KR20040048769A - Load sharing apparatus in the softswitch system and method thereof - Google Patents

Abstract

PURPOSE: An apparatus and a method for distributing loads in a soft switch system is provided to distribute calls in order to effectively process a large capacity PSTN call. CONSTITUTION: An apparatus for distributing loads in a soft switch system comprises a factor extraction part(310), a soft switch determination part(320), and a call distribution part(330). The factor extraction part(310), in the case of an ISUP message, extracts necessary factors among a DPC(Destination Point Code), an OPC(Own Point Code), and a CIC(Circuit Identification Code) according to a distribution condition and transmits them to the soft switch determination part(320). In the case of an SCCP message, the factor extraction part(310) extracts necessary factors among a DPC, an OPC, a TID(Transaction ID), and an SSN(SubSystem Number) according to a distribution condition and transmits them to the soft switch determination part(320). The soft switch determination part(320) substitutes the factors transmitted from the factor extraction part(310) for a stored distribution condition and determines a soft switch to distribute calls. The call distribution part(330) distributes calls to a soft switch, determined by the soft switch determination part(320), through an interface handler.

Description

Load sharing apparatus in soft switch system and method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft switch system, and more particularly, to a load distribution device and a method for distributing a call so as to effectively handle a large capacity PSTN call in a soft switch system having a plurality of soft switches.

In line with the recent trend of changing telecommunication networks, the composition of corporate telecommunications networks, access networks, and public telephone networks is also changing. The corporate telecommunications network is an integrated network that connects headquarters and branch offices using intranet for voice and data through integration of existing private telephone network and data network.

By using this integrated network to service voice, fax, and data together, the network can be used efficiently and easily. In particular, the CTI (Computer Telephony Interface) and UMS (Unified Message Service) services can be easily provided based on this.

The use of Internet telephony can reduce intercity and international telephony costs and provide new application services. In addition, SOHO (Small Office Home Office) customers will evolve into a communications network that will provide data and low-cost voice services, as well as application services to businesses.

As the high-speed Internet infrastructure is established, many households will be able to receive Internet service, and will develop into a communication network that can provide Internet telephony and multimedia services in addition to the Internet service. In general, voice services are one of the most important killer applications because they are very useful to users.

Recently, the structure of a public telephone network has been changed from a circuit switched scheme to a packet switched scheme. For efficient operation of the network for transmitting voice and data, it will evolve into a communication network that constitutes a packet-based backbone network.

The next generation network structure is being developed into a structure in which signaling and media transmission are separated and supported. It is divided into SG (Signaling Gateway) which converts and provides signaling in the interworking of public telephone network and IP network, and MG (Media Gateway) which converts media transmission type such as voice and video, and MGC (Media which controls overall signaling control) Gateway Controller).

In the future, integrated services should be provided by linking various services such as subscriber networks, public telephone networks, and corporate communication networks. Interworking between different networks is performed at the gateway, and MG is needed to handle these various services. The function of processing various signaling protocols and providing signaling control is called SoftSwitch.

SoftSwitch supports various protocols such as SS7, H.323, MGCP, SIP, SIGTRAN, MEGACO, etc. The main functions include support for media gateway, Internet protocol (IP) phone, integrated access device (IAD). Interworking with a circuit-switching network; and the like.

In particular, the soft switch can transmit various media such as voice, video, and data by adopting an open standard, and has the advantage of providing a value-added service than the function provided by the existing wired telephone network (PSTN).

Softswitch, therefore, is expected to transform an existing closed communications infrastructure along with intelligent networking equipment into an open environment.

Applications that can lower costs while using softswitches to perform common PSTN functions include long-distance and international calls, packet relay switching, Internet telephony switching, and IP voice communications clusters.

SoftSwitch will also be able to deliver the new services customers expect, which is difficult to implement because the equipment and network are not yet installed. This enables not only to provide basic and enhanced services to home customers through direct voice communications over broadband, business PBX access, and integrated access devices, but also to provide value-added services. Softswitches enable the delivery of new, higher-quality services over networks that concentrate voice and data communications.

