rewritten from "0" to "1", and the mutual communication is possible. In this way, when the first flag is rewritten to "1", the answer to step S1 becomes affirmative (Yes), and in the following step S2, the second ATM hub 2 to the third ATM hub 3 and the third ATM hub 3 Second from ATM hub 3
Of the respective comparison cells to the ATM hub 2 of the other, and the own second ID number and the second ID number of the other party stored in the respective fifth storage areas 20 (5) and 21 (5) are sent. Compare. Then, in the second ATM hub 2, the second ID number of its own is set to "2", and the other third A
Since the second ID number of the TM hub 3 is set to "3", the answer in step S3 becomes affirmative (Yes), and the second
The ID number is maintained as it is and the third flag is rewritten to "2" indicating that the master clock can be transmitted (step S4), and the process proceeds to the internal comparison routine (step S5).
That is, it is determined that the second ATM hub 2 has a higher priority than the third ATM hub 3, and the process proceeds to the internal comparison routine.

On the other hand, in the third ATM hub 3, the second ID number of its own is set to "3", and the second ID number of the other second ATM hub 2 is set to "2". Therefore, the answer in step S3 is negative (No),
Rewrite the second ID number to "2" (step S6),
Next, the third flag is rewritten to "3" indicating that the master clock can be received (step S7), and the process proceeds to the waiting cell transmission routine (step S8).

Similarly, the third ATM hub 3 and the fourth AT
The comparison routine is also executed with the M hub 4.

That is, the first predetermined cell is transmitted from the network interface 14 of the third ATM hub 3 to the network interface 16 of the fourth ATM hub 4 via the network line 8, and the first response thereto is sent. By receiving the cell, the first flag stored in the first storage area 22 (1) of the network interface 14 is rewritten from "0" to "1",
Further, the first predetermined cell is transmitted from the network interface 16 of the fourth ATM hub 4 to the network interface 14 of the third ATM hub 3 via the network line 8 and the first response cell to the same is received. As a result, the first flag stored in the first storage area 24 (1) of the network interface 16 is rewritten from "0" to "1", making them mutually communicable. When the first flag is rewritten to "1" in this way, the answer to step S1 becomes affirmative (Yes), and in the following step S2, the third ATM hub 3 to the fourth ATM hub 4 and the fourth ATM hub 4 ATM hub 4 to 3
Of the comparison cells to the ATM hubs 3, and the own second ID number and the second ID number of the other party stored in the respective fifth storage areas 22 (5), 24 (5) are transmitted. Compare. Then, in the third ATM hub 3, the second ID number of its own is set to "3", and the other fourth A
Since the second ID number of the TM hub 4 is set to "4", the answer in step S3 becomes affirmative (Yes), and the second
The ID number is maintained as it is and the third flag is rewritten to "2" indicating that the master clock can be transmitted (step S4), and the process proceeds to the internal comparison routine (step S5).
That is, it is determined that the third ATM hub 3 has a higher priority than the fourth ATM hub 4, and the process proceeds to the internal comparison routine.

On the other hand, in the fourth ATM hub 4, the second ID number of its own is set to "4", and the second ID number of the other party's third ATM hub 3 is set to "3". Therefore, the answer in step S3 is negative (No),
Rewrite the second ID number to "3" (step S6),
Next, the third flag is rewritten to "3" indicating that the master clock can be received (step S7), and the process proceeds to the waiting cell transmission routine (step S8).

FIG. 4 shows the value of each flag and each ID number set by the execution of the above-mentioned comparison routine between the ATM hubs.

As is apparent from FIG. 4, the network interface 11 and the third ATM of the second ATM hub 2 in which the third flag is set to "3" and the master clock can be received. A queue cell transmission routine is executed in the network interfaces 13 and 15 of the hub 3 and the network interface 16 of the fourth ATM hub 4.

FIG. 5 is a flow chart of the waiting cell transmission routine.

That is, the network interface 11 of the second ATM hub 2 transmits a second predetermined cell (waiting cell) to the network interface 9 of the first ATM hub 1 (step S11), Second storage area 19 of interface 11
The second flag stored in (2) is rewritten to "1" (step S12) and the second response cell waits for a response from the network interface 9 (step S13).

Similarly, the network interface 15 of the third ATM hub 3 transmits a second predetermined cell (waiting cell) to the network interface 10 of the first ATM hub 1 (step S11), and the network -Second storage area 23 of interface 15
The second flag stored in (2) is rewritten to "1" (step S12), and the response from the network interface 10 by the second response cell is waited for (step S13).

