KR101117440B1 - A Device And Method For Providing Free Number Service in the IP Multimedia Subsystem - Google Patents

Abstract

A method for providing a virtual number service based on an IMS network according to the present invention comprises adding a real number corresponding to the virtual number to a message body field of a SIP message whose virtual number is a called number, Call processing based on the actual number is performed by generating trigger information for access in the message header field.

Virtual number, IMS, SIP message

Description

A device and method for providing free number service in the IP multimedia subsystem

The present invention relates to a virtual number service in an IP multimedia subsystem (IMS). More specifically, the present invention relates to a virtual number using an extension function of a Session Description Protocol (SDP) parameter of a Session Initiation Protocol (SIP) message. A method and apparatus for providing a service are provided.

As mobile communication technology develops and mobile communication network evolves, the 3rd generation mobile communication system (IMT-2000) essentially provides Internet services, and has a unique Internet Protocol (IP) address assigned by an Internet service provider (ISP). With the IMT-2000 network, it provides mobile IP that can receive internet service. The adoption of IP-based Internet protocols in mobile networks has been accepted as a gradual trend, and Internet protocols are becoming a part of mobile network technologies. The European-led 3GPP (3rd Generation Project Partnership) and the North American-led 3GPP2, which proceeds with the standard of IMT-2000, do not stay here and take the notion of 'ALL IP NETWORK', which replaces all infrastructures of mobile communication with IP. Introduced, ALL IP network is a next-generation mobile communication network that is included in the category of IMT-2000 network but has a completely different infrastructure.

The biggest feature of ALL IP network is that it is the first 3GPP network to support IP multimedia service. This feature is specifically implemented by newly added nodes to support IP multimedia services, collectively called the Internet Protocol Multimedia Subsystem (IMS).

That is, IMS is a set of nodes newly introduced to provide an IP multimedia service, and includes a call session control function (CSCF), a home subscriber server (HSS) and an application server (AS). And the like.

1 is a block diagram schematically illustrating a typical IMS service network.

Referring to FIG. 1, the IMS service network stores user equipment (UE) 10 and all data on subscriber data, and manages user profiles and information management functions and authorities for UE mobility management. Call session controller (CSCF) for performing multimedia call control based on Session Initiation Protocol (SIP) and HSS (Home Subscriber Server) 25 that performs functions such as authentication (Authorization) Control functions (21), 22, and 23, and an application server (AS) 30 for providing various IMS services.

The HSS 25 and the call session controller (CSCF) 21, 22, and 23 form an IMS core network 20, and the application server 30 forms an IMS service network.

The call session controller (CSCF) performs an incoming call gateway, call control, serving profile management, and address processing. Specifically, the CSCF uses a proxy-call session control function (P-CSCF) 23, an interrogating-call session control function (I-CSCF) 22, and a serving-call session control function (S-CSCF) 21. Have

The P-CSCF 23 serves as a proxy and a user agent. The P-CSCF 23 is the first point point at which the user terminal (UE) 10 connects to the IMS core network 20. The P-CSCF 23 forwards the Session Initiation Protocol (SIP) registration request message received from the user terminal (UE) 10 to the I-CSCF 22 with reference to the home domain of the user terminal (UE) 10. do.

The I-CSCF 22 is the first point of the user terminal (UE) 10 accesses the home network, and a plurality of I-CSCFs 22 may exist in one network domain. The I-CSCF 22 receives the address of the S-CSCF 21 which performs SIP registration of the UE 10 from the HSS 25, and then the S-CSCF 21 to be in charge of actual registration. Allocate In addition, the I-CSCF 22 routes the SIP message received from the other network to the S-CSCF 21.

The S-CSCF 21 serves as a register and controls a session of a registered endpoint. The S-CSCF 21 is registered in the HSS 25 so as to correspond to the user terminal (UE) 10, and then downloads and stores subscriber information of the user terminal (UE) 10. In addition, the S-CSCF 21 performs a control service while managing session state of an actually registered user terminal (UE) 10. The S-CSCF 21 provides information related to service resources to the user terminal (UE) 10. In addition, the S-CSCF 21 performs authentication with the authentication information received from the HSS 25 at the time of registration of the user terminal (UE) 10.