These services include integrated messaging services, click-to-dial services, and text messages that send e-mails and reply to incoming calls. In addition, it will be able to provide new services that have not been available so far.

As described above, softswitches have various applications and perform various functions in combination. In addition, the trend of increasing capacity has led to the necessity of load sharing in order to effectively handle large-capacity PSTN calls, as the soft switch system has a distributed call processing structure to expand performance.

In particular, as the conventional soft switch system can be seen in Figure 1 as a small capacity soft switch system, the signaling gateway 120 and the soft switch 130 has a 1: 1 relationship, which is not suitable for large capacity. In order to handle calls effectively, the role of load sharing is needed for each protocol of SS7 in signaling gateway.

Accordingly, an object of the present invention is to provide a load distribution device and a method for distributing a call for effectively processing a large PSTN call.

1 is a block diagram of a soft switch system according to the prior art.

Figure 2 is a block diagram of a soft switch system having a load distribution device according to an embodiment of the present invention.

Figure 3a is an internal block diagram of a load distribution device according to an embodiment of the present invention, Figure 3b is an internal block diagram of a load distribution device according to another embodiment of the present invention.

4A is a flowchart of a load distribution method in a soft switch system according to an embodiment of the present invention, and FIG. 4B is a flowchart of a load distribution method in a soft switch system according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

200: signal transfer point 210: signaling gateway

211: message delivery unit

212, 221, 226: User Information Network

213, 222, 225: signal connection control unit / question and answer processing unit

214: load distribution device 215, 224, 228: interface handler

223, 227: basic call processing unit / intelligent network processing unit

310: factor extraction unit 320: soft switch determination unit

330: call distribution unit 340: load management unit

In order to achieve the above object, the present invention distributes a call by substituting a factor extractor for extracting elements necessary for load distribution upon receiving a PSTN call and load distribution conditions for storing elements extracted by the factor extractor. And a call distribution unit for distributing the call to the soft switch determined by the soft switch determination unit.

In addition, the present invention provides a soft switch system comprising a signaling gateway and a plurality of soft switches, comprising: a load manager configured to store load state information of a plurality of soft switches; A soft switch determination unit receiving load status information on a plurality of soft switches from the load management unit to determine a soft switch having the least load as a soft switch to distribute a call; And a call distribution unit for distributing the call to the soft switch determined by the soft switch determination unit.

The present invention also provides a soft switch system including a signaling gateway and a plurality of soft switches, comprising: a soft switch determination unit configured to determine a soft switch to distribute a load according to a round robin method when a PSTN call is received; And a call distribution unit for distributing the call to the soft switch determined by the soft switch determination unit.

The present invention also provides a load distribution method applied to a signaling gateway having a load distribution device and a soft switch system including a plurality of soft switches, wherein the load distribution device receives a PSTN call and is required for load distribution. Extracting the first step; A second step of determining the soft switch to distribute the call by substituting the load distribution condition storing the element extracted in the first step; And a third step of distributing a call to the soft switch determined in the second step.

In addition, the present invention, in the load distribution method applied to a signaling gateway having a load distribution device and a soft switch system consisting of a plurality of soft switches, when the load distribution device receives a PSTN call of the plurality of soft switches A first step of identifying a load condition; A second step of selecting the soft switch having the least load among the load states of the plurality of soft switches identified in the first step as the soft switch to distribute the call; And a third step of distributing a call to the softswitch selected in the second step.

In addition, the present invention is a load distribution method applied to a signaling gateway having a load distribution device and a soft switch system comprising a plurality of soft switches, when the load distribution device receives a PSTN call according to a round robin method A first step of determining the softswitch to distribute; And a second step of distributing a call to the soft switch determined in the first step.

Now, with reference to the drawings of Figure 2 will be described in detail a preferred embodiment of the present invention.

2 is a configuration diagram of a soft switch system having a load distribution device according to an embodiment of the present invention.

Referring to the drawings, a soft switch system having a load distribution device according to an embodiment of the present invention includes a signal transfer point 200, a signal gateway 210, and a plurality of soft switches 1. ~ N).

