JP3196164B2 - LAN system and remote bridge using ISDN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LA using ISDN.
N system , in particular, a LAN system as a connection method when a remote LAN terminal device makes a call connection to a LAN, and
Regarding remote bridge .

[0002]

2. Description of the Related Art As shown in FIG. 12, a remote LAN terminal 12 serving as a client terminal of a LAN 124 is provided.
0 is connected to the LAN 124 via the remote bridge 121, the ISDN 122, and the bridge 123. In general, remote terminals including the remote LAN terminal device 120 and the remote bridge 121 are installed at a plurality of locations. In this configuration, the connection between the ISDN 122 and the remote bridge 121 and the bridge 123 uses a circuit switching method having an advantageous data transmission speed.

If the number (port number) of the remote bridge 121 and the bridge 123 is the same or the number of the bridges 123 is larger than the number of the remote bridges 121, the remote bridge 121 and the bridge 123 are completely connected. Can be supported, and therefore remote LAN
This cannot occur if the terminal device 120 cannot access the LAN 124.

However, in the construction of a LAN system, the cost of communication and the system, the form of system use, the frequency of system use, and the like are taken into consideration.
In the AN system, the number of remote bridges 121 is smaller than the number of bridges 123. In the case of such a LAN system, when all the bridges 123 are in use (so-called all-line busy state), the other remote LAN terminal devices 120 cannot access the LAN 124.

In such a state, conventionally, the remote bridge 121 automatically makes a re-call several times, until the line becomes empty and a communication path with the bridge 123 is established.
The data from the remote LAN terminal device 120 has been canceled.

[0006]

The above-mentioned prior art has a problem that the remote LAN terminal device cannot access the LAN at all, so that the serviceability to the user of the remote LAN terminal device is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. Even in a LAN system in which the number of remote bridges is smaller than the number of bridges, the remote LAN
A LAN system using ISDN that can prevent a terminal device from being unable to access the LAN at all; and
The purpose is to provide a remote bridge .

[0008]

SUMMARY OF THE INVENTION The present invention provides a remote LA
In a LAN system using ISDN in which N terminal devices are communicatively connected to a LAN via ISDN,
And a circuit-switched bridge connected to the LAN and the ISDN in a circuit-switched manner, and a circuit-switched bridge connected to the LAN and the ISDN and connected between the LAN and the ISDN. A packet-switching bridge for connecting a call between them by a packet-switching method, and the ISDN
And a remote block connecting the remote LAN terminal
A first call connection means for making a call connection between the ISDN and the ISDN by a circuit switching method, and a second call connection means for making a call connection between the ISDN and the remote LAN terminal device by a packet switching method means and said first control the call connection means and the second call connection means, transmitting control hand a call connection to the circuit switching bridge and packet switching bridge
Between the ISDN and the remote LAN terminal device
A non-communication monitoring means for monitoring a non-communication state;
The first allowable time for determining whether the line with the bridge can be disconnected
First storage means for storing, and the packet switching bridge
A second permissible time for determining whether or not the line can be disconnected is stored.
The second storage means and the transmission control means store the first call connection
If the connection is made by the connection means,
When a non-communication state is detected between
The call is disconnected, and the transmission control means is connected by the second call connection means.
In the case where the communication is continued,
Disconnects the call with the above ISDN when detecting the condition
A remote bridge having disconnection control means .

[0009]

With the above arrangement, the remote LAN terminal apparatus can always perform the logical switching using the packet switching bridge even if the line by the circuit switching system using the circuit switching bridge is blocked. ,
You can access the LAN. Therefore, the number of remote bridges is smaller than the number of bridges in LA.
Even in the N system, it is possible to prevent a state in which the remote LAN terminal device cannot access the LAN at all.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a LAN system showing an embodiment of the present invention. In FIG. 1, Ether-LA
N, LAN terminal devices 5a, 5b and 5c as clients and a server 6 are connected to the Ether-LAN. Furthermore, Ether-
The LAN includes a bridge for interfacing with the ISDN 3, and a circuit-switched bridge 4a having a connection control procedure corresponding to a connection method based on the circuit-switching of the ISDN 3,
And a packet switching bridge 4b having a connection control procedure corresponding to a connection method by B channel packet switching of the ISDN 3.