Similarly, the network interface 13 of the third ATM hub 3 transmits a second predetermined cell (waiting cell) to the network interface 12 of the second ATM hub 2 (step S11), and the network The second storage area 21 of the interface 13
The second flag stored in (2) is rewritten to "1" (step S12) and the second response cell waits for a response from the network interface 12 (step S13).

Similarly, the network interface 16 of the fourth ATM hub 4 transmits a second predetermined cell (waiting cell) to the network interface 14 of the third ATM hub 3 (step S11), and the network The second storage area 24 of the interface 16
The second flag stored in (2) is rewritten to "1" (step S12) and the second response cell waits for a response from the network interface 22 (step S13).

In FIG. 6, the second flags of the network interfaces 11, 13, 15, 16 are "1".
Is set to indicate that these network interfaces 11, 13, 15, 16 are waiting for a response, and as will be described later, by receiving a response, each of these second
Flag is rewritten to "0" and the waiting cell routine is ended.

Next, FIG. 7 is a flowchart of the internal comparison routine executed in each of the ATM hubs 1 to 4.

That is, the second IDs stored in the fifth storage areas 17 (5) and 18 (5) of the network interfaces 9 and 10 in the first ATM hub 1.
It is determined whether the numbers are the same (step S21). At this time point, as shown in FIG. 6, both the second ID numbers are set to "1", so that the answer is affirmative (Yes.
s), the process proceeds to step S23, and it is determined whether or not there is one or less network interface that receives the master clock. At this time, as shown in FIG. 6, the third flags of the network interfaces 9 and 10 are both set to "2", and the master clock transmission mode is set. That is, it is determined that the number of network interfaces that receive the master clock is one or less, and the process proceeds to step S24, and the second response cell is transmitted to the network interface that transmitted the second predetermined cell, that is, the network interfaces 11 and 15. Then, the process proceeds to the master clock determination routine (step S25). As a result, the value of the second flag is reset to "0" in the waiting cell transmission routine (FIG. 5) described above (step S14), and the internal comparison routine of the second ATM hub 2 can be executed. (Step S1
5).

In the internal comparison of the second ATM hub 2, the fifth storage area 19 of the network interfaces 11 and 12 is the same as the first ATM hub 1 described above.
It is determined whether or not the second ID numbers stored in (5) and 20 (5) are the same (step S21). At this point, as shown in FIG. 6, the second ID number of the network interface 11 is "1", while the second ID number of the network interface 12 is 2.
Since the number is “2” and both are not the same value, the process proceeds to step S22 and the network interface 12
The second ID number of the network interface 12 is rewritten to "1" which is the minimum value of the two.
And the third flag is set to "0" and the comparison routine (FIG. 3) is executed again for the network interface 12.

In the comparison routine, the network
By transmitting the first predetermined cell again from the interface 12 to the network interface 13 and receiving the first response cell to the first predetermined cell, the first predetermined cell stored in the first storage area 17 (1) is received. Flag is "1"
(In the case of the present embodiment, the first flag has already been set to “1”), the answer to step S1 becomes affirmative (Yes), the process proceeds to step S2, and the fifth step of the network interface 12 is performed. The second ID number and network of its own stored in the storage area 20 (5).
The second ID number of the other party stored in the fifth storage area 21 (5) of the interface 13 is compared. Then, while the second ID number of the self is rewritten to "1" in step S22 described above, the second I
Since the D number is set to "2" (see FIG. 6), the answer in step S3 is affirmative (Yes), and the second ID number remains the same value "1" and the third flag is set. It is rewritten to "2" indicating that the master clock can be transmitted (step S4), and the internal comparison routine (step S5) is performed again.

On the other hand, the network interface 1
In No. 3, since the second ID number of the self is set to "2" and the second ID number of the partner network interface 12 is set to "1", the answer to step S3 is negative ( No), the second ID number is rewritten to "1" (step S6), and then the third flag is rewritten to "3" indicating that the master clock can be received (step S7). Wait cell transmission routine (step S7)
Proceed to 8).

That is, the network interface 13 again executes the waiting cell transmission routine of FIG. 5 and rewrites the second flag to "1" (step S1).
2) Wait for a response from the network interface 12 by the second response cell (step S13).

Since the network interface 12 has proceeded to step S5 as described above, the second ATM hub 2 having the network interface 12 again executes the internal comparison routine shown in FIG.