On the other hand, the HSS 25 is responsible for all the information of the UE (UE) subscriber for call / session control. This includes all the functions of the home location register (HLR) in the existing 3G network, and also includes the signaling protocol related to the information about the IMS subscriber. One or several such HSSs 25 may exist in one same network, depending on the number of subscribers and the configuration capability of the network.

The HSS 25 is a subscriber's master database with basic information related to the subscriber. Such information includes subscriber identifier (ie number and address information), subscriber security information (ie network access control information for authentication and authorization verification), subscriber location information (ie registration and inter-system level mobility information). ) And subscriber profile information.

Based on the above information, the HSS 25 largely provides a home location register / authentication (HLR / AUC) function and an IP multimedia function for an IP multimedia service. In the figure, a user terminal (UE) 10 transmits a service request message to the P-CSCF 23 for a multimedia service. The P-CSCF 23 sends this service request message back to the I-CSCF 22 and selects the corresponding S-CSCF 21 from the I-CSCF 22. The S-CSCF 21 then provides the information related service to the endpoint.

When there are a plurality of HSSs 25 in the operator's IMS network, the S-CSCF 21 needs to access the registered HSS 25 to acquire the subscriber's information. The S-CSCF 21 performs a procedure of acquiring the address of the HSS 25 using a subscriber locator function (SLF) (not shown) to find the registered HSS 25 among the plurality of HSSs 25. do.

The application server (AS) 30 includes Instant Messaging (IM), Presence (Voice), Voice Call Continuity (VCC), Push-To-Talk (PTT), Voice over Internet Protocol (VoIP), Group List Management (GLMS) Network element for providing subscribers with IP multimedia services including Server), IMS Centralized Services (ICS), and virtual number services.

The user registers with IMS using the prescribed SIP REGISTER method. This is a mechanism for notifying the IMS of addresses belonging to the IMS and from which SIP user identification can be reached. In 3GPP, when an IMS terminal (or SIP terminal) performs registration, the IMS authenticates the user and assigns the S-CSCF to the user from the set of available S-CSCFs. While the criteria for allocating S-CSCF are not defined by 3GPP, they may include load sharing and service requirements. It should be noted that the assignment of S-CSCF is a key factor in controlling user access to IMS-based services.

During the registration process, the I-CSCF is responsible for selecting an S-CSCF if it has not already been selected. The I-CSCF receives the required S-CSCF capability from the home subscriber server (HSS) of the home network and selects an appropriate S-CSCF based on the received capability. When a registered user continues to send a session request to the IMS, the P-CSCF may forward the request to the selected S-CSCF based on the information received from the S-CSCF during the registration procedure. In an IMS service network, application servers (ASs) are provided to implement IMS service functionality. The application server provides the service to the end user in the IMS system and can be connected as an end point via the 3GPP-compliant Mr interface or "linked" by the S-CSCF via the 3GPP-compliant ISC interface. In the latter case, the Initiation Filter Criterion (IFC) is used by the S-CSCF to determine which application server should be "linked" during SIP session establishment. The IFC is received by the S-CSCF from the HSS during the IMS registration procedure as part of the subscriber profile (see Figure 4).

Free Number means a virtual telephone number used instead of a real telephone number to protect his privacy. A voice call processing technology for implementing such a virtual number service is disclosed in Korean Patent No. 0795585 (Patent Document 1) and Korean Patent No. 0800083.

Patent document 1 relates to a method for realizing a virtual number service in a CDMA based network, and patent document 2 relates to a method for realizing a virtual number service in a WCDMA based network.

This virtual number service is applicable not only in voice call processing but also in multimedia call processing, in particular, multimedia service using IP multimedia subsystem.

The procedure for providing virtual number service in IMS network is as follows. That is, the calling CSCF receiving the SIP message from the subscriber checks the IFC of the subscriber profile and routes the SIP message to a predetermined application server. The application server changes the virtual number of the "TO" tag in the message header field of the SIP message to a real number and returns it to the calling CSCF.

In this case, the following problem occurs due to the charging generation characteristics of the IMS network.