Further, the remote LAN terminal devices 1a and 1
b, and the remote terminal devices 1 a and 1
b is ISDN by the remote bridges 2a and 2b.
3 is made. The remote bridges 2a and 2b are interfaces for interfacing with the ISDN 3, and have a control procedure corresponding to the connection method by circuit switching of the ISDN 3 and a connection procedure corresponding to the connection method by B-channel packet switching. is there.

Thus, the remote LAN terminal device 1a
And 1b are remote bridges 2a and 2b, ISDN
3. Connected to the Ether-LAN via the circuit switching bridge 4a or the packet switching bridge 4b,
It is a LAN terminal device as a client that can access the her-LAN.

The remote LAN terminals 1a and 1a
b, and the LAN terminal devices 5a, 5b, and 5c are composed of ordinary personal computers, workstations, and the like.

FIG. 2 is a bridge diagram showing a configuration of a remote bridge according to the present invention. In FIG. 2, remote bridges 2a and 2b have remote LAN terminal devices 1 connected thereto.
a and 1b, and a LAN interface circuit 21 for interfacing with each other by, for example, 10BASE-T. The buffer 22 is a buffer for temporarily storing transmission / reception data, and a communication control circuit 23 for performing matching control of data speed, logical interface, protocol, and the like.
Is connected to the LAN interface circuit 2 via the buffer 22.
1 connected.

The communication control circuit 23 includes an ISDN3
And an ISD which is connected based on the I basic interface, and which is interconnected with the ISDN 3 in either a control procedure corresponding to a connection method by circuit switching or a control procedure corresponding to a connection method by B channel packet switching.
The N interface line 24 is connected.

The control circuit 25 is a processor for controlling the entire remote bridges 2a and 2b.
According to the control program, control data, table, and the like stored in the memory 26, the LAN interface circuit 2
1, a buffer 22, a communication control circuit 23, and an ISDN interface circuit 24. The panel 27 is used for displaying a communication state, making and receiving calls, and setting various data.

FIG. 3 is a block diagram showing the configuration of the circuit switching bridge according to the present invention. In FIG. 3, the circuit-switching bridge 4a has an Ether-LAN and, for example, 1
LAN for mutual interface by 0BASE-T
An interface circuit 21 is provided. The filtering circuit 32 has an address table.
When a data packet is received from the her-LAN, by referring to the destination address of the data packet and the address stored in the address table, whether to pass the received data packet to another segment side (ISDN3 side) It is to determine whether or not. The buffer 33
A buffer for temporarily storing transmission / reception data, and a communication control circuit 34 for performing matching control such as a data rate, a logical interface, and a protocol are connected to the LAN interface circuit 31 via a buffer 33 and a filtering circuit 32. .

The communication control circuit 33 includes an ISDN3
And an ISDN interface circuit 35 for interconnecting with the ISDN 3 in a control procedure corresponding to a connection method by circuit switching.

Further, the control circuit 3 6 is a processor for controlling the entire circuit switching bridge 4a, memory 3
7 , a LAN interface circuit 31, a filtering circuit 32, a buffer 33, a communication control circuit 34,
And the ISDN interface circuit 35. The panel 38 is used for displaying a communication state and setting various data.

The packet-switching bridge 4b has substantially the same configuration as the circuit-switching bridge 4a. The main difference is that the ISDN interface circuit 35 controls the ISDN 3 in a control procedure corresponding to the connection method by packet switching.
Since only the interconnection is performed, detailed description is omitted.

Next, data set in the remote bridge in advance will be described.