That is, in the same manner as described above, the fifth storage area 19 of the network interfaces 11 and 12
It is determined whether or not the second ID numbers stored in (5) and 20 (5) are the same (step S21). At this point, the second ID numbers are both set to "1" (FIG. 6, fifth storage area 19 (5) and step S22 at the time of executing the previous internal comparison routine), and therefore the answer is affirmative. (Yes), and the process proceeds to step S23, and it is determined whether or not there is one or less network interface that receives the master clock. At this point, the third flag of the network interface 11 is set to "3" and the third flag of the network interface 12 is set to "2", as shown in FIG. Since the network interface that receives the clock is only the network interface 11, the answer is affirmative (Yes), and the process proceeds to step S24, that is, the network interface that has transmitted the second predetermined cell, that is, the network interface.
The second response cell is transmitted to the interface 13, and the process proceeds to the master clock determination routine (step S25).
As a result, the second flag of the network interface 13 of the third ATM hub 3 is reset to "0" in the waiting cell transmission routine (FIG. 5) described above (step S14), and the internal comparison routine is proceeded to. It becomes possible (step S15).

That is, each second flag of the third ATM hub 3 is set to "0", and then the third ATM hub 3 is set.
The internal comparison routine is executed for the TM hub 3.

In the third ATM hub 3, the second ID numbers stored in the fifth storage areas 21 (5), 22 (5) and 23 (5) of the network interfaces 13 and 1415 are the same. It is determined whether or not (step S
21). At this point, as shown in FIG. 6, the second ID number of the network interface 14 is "3", the second ID number of the network interface 15 is "1", and the network
The second ID number of the interface 13 is set to "1" in step S6 of FIG. 3 from the value "2" shown in FIG. 6 as described above. Therefore, step S21
Is negative (No), the process proceeds to step S22, the second ID number of the network interface 14 is rewritten to the minimum value "1", and the second and third flags of the network interface 14 are set. Set to "0" and the network interface 14
Then, the comparison routine (FIG. 3) is executed again.

In the comparison routine, the network interface 14 and the network interface 1
6 retransmits the first predetermined cell to the other party and receives the first response cell to set each first flag to "1".
(In the case of the present embodiment, each of the first flags is already set to "1"), the answer to step S1 becomes affirmative (Yes), the process proceeds to step S2, and the network interface 14 Fifth storage area 22
The second ID number of its own stored in (5) and the fifth storage area 24 of the network interface 16
The second ID number of the other party stored in (5) is compared. Then, while the second ID number of the self is rewritten to "1" in step S22 described above, the second ID number of the other party is set to "3" (see FIG. 6).
The answer of step S3 is affirmative (Yes), and the second ID number is the third ID while keeping the value "1" as it is.
Is rewritten to "2" indicating that the master clock can be transmitted (step S4), and the process proceeds to the internal comparison routine (step S5) again.

On the other hand, the network interface 1
In No. 6, since the second ID number of the self is set to "3" and the second ID number of the partner network interface 14 is set to "1", the answer to step S3 is negative ( No), the second ID number is rewritten to "1" (step S6), and then the third flag is rewritten to "3" indicating that the master clock can be received (step S7). Wait cell transmission routine (step S7)
Proceed to 8).

That is, the network interface 16 again executes the waiting cell transmission routine of FIG. 5 and rewrites the second flag to "1" (step S1).
2) Wait for a response from the network interface 14 by the second response cell (step S13).

Since the network interface 14 has proceeded to step S5 as described above, the third ATM hub 3 having the network interface 14 again executes the internal comparison routine shown in FIG.

That is, the second ID numbers stored in the fifth storage areas 21 (5), 22 (5), 23 (5) of the network interfaces 13, 14, 15 are the same as described above. It is determined whether or not (step S2)
1). At this point, all the second ID numbers are set to "1" (FIG. 6, step S22 at the time of execution of the previous internal comparison routine and the fifth storage area 23 (5), execution of the previous comparison routine). Step S6), the answer is affirmative (Yes), and the process proceeds to step S23,
It is determined whether or not the number of network interfaces receiving the master clock is one or less. At this point, as shown in FIG. 6, the third flag of the network interface 14 is set to "2", but the third flags of the network interface 13 and the network interface 15 are both set to "3". Since it has been set, therefore, there are two network interfaces that receive the master clock, and the process proceeds to step S26. That is, it is necessary to determine only one network interface for receiving the master clock, and in this embodiment, the network interface 13 is "1", the network interface 14 is "2", and the network interface is "3" in advance. Is set, and the network interface to receive is determined to be the minimum one, that is, the network interface 13. As another method for determining one receiving network interface when there are a plurality of receivable network interfaces, if the network interface is a slot type card, it depends on the number determined by the slot position. Alternatively, it is preferable to compare the values set by the DIP switch attached to the network interface.