Signal Transfer Point 200 routes or exchanges all signaling messages in the network. At this time, it is made by the reception point code address or routing information in the message.

In addition, in order to provide high reliability, the signal transmission points 200 are configured in pairs, and the pair of signal transmission points 200 perform the same function.

The home signal transfer point 200 is directly connected to a service switching point or a service control point.

One of the most important functions of the signal transmission point 200 is Global Title TRanslation (GTT). GTT is to find the service control point that has the correct database, and it is possible to get the information necessary for routing by searching the database with the necessary information.

Like the switch structure, the structure of the signal transmission point 200 is hierarchically configured by a local signal transmission point, a regional signal transmission point, a national signal transmission point, an international signal transmission point, and a gateway signal transmission point.

The signaling gateway 210 receives a signal message from the signal transmission point 200 and distributes the signal message to the plurality of soft switches 1 to N.

The signaling gateway 210 includes a message transfer unit (MTP 1 to 3) 211, an integrated information network user unit (ISUP: ISDN User Part) 212, and a signal connection control unit (SCCP). And a Signaling Connection Control Part (TCAP) Transaction Response Capability (TCAP) 213, a Load Sharing Group (LSG) 214, and an Interface Handler 215.

Here, the message transfer unit 1 level 211 is a physical layer that carries a signal message to a transmission path electrically. It defines the physical and electrical characteristics of the transmission path. Currently available network interfaces are T1, DS-0, E1, 56 / 64KBPS, and V.35, the most common of which is 56 / 64kbps.

The message transfer unit second level 211 is a data link layer that provides reliable transmission between two points. Error control, packet order, and link status of signals transmitted and received via the data link are shown. A packet used to transmit an SS7 message is called a signal unit. The signal unit is composed of variable lengths in octet units, and there are three types of signal units.

SU (Message Signal Unit): Provides a unit structure that carries user data from level 4.

SSU (Link Status Signal Unit) provides link status information.

Fill-in Signal Unit (ISU): Provides error detection on the link.

The message transfer unit 3 level 211 is a network layer that routes SS7 messages to their destinations.

The message transfer unit 3 level 211 provides a signaling message handling (SMH) function and a signaling network management (SNM) function.

The signaling message processing function determines the destination address by routing label (RL) and routes the SS7 message, and the arriving MSU sends it to Level 4 accordingly.

Signaling network management can prevent loss or error of signal in case of abnormality in signal link or signal relay station, and has automatic processing procedure to prevent service degradation by setting up bypass route quickly.

Signaling network management performs traffic management, routing management, link management, and the like of signal information.

The comprehensive information network user unit (ISUP: ISDN User Part) 212 and the Signaling Connection Control Part (SCCP) / Transaction Capability (TCAP) 213 of the signaling gateway 210 are respectively It transmits the relevant signal message of the soft switch (1 ~ N) to the corresponding device.

In addition, the load distribution device 214 has load information of the plurality of soft switches 1 to N and information on which soft switches 1 to N are calling a specific call and performs call distribution.

In addition, the load distribution device 214 stores the load distribution conditions, the load conditions are generated and changed by the operator.

The interface handler 215 is a part in charge of the interface function between the signaling gateway 210 and the soft switches 1 to N.

The soft switches 1 to N include an integrated information network user unit (ISUP: ISDN User Part) 221 and 226, a signaling connection control part (SCCP) and a question and answer processing function unit (TCAP: Transaction CAPabilities) ( 222 and 225, and an intelligent network processing unit (SSF) / basic call processing unit (CCF: Call Control Function) 223.

Integrated telecommunication network user unit (221, 226) supports call establishment, management, and termination of voice and data services, and is an advanced form of TUP that can support not only existing telephone network service but also ISDN service and add new signaling information. It is an easy structure. It provides basic phone service and supports additional services such as Caller ID and Call Forward.

In addition, it provides end-to-end signaling to exchange signaling functions between sender and receiver.