FIG. 4 is an automatic call table for storing call destination information when the remote bridges 2a and 2b make an automatic call. The automatic call table includes the remote bridges 2a and 2b.
b is stored in the memory 26. The call destination information is set in advance by the user or the maintenance person on the panel 27.

FIG. 4A shows an example of the configuration of an automatic call table for storing call destination information. The table 401 is for a connection method by circuit switching, and the table 401 is for a connection method by packet switching. Table 402 shows a state in which one call destination is registered.

FIG. 4B shows another example of the structure of an automatic call table for storing call destination information. The table 403 in the case of the connection system by circuit switching includes a plurality (for example, 2 Table 404 in the case of the connection method by registering the call destination of the packet exchange and the packet exchange shows the state when one call destination is registered.

Next, FIG. 5 shows the remote bridges 2a and 2a.
b is a non-communication monitoring time table that stores an allowable time for determining whether or not disconnection is possible when the non-communication state is recognized, and is a memory 2 of the remote bridges 2a and 2b.
6 is stored. The allowable time is set in advance by a user or a maintenance person on the panel 27.

In FIG. 5, a circuit-switched non-communication monitoring table 501 registers an allowable time T1 in the case of the circuit-switched communication, and a packet-switched non-communication monitoring table 502 stores a packet-switched non-communication monitoring table. This shows a state where the allowable time T2 in the case is registered.

The reason why the allowable time T1 in the case of the communication using the circuit switching method and the allowable time T2 in the case of the communication using the packet switching method are required is that the response time of the communication using the packet switching method is Therefore, it is necessary to set a value such that T1 <T2.

Hereinafter, the connection operation according to the present invention will be described.

First, the outgoing connection and disconnection operations when the port of the circuit switching bridge is idle will be described.

FIG. 7 is a sequence diagram showing an outgoing connection and disconnection operation when the port of the circuit switching bridge is in an idle state. Hereinafter, in the LAN system configuration shown in FIG. 1, the remote LAN terminal device 1a
-An operation when accessing the LAN will be described as an example.

First, when the remote LAN terminal 1a transmits data to the remote bridge 2a (S701), the remote bridge 2a detects the data (S702),
Perform calling processing. That is, referring to the table 401 of FIG. 4A, the call destination information (address) is extracted by the circuit switching method ( S703), and the call information is transmitted to the ISDN 3.

Upon receiving the outgoing call information, the ISDN 3 sends out the incoming call information to the circuit switching bridge 4a that is the connection destination (S705). Then, the circuit switching bridge 4a detects this incoming call (S706), and determines whether or not it can respond to this incoming call (S707). If the communication line is free and the response is possible, response information is returned to the ISDN 3 (S708), and internal control such as preparation for performing this communication is performed (S709). That is, at this time, the address of the call destination remote LAN terminal device 1a is stored in the address table of the filtering circuit 32, and the fact that the remote LAN terminal device 1a is connected is stored.

On the other hand, the ISDN 3
In response to the response information from a, response information is transmitted to the remote bridge 2a (S710). Then, the remote bridge 2a performs internal control such as preparation for performing the communication (S711), and thereafter, the remote LAN terminal device 1a and the Ether-LAN are in a state where they can communicate with each other by the circuit switching method of the ISDN3. (S71
2).

Next, when the remote bridge 1a detects a non-communication state (no data transmission / reception) (S713),
The non-communication monitoring timer is started (S714), and it is determined whether the non-communication state is maintained during the allowable time T1 stored in the circuit switching non-communication monitoring table 501 shown in FIG. 5 (S715). If any data has been transmitted or received during the allowable time T1, the communication state shown in step S712 is maintained. On the other hand, if the non-communication state has been continued until the allowable time T1 expires, it is determined that communication has ended, a disconnection process is performed (S716), and further, disconnection information is sent to the ISDN 3 (S717).