Then, the third flag of the network interface 15 is rewritten to "1" for instructing not to transmit / receive the master block, and the network
After instructing the interface 12 to set the third flag to "1" (step S27), the second response cell is transmitted to the network interface that transmitted the second predetermined cell, that is, the network interface 16. , And proceeds to the master clock determination routine (step S25). As a result, the second flag of the network interface 16 of the fourth ATM hub 4 is reset to "0" in the waiting cell transmission routine (FIG. 5) described above (step S14), and the internal comparison routine is executed. Is enabled (step S1)
5).

Thus, the fourth ATM hub 4 has only a single network interface 16,
In the internal comparison routine, the answers to step S21 and step S22 are both affirmative (Yes), and since the second predetermined cell has not been received, the process immediately proceeds to step S25.

FIG. 8 shows the value of each flag and each ID number set by the above method.

In the clock master determination routine of step S25, an ATM hub capable of receiving the master clock is selected and the clock master is determined. Specifically, in FIG. 7, the ATM hub in which the third flag is set to "1" and the master clock can be received is excluded to determine the clock master. That is, only the first ATM hub 1 is "2" (network interface 9) indicating the transmission of the clock master and "1" (network interface 1) not transmitting or receiving the clock master.
0) is indicated by the third flag, and the first ATM hub 1 is determined to be the master clock supply source, that is, the clock master.

By the way, the first to the fourth ATM hubs 1 to 4
In each of the network interfaces 9 to 16 of the above, if the change state of the second ID number is traced, the first ATM
The network interfaces 9 and 10 of the hub 1 maintain the state of "1" from beginning to end.

Regarding the network interfaces 11 and 12 of the second ATM hub 2, the second ID number of the network interface 11 is “2” →
Change to "1" and network interface 12
The second ID number of the item changes from “2” → “2” → “1”.

Further, regarding the network interfaces 13, 14, 15 of the third ATM hub 3, the second ID number of the network interface 13 changes from "3" to "2" to "1", -The second ID number of the interface 14 is "3" → "3" →
Change to "1" and network interface 15
The second ID number of changes from "3" to "1".

Regarding the network interface 16 of the fourth ATM hub 4,
The second ID number of the interface 16 is “4” →
It changes from "3" to "1".

Therefore, in FIG. 8, the first ATM hub 1 to the second ATM hub 2 that have become clock masters.
Is transmitted from the network interface 9 having the third flag "2" to the network interface 11 having the third flag "3" via the network line 5, and clocked to the third ATM hub 3. The master transmission is not from the network interface 10 of the first ATM hub 1 but from the network interface 12 of the second ATM hub 2 whose third flag is "2" and the third flag is "3". It is sent to the network interface 13 via the network line 7. Further, the clock master transmission to the fourth ATM hub 4 is performed by the third A with the third flag set to "3".
It is sent from the network interface 14 of the TM hub 3 to the network interface 16 via the network line 8.

As a result, the first to fourth ATM hubs 1 to
The synchronization of No. 4 is automatically and easily established and the master clock supply route is uniquely determined. Therefore, the master clock is not supplied from multiple routes and there is a problem due to a time delay during reception. Does not occur.

Next, after the synchronization is established as in the first embodiment, the power source is turned off due to, for example, a failure of the second ATM hub 2 among the first to fourth ATM hubs 1 to 4. A master clock supply route determination method when the state is brought into a state will be described in detail as a second embodiment based on the flowchart shown in FIG.