The signal connection controller provides a network service on the three levels of the message transmitter. The question and answer processing unit may search the database using the signal connection control unit. That is, when the signal connection control unit sends a unit data message (UDT) requesting a database search to perform global title translation (GTT), a unit data service message (UDTS) is returned.

The question-and-answer function provides a transaction service. It supports 800, 888, 900 services, the ability to access databases such as LNP, LIDB, HLR, VLR, and remote execution of intelligent network services such as Automatic Callback.

The basic call processing unit / intelligent network processing unit 223 and 227 interwork with the exchange, the message transfer unit 211, and the signal connection control unit / answering function function unit.

The basic call processor performs a function of processing Calls of an analog subscriber, a digital subscriber, and a relay line, and the intelligent network processor performs a function of processing an intelligent network call when the intelligent call is detected from the basic call processor.

That is, the basic call processing unit analyzes the collected number and determines whether it is an intelligent network call when the calling subscriber dials or the call is received through the relay line. When it is determined that the intelligent network call, the intelligent network processor sends a message informing the intelligent network processor to notify the intelligent network signal.

Hereinafter, with reference to Figure 2 will be described in detail the operation of the load distribution device according to an embodiment of the present invention.

The soft switches 1 to N perform signaling through a common channel signaling (CCS) method through the signaling gateway 210 to interwork with an external PSTN network.

The CCS forms a communication network such that each exchange is a signaling end station (SEP), and a signaling transfer point (STP) 200 exists between signaling end stations, and between an exchange corresponding to a signaling end station and an exchange corresponding to a relay station. It is a method implemented to transmit variable length control information (or signal message) through a link through a common channel signaling equipment (CSE).

To this end, the CCS is divided into a message transfer part (hereinafter referred to as MTP) 211 and a user part (hereinafter referred to as UP) 212.

The CCS ISUP 212 is an UP that controls the inter-station signal section (or relay network section) of the ISDN, and transmits a communication line (or data link) signal during the switching period, and establishes a link during the switching period. It plays a role of setting.

That is, it is possible to control the ISDN circuit switched call in the same procedure as the existing telephone exchange call and data exchange call. Therefore, the ISUP section of the CCS becomes a section between the calling ISDN exchange and the called ISDN exchange.

ISUP signal messages such as call setup message, communication message, and call disconnection message transmitted through the data link set in the ISUP section of this CCS are used when the ISUP signal message is transmitted. DPC), local signaling point code (hereinafter referred to as OPC), circuit identification code (hereinafter referred to as CIC) and user data are carried on each other.

At this time, the DSC and the OPC are fixed IDs (IDentifiers) for each signal station, and the CIC information is path information assigned to the subscriber. Thus, the acceptable relay line capacity per one signal station is determined by the CIC information bits.

According to the ITU-T Recommendation, the above-mentioned CIC information is allocated 12 bits, 7 of which are MP (MP #), LP (LP #), E1 board (E1- board) connected to the subscriber. #), And 5 bits are used to indicate the assigned trunk channel information (TRK #).

When the signaling gateway 210 receives the ISUP message from the power station, the integrated information network user unit 212 transmits the ISUP message to the load distribution device 214 to request load distribution.

The load distribution device 214 extracts the DPC (Destination Point Code), OPC (Own Point Code), and CIC (Circuit Identification Code) from the ISUP message, according to the load distribution conditional formula that stores the extracted DPC, OPC, and CIC. The soft switches 1 to N to distribute the message are determined, and the ISUP message is distributed to the determined soft switches 1 to N through the interface handler 215.

Here, the load distribution conditional expression stored in the load distribution device 214 is a method of fixedly distributing a call to specific soft switches 1 to N for DPC and OPC, and a range or condition of a CIC value (multiple of N). ,>, <, =) To distribute the call to specific soft switches 1 to N, to distribute the call according to the load state of soft switches 1 to N, and to round robin. There is a way to distribute the call according to the Robin method.

Here, the method of distributing a call to a specific soft switch (1 to N) according to the range or condition of the CIC value is a unique number for identifying the line between the switching centers. Therefore, the CIC value included in the common line signal message generated or received by the exchange is almost evenly distributed in the range between 0 and (2 ¹² -1), which is a good selection criterion for load distribution.

