KR0174966B1 - Error Detection of Setup Message in Asynchronous Transfer Mode - Google Patents

Abstract

In the Asynchronous Transmission Mode (abbreviated to ATM), the present invention is included in the broadband lower layer information, especially in the Q.93B protocol, which is sent to the terminal by the calling user or provided to the terminal from the network. The present invention relates to a method for detecting an error in a setup message used to initialize a setup. A first step of initializing a counter value for detecting next information; A second step of performing an error check of a protocol determination signal included in the setup message; When the protocol determination signal is detected, the counter value is increased by one, and then error checking of a call reference signal having a predetermined number of octets is performed. Then, the call reference signal is stored at a predetermined address of the message and the counter value A third process of increasing 1; A fourth step of performing an error check of a message format signal following the call reference signal and detecting the presence of an extension bit present in a second octet thereof; A fifth step of judging whether it is included in a predetermined total length category of content length information which is a plurality of variable length information optionally included following the message length signal of the setup message; Detecting a plurality of kinds of variable length information included in the setup message subsequent to its header information, which is essential or optional, and comparing the detected length information value with the preset total length information value except for the header information, and comparing the same. A sixth step of efficiently providing the network or user with service information indicating an error or no error together with the variable length information following the message length signal correspondingly to the result; By quickly providing corresponding service information (no errors or errors) to the network or user, it is possible to effectively prevent unexpected communication errors that may be caused by setup message errors during communication between the terminal and the network. It is.

Description

Error detection method of setup message in asynchronous transmission mode

The present invention relates to a method for detecting an error in a setup message included in broadband sublayer information in the A. synchronous transfer mode (ATM), in particular in the Q.93B protocol. .

In general, ATM is a communication method for implementing a Broadband Integrated Service Digital Network (hereinafter, abbreviated as BISDN) and has a special form using an asynchronous time division multiplexer (abbreviated as ATDM). Packet-type message delivery.

On the other hand, in BISDN, information is transmitted by a continuous flow of packets having a certain size. The packets of fixed size are called ATM cells. More specifically, the ATM cell divides a plurality of service information 11 having a predetermined bit rate (identity bit rate, variable bit rate, etc.) into short cells 12 of fixed length, as shown in FIG. After that, packetized information is attached by attaching 5 bytes of header information 12a to each cell, and each ATM cell has a total of 53 bytes (data information 48 + header information 5). Each of these ATM cells, as shown at the bottom of FIG. 1, is multiplexed 13 and transmitted over a transport channel to a terminal or network.

In addition, the ATM cell as described above is a connectivity method, and establishes a virtual channel to transmit service information. Whenever a virtual channel is established, an identification number for connection is given and the identification number is released together when the connection is released. . In addition, the order between ATM cells in a certain virtual channel is preserved by the function of the ATM layer, and signal information for connection establishment is transmitted through a separate ATM cell.

Meanwhile, the ATM communication scheme as described above defines a layered protocol standard model for systematic and flexible information delivery. At this time, the protocol layer envisioned is a physical layer 21, an ATM layer 22, an ATM adaptation layer 23, and a higher layer 24, as shown in FIG. As follows.

That is, the protocol reference model of ATM consists of a management plane (A), a control plane (B), and a user plane (C), and the functions of the management plane (A) among the three planes (A, B, and C) are planes. It is divided into management and hierarchy management.

Here, plane management means overall management of the system, and hierarchy management means management of resources and variables used. In addition, the control plane (B) manages call control and connection control information, and the user plane (C) manages the transfer of user information.

Furthermore, the protocol of the control plane (B) and the user plane (C) is divided into a higher layer 24, an ATM adaptation layer (AAL) 23, an ATM layer 22, a physical layer 21, and the like. Although not shown in the figure, the ATM adaptation layer 23 is classified vertically, and the ATM sublayer and protocol data unit are cut into a predetermined size to make user service information of the upper layer 24 into protocol data units. It consists of a cut and a recombination layer forming a user information section of.

In addition, when the ATM adaptation layer 23 is horizontally classified, the U-SDU (service data unit) having an equal bit rate is transmitted between the information source and the destination at the same bit rate along with related time information, and the recovery error and AAL-1, a real-time adult U-SDU, which provides services such as unrecovered error indication to the upper layer protocol 24 shown in FIG. 2 and provides the function of dividing and reassembling user information at a variable bit rate AAL-2, which provides services such as error recovery and unrecovered error indication to the upper layer protocol 24, and also functions to segment and reassemble user information. High-speed data communication due to the complexity of AAL-3 / 4 and communication protocols that provide the ability to deliver service data with variable bit rate in a connected or disconnected manner Simplifies unsuitable different functions of the AAL-3/4 There are AAL-5, which provides high-speed data transmission function.