The network interface 9 of the first ATM hub 1 is the network interface of the second ATM hub 2.
The first predetermined cell is transmitted to the interface 11 via the network line 5 (step S31), and the second cell is transmitted.
The flag is rewritten to "1" and the response waiting state is set (step S32). Then, a predetermined time waiting for the first response cell to the first predetermined cell is measured (step S3
3) It is determined whether a predetermined time has passed (step S34). By the way, when the predetermined time has not elapsed, the determination in step S34 is negative (No), but since the power of the second ATM hub 2 is turned off as described above, the network interface 9 is Therefore, the answer of step S36 becomes negative (No), and as a result, the answer of step S34 becomes affirmative (Yes) after a lapse of a predetermined time. And the first
Is reset to "0" to set the communication disabled state (step S37), and then the other flags and the second ID number of the network interface 9 are returned to the initial values (step S38). That is, the second and third flags are reset to "0" and the second ID number is maintained at "1". Then, in step S39, it is determined whether or not the third flag of the other network interface of the first ATM hub 1, that is, the network interface 10 is "2" indicating the transmission mode. Since the third flag is set to "1" that does not perform transmission / reception as shown in FIG. 8, the answer in step S39 is negative (No), and in step S41, each flag and ID number are set to the initial value shown in FIG. The value is reset, and the process returns to step S31 to execute the above steps for other network interfaces.

Next, the first predetermined cell is transmitted from the network interface 13 of the third ATM hub 3 to the network interface 12 of the second ATM hub 2 via the network line 7 (step S3).
1), the second flag is rewritten to "1" to set the response waiting state (step S32), and the predetermined time for waiting the first response cell for the first predetermined cell is measured (step S3).
3) It is determined whether a predetermined time has passed (step S34). Then, when a predetermined time elapses without receiving the first response cell (step S36), step S3
The answer to No. 4 is affirmative (Yes), and the communication is not possible, and the first flag is rewritten to "0" (step S3).
7), then reset the second and third flags of the network interface 13 to "0", the second ID
Keep the number at "1". Then, in step S39, another network interface of the third ATM hub 3, namely the network interface 14,
It is determined whether the third flag of 15 is “2” indicating the transmission mode. As shown in FIG. 8, the third flag of the network interface 15 is set to "1" which does not transmit / receive the master clock,
Since the third flag of the interface 14 is set to "2", the answer in step S39 becomes affirmative (Yes), and the third interface from the network interface 14 to the network interface 16 via the network line 8 Send a specified cell,
After resetting each flag and the second ID number of the interface 16 to the initial values (step S40), the network interface 14 other than the network interface 13 in the third ATM hub 3,
Each flag and ID number of 15 are reset to initial values (step S41), and the process returns to step S31 to execute the above steps for other network interfaces.

At this time, each flag and I of the network interface 16 of the fourth ATM hub 4 which has received the third predetermined cell transmission in the above step S40.
The D number is reset to the initial value shown in FIG.

Thus, the network interface 9 and the network interface 13 described above are used.
For other network interfaces other than, ATM of the other party to which the network line is connected
Since the power of the hub is turned on, when the first predetermined cell is transmitted from the other network interface, that is, the network interface 10, 14, 15, 16 to the destination network interface, the predetermined time is passed. Since the first response cell is transmitted from the destination network interface, the answer in step S36 becomes affirmative (Yes). Therefore, the second flag is set to "0" to stop the measurement (step S42) and cancel the response waiting state (step S4).
3) Then, the first flag is rewritten to "1" to make it in a communicable state (step S44), the process returns to the comparison routine (FIG. 3), and the above-described processing is repeated. Then, the respective flags and the respective ID numbers of the first, third and fourth ATM hubs finally become as shown in FIG.

Therefore, the clock master has an AT in which the third flag has only a value other than "3" indicating the reception mode.
First, the third flag of the network interface 9 is “0” and the third flag of the network interface 10 is “2”, as is clear from FIG. ATM hub 1 serves as a clock master.

Further, the master clock is transmitted from the network interface 10 of the first ATM hub 1 to the third ATM hub 1.
It is transmitted to the network interface 15 of the TM hub 3, and further transmitted from the network interface 14 of the third ATM hub 3 to the fourth network interface 16.

As described above, according to the second embodiment,
After synchronization is established between the fourth ATM hubs 1 to 4, even if one ATM hub, for example, the second ATM hub 2 is powered off due to a failure or another reason, the clock master is re-established. The ATM hub and the master clock supply route are quickly determined, and the network synchronization can be easily established.

Next, a case where the power supply is turned off due to a failure of the first ATM hub 1 which is the clock master after the synchronization of the ATM hub is established will be described as a third embodiment.

In this case as well, the synchronization can be established by the same procedure as in the flowchart of FIG. 9, and therefore the third embodiment will be described with reference to the flowchart of FIG.