That is, since the CIC values are distributed almost evenly in the range of 0 and (2 ¹² -1), it can be said that distributing a call according to the range or condition of the CIC value is equally distributing the call. The probability that a value is assigned to a particular signal message is ^2-12 , which means that if an exchange has generated a total of M messages, the message with any one CIC value is M * 2 ^-12 . .

Next, in the method of distributing a call according to the load state of the soft switches 1 to N, the load distribution device 214 manages the load state of the soft switches 1 to N, and when the ISUP call is input, the smallest number is currently present. Distribute the call to the soft switches (1 to N) under the load.

In addition, the round robin method distributes the load in a rational order to all the soft switches 1 to N in the soft switch system. In general, when the ISUP call arrives, the soft switches (1 to N) are sequentially ordered. To call).

In this case, unlike the distribution of the ISUP call to the soft switches 1 to N in order according to the arrival order, the call may be distributed to the soft switches 1 to N at a predetermined time. In other words, as a way to give the soft switches 1 to N a fair opportunity to process a call, a predetermined time is allocated to each of the soft switches 1 to N, and the soft time passes after the assigned time. The switches 1 to N hold for a while and then give the other soft switches 1 to N a chance, and then the soft switches 1 to N, which in turn give the opportunity.

On the other hand, in general, in the No.7 signaling network, SCCP signaling messages are sent through the SCCP 213 and the MTP (Message Transfer Part) 211 by separate connectionless and connected services selected by the SCCP user part. It is delivered to the SCCP user part.

The connectionless service corresponds to protocol classes 0 and 1, and does not require the SCCP user to require separate connection establishment and release procedures for signaling messages, and is included in the signaling message every time the signaling message is delivered. The address of the destination must be translated in the SCCP 213.

In addition, the SCCP user part of the called point to receive the signaling message should be checked and it is used when delivering a small amount of messages or not in real time service because the signaling message is transmitted without the signal connection between the controllers for the SCCP signal connection. .

Connected services correspond to protocol classes 2 and 3, and the SCCP user part should request to establish and release the connection of the connected service. When the connection type service is set up, when the routing of the signaling message is simplified, the address translation procedure of the called point is simplified and the signaling message is transmitted between the SCCP user part of the calling point and the SCCP user part of the called point. Is used.

In case of SCCP message, protocol class 0 and 1, which is a connectionless method used to interwork with intelligent network SCP, cannot be obtained from SCCP message for each message. Is called "TID").

Therefore, the combination of DPC, OPC, SSN (SubSystem Number), and TID in the SCCP message becomes a key for separating calls. The load sharing scheme is the same as that of the ISUP message, and the CIC is matched with the Transaction ID (TID). In addition, the load may be distributed to specific soft switches 1 to N according to the SSN.

In other words, the load distribution conditional expression stored in the load distribution device 214 is a method of fixedly distributing a call to specific soft switches 1 to N for DPC and OPC, and the range or condition of the TID value (N The method of distributing the arc to specific soft switches 1 to N according to the multiple of>, <, and =), the method to distribute the arc according to the load state of the soft switches 1 to N, and the round robin. It is possible to distribute the call according to the round robin method, and to distribute the load to the specific soft switches 1 to N according to the SSN.

3A is an internal block diagram of a load distribution device according to an embodiment of the present invention, and includes a factor extractor 310, a soft switch determiner 320, and a call distributor 330.

The factor extractor 310 extracts the necessary elements from the DPC, OPC, and CIC according to the distribution condition in the case of the ISUP message, and transmits the necessary elements to the soft switch determination unit 320, and the DPC, OPC, TID, and SSN in case of the SCCP message. The necessary elements are extracted according to the distribution condition among them and transmitted to the soft switch determination unit 320. For example, in case of distributing a call based on DPC and OPC in distributing ISUP message, DPC and OPC are extracted from ISUP message, and in case of distributing call based on CIC, CIC is extracted.