The charging condition of each network element in the IMS generates one CDR based on the "Call-ID" tag, the "TO" tag, and the "FROM" tag of the SIP message. That is, when both the "Call-ID" tag, the "TO" tag, and the "FROM" tag match before and after the message is transmitted, one CDR is determined as one call processing and the one "Call-ID" is generated. If any one of the " tag, " TO " tag and " FROM " tag is changed, another call processing is judged to generate another new CDR.

Therefore, when the virtual number of the "TO" tag in the message header field is changed to the real number in the application server as in the conventional IMS virtual number service, the CDR based on the virtual number and the CDR based on the real number are duplicated. There is a problem that the charge is duplicated for one service.

Therefore, in implementing the virtual number service in the IMS network, a new call processing scheme is required that does not cause the problem of duplicate charging as in the prior art.

The inventors have found that the reason for the duplicate charging in the conventional virtual number service is that the application server changes the "TO" tag information in the message header field.

In addition, the present inventors have found that specific SDP parameters of SIP messages can be extended according to a subscriber's use, and when using these scalable parameters, it is possible to provide a virtual number service without changing "TO" tag information.

Accordingly, an object of the present invention is to prevent a problem of duplicate charging when providing a virtual number service in an IMS network.

It is another object of the present invention to extend a function of a specific SDP parameter of a SIP message so that call processing to an actual number can be performed without changing a specific parameter of a message header field.

Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. Further, objects and advantages of the present invention can be realized by the means and the combination shown in the appended claims.

An application server for providing a virtual number service based on an IMS network according to the first aspect of the present invention, comprising: means for receiving a first SIP message having a virtual number as a called number from a calling party session controller (CSCF); ; Means for adding a real number corresponding to the virtual number to a message body field of the first SIP message; Means for generating trigger information in a message header field of the SIP message to access the actual number; Means for generating a second SIP message comprising the trigger information and a real number; And means for transmitting the second SIP message to the originating call session controller.

Further, a call session control apparatus located in an originating IMS core network according to a second aspect of the present invention, includes: first receiving means for receiving a first SIP message having a virtual number as a called number from an originating subscriber; First routing means for routing the first SIP message to an application server providing a virtual number service according to trigger information of an Initial Filter Criteria (IFC) of a subscriber profile; Second receiving means for receiving from the application server a second SIP message including a real number corresponding to the virtual number in a message body field; And second routing means for identifying a real number from the second SIP message and routing the second SIP message to a called party call session controller that is in charge of the real number. In this case, the real number is added using the SDP parameter of the message body field of the second SIP message, and the trigger information for accessing the real number is included in the message header field of the second SIP message. The second routing means checks the actual number according to the trigger information.

The second routing means obtains a routing path to the called party session controller by querying a home subscriber server (HSS) using the actual number, and the first routing means obtains the IFC of the subscriber profile. It checks whether the called subscriber subscribes to the virtual number service, and routes the first SIP message to the application server before the call processing according to the virtual number according to trigger information of the IFC.

A method for providing a virtual number service based on an IMS network according to a third aspect of the present invention comprises: adding a real number corresponding to the virtual number to a message body field of a SIP message whose virtual number is a called number; By generating trigger information for accessing the actual number in the message header field, call processing based on the actual number is performed.

According to a fourth aspect of the present invention, there is provided a method of processing a SIP message using a virtual number as a called number in an originating IMS network, the method comprising: receiving a first SIP message using a virtual number as a called number from an originating subscriber; Generating a second SIP message by adding a real number corresponding to the virtual number to a message body field of the first SIP message and generating trigger information for accessing the real number in a message header field; Confirming the actual number according to trigger information of the second SIP message; And processing the second SIP message to the called party's network node using this actual number as the called number.

A method for providing a virtual number service based on an IMS network according to a fifth aspect of the present invention, the method comprising: receiving, at an originating network node, a first SIP message having a virtual number as a called number from an originating subscriber; Routing the first SIP message to an application server for providing a virtual number service according to trigger information of an Initial Filter Criteria (IFC) of a subscriber profile before an incoming call processing; At the application server, add a real number corresponding to the virtual number to the first SIP message using an extensible Session Description Protocol (SDP) parameter of a message body field of a SIP message and trigger to access this real number Generating a second SIP message by generating information in a message header field of the first SIP message and transmitting it to the originating network node; And identifying, at the calling network node, the actual number according to the trigger information of the second SIP message, and processing the second SIP message by using the actual number as a called number.