The second interface connected to the network interface 9 of the first ATM hub 1 by the network line 5.
ATM hub 2 network interface 11
Transmits the first predetermined cell to the network interface 9 (step S31), and rewrites the second flag stored in the second storage area 19 (2) of the network interface 11 to "1". , Starts measuring for a predetermined time (step S33). Since the power of the first ATM hub 1 is off, the predetermined time elapses without receiving the first response cell (step S36) (step S34), and the process proceeds to step S37, and the network interface 11 First storage area 19 of
The first flag stored in (1) is rewritten from "1" to "0", and other flags of the network interface 11, that is, the second and third flags are reset to "0", The second ID number is reset to "2" (step S38).

Next, in step S39, the second AT
It is determined whether the third flag of the other network interface of the M hub 2, that is, the network interface 12 is "2". As shown in FIG. 8, since the third flag of the network interface 12 is set to "2", the answer is affirmative (Yes).
Then, the third predetermined cell is transmitted to the network interface 13 of the third ATM hub 3 which is the destination of the network interface 12, and all the flags and the second ID numbers are reset to the initial values (step S4
0) Further, after resetting each flag and each ID number of the network interface 13 to the initial values (step S41), the process returns to step S31 to repeat the above process for another network interface.

Next, the network interface 15 of the third ATM hub 3 connected to the network interface 9 of the first ATM hub 1 by the network line 6 sends the first predetermined cell to the network interface 10. The second storage area 23 of the network interface 15 is transmitted (step S31).
The second flag stored in (2) is rewritten to "1" and the measurement of a predetermined time is started (step S33). Then, without receiving the first response cell (step S
36) After the lapse of a predetermined time (step S34), the process proceeds to step S37, and the network interface 15
Rewrite the first flag stored in the first storage area 23 (1) from "1" to "0", and further change the other flags of the network interface 15, that is, the second and third flags. Reset to "0" and the second ID
The number is reset to "2" (step S38).

Next, in step S39, the second AT
It is determined whether the third flag of the other network interface of the M hub 2, that is, the network interface 12 is "2". As shown in FIG. 8, since the third flag of the network interface 15 is set to "2", the answer is affirmative (Yes).
Then, the third predetermined cell is transmitted to the network interface 16 of the fourth ATM hub 4, which is the destination of the network interface 15, and all the flags and the second ID numbers are reset to the initial values (step S
40) Further, after resetting each flag and each ID number of the network interface 15 to the initial values (step S41), the process returns to step S31 and the above process is repeated for another network interface.

Thus, the above-mentioned network interface 11 and network interface 1
For other network interfaces other than 5, the destination ATM to which the network line is connected
Since the power of the hub is turned on, when the first predetermined cell is transmitted from the other network interface, that is, the network interface 12, 13, 14, 16 to the destination network interface, it takes a predetermined time. Since the first response cell is transmitted from the destination network interface, the answer in step S36 becomes affirmative (Yes). Therefore, the second flag is set to "0" to stop the measurement (step S42) and cancel the response waiting state (step S4).
3) Then, the first flag is rewritten to "1" to establish a communicable state (step S44), and the process returns to the comparison routine (Fig. 3) to repeat the above process. The flags and ID numbers of the first, third and fourth ATM hubs finally become as shown in FIG.

Therefore, the clock master has an AT in which the third flag has only a value other than "3" indicating the reception mode.
It is necessary to be the M hub, and as shown in FIG.
Second ATM whose flag is "0" and the third flag of the network interface 12 is "2"
The hub 2 becomes the clock master.

Further, the master clock is transmitted from the network interface 12 of the second ATM hub 2 to the third ATM hub 2.
It is transmitted to the network interface 13 of the TM hub 3, and further transmitted from the network interface 14 of the third ATM hub 3 to the fourth network interface 16.

As described above, according to the third embodiment,
After synchronization is established between the fourth ATM hubs 1 to 4, even if the first ATM hub 1 which is the clock master is powered off due to a failure or other reasons, the ATM that becomes the clock master again. The supply routes of the hub and the master clock are quickly determined, and the network synchronization can be easily established.

[0093]

As described above in detail, according to the asynchronous transfer mode hub (ATM hub) synchronization establishing method and the asynchronous transfer mode intra-area network (ATM-LAN) switching system of the present invention, the number of ATM hubs is irrelevant. ATM-LAN
One ATM hub that supplies the clocks is automatically determined, and synchronization between the ATM hubs can be easily established.

Further, since the clock from the specified ATM hub is supplied by the uniquely determined supply route, there is no time delay due to the supply from a plurality of routes.