When receiving the disconnection information from the remote bridge 1a, the ISDN 3 sends the disconnection information to the circuit switching bridge 4a in response to the reception (S718). Then, the circuit switching bridge 4a is connected to the filtering circuit 32.
Destination remote LA stored in the address table of
A disconnection process such as erasing the address of the N terminal device 1a is performed (S719), and disconnection confirmation information is sent to the ISDN 3 (S720), and the standby state is maintained in preparation for the next incoming call.

Upon receiving the disconnection confirmation information from the circuit switching bridge 4a, the ISDN 3 sends the disconnection confirmation information to the remote bridge 2a in response to this (S72).
1). On the other hand, upon receiving the disconnection confirmation information from the ISDN 3, the remote bridge 2a keeps the standby state in preparation for the next call and ends the communication processing.

Next, the outgoing connection and disconnection operations when the port of the circuit switching bridge is in the closed state will be described.

FIG. 8 is a sequence diagram showing an outgoing connection when the port of the circuit switching bridge is in a closed state, and FIG. 9 is a sequence diagram showing a disconnection operation in this case. Hereinafter, as shown in FIG.
The AN terminal device 1a is connected to the remote bridge 2a,
3 and Ether-L via the circuit switching bridge 4a.
When the communication with the AN is being performed (the state of step S712 in FIG. 7) and the communication port of the circuit switching bridge 4a is blocked, the remote LAN terminal device 1b transmits
The operation when accessing the r-LAN will be described as an example.

First, when the remote LAN terminal device 1b transmits data to the remote bridge 2b (S801),
The remote bridge 2b detects the data (S80
2) Perform call processing.

That is, referring to the table 401 of FIG. 4A, call destination information (address) by the circuit switching method is extracted (S803), and the call information is transmitted to the ISDN 3 (S804).

Upon receiving the outgoing call information, the ISDN 3 sends out the incoming call information to the circuit switching bridge 4a, which is the connection destination (S805). Then, the circuit switching bridge 4a detects the incoming call (S806), and determines whether or not the incoming call can be answered (S807). If the communication line is blocked and cannot respond, it returns disconnection information to the ISDN 3 (S808).

On the other hand, the ISDN 3
The disconnection information is transmitted to the remote bridge 2b according to the disconnection information from a (S809). Then, the remote bridge 2b recognizes that connection by the circuit switching method is impossible (S810), and switches the mode to the communication operation by the B channel packet switching method. That is,
The remote bridge 2b conforms to X.32 of the ITU-T recommendation. According to the 25 procedures, a link for establishing a B-channel packet switching connection with the ISDN 3 is established (S811).

Next, the remote bridge 2b is
With reference to the table 402 of (a), call destination information (address) by the B channel packet switching method is extracted (S
812), and sends outgoing call information (CR packet) to ISDN3 (S813).

[0045] ISDN3 Upon receiving the outgoing call information, and sends the call information (C N packet) to the packet switching bridge 4b is a connection target destination (S815). Then
The packet switching bridge 4b detects this incoming call (S8).
16), sends back the response information (C A packet) to ISDN3 to respond to the incoming call (S817),
Internal control such as preparation for performing this communication is performed (S81).
8). That is, at this time, stores the address of the called remote LAN terminal device 1b in the address table of the filtering circuits 32 stores the fact of connecting the remote LNA terminal device 1b.

As shown in step S814, the packet switching bridge 4b has previously established a link for performing a B-channel packet switching connection with the ISDN 3. In the case of the connection method using B channel packet switching, since logical multiplexing is possible, the packet switching bridge 4b is connected to the IS
When the incoming call information is detected from the DN 3, the response information to the incoming call can be returned to the ISDN 3.

On the other hand, the ISDN 3
b, the response information (CC packet) is transmitted to the remote bridge 2b in response to the response information from the remote bridge 2b (S81).
8). Then, the remote bridge 2b performs internal control such as preparation for performing this communication (S819), and thereafter, the remote LAN terminal 1b and the Ether-LAN
Means that mutual communication can be performed by the ISDN3 B-channel packet switching system (S820).

Next, the disconnection operation for releasing the communication state in step S820 will be described with reference to the sequence diagram shown in FIG.