In case of distributing calls based on DPC and OPC in distributing SCCP messages, DPC and OPC are extracted from SCCP messages, and in case of distributing calls based on TID, TID is extracted and based on SSN. In case of call distribution, SSN is extracted.

Then, the soft switch determination unit 320 determines the soft switches 1 to N to which the call is to be distributed by substituting the element values transmitted from the factor extraction unit 310 to the distribution condition stored.

At this time, as the load distribution condition, the call is fixedly distributed to a specific soft switch for DPC and OPC, and the call is assigned to a specific soft switch according to the range or condition (multiple of N,>, <, =) of CIC value. There are a method of distributing a call, a method of distributing a call according to a load state of a soft switch, and a method of distributing a call according to a round robin method.

Here, in the call distribution according to the round robin method, there are a method of sequentially distributing an incoming call and a method of distributing a call based on a predetermined time.

The call distribution unit 330 distributes the call to the soft switches 1 to N determined by the soft switch determination unit 320 through the interface handler 215.

3B is an internal block diagram of a load distribution device according to another embodiment of the present invention, and includes a soft switch determination unit 320, a call distribution unit 330, and a load management unit 340.

The load management unit 340 has information on the load state of the soft switches 1 to N and information on which soft switches 1 to N are calling a specific call.

In addition, when receiving the ISUP message or the SCCP message, the soft switch determination unit 320 connects to the load management unit 340 to perform call processing on information on the load state and a specific call in any soft switch 1 to N. After receiving the information on whether or not it is received, the soft switch (1 ~ N) in the state of the least load is determined as the soft switch (1 ~ N) to distribute the call.

The call distribution unit 330 distributes the call to the soft switches 1 to N determined by the soft switch determination unit 320.

4A is a flowchart of a load distribution method in a soft switch system according to an embodiment of the present invention.

Referring to the drawing, first, when the load distribution device receives the ISUP message or the SCCP message (step S100), it extracts the necessary elements from the DPC, OPC, CIC, SSN, TID according to the load distribution conditions (step S110).

For example, in case of distributing a call based on DPC and OPC in receiving and distributing ISUP message, DPC and OPC are extracted from ISUP message, and in case of distributing a call based on CIC, CIC is extracted.

Also, in case of distributing a call based on DPC and OPC in receiving and distributing SCCP message, DPC and OPC are extracted from SCCP message, and in case of distributing call based on TID, TID is extracted and based on SSN. In case of distributing a call, the SSN is extracted.

Next, the soft switch to which the call should be distributed is determined by substituting the load distribution condition in which the extracted element is stored (step S120), and the call is distributed by the determined soft switch (step S130).

At this time, as the load distribution condition, the call is fixedly distributed to the specific soft switch by DPC and OPC, and the call is assigned to the specific soft switch by the range or condition (multiple of N,>, <, =) of the CIC value. There are a method of distributing a call, a method of distributing a call to a specific soft switch according to a load state of the soft switch, and a method of distributing a call to a soft switch according to a round robin method.

In the case of distributing a call according to a round robin method, there may be 1) a method of sequentially distributing an incoming call, and 2) a method of distributing a received call to a specific soft switch based on a predetermined time. have.

4B is a flowchart of a load distribution method in a soft switch system according to another embodiment of the present invention.

Referring to the drawing, first, the load distribution device determines the load state of the soft switches when receiving the ISUP message or the SCCP message (step S200) (step S210).

Next, the load distribution device determines the soft switch with the least load as the soft switch to distribute the call as a result of determining the load state of the soft switches (step S220), and distributes the call to the determined soft switch (step S230). .

In the meantime, the method for distributing a call when the soft switch operates normally has been described. However, when a soft switch fails and cannot operate normally, the call can be distributed only to the soft switch that operates normally. At this time, if there is one soft switch that operates normally, all the soft switches that operate normally are loaded.

In addition, the load distribution device is implemented to handle call distribution for the ISUP message and call distribution for the SCCP message separately, but can be implemented to be interlocked. Certain soft switches process only the ISUP message and other soft switches process the SCCP message. It can also be implemented.