Herein, the present invention is the AAL- having a high-speed data transmission function, which is one of performing the interfacing of the signaling message between each terminal and the network and classifying the ATM adaptation layer 23 horizontally. It is related to 5.

In addition, the ATM layer 22 controls user-to-network access and information flow, translates a virtual path identification number and a virtual channel identification number, connects to service access points, performs multiplexing and demultiplexing of cells, and physical layer 21. ) Is composed of a transport convergence sublayer and a physical medium sublayer, and performs cell separation, generation and verification of header error control bytes, and detection of cell boundary points.The upper layer 24 of the user plane C Provides a function for processing service information.

In addition, the upper layer 24 of the control plane B provides functions related to call setup, call control, and call connection, which are achieved by exchanging control signal messages between user networks. The control signal message can be divided into call setup, call information, call release, and additional information message according to each function.

Here, the call setup message is subdivided into call processing, connection, connection recognition, call setup, etc., the call information message is subdivided into call resume, resume recognition, etc., and the call release message is released. The ITU-TS Recommendation Q.93B protocol message control format for each control signal message described above is shown in FIG.

That is, the user-to-many ATM call and the connection control message may include a protocol discriminator 31 for determining a user-to-manage call control message from another message, as shown in FIG. Call reference signal (32), message type signal (33), message length signal (34) and message length (34) are basically configured to detect call destinations that have sent messages. The variable length information 35 required according to the function of the signal message is defined to be included.

In practice, the user-to-many ATM call and connection control messages as described above are call establishment messages, call progress, connect, connect acknowledge, and setup messages. There are RELEASE and RELEASE COMPLETE messages as Call clearing messages, and Status and STATUS ENQUIRY messages as Miscellaneous messages.

On the other hand, related to the present invention, as shown in FIG. 3, the general setup message required for each function is included in the user-to-manufactured ATM call and connection control message, as shown in FIG. Substantially 1 to 20 octets of the AAL parameter corresponding to the protocol identification signal of 1 octet, the call reference signal of 4 octets, the message format signal of 2 octets, the message length signal of 2 octets, and the variable length information. ATM user cell rates of 12 to 30 octets, broadband bearer capability of 6 or 7 octets, broadband high layer information of 4 to 13 octets, and broadband repeat indication information of 5 octets repeat indicator, 4 to 17 octets of broadband low layer information, 25 octets called party number, 4 to 25 octets called party subad Called party subaddress, 4 to 26 octets of calling party number, 4 to 25 octets of calling party subaddress, 9 octets of connection identifier, 6 octets of It consists of a QoS parameter, a broadband sending complete signal of 5 octets, a transit network selection of 4 to 8 octets, and an endpoing reference signal of 7 octets.

Herein, among the variable length information which can be included in the setup message related to the present invention, the ATM user cell rate, the broadband transmission capacity, the called party number, and the QoS parameters are not necessarily included but are required (mandatory). Other information elements are optionally included.

As described above, the information elements included in the setup message used to initiate call setup sent by the calling user to the network or provided to the called user from the network have a format specified in accordance with Q.93B.

On the other hand, the protocol determination signal included in the above setup message has a bit value of '00001001', as shown in Fig. 5A.

In addition, the call reference signal included in the setup message according to the present invention includes call reference signal length information having a bit value of '00000011' and call reference signal value of 3 octets, as shown in FIG. Has information.

Furthermore, the message format signal included in the setup message according to the present invention includes message format information having a bit value of '00000111', an extension bit of 1 bit, and an action indicator as shown in FIG. It has information of 1 octave to be provided. In addition, message format information added according to the type of each message is as shown in FIG.

On the other hand, the message length signal included in the setup message according to the present invention has length information of two octets, as shown in Fig. 5E.

However, a setup message made up of the above-mentioned information may be caused by various uncertainty factors in communication such that information received substantially loses reliability or an information error occurs in a message generated by a terminal for transmission to a network. The case is always present. Accordingly, there is a problem in that when the error occurring at the time of the interface of the setup message information between the network and the terminal is not recognized, unexpected results such as reception of incorrect information or loss of information are caused. However, there has been no description on how to effectively detect an information error of a setup message which may occur at the data interface between the network and the terminal, or a device for realizing the same.