When the remote bridge 1b detects a non-communication state (no data transmission / reception) (S821), it starts a non-communication monitoring timer (S822) and stores it in the packet exchange non-communication monitoring table 502 shown in FIG. It is determined whether or not the non-communication state is maintained during the allowable time T2 (S823). If any data is transmitted or received during the allowable time T2, the communication state shown in step S820 is maintained. On the other hand, if the non-communication state is continued until the allowable time T2 expires, it is determined that the communication has ended, the disconnection process is performed (S824), and the recovery information (CQ packet) is transmitted to the ISDN 3 (S825). .

When receiving the restoration information from the remote bridge 1b, the ISDN 3 sends out the disconnection information (CI packet) to the packet switching bridge 4b in response to this (S826). Then, the packet switching bridge 4b
Performs a disconnection process such as deleting the address of the call destination remote LAN terminal device 1b stored in the address table of the filtering circuit 32 (S827), and
The recovery confirmation information (CF packet) is transmitted to the DN 3 (S828), and thereafter, the standby state is maintained in preparation for the next incoming call.

The ISDN 3 is a packet switching bridge 4b
Receiving the acknowledgment information from the remote bridge 2b in response to the acknowledgment information (CF packet)
Is transmitted (S829). On the other hand, the remote bridge 2b
Upon receiving the disconnection confirmation information from the ISDN 3, the terminal recognizes the disconnection of the line (S830), and prepares for the next call (call based on the circuit-switched connection method) in accordance with ITU-T Recommendation X.3. According to the 25 procedures, the link established for performing the B-channel packet switching connection with the ISDN 3 is released (S831), and the communication process is terminated.

Next, another disconnection operation for releasing the communication state in step S820 will be described.

FIG. 10 is a sequence diagram showing another disconnection operation for releasing the communication state in step S820.

In FIG. 10, when the remote LAN terminal 1b sends disconnection request information to the remote bridge 2b (S1001), the remote bridge 2b detects this disconnection request information (S1002), and proceeds to step S824 in FIG. (S10)
03). The subsequent sequence (step S1004)
9 to S1010) are the same as the sequences shown in Steps 825 to S831 in FIG.

The disconnection operation sequence for releasing the communication state shown in FIG. 10 can be applied to the disconnection of the communication by the circuit switching system shown in FIG. 7, and in this case, FIG.
It is not necessary to perform the link release processing of step S1010 in.

Next, the circuit switching bridge 4a has a plurality of ports and is connected to the ISDN 3 by a plurality of lines, or the plurality of circuit switching bridges 4a are connected to the Ether-LAN. As shown in FIG. 4B, the table 4 in the case of the connection method by circuit switching is used.
03, a connection operation in the case where a plurality of (for example, two) call destinations are registered will be described.

FIG. 11 is an outgoing connection sequence diagram in the case where two call destination addresses are registered in the automatic call table for circuit switching. Hereinafter, the LAN shown in FIG.
When the circuit switching bridge 4a of the system has a plurality of ports, the remote LAN terminal 1a
The operation when accessing the Ether-LAN will be described as an example.

First, when the remote LAN terminal device 1a transmits data to the remote bridge 2a (S110)
1), the remote bridge 2a detects the data (S
1102), call processing is performed. That is, with reference to the table 403 of FIG. 4B, one of the call destination information (address) by the circuit switching method is extracted based on the priority (S1).
103), and sends outgoing call information to ISDN3 (S
1104).

Upon receiving the outgoing call information, the ISDN 3 sends out the incoming call information to the circuit switching bridge 4a, which is the connection destination (S1105). Then, the circuit switching bridge 4a detects the incoming call (S1106), and determines whether or not it can respond to the incoming call (S1107). If the communication line is blocked and cannot respond, ISD
The disconnection information is returned to N3 (S1108).