Although the present invention has been described in detail with reference to preferred embodiments, the scope of the present invention is not limited to the specific embodiments, and should be interpreted by the appended claims.

According to the present invention as described above, there is an effect to effectively process a large-capacity PSTN call in the soft switch system.

In addition, according to the present invention, it is possible to distribute the load to a specific soft switch, there is an effect that the specific soft switch can be down or replaced with a new version of the software during operation of the soft switch system.

In addition, according to the present invention, since it is possible to separate a specific protocol to a specific server, there is an effect that can help when evaluating the performance of the soft switch for the relay and intelligent network calls of each server.

Claims (12)

In the soft switch system consisting of a signaling gateway and a plurality of soft switches, A factor extractor for extracting elements necessary for load distribution upon receiving a PSTN call; A soft switch determination unit which determines the soft switch to distribute the call by substituting the load distribution condition that stores the elements extracted by the factor extraction unit; And And a call distribution unit for distributing a call to the soft switch determined by the soft switch determination unit. The method of claim 1, The load distribution condition stored in the soft switch determination unit is In the case of ISUP message, it is a condition to distribute the load based on at least one of DPC (Destination Point Code), OPC (Own Point Code) and CIC (Circuit Identification Code), and in case of SCCP message, DPC (Destination Point Code) And a condition for distributing the load based on at least one of an OPC (Own Point Code), a SSN (Subsystem number), and a TID (Transaction ID). In the soft switch system consisting of a signaling gateway and a plurality of soft switches, A load management unit storing load state information of the plurality of soft switches; A soft switch determination unit which receives load state information on the plurality of soft switches from the load management unit and determines the soft switch with the least load as the soft switch to distribute a call when receiving a PSTN call; And And a call distribution unit for distributing a call to the soft switch determined by the soft switch determination unit. In the soft switch system consisting of a signaling gateway and a plurality of soft switches, A soft switch determining unit that determines the soft switch to distribute the load according to a round robin method when receiving a PSTN call; And And a call distribution unit for distributing a call to the soft switch determined by the soft switch determination unit. The method of claim 4, wherein And the soft switch determining unit determines the soft switch to distribute the call in a round robin manner according to the order in which the PSTN call arrives. The method of claim 4, wherein And the soft switch determination unit sequentially activates the plurality of soft switches for a predetermined time to distribute the call to the activated soft switches when the PSTN call arrives. A load distribution method applied to a signaling gateway having a load distribution device and a soft switch system including a plurality of soft switches, A first step of extracting elements necessary for load distribution when the load distribution device receives a PSTN call; A second step of determining the soft switch to distribute the call by substituting the load distribution condition storing the element extracted in the first step; And And a third step of allocating a call to the softswitch determined in the second step. The method of claim 7, wherein The load distribution condition of the second step, In the case of an ISUP message, the call is distributed based on at least one of a DPC (Destination Point Code), an OPC (Own Point Code), and a CIC (Circuit Identification Code). In the case of an SCCP message, a DPC (Destination Point Code) And a condition for distributing a call based on at least one of OPC (Own Point Code), SSN (Subsystem number), and TID (Transaction ID). A load distribution method applied to a signaling gateway having a load distribution device and a soft switch system including a plurality of soft switches, A first step of determining a load state of the plurality of soft switches when the load distribution device receives a PSTN call; A second step of selecting the soft switch having the least load among the load states of the plurality of soft switches identified in the first step as the soft switch to distribute the call; And And a third step of allocating a call to the softswitch selected in the second step. A load distribution method applied to a signaling gateway having a load distribution device and a soft switch system including a plurality of soft switches, A first step of determining, by the load distribution device, the soft switch to distribute the call according to a round robin method when receiving the PSTN call; And And a second step of distributing a call to the soft switch determined in the first step. The method of claim 10, And wherein the round robin method of the first step determines the soft switch to distribute the call according to the order in which the PSTN calls arrive. The method of claim 10, In the first round robin method, the plurality of soft switches are sequentially activated for a predetermined time, and the call is distributed to the activated Sykes soft switch when the PSTN call arrives.