Further, the method according to the fifth aspect of the present invention includes: receiving, at a called network node, the second SIP message from the calling network node; And converting the SIP-URI of the start line field of the second SIP message by using the IP for the actual number.

The first and second SIP messages are SIP INVITE messages, and a virtual number is linked to a To tag of a message header field of the first and second SIP messages.

According to the present invention, in providing a virtual number service through an IMS network, since the existing tag information (CALL-ID, TO, FROM) of the message header field of the SIP message is not changed, billing information is duplicated. You can prevent it.

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

First, FIG. 2 is a block diagram of an IMS network system for implementing a virtual number service according to a preferred embodiment of the present invention.

The IMS network system according to FIG. 2 is largely composed of a calling party IMS core network 100, a called party IMS core network 200, and an application server 300.

The source IMS core network 100 and the destination IMS core network 200 include other network elements such as P-CSCF, I-CSCF and HSS in addition to the S-CSCFs 110 and 210 shown in the figure. Specific configurations and functions of these elements are omitted by referring to FIG. 1 and its description.

After the calling party S-CSCF 110 receives the SIP message (eg, the INVITE message) from the calling party, the calling party S-CSCF 110 according to the trigger information of the Initial Filter Criteria (IFC) of the called party profile is applied. The SIP message is routed to the application server 300 for the virtual number service. The application server 300 receiving the SIP message from the originating S-CSCF 110 adds the real number to the message body field of the SIP message so that the message routing can be based on the real number, and adds trigger information to the message header field. In addition, it generates a new response message (eg, 100Trying message).

Upon receipt of the response message from the application server 300, the calling party S-CSCF 110 forwards the SIP message with the actual number added to the message body field to the called party S-CSCF 210.

The called party S-CSCF 210 converts the URI of the start line field based on the actual number of the SIP message and transfers the URI to the P-CSCF.

Hereinafter, a detailed configuration of IMS network elements for implementing a virtual number service according to the present invention will be described with reference to FIG. 2.

First, the calling party S-CSCF 110 routes the SIP message to the application server for the virtual number service, extracts the real number from the SIP message from the application server, and transmits the real number to the called party S-CSCF. To this end, as shown in FIG. 2, the control unit 113, the triggering unit 112, and the functional elements such as the real number extraction unit 111 are included.

As the SIP module receives the SIP message from the calling subscriber, the filtering module 113 checks the IFC of the subscriber profile downloaded from the HSS to check whether the called subscriber is subscribed to the virtual number service.

When the called subscriber is subscribed to the virtual number service, the triggering module 112 triggers the SIP message received from the calling subscriber to the application server 300 providing the virtual number service.

4 shows a schematic configuration of a subscriber profile. The portion of the subscriber profile 400 that sets the type of service and its contents is stored in the ServiceInfo portion of the IFC (Initial Filter Criteria) 410 of the subscriber profile. That is, the subscriber profile may set whether to subscribe to the virtual number service and an operation when the SIP message is originated or received by using an incoming / outgoing trigger of the SIP message. The trigger information causes the calling S-CSCF to first trigger the application server 300 providing the virtual number service without immediately processing the SIP message when the called subscriber is subscribed to the virtual number service.

That is, the filtering unit 113 and the triggering unit 112 of the calling party S-CSCF 100 check the IFC 410 of the subscriber profile 400 to determine whether the called party is subscribed to the virtual number service. In the case of subscribing to the virtual number service, the SIP message is first triggered by the application server 300 providing the virtual number service.

The real number extraction unit 111 extracts a real number from the message body field of the SIP message received from the application server 300 providing the virtual number service, and based on the real number, the called party S- Route the SIP message to the CSCF 210.

The application server 300 that provides the virtual number service includes a SIP interface 330, a trigger information generator 320, and an actual number adder 310 as shown in FIG.

First, the SIP interface unit 330 transmits and receives an originating S-CSCF 110 and an INVITE message based on SIP.

Before describing the trigger information generation unit 320 and the actual number addition unit 310, a SIP message format will be described with reference to FIG.