Accordingly, the present invention efficiently detects and corresponds to an information error of a setup message sent by the calling user to the network or provided to the terminal from the network in the Q.93B protocol and included in the broadband lower layer information used to initialize the call setup. The purpose is to provide a method for providing a service to a network or a user.

In order to achieve the above object, the present invention provides a method for detecting an error in a setup message in an ATM cell sent to a network or provided to a corresponding terminal from a network by a calling user through a transport channel in an asynchronous transmission mode, the information from the network. A first step of storing, at a predetermined address in a memory, the setup message input to or generated by the terminal via a provider and then initializing a counter value for information detection; A second step of detecting a protocol determination signal included in the setup message and generating service information for notifying an error occurrence and providing it to the network or the user when the protocol determination signal included in the setup message is not a preset value; A third step of, if the protocol determination signal is detected, incrementing the counter value by one, then detecting a call reference signal having a predetermined number of octets, storing the call reference signal in a predetermined address of the memory, and incrementing the counter value by one; Checking the error occurrence of the message format signal following the call reference signal, detecting the presence of the extension bit present in the second octet, and providing service information for informing the error occurrence when an error occurrence of the message format signal is detected. A fourth step of generating and providing the same to the network or the user; Detects whether the content length of the required or optionally included variable length information following the message length signal of the setup message is included in a predetermined total length category, and the content length of the variable length information is detected. A fifth step of generating service information for notifying occurrence of an error if not included in the preset full length category and providing the service information to the network or the user; And detecting a plurality of types of variable length information, which is essential or selectively included after the header information of the setup message, and checking whether the detected essential variable length information is included in the predetermined total length information value except for the header information. And a sixth step of selectively providing the network or the user with service information indicating an error occurrence or no error together with the optional or mandatory variable length information following the message length signal based on the check result. Provides an error detection method for setup messages in asynchronous transmission mode.

1 is a format diagram showing a data structure for a typical ATM cell.

2 is a general protocol reference model diagram of a wideband asynchronous transmission mode.

3 is a format diagram for message types of a general Q.93B protocol.

4 is a diagram showing various kinds of information included in a general setup message related to the present invention.

5 is a format diagram for the type of each header information in a setup message related to the present invention.

6 is a schematic block diagram of a system for realizing error detection of a setup message according to the present invention.

7 is a flowchart showing a process of detecting an error of setup message information according to a preferred embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10: information provider 10a: ATM

10b: AAL format 5 12: control unit

14: storage unit

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

6 shows a schematic block diagram of a hardware system for detecting errors in setup message information in accordance with the present invention.

As shown in the figure, a hardware system for detecting an error in a setup message according to the present invention comprises an ATM 10a and an AAL format 5 10a, which is input from a network via a transport channel, not shown. Q.93B information providing unit 10, which receives information about the 93B protocol, in particular the setup message related to the present invention, or provides the network with a setup message generated from the terminal, from the information providing unit 10. Receiving information about the Q.93B protocol and checking whether there is an error in the setup message according to the present invention, and outputting the service information corresponding to the result of the check and providing it to the network or the user, or from the terminal to the network for communication. The control unit 12 for controlling the generation of various messages (setup message, etc.), and the control unit 12 is provided for the error check of the setup message information. Includes a storage 14 for storing the received or generated setup message.

In FIG. 6, the control unit 12 is a user, as shown in FIG. 3, in an ATM cell provided from the Q.93B information providing unit 10 described above at the interface for communication between each terminal and the network. A protocol determination signal 31 for determining a network call control message, a call reference signal 32 for detecting a call destination for transmitting a message of a user-network interface, a message format signal 33, and a message length signal 34 After receiving the information about the basic configuration for the message about the general Q.93B, and receiving the information about the broadband sublayer, and storing the corresponding message for error check of the message information about the broadband sublayer information ( 14).

In addition, the control unit 12 stores the message in the storage unit 14 to check its error prior to transmitting the setup message generated in the terminal to the network for the interface for communication between the terminal and the network.

Accordingly, the control unit 12 checks whether there is an error in the setup message of the broadband lower layer information received from the network or generated in the terminal and stored in the storage unit 14, and the service information corresponding to the result of the check is checked. By providing the user, it is possible to effectively perform the interface of the message for communication between the network and the corresponding terminal through the transmission channel (not shown) without receiving a message error, such as receiving the wrong information and information loss.

