KR100263078B1 - Method for connection in isdn in digital private branch exchange system - Google Patents

Abstract

PURPOSE: A network connection processing method is provided to prevent a call from being interrupted while talking over the telephone, owing to synchronous loss and error at network connection with an integrated service digital network(ISDN). CONSTITUTION: A primary rate interface(PRI) for performing network connection with an ISDN judges whether a normal operation frame is inputted in the first time established by the first timer, when a synchronous error arises at a physical layer(301-304). If the normal operation frame is not inputted in the first time, a message(PH_DEA_IND) informing that the physical layer is at an inactive state is transferred to a data link layer(305). The data link layer clears all calls in response to the inactive state directing message(306). In the case where the normal operation frame is inputted(303), the PRI judges whether the normal operation frame continues to be inputted during the second time established by the second timer(307,308,209). If so, an active state directing message(PH_ACT_IND) indicating that the physical layer is at an active state is transferred to the data link layer(310).

Description

METHOD FOR CONNECTION IN ISDN IN DIGITAL PRIVATE BRANCH EXCHANGE SYSTEM}

The present invention relates to a network connection method of a digital switching system, and more particularly, to a network connection processing method at an interface of a digital switching system for connection with a comprehensive information communication network.

With the development of digital communication technology, digital communication networks such as Integrated Services Digital Network (hereinafter referred to as "ISDN") have already been proposed, and private switching systems are being developed in such a way that they can be connected to such ISDN. There is a trend. Currently, most private exchange systems use not only T1 trunks but also E1 PRI (Primary Rate Interface), which is a component that enables connection between private exchange systems and digital communication networks such as ISDN. . That is, the private switching system includes a T1 trunk, an analog network interface for connecting to a public switched telephone network (hereinafter referred to as a "PSTN"), and an E1 PRI, a digital communication network interface for connecting to an ISDN. It is provided.

Meanwhile, in the digital switching system, the network connection with the digital communication network such as ISDN is performed at PRI 110 shown in FIG. 1, and is performed according to the Open Systems Interconnection (OSI) model as shown in FIG. 2. do.

According to the prior art, when a Loss Of Sync (LOS) or Sync Error occurs immediately after a physical layer is normally activated during an ISDN network connection, a Datalink Layer is immediately available. ) To disconnect the data link by sending a PH_DEA_IND primitive to indicate this. Therefore, call setup is in progress or an already connected call is immediately disconnected by the network layer. Therefore, even when a momentary synchronization error occurs, a problem arises in that the call was disconnected. This problem is quite serious considering the fact that the actual motivation error can occur frequently depending on the network situation.

In addition, the physical layer immediately sends a PH_ACT_IND primitive indicating the fact to the data link layer as soon as a normal frame is detected. As a result, when the synchronization is unstable, PH_DEA_IND and PH_ACT_IND alternate between the data link layer. Therefore, if the synchronization is unstable, there is a possibility that the data link layer and network layer can be unstable.

Accordingly, an object of the present invention is to provide a method for solving a problem in which a call is disconnected due to a synchronization loss or a synchronization error when connecting to an ISDN network in a digital switching system.

Another object of the present invention is to provide a method for solving the problem that the data link layer and the network layer become unstable as synchronization becomes unstable when connecting to the ISDN network in a digital switching system.

It is still another object of the present invention to provide a method for preventing a call from being disconnected due to an instantaneous state change of a network when connecting to an ISDN network in a digital private exchange system.

The present invention for achieving the above object is a processing method for network connection in the interface of a digital switching system having an interface for connection with a comprehensive information communication network: a first set time when a synchronization error occurs in the physical layer (A) determining whether or not a normal recovery frame is received within the frame; (B) transmitting a message indicating that the physical layer is in an inactive state to the data link layer when it is determined that the normal recovery frame does not enter within the first preset time; (C) determining whether at least one normal recovery frame comes in during a second predetermined time when it is determined that the normal recovery frame has been entered within the first preset time; (D) returning to step (a) if it is determined that no one of the normal recovery frames has been entered during the second set time; And (e) transmitting a message indicating that the physical layer is in an active state to the data link layer when it is determined that at least one normal recovery frame is input during the second set time. In response to the message indicating that the physical layer is in an inactive state in step (b), the data link layer clears all calls. The present invention has an effect of preventing the call from being disconnected according to the instantaneous network state change by determining whether the synchronization error or recovery is stable when the synchronization error occurs or when the physical layer is normally restored.

1 is a view showing the configuration of a digital switching system to which the present invention is applied.

FIG. 2 is a diagram illustrating an Open System Interconnection (OSI) model which is a base for network connection with an ISDN.

Figure 3 is a flow chart of the operation of the interface (PRI) of the digital switching system for the network connection with the ISDN in accordance with the present invention.

FIG. 4 is a detailed flowchart of a processing operation for the network connection shown in FIG. 3; FIG.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, the terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of the user or chip designer, and the definitions should be made based on the contents throughout the present specification.

First of all, the present invention is applied to a digital private exchange system as shown in FIG. 1, and it is understood that the operation is performed based on the OSI model as shown in FIG.

Referring to FIG. 1, a digital private exchange system (PABX) 100 to which the present invention is applied includes a PRI 110, which is a digital network interface for network access with an ISDN. Is done at this PRI 110. In addition, the digital private switching system includes an T1 trunk 120, an analog network interface for network connection with a PSTN, a subscriber line interface (SLI) 140 that accommodates a plurality of extension subscribers, and an ISDN between a PSTN subscriber and an extension subscriber. And a switching circuit 130 that forms a communication path between the subscriber and the subscriber and between the subscriber and the subscriber, and a central processing unit (CPU) 150 that controls the overall operation of the digital private exchange system.

