JPH03201849A - Data link control system - Google Patents

Abstract

PURPOSE:To prevent the state of a non-integrated service digital network (ISDN) terminal from being erroneously recognized by a host computer unit by releasing data link between a non ISDN terminal and an ISDN exchange network when the non ISDN terminal is set in an uncommunicapable state. CONSTITUTION:To an ISDN network 12, a host computer unit 11 is connected and an ISDN packet terminal 13 according to ISDN or a non ISDN packet terminal 14 not according to the ISDN is connected. Corresponding to the state of the non ISDN terminal 14, the data link between the non ISDN terminal 14 and the ISDN exchange network 12 is set/released. By such data link control, the state of the non ISDN terminal 14 is informed to the ISDN exchange network 12 and thus, the host computer unit 11 of the ISDN exchange network 12 can normally recognize the state of the non ISDN terminal 14.

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) The present invention relates to a data link control method, particularly for non-ISD
The present invention relates to a data link control method for connecting N terminals to an ISDN switching network.

(Prior art) In general, ISDN (integrated SDN)
erviccsD 1g1tal N etwor
k) In packet-switched networks, ISDN-compliant I
SDN packet-type terminals are directly connected to the ISDN packet-switched network, but non-ISDN terminals that are not ISDN compliant
The N terminals are connected to the ISDN packet switching network via terminal adapters.

In such a network system, when an ISDN packet-type terminal is in a communicable state, a packet containing a cause code of, for example, "09" is transmitted from the ISDN packet-type terminal to the ISDN packet switching network, and the ISDN packet-type terminal A data link between the ISDN packet-switched network and the ISDN packet-switched network is established. Furthermore, when an ISDN packet-type terminal is in a communication-disabled state, a packet containing a cause code of, for example, "01" is transmitted from the ISDN packet-type terminal to the ISDN packet-switched network, and the ISDN packet-type terminal and the ISDN packet-switched network are The data link between them is released.

On the other hand, data link control between a non-ISDN terminal and an ISDN packet switching network is performed by a terminal adapter. Normally, this terminal adapter always maintains an established data link between a non-ISDN terminal and an ISDN packet-switched network. In this case, it has been determined by the recommendation that the aforementioned cause codes "09" and "01" cannot be used in packets sent from the terminal adapter to the ISDN packet switching network.

Therefore, even if a packet containing a cause code of "o9" or "01" is supplied to the terminal adapter from a non-ISDN terminal, the cause code included in the packet sent from the terminal adapter to the ISDN packet switching network is " 09
" or "ol", but instead is set to "00", for example. In this way, the cause codes sent to the ISDN packet-switched network are different for ISDN terminals and non-ISDN terminals, and as a result, the notification of the terminal's transmission enabled/disabled status from the ISDN packet-switched network to the host computer is also transmitted to the ISDN terminal. This will differ between the terminal and the non-ISDN terminal.

This means that non-ISDN
This is a common cause of misrecognition of the device status.

Additionally, some terminal adapters do not send any packets indicating whether or not they can be sent to the ISDN packet switching network even if a packet containing a cause code of "09" or "01" is sent from a non-ISDN terminal. There are some, but
In this case as well, the non-ISDN
This causes misrecognition of the device status.

(Problem to be Solved by the Invention) Conventionally, notification of whether or not a terminal is capable of transmitting from an ISDN packet switching network to a host computer device is transmitted via ISDN.
This is different between terminals and non-ISDN terminals, and this causes the host computer to incorrectly recognize the status of non-ISDN terminals.

This invention was made in view of the above points, and is a non-ISD.
An object of the present invention is to provide a data link control method that can properly notify a host computer of the status of N terminals.

[Structure of the Invention] (Means for Solving the Problems) A data link control method according to the present invention is for connecting a non-ISDN terminal to an ISDN switching network, and the data link control method is for connecting a non-ISDN terminal to an ISDN switching network, and the data link control method is for connecting a non-ISDN terminal to an ISDN switching network, and the data link control method is for connecting a non-ISDN terminal to an ISDN switching network. determining means for determining which state the non-ISDN terminal is set to;
data link control means for setting up a data link between the DN terminal and the ISDN switching network, and releasing the data link between the non-ISDN terminal and the ISDN switching network when the ISDN terminal is set to a communication disabled state; It is characterized by comprising the following.

(Operation) In this data link control system, a data link between a non-ISDN terminal and an ISDN switching network is established/released depending on the state of the non-ISDN terminal. Such data link control notifies the ISDN switching network of the status of the non-ISDN terminal, thereby enabling the host computer device of the ISDN switching network to correctly recognize the status of the non-ISDN terminal.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows the configuration of a network system for realizing a data link control method according to an embodiment of the present invention. In FIG. 1, an ISDN switching network 12 is for centrally providing various communication services such as telephone, data communication, facsimile, and image communication. is connected, and ISDN-compliant ■SDN packet type terminal 13 and ISDN1. :/!
It is well known based on

The ISDN packet type terminal 13 is directly connected to the ISDN switching network 12, while the non-ISDN packet type terminal 1
4 connects to the ISDN switching network 1 via the terminal adapter 15
Connected to 2. Non-ISDN packet type terminal 14
is a packet type terminal that complies with, for example, X.25.