Next, a preferred embodiment of the present invention, which effectively detects an error in a setup message sent to or from a network by a calling user as described above, is described in detail with reference to FIG. do.

FIG. 7 is a flowchart illustrating a process of detecting an error of a setup message included in broadband lower layer information according to the present invention.

First, as can be seen from the diagram, the setup message is transmitted via the transport channel from the network (not shown) which receives the setup message from the calling user. The ATM 10a and the AAL format 5 (in the information providing unit 10 on the called user side) When received through 10b) and provided to the control unit 12 or a message for transmission from the terminal to the network is generated, the control unit 12 stores this setup message in the memory m in the storage unit 14, Clear counter C to 0 (step 100).

Next, the control unit 12 determines that the m [C] value representing the first octet of the setup message stored in the memory in the storage unit 14 is the protocol determination signal PD, as shown in FIG. It is determined whether the number 9, that is, the information of the first octet is binary '00001001' (step 102).

If it is determined in step 102 that the information of the corresponding octave is not the protocol determination signal of the setup message, the process proceeds directly to step 154, which will be described later, whereby the controller 12 controls the network or terminal user. By providing the service information to indicate that the protocol discrimination signal is an error, the error of the information is recognized between the terminal and the network or by the user, thereby enabling a quick response action.

On the other hand, if it is determined in step 102 that the information of the corresponding octet is the protocol determination signal of the setup message, that is, binary '00001001', the controller 12 increases the counter value C by one (step 104). Again, it is checked whether m [C] is number 3 (step 106). Here, the reason for checking the value of m [C] is to determine whether the three octets are equal in length to the call reference signal CR, as can be seen from FIG.

If it is determined in step 106 that the value of [C] is not number 3, the process proceeds directly to step 156 described later, whereby the control unit 12 calls the corresponding network or terminal user. By providing service information to indicate that the reference signal is an error, an error of the information is recognized between the terminal and the network or by the user, thereby enabling a quick response action.

On the other hand, if it is determined in step 106 that the value of m [C] is number 3, the controller 12 increments the counter value C by one (step 108).

Then, the control unit 12 uses the dummy value a to convert the call reference signal of 4 octets, which is the unit of the octet (8 bits) of the setup message, into the unit of the integer (16 bits), and the dummy value a = m [C ] And increase the counter value C by 1, then shift the value of a 8 times to the left (actually it is the result of shifting the upper octets of the 2 octets of the reference signal 8 bits to the left), and again a dummy value a = a + m [C] and increase the counter value C by 1, then shift the value of a 8 times to the left (actually 8 bits to the left of the upper octet of the call reference signal of the remaining 2 octets) Set the dummy value a = m [C] and increment the counter value C by one (step 110).

Here, the conversion of the message information stored in the memory into the unit of octet by the logical multiplication operation is performed by the unit of octet (8 bits) in the ATM communication protocol. 16 bits).

Next, the controller 12 checks whether the call reference signal value information is all zero (step 112), and if it is determined that all are not zero, the process proceeds directly to step 156 which will be described later. 12) provides service information for indicating that the call reference signal is an error to the corresponding network or the terminal user, so that the error of the information is recognized by the terminal and the network or by the user, thereby enabling a quick response action.

On the other hand, if it is determined in step 112 that the call reference signal value information is all zero, the control unit 12 again returns the format information value of the first octet of the message format signal MT, FIG. As shown in d), it is checked whether the number 5, that is, the binary number '00000101' (step 114).

If it is determined in step 114 that the information value of the first octet of the message format signal MT is not the number 5, the process proceeds directly to step 158 described later, whereby the control unit 12 By providing service information for indicating that a message format signal is an error to a corresponding network or terminal user, an error of the information is recognized between the terminal and the network or by the user, thereby enabling a quick response action.

On the other hand, if it is determined in step 114 that the information value of the first octet of the message format signal MT is number 5, then the control unit 12 increments the counter value C by one (step 116). Again, it is determined whether the value of m [C] is greater than number 127, i.e. the 8th bit, the extension bit in the second octet of the message format signal, must always be 1, so that the information bit is greater than the binary number '01111111'. It is determined whether or not (step 118).

If it is determined in step 118 that the value of m [C] is not greater than number 127, the process proceeds directly to step 158 described later, whereby the control unit 12 sends a message to the corresponding network or terminal user. By providing the service information to indicate that the second octet information of the format signal is an error, the error of the information is recognized by the terminal and the network or the user to enable a quick response accordingly.