As described above, according to the present invention, the ATM-LA
It is possible to automatically unify the clocks in the N network, and to realize real-time transmission of multimedia without causing a clock shift during data transfer.

[Brief description of drawings]

FIG. 1 is in an asynchronous transfer mode area (ATM-
It is a schematic block diagram which shows one Example of a LAN) exchange system.

FIG. 2 is a block diagram showing a concept of a synchronization establishing method.

FIG. 3 is a flowchart of a comparison routine.

FIG. 4 is a diagram showing the value of each flag and each ID number at the end of the first execution of the comparing means executed between the ATM hubs.

FIG. 5 is a flowchart of a waiting cell transmission routine.

FIG. 6 is a diagram showing the value of each flag and each ID number at the end of the second response cell waiting step of the waiting cell transmission routine.

FIG. 7 is a flowchart of an internal comparison routine.

FIG. 8 is a diagram showing values of flags and ID numbers when synchronization is established.

FIG. 9 is a flowchart showing a second embodiment.

FIG. 10 is a diagram showing the value of each flag and each ID number when synchronization is established in the second embodiment.

FIG. 11 is a diagram showing the value of each flag and each ID number when synchronization is established in the third embodiment.

[Explanation of symbols]

1 to 4 1st to 4th ATM hubs (asynchronous transfer mode hubs) 5 to 8 communication lines 9 to 16 network interfaces (interface units) 17 (1) to 24 (1) first storage area 17 (2) to 24 (2) Second storage area 17 (3) to 24 (3) Third storage area 17 (4) to 24 (4) Fourth storage area 17 (5) to 24 (5) Fifth storage Area 25 Comparison Routine (Comparison Means) 26 Internal Comparison Routine (First and Second Internal Comparison Means 27 Wait Cell Sending Means (Response Information Waiting Means) 28 Clock Master Determining Means (Determining Means)

Claims (8)