On the other hand, the ISDN 3
The disconnection information is transmitted to the remote bridge 2a according to the disconnection information from a (S1109). Then, the remote bridge 2a refers to the table 403 in FIG. 4B to extract the call destination information (address) by another circuit switching method (S1110), and sends the call information to the ISDN 3 again. Is transmitted (S1111).

Upon receiving the outgoing call information, the ISDN 3 sends out the incoming call information to the circuit switching bridge 4a that is the connection destination (S1112). Then, the circuit switching bridge 4a detects this incoming call (S1113) and determines whether or not it is possible to respond to this incoming call (S1114). If the communication line is blocked and cannot respond, ISD
The disconnection information is returned to N3 (S1115).

On the other hand, the remote bridge 2a
3, when the disconnection information is received again, it is recognized that connection by the circuit switching method is not possible (S1117),
The mode is switched to the communication operation by the B channel packet switching system. That is, the remote bridge 2a is connected to the ITU-
X. of T Recommendation. 25, a link for establishing a B-channel packet switching connection with the ISDN 3 is established (S1).
118).

Next, the remote bridge 2a is
Referring to the table 404 of (b), call destination information (address) by the B-channel packet switching method is extracted (S).
1119), and sends outgoing call information (CR packet) to the ISDN 3 (S1120).

Upon receiving the outgoing call information, the ISDN 3 sends out the incoming call information (CN packet) to the packet switching bridge 4a which is the connection destination (S1121). Then, the packet switching bridge 4b detects this incoming call (S1123).

The subsequent connection operation is performed in the same manner as the sequence shown in steps 817 to S820 in FIG. That is, the remote bridge 2a and the packet switching bridge 4b are connected by the ISDN3 B-channel packet switching method, and the remote LAN terminal 1a and the Et are connected.
It becomes possible to perform mutual communication with the her-LAN.

If any one port (line) of the circuit-switching bridge 4a is idle and the circuit-switching bridge 4a responds to a call from the remote bridge 2a by the circuit-switching method. Similarly to the sequence shown in FIG. 7, the remote bridge 2a and the circuit switching bridge 4a are connected by the circuit switching method of the ISDN 3, and the remote LAN terminal device 1a and the Ether-L
It becomes possible to perform mutual communication with the AN.

In the above description, the operation of connecting to the packet switching bridge 4b when the circuit switching bridge 4a is closed has been described as an example.
Can be similarly connected to the packet switching bridge 4b. In this case, the packet switching bridge 4b functions as a backup bridge.

[0068]

According to the present invention, even in a LAN system in which the number of remote bridges is smaller than the number of bridges, a state where the remote LAN terminal cannot access the LAN cannot occur at all. Constant connectivity can be maintained in the device.

Further, by utilizing the logical multiplexing function by the B-channel packet switching system, the number of bridges by the circuit switching system and the number of lines between the bridge and the ISDN can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a LAN system using ISDN of the present invention.

FIG. 2 is a block diagram of a remote bridge according to the present invention.

FIG. 3 is a block diagram of a bridge according to the present invention.

FIG. 4 is a diagram illustrating a configuration example of an automatic call table in a remote bridge.

FIG. 5 is a diagram illustrating a configuration example of a non-communication allowable time table in a remote bridge.

FIG. 6 is a configuration diagram of a LAN system using ISDN for explaining the operation of the embodiment of the present invention.

FIG. 7 is a sequence diagram showing a calling operation and a disconnection operation 11 when a port of the circuit switching bridge is in an idle state.

FIG. 8 is a sequence diagram showing a calling operation when a port of the circuit switching bridge is in a closed state.

FIG. 9 is a sequence diagram illustrating a disconnection process when a port of the circuit switching bridge is in a closed state.

FIG. 10 is a sequence diagram illustrating another disconnection process when a port of the circuit switching bridge is in a closed state.

FIG. 11 is an outgoing connection sequence diagram in a case where two call destination addresses are registered in an automatic call table for circuit switching.

FIG. 12 is a configuration diagram of a conventional LAN system using ISDN.