On the other hand, if it is determined in step 118 that the value of m [C] is greater than number 127, the controller 12 increments the counter value C by one again (step 120).

Then, the control unit 12 sets the dummy value a = m [C] and increments the counter value C by 1 to store the message length signal information of 2 octets in Lm using the dummy value a, In order to form the message length signal information of 2 octets in an integer unit (16 bits), the value of a is shifted 8 times to the left (actually, it is the result of shifting the upper octets of the message length information 8 bits to the left). Then, the dummy value a = a + m [C] again, the counter value C is increased by one, and the information value a is stored in Lm (step 122).

Here, converting the message length signal stored in the memory in the unit of octet through the logical product operation to the unit of the integer is substantially the same as the above-described reason.

Next, the control unit 12 determines whether or not the variable length information of the entire setup message according to the message format signal MT stored in Lm is within a range that is variably determined, that is, as can be seen from FIG. 4, Lm. It is checked whether or not there is between the minimum length number 49 (octane number) and the maximum length 228 (octane number) of the variable length information included in this setup message (step 124).

Here, the minimum length of the variable length information that can be included in the setup message means the total octet length of each variable length information that must be included as shown in FIG. 4, and the maximum length means the message format signal. The total octet length of the total variable length information that can be included as essential or optional.

If it is determined in step 124 that the Lm value does not exist between the numbers 49 and 228, the process proceeds directly to step 160, whereby the controller 12 sets up the corresponding network or terminal user. By providing the service information to indicate that the total length information of the message is an error, the corresponding information is recognized by the user between the terminal and the network or by the user, thereby enabling quick response.

On the other hand, if it is determined that the Lm value exists between the numbers 49 and 228 as a result of the check in the step 124, the control unit 12 uses a flag F used to confirm whether there is an information element that is essentially included in the setup message. Is initialized to 0 (step 126), and then the bit value of the next octet, i.e., m [C], is checked to determine a plurality of kinds of variable length information that is optionally followed based on the message format signal. Check whether it is an information identifier of (step 128).

If it is determined in the step 128 that the information value is the information identifier of the ATM user cell rate, the control unit 12 adds the counter value C as many as 12 to 30 octets of the ATM user cell rate. (Step 130), add 1 to the flag F (step 140), and if it is determined that the information value is the information identifier of the broadband transmission capacity, then the control unit 12 adds the number of octets of the broadband transmission capacity to the counter value C (6 Or 7) (step 132), then add 1 to the flag F (step 140), and the process proceeds to step 144.

In addition, if it is determined that the information value is the information identifier of the called party number, the control unit 12 adds 25, which is the number of octets of the called party number, to the counter value C (step 128). 134), add 1 to the flag F (step 140), and if it is determined that the information value is an information identifier of the QoS parameter, the control unit 12 adds 6, the octet number of the QoS parameter, to the counter value C (step 136, add 1 to the flag F (step 140), and the process proceeds to step 144.

On the other hand, if it is determined in the step 128 that the information value is an information element (IE) other than the information elements that must be included as described above, the control unit 12 corresponds to the counter value C. Is added (step 142), and the process proceeds to step 144.

On the other hand, if the check in step 128 indicates that the information value is any other value than the information identifier of the information elements as described above, the process proceeds directly to step 162, whereby the control unit 12 By providing the service information to indicate that the total length information of the setup message is an error to the corresponding network or the terminal user, an error of the information is recognized between the terminal and the network or by the user, thereby enabling a quick response action.

Next, the control unit 12 subtracts the octet number 9 of the header information from the counter value C obtained through the above-described process (C-9), that is, the preset value and the length information value for the detected information elements ( Lm) are compared with each other (step 144).

Then, if the comparison in step 144 determines that the Lm value is smaller than the C-9 value, the process proceeds directly to step 162, whereby the control unit 12 sets up the network or terminal user. By providing the service information to indicate that the message length information is an error, the error of the information is recognized by the terminal and the network or the user, thereby enabling a quick response action.

On the other hand, if it is determined in step 144 that the Lm value is not at least smaller than the C-9 value, the control unit 12 checks again whether the Lm value is the same as the C-9 value (step 146). .

If it is determined that the Lm value and the C-9 value are not the same as the result of the comparison in the step 146, the process returns to the above-described step 128 and the subsequent steps are repeated.

Accordingly, the error checking is performed simultaneously with the inclusion of the information elements and other information elements that must be included through the above-described steps 144 and 146.