The terminal adapter 15 is an SABM (layer 2
link setting command; modulo 8) SABME (layer 2 link setting command; modulo 12), UA (
It exchanges control data such as layer 2 response), CR (layer 3 calling packet), and Disc (layer 2 link release command). When a link setting request is received from the non-ISDN packet type terminal 14, the terminal adapter 15 connects the terminal adapter 15 and the ISDN.
A data link between switching networks 12 is established.

Further, when the non-ISDN packet type terminal 14 becomes unable to communicate, the terminal adapter 15 releases the data link between the terminal adapter 15 and the ISDN switching network 12.

Such data link control by the terminal adapter 15 is realized by disconnecting/establishing the ISDN D channel between the terminal adapter I5 and the ISDN switching network 12.

FIG. 2 shows an example of a specific configuration of the terminal adapter 15. As shown in FIG. 2, the terminal adapter 15 is connected to the ISDN D channel controller 3.
1 and an X, 25 procedure control unit 32.

The X,25 procedure control unit 32 controls the data link between the non-ISDN packet type terminal 14 and the terminal adapter 15.
When the SDN packet type terminal 14 becomes unable to communicate, requests the D channel control unit 31 to release the data link between the ISDN switching network 12 and the terminal adapter 15,
When the non-ISDN packet/soto type terminal 14 recovers and becomes ready for communication, the ISDN is sent to the D channel control unit 31.
A request is made to set up a data link between the switching network 12 and the terminal adapter 15.

On the other hand, the D channel control unit 31
2, the ISDN switching network 12 and the terminal adapter 15
When the D channel is disconnected, the data link between the ISDN switching network 12 and the terminal adapter 15 is released, and when the D channel is established, the data link between the ISDN switching network 12 and the terminal adapter 15 is released. A data link between terminal adapters 15 is established.

By disconnecting/establishing the channel in this way, the ISDN switching network 12 can determine that the non-ISDN packet type terminal 14 is unable to communicate/has recovered. As a result, a reset instruction packet with a cause code of "01" or "09" is transmitted from the ISDN switching network 12 to the host computer device 11, which allows the host computer device i1 to correctly check the status of the non-ISDN packet type terminal 14. It becomes possible to judge.

Next, referring to FIG. 3, control data by the terminal adapter I5, that is, SABM (layer 2 link setting command; modulo 8), SABME (layer 2 link setting command: modulo 12), UA (layer 2 response), ), CR (Layer 3 calling packet), and DISC (Layer 2 link release command) transmission and reception operations will be explained.

FIG. 3(A) shows the operation when a link is set up from the non-ISDN packet type terminal 14. In this case, first, an SABM signal is transmitted from the non-ISDN packet-type terminal 14 to the is SA
A BME signal is transmitted. Next, the ISDN switching network 12
The UA multiplied signal is sent back to the D channel control section 31, and in response, the UA multiplied signal is also sent back from the X, 25 procedure control section 32 to the non-ISDN packet type terminal 14. Then, the non-ISDN packet type terminal 14 that received the UA double signal sends a CR signal to the X, 25 procedure control unit 32, and in response, the D channel control unit 31 transmits the
A CR signal is also sent to 2. In this way, non-ISD
A data link between the N-packet type terminal 14 and the ISDN switching network 12 is established.

FIG. 3(B) shows the operation when a failure occurs in the non-ISDN packet type terminal 14 and the link is released. In this case, first, a Disc signal is transmitted from the D channel control section 31 to the ISDN switching network I2 under the control of the X, 25 procedure control section 32 of the terminal adapter 15. ISDN switching network 12 that received this Disc signal
From the ISDN switching network 12 to the D channel control unit 31
The UA signal is returned to ISDN switching network 1.
2 and the terminal adapter 15 is released.

[Effects of the Invention] As described above, according to the present invention, a data link between a non-ISDN terminal and an ISDN switching network is established/released depending on the state of the non-ISDN terminal. Such data link control notifies the ISDN switching network of the status of the non-ISDN terminal, thereby enabling the host computer device of the ISDN switching network to correctly recognize the status of the non-ISDN terminal.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing a network system for realizing a data link control method according to an embodiment of the present invention, and FIG. 2 shows a specific example of a terminal adapter provided in the network system shown in FIG. FIG. 3 is a block diagram showing an example of a typical configuration, and is a diagram for explaining the operation of the terminal adapter shown in FIG. 2. 11... Host computer, 12... ISDN packet switching network, 13... ISDN packet type terminal,
14...Non-ISDN packet type terminal, 15...Terminal adapter.

Claims (1)

[Claims] A data link control method for connecting a non-ISDN terminal to an ISDN switching network, comprising: a judgment for determining whether the non-ISDN terminal is set to a communicable state or a communicable state; means for establishing a data link between the non-ISDN terminal and the ISDN switching network when the non-ISDN terminal is set to a communicable state; and when the non-ISDN terminal is set to a communicable state, the non-ISDN terminal and data link control means for releasing the data link between the ISDN switching networks.