[Explanation of symbols]

 1a, 1b Remote LAN terminal 2a, 2b Remote bridge 3 ISDN 4a Circuit switching bridge 4b Packet switching bridge 5a, 5b, 5c LAN terminal 6 Server

Continuation of the front page (56) References JP-A-5-114904 (JP, A) JP-A-4-35440 (JP, A) JP-A-6-29983 (JP, A) JP-A-6-197131 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 12/46 H04L 12/28 H04L 12/66

Claims (6)

(57) [Claims] In a LAN system using an ISDN in which a remote LAN terminal device is communicatively connected to a LAN via an ISDN, the remote LAN terminal device is connected to the LAN and the ISDN;
A circuit-switched bridge for connecting a call between the AN and the ISDN in a circuit-switched manner; and a LAN connected to the LAN and the ISDN;
Connecting a packet-switched bridge for call connection in a packet-switched between AN and the ISDN, the said ISDN and the remote LAN device
A first call connection means for making a call connection between the ISDN and the remote LAN terminal device using a circuit switching method, and a second call connection means for making a call connection between the ISDN and the remote LAN terminal device using a circuit switching method. Call connection means; transmission control means for controlling the first call connection means and the second call connection means to make a call connection to the circuit switching bridge and the packet switching bridge ; the ISDN and the remote LAN terminal device No communication between
A non-communication monitoring means for monitoring the status, and a first for determining whether or not the line can be disconnected from the circuit-switched bridge.
Storage means for storing the permissible time of the packet switching, and determining whether or not the line can be disconnected from the packet switching bridge.
A second storage unit for storing a second permissible time, and the transmission control unit being connected by the first call connection unit;
In some cases, the non-communication state for the first allowable time is detected.
When the call is issued, the call to the ISDN is disconnected, and
When the control means is connected by the second call connection means,
When a non-communication state for the second allowable time is detected
And a remote bridge having disconnection control means for disconnecting the call from the ISDN, and a LAN system using the ISDN. 2. The transmission control means according to claim 1, wherein
2. The method according to claim 1, wherein, when a connection request to the LAN is made from the N terminal device, the first call connection means is preferentially selected, and a call is controlled to the circuit switching bridge. LAN system using ISDN. 3. The transmission control means selects the first call connection means and controls calling to the circuit switching bridge, and receives information indicating connection refusal from the circuit switching bridge. 3. A LAN using ISDN according to claim 2, wherein said call control means selects said second call connection means and controls calling to said packet switching bridge.
system. 4. An allowable time stored in said first storage means.
Is longer than the allowable time stored in the second storage means.
The ISDN according to claim 1, wherein the ISDN is small.
LAN system. 5. Connecting a remote LAN terminal device
The remote LAN terminal device to ISDN and
To LAN via switching bridge or packet switching bridge
In a remote bridge to be connected, a first call connection is made between the ISDN and the ISDN by a circuit switching method.
Call connection means, and communication between the ISDN and the remote LAN terminal device.
A second call connection means for making a call connection by a packet exchange method, and controlling the first call connection means and the second call connection means.
For circuit-switched bridges and packet-switched bridges
Outgoing call control means for performing call connection processing, and no communication between the ISDN and the remote LAN terminal device
A non-communication monitoring means for monitoring the status, and a first for determining whether or not the line can be disconnected from the circuit-switched bridge.
Storage means for storing the permissible time of the packet switching, and determining whether or not the line can be disconnected from the packet switching bridge.
A second storage unit for storing a second permissible time, and the transmission control unit being connected by the first call connection unit;
In some cases, the non-communication state for the first allowable time is detected.
When the call is issued, the call to the ISDN is disconnected, and
When the control means is connected by the second call connection means,
When a non-communication state for the second allowable time is detected
Disconnecting control means for disconnecting the call with the ISDN . 6. An allowable time stored in said first storage means.
The interval is longer than the allowable time stored in the second storage means.
The method according to claim 5, characterized in that it is small.
Onboard remote bridge.