If it is determined in step 146 that the Lm value and the C-9 value are the same, the controller 12 checks whether the flag F, which means the number of information elements that must be included, is 4 (step 150). If it is determined that the value is not 4, the process proceeds directly to step 162, whereby the control unit 12 indicates service information for indicating that the required variable length information of the setup message is an error to the corresponding network or terminal user. By providing an error of the corresponding information between the terminal and the network or by the user to enable a quick response accordingly.

In addition, if it is determined in the step 150 that the flag F is 4, then the setup message together with service information about no error of the setup message to perform error detection finally received from the network according to the present invention is included. Variable length information other than the header information of the nine octets is provided to the user, or a setup message generated by the terminal is output to the corresponding network through the information providing unit 10 (step 152).

Accordingly, as described above, service information indicating an error or no error in the setup message received from the network or generated in the terminal for transmission to the network can be efficiently detected and quickly provided to the network or the user, thereby allowing the terminal or the network or Error-free recognition of the information is effectively realized by the user.

As described above, according to the message error detection method of the present invention, an error of a setup message transmitted and received between a terminal and a network is efficiently detected through a transmission channel, and corresponding service information (no errors or errors) is transmitted to the corresponding network or user. By providing it quickly, it is possible to effectively prevent the unexpected communication error that may be caused by the error of the setup message in the communication between the terminal and the network.

Claims (3)

A method for detecting an error in a setup message in an ATM cell sent to a network or provided from a network to a terminal by a calling user in an asynchronous transmission mode, the method being input to the terminal via an information park from the network; A first step of storing the setup message generated in the terminal at a predetermined address of a memory and initializing a counter value for information detection; A second step of detecting a protocol determination signal included in the setup message and generating service information for notifying an error occurrence and providing it to the network or the user when the protocol determination signal included in the setup message is not a preset value; A third step of, if the protocol determination signal is detected, incrementing the counter value by one, then detecting a call reference signal having a predetermined number of octets, storing the call reference signal in a predetermined address of the memory, and incrementing the counter value by one; Checking the error occurrence of the message format signal following the call reference signal, detecting the presence of the extension bit present in the second octet, and providing service information for informing the error occurrence when an error occurrence of the message format signal is detected. A fourth step of generating and providing the same to the network or the user; Detects whether the content length of the required or optionally included variable length information following the message length signal of the setup message is included in a predetermined total length category, and the content length of the variable length information is detected. A fifth step of generating service information for notifying occurrence of an error if not included in the preset full length category and providing the service information to the network or the user; And detecting a plurality of types of variable length information, which is essential or selectively included after the header information of the setup message, and checking whether the detected essential variable length information is included in the predetermined total length information value except for the header information. And a sixth step of selectively providing the network or the user with service information indicating an error occurrence or no error together with the optional or mandatory variable length information following the message length signal based on the check result. Error detection method of setup message in asynchronous transmission mode. The method of claim 1, wherein the third process comprises: a; Checking whether an information value of each octet of the call reference signal is a preset value; And generating a service information for notifying occurrence of an error when the information value of each octet is not the preset value and providing the service information to the network or the user as a result of the check. How to detect errors in messages. The method of claim 1, wherein the sixth process comprises: If the content lengths of the plurality of variable length information are included in a predetermined total length category, the flag for checking the required variable length information is set to zero, and then the bit value of the next octet following the message format signal is determined by which information. A sixty-first step of detecting whether the information is an identifier; Step 62, when the detected information identifier is an information identifier of essential variable length information, increasing a counter value by a predetermined number of octets corresponding to the required variable length information, and then increasing the flag value by one; Step 63, when the detected information identifier is an information identifier of optional variable length information, increasing a count value by a predetermined number of octets corresponding to the optional variable length information; And comparing the size of the preset total length information value excluding the header information and the counter value increased in each step, and when the increased counter value is less than or equal to the preset total length information value excluding the header information, the sixty-first step; A sixty-sixth process of repeating the processes to the 63rd process; As a result of the comparison, if the incremented counter value and the preset full length information value coincide with each other, it is checked whether the increased flag value matches the number of necessary variable length information to be included in the preset full length information value. 65th process of doing; As a result of the check, if the increased flag value does not match the number of the required variable length information, service information for informing an error occurrence of the required variable length information following the message length signal is generated to the network or the user. Providing a sixty-sixth process; And if the increased flag value matches the number of the required variable length information, the network or user provides service information indicating that there is no error together with the required or optional variable length information following the message length signal. And a 67 th step of providing the error message to the setup message in the asynchronous transmission mode.