[Claims] 1. A method for establishing synchronization of asynchronous transfer mode hubs for establishing synchronization of a plurality of asynchronous transfer mode hubs arranged on a communication network, the method comprising: providing identification information to each of the plurality of asynchronous transfer mode hubs; Synchronization of the asynchronous transfer mode hub characterized by comparing the identification information and determining a clock supply route with one asynchronous transfer mode hub that supplies a clock to all other asynchronous transfer mode hubs based on the comparison result. How to establish. 2. A method for establishing synchronization of an asynchronous transfer mode hub for establishing synchronization of a plurality of asynchronous transfer mode hubs having at least one interface section arranged on a communication network, the method comprising: After the identification information is given to each, the superiority or inferiority of the identification information is compared between the interface parts of different asynchronous transfer mode hubs, and the interface part of the asynchronous transfer mode hub that has been predominant is set to the clock transmittable state, while it is inferior. After rewriting the identification information of the interface section of the asynchronous transfer mode hub that was set to the identification information of the superior asynchronous transfer mode hub and setting the interface section to the clock receivable state, the interface set to the transmittable state Until the response information from the department is received Set the interface unit set in the signal state in the communication standby state, when the identification information between the interface unit of the asynchronous transfer Modohabu set in the transmittable state is not equivalence,
After rewriting the identification information to the most dominant value and setting the response information and the clock transmittable / receivable information to the initial state, the advantages and disadvantages of the identification information are compared again between the interface parts of the different asynchronous transfer mode hubs. When the identification information between the interface units of the asynchronous transfer mode hub set to the transmittable state has the same value, the number of interface units that can receive the clock is set to 1 or less and the response information is transmitted to the interface unit. Similar to the asynchronous transfer mode hub set to the transmittable state by transmitting the response information to the interface unit that has transmitted the request, and further canceling the communication standby state of the asynchronous transfer mode hub regarding the interface unit that received the response information. A series of operations are performed on the interface of the asynchronous transfer mode hub. Then, all interface units of the asynchronous transfer mode hub are set to a state other than the receivable state, and the asynchronous transfer mode hub is determined as the clock source and the transmission / reception of each interface unit is possible. A method for establishing synchronization of an asynchronous transfer mode hub, characterized in that the supply route of the clock is determined based on information. 3. When the interface unit of the asynchronous transfer mode hub is refused the connection of the communication line with the interface unit of the specific asynchronous transfer mode hub, the interface unit that can be connected to the interface unit of the other asynchronous transfer mode hub cannot communicate. 3. The asynchronous transfer mode hub according to claim 2, wherein the clock transmission / reception enable information, the response information, and the identification information regarding the asynchronous transfer mode hub whose communication line connection is rejected are set to an initial state while being set to a state. Synchronization establishment method. 4. An asynchronous transfer mode intra-area network switching system in which a plurality of asynchronous transfer mode hubs are arranged on a communication network, and identification information giving means for giving identification information to each of the plurality of asynchronous transfer mode hubs. A comparison means for comparing the identification information given by the identification information giving means between the plurality of asynchronous transfer mode hubs, and a single one for supplying a clock to all other asynchronous transfer mode hubs from the comparison result of the comparison means. An asynchronous transfer mode intra-area network switching system, comprising: an asynchronous transfer mode hub; and a determining means for determining a clock supply route. 5. An asynchronous transfer mode intra-area network switching system in which a plurality of asynchronous transfer mode hubs having at least one interface unit are arranged on a communication network, wherein identification information is provided to each of the plurality of asynchronous transfer mode hubs. And an comparing means for comparing the superiority or inferiority of the identifying information given by the identifying information giving means between the plurality of asynchronous transfer mode hubs, and the comparing means giving the superiority between the asynchronous transfer mode hubs. The first internal comparison means by which the asynchronous transfer mode hub performs internal comparison between the interface parts inside the asynchronous transfer mode hub, and the asynchronous transfer mode hub that is inferior to the asynchronous transfer mode hub by the comparison means are given the superiority. Response information waiting means for waiting response information from the asynchronous transfer mode hub, and the response The when receiving the response information from the broadcast wait means for internal comparison between the interface unit 2
Internal comparison means, and one asynchronous transfer mode hub for supplying a clock to all other asynchronous transfer modes and a clock supply route are determined based on the comparison results of the first and second internal comparison means. An asynchronous transfer mode intra-area network switching system comprising: a determining means. 6. The interface unit stores a first storage area for storing a first flag indicating whether or not communication is possible, and a second storage area for storing a second flag indicating whether or not in the response information standby state. A second storage area, and a third storage area for storing a third flag indicating the clock transmittable / receivable state,
A fourth storage area for storing first identification information unique to the asynchronous transfer mode hub, and a second rewritable area according to the execution results of the comparison means and the first and second internal comparison means.
And a fifth storage area for storing identification information of the different asynchronous transfer mode hubs connected by a communication line when the first flag is set to the communicable state. A priority order determining means for comparing the second identification information between the second identification information and a priority order determining means, and a third flag of the interface section determined by the priority order determining means to be superior to the clock transmittable state. No. 1 setting means, and the second identification information of the interface section determined to be inferior by the priority determination section to the second identification section of the interface section determined to be superior.
Second setting means for setting the third flag to a receivable state and setting the third flag to the receivable state, wherein the first and second internal comparing means have a second interface section of the asynchronous transfer mode hub. Determining means for determining whether or not all the identification information of the
If it is determined by the determination means of No. 2 that they are not the same value, the second identification information is set to a value that is the most advantageous and the second
And a third setting means for setting the third flag to an initial value, and the second setting information is set to the most dominant value by the third setting means, and the second and third flags are initialized. When it is set to a value, re-comparison execution means that executes the comparison means again, and when the first judgment means determines that the values are the same, the number of interface units that can receive the clock is set to one or less. 6. The asynchronous transfer mode intra-area network switching system according to claim 5, further comprising receiving interface section determining means. 7. A first connection requesting means for causing an interface unit of the asynchronous transfer mode hub to request a communication line connection to an interface unit of another asynchronous transfer mode hub,
Second judging means for judging whether or not a predetermined time has passed without responding to the request for connection to the communication line, and the first judging means when the second judging means judges that the predetermined time has passed And a fourth setting means for setting the second flag, the third flag, and the second identification information of the interface unit to initial values.
It is provided with a fifth setting means for setting the first to third flags and the second identification information of all the interface units of the asynchronous transfer mode hub that has requested the communication line connection to initial values. The asynchronous transfer mode intra-area network switching system according to claim 6. 8. If the second determination means determines that the predetermined time has elapsed, then whether the clock of the other interface section of the asynchronous transfer mode hub requesting the communication line connection is ready for transmission. And a second connection requesting means for requesting a communication line connection to the other interface section when the clock of the other interface section is in a transmittable state. 8. The asynchronous transfer mode intra-area network switching system according to claim 7, wherein.