On the other hand, although not shown in Figure 1, it is known that the PABX 100 further comprises a ring detector, a tone generator, a dual tone multi frequency (DTMF) receiver, DTMF generator, etc. Self-explanatory facts.

Referring to FIG. 2, the PRI 110 of FIG. 1 is based on an OSI model having seven hierarchical structures for connecting to ISDN. The OSI model includes a physical layer as a first layer, a data link layer as a second layer, a network layer as a third layer, and a transport layer as a fourth layer. Layer), a session layer as a fifth layer, a presentation layer as a sixth layer, and an application layer as a seventh layer. It should be noted that in the OSI model having such a hierarchy, the operation according to the present invention is performed at the physical layer.

Among the contents to be described below, "F1 state" and "F3 state" represent Layer 1 states on the user side of the interface, that is, states of the physical layer. States are already defined under ITU-T Recommendation I.431 (03/93), title "PRIMARY RATE USER-NETWORK INTERFACE-LAYER 1 SPECIFICATION". For reference, Recommendation I.431 defines the states of the first layer in the user-side interface as the F0 state to the F6 state. The FO state represents loss of power on the user side, the F1 state represents an operational state, and the F2 state represents a fault condition No. 1. , F3 state is a state indicating fault condition No. 2, F4 state is a state indicating fault condition No. 3, F5 state is a state indicating fault condition No. 4, and F6 state is a power on state state). That is, the F1 state used in the present invention means a state in which a network timing and a first layer (physical layer) service are available and a user side can transmit and receive a frame. In contrast, the F3 state is a fault state corresponding to the fault condition FC2, in which network timing is not useful on the user side and the user side detects a loss of an incoming signal associated with a loss of frame alignment. It is a state.

3 is a diagram illustrating a processing flow for network connection with an ISDN at an interface (PRI) of a digital switching system according to the present invention.

Referring to FIG. 3, the PRI 110 of FIG. 1 performing a network connection with an ISDN has a first time T101 set by the first timer T101 when a synchronization error occurs in step 301, in steps 302 and 304. In step 303, it is determined whether a normal operation frame (NOF) is input or not, and the message “PH_DEA_IND” indicating that the physical layer is inactive is notified to the data link layer (step 305). . The data link layer notified of the deactivation status indication message " PH_DEA_IND " clears all calls in response (step 306).

When the normal recovery frame is received (step 303), the PRI 110 determines whether the normal recovery frame continues for the second time set by the second timer T102 (steps 307 and 309) (step 308). In step 310, an activation state indication message "PH_ACT_IND" indicating that the physical layer is activated is transmitted to the data link layer.

FIG. 4 is a diagram illustrating a more detailed processing flow for the processing operation for the network connection shown in FIG. 3.

Referring to FIG. 4, when a synchronization error occurs in the physical layer of the PRI 110 (step 401), driving of the second timer T102 is stopped (steps 402 and 403) and is currently in a normal state (F1 state). If it is determined (step 404), the first timer T101 is driven (step 405), and the state transitions to the F3 state (step 406). After the normal recovery frame NOF is entered (step 411), the second timer (T102) is driven to determine whether the steady state is stable (step 413), and transitions to the F1 state (step 414).

If the normal recovery frame NOF does not come within the time set by the first timer T101, the first timer T101 expires (steps 421 and 422). In this case, it is determined whether the second timer T102 is being driven (step 423), and only when it is not driven, the PH_DEA_IND primitive is transmitted to the datalink layer to disconnect all calls with the datalink (step 424). If the second timer T102 is being driven, it means that the normal recovery frame NOF has been at least once within the time set by the first timer T101, and the first timer T101 is re-driven (step 425).

When the normal recovery frame NOF is received after the normal recovery frame NOF (step 411), the device transitions to the F1 state (step 414), and the second timer (T102) is driven to determine whether the steady state is stable. (Step 413).

If it is determined that the physical layer is normal while the second timer T102 times out (step 431), driving of the first timer T101 is stopped (steps 433 and 434), and a PH_ACT_IND primitive is transmitted to the data link layer. The physical layer is informed that the physical layer is normal (step 435). However, if it is determined that the physical layer is not normal within the time set by the second timer T102, that is, when a synchronization error occurs, the driving of the timer T102 is stopped and the first timer T101 is driven. The operation of determining whether the error is a continuous physical layer is performed.

As described above, the present invention determines whether this error or recovery is continuous when a synchronization error occurs or during normal recovery of the physical layer, thereby preventing call disconnection due to a synchronization error due to a momentary change in network state, thereby preventing instability of the physical layer. There is an advantage to solve the problem.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

Claims (2)

A processing method for a network connection at an interface of a digital switching system having an interface for connection with a general information communication network, the method comprising: (A) determining whether a normal recovery frame is received within a first set time when a synchronization error occurs in the physical layer; (B) transmitting a message indicating that the physical layer is in an inactive state to the data link layer when it is determined that the normal recovery frame does not enter within the first preset time; (C) determining whether at least one normal recovery frame is received during the second predetermined time when it is determined that the normal recovery frame is received within the first preset time; (D) returning to step (a) if it is determined that no one of the normal recovery frames has been entered during the second predetermined time; And (e) transmitting a message indicating that the physical layer is in an active state to the data link layer when it is determined that at least one normal recovery frame is input during the second set time. The method of claim 1, further comprising the step of clearing all calls by the data link layer in response to a message indicating that the physical layer is in an inactive state in step (b).

Images