As shown in FIG. 5, the SIP message 500 includes a start line field 510, a message header field 520, a carriage-return line-feed (CRLF) 530, and a message body field 540 according to SIP protocol. It is composed of

The start line field 510 includes data about a method type to request, a SIP URI indicating an address of a target receiving the request, and a SIP version.

The message header field 520 includes a Via tag, a From tag, a To tag, a Call-ID tag, a Contact tag, and the like for controlling a session.

The message body field 530 uses a Session Description Protocol (SDP) that allows the receiving party to participate in the session by transferring the media stream information of the session. The message body field 530 includes various SDP parameters such as an m parameter, a c parameter, a parameter, and the like. In particular, the a parameter can be extended to a user's purpose.

The real number adding unit 310 confirms the virtual number through the "TO" tag of the SIP message received through the SIP interface unit 330, and expands the a parameter of the message body field 530 of the SIP message to virtual The actual number corresponding to the number is added. That is, the real number adding unit 310 extends the a parameter by adding "svc-type: real number" to the a parameter of the message body field.

In addition, the trigger information generation unit 320, when other IMS network elements (eg, S-CSCF) filters the SIP message, the message body field, not the virtual number in the "TO" tag of the message header field Create trigger information in the message header field based on the actual number of "a = svc-type". This trigger information is added in the form of "User-Agent: svc-type" in the message header field.

The SIP message newly generated by the real number adding unit 310 and the trigger information generating unit 320 is transmitted to the calling party S-CSCF through the SIP interface unit 330.

In addition, the receiving side S-CSCF 210 according to the present invention includes a filtering unit 212 and a URI conversion unit 211 as shown in FIG.

The filtering unit 212 determines whether trigger information ("User-Agent: svc-type") exists in the message header field by filtering the SIP message received from the originating S-CSCF 110, and trigger information If present, the SIP message is transmitted to the URI conversion unit 211.

The URI conversion unit 211 extracts a real number from "a = svc-type: real number" of the message body field according to trigger information ("User-Agent: svc-type") of the message header field, and this real number Convert the SIP URI of the Start Line field to IP for.

A virtual number service providing method of the present invention based on the system having the above configuration will be described with reference to FIGS. 3 and 6.

The calling subscriber station UE # 1 transmits a SIP INVITE message (1) 600 having a format as shown in FIG. 6A to the calling party S-CSCF # 1. The virtual number is described in the "TO" tag 610 of the message header field of the SIP INVITE message (1) (600) (S110).

The calling party S-CSCF # 1 transmits 100 attempts to the SIP INVITE message to the calling subscriber station UE # 1 (100 Trying).

The calling party S-CSCF # 1 is to provide a virtual number service for the SIP INVITE message (2) 600 having the format as shown in FIG. 6 (a) according to trigger information of IFC (initial filtering criteria) of the called party profile. Routing to the application server (AS) (S117).

Accordingly, the application server AS transmits 100 attempt responses to the calling party S-CSCF # 1, which is the same as the process of S113 (S119).

The application server receiving the SIP INVITE message (2) 600 such as (a) of FIG. 6 from the calling party S-CSCF # 1 expands the a parameter in the message body field of the corresponding SIP message and indicates "a = svc-type." : Add a real number through the information "real number" (630), and insert the trigger tag "User-Agent: svc-type" (620) in the message header field to a new format of the format as shown in (b) of FIG. Generate a SIP INVITE message (3) (S121).

The SIP INVITE message (3) thus generated is sent back to the calling party S-CSCF # 1 by the application server (S123), and the calling party S-CSCF # 1 makes 100 attempts to the application server (AS). Send a response (S125).

The originating S-CSCF # 1 that has received the SIP INVITE message 3 from the application server, according to the trigger information "User-Agent: svc-type" 620 in the message header field, "a = svc" in the message body field. -type "630 extracts the actual number from the parameter. (S129)

The calling party S-CSCF # 1 sends a query to the home subscriber server (HSS) based on the extracted real number to find the called party S-CSCF # 2 located in the called party IMS network (S129, S131).

Thereafter, the calling party S-CSCF # 1 sends a SIP INVITE message 4 of the form as shown in FIG. 6 (c) to the called party S-CSCF # 2, and the called party S-CSCF # 2 sends the calling party. 100 attempt responses are sent to the S-CSCF # 1 on the side (S133, S135). In this SIP INVITE message 4, the virtual number is described in the "TO" tag 610 of the message header field, and the "User-Agent". The trigger information “svc-type” 620 is added, and the message body field includes extended parameter information “a = svc-type: actual number”.

The called party S-CSCF # 2 that has received the SIP INVITE message 4 filters the SIP INVITE message 4 and according to trigger information called "User-Agent: svc-type" 620 in the message header field. The actual number is extracted from the field, and the " SIP-URI " of the start line field is converted to the IP for this actual number to generate a SIP INVITE message 5 as shown in FIG.

The SIP INVITE message 5 thus generated is transmitted and completed to the called subscriber station UE # 2 via the called party's P-CSCF # 2 (S139, S141, S143, S145).

As such, the virtual number service according to the present invention does not cause the problem of the conventional billing because it enables the message routing according to the actual number without changing the virtual number of the "TO" tag of the SIP message.

In the above described with reference to the accompanying drawings, preferred embodiments of the present invention in detail. However, embodiments of the present invention can be variously modified or applied by those skilled in the art, the scope of the technical idea according to the invention to be defined by the claims to be described later will be.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical spirit of the present invention, the present invention includes matters described in such drawings. It should not be construed as limited to.

1 is a block diagram of an IP multimedia subsystem.

2 is a block diagram of an IP multimedia subsystem for providing a virtual number service according to the present invention;

3 is a call processing flow diagram for implementing a virtual number service in accordance with the present invention.

4 is a schematic data format of a subscriber profile.

5 is a message format of a SIP message.

6 is a message format conversion diagram of an INVITE message according to the call processing flow of FIG.

Claims (22)

An application server for providing a virtual number service based on an IMS network, Means for receiving a first SIP message with a virtual number as a called number from a calling party session controller (CSCF); Means for adding a real number corresponding to the virtual number to a message body field of the first SIP message; Means for generating trigger information in a message header field of the first SIP message to access the actual number; Means for generating a second SIP message including the trigger information and a real number; And Means for sending said second SIP message to said calling party session control device. The method of claim 1, The actual number is added using the expandable parameters of the Session Description Protocol (SDP) parameters. The method of claim 2, Wherein the virtual number is linked to a To tag of the first and second SIP messages. The method of claim 3, wherein Wherein the first and second SIP messages are SIP INVITE messages. A call session controller located in an originating IMS core network, First receiving means for receiving a first SIP message having the virtual number as the called number from the calling subscriber; First routing means for routing the first SIP message to an application server providing a virtual number service according to trigger information of an Initial Filter Criteria (IFC) of a subscriber profile; Second receiving means for receiving from the application server a second SIP message including a real number corresponding to the virtual number in a message body field; And A second routing means for identifying a real number from the second SIP message and for routing the second SIP message to a called party session control device which is in charge of the real number; . The method of claim 5, The real number is added using the SDP parameter of the message body field of the second SIP message, trigger information for accessing this real number is included in the message header field of the second SIP message, As a result, the second routing means checks the actual number according to the trigger information. The method of claim 6, And the second routing means obtains a routing path to the called party session controller by querying a home subscriber server (HSS) using the actual number. The method according to any one of claims 5 to 7, The first routing means confirms whether or not the called party subscribes to the virtual number service through the IFC of the subscriber profile, and first sends the first SIP message to the application server before processing the call according to the virtual number according to the trigger information of the IFC. An originating call session controller, characterized in that for routing. The method of claim 8, And the virtual number is linked to a To tag of the first and second SIP messages. The method of claim 9, And the first and second SIP messages are SIP INVITE messages. A method for providing a virtual number service based on an IMS network, Call based on the actual number by adding the actual number corresponding to the virtual number to the message body field of the SIP message whose virtual number is the called number, and generating trigger information for accessing the actual number in the message header field. Virtual number service providing method characterized in that the processing is made. The method of claim 11, And wherein the virtual number is linked to a To tag of a message header field of the SIP message. 13. The method of claim 12, The actual number is added to the message body field using an extensible parameter of the SDP parameters. A method of processing a SIP message using a virtual number as a called number in a calling IMS network, Receiving a first SIP message from the calling subscriber with the virtual number as the called number; Generating a second SIP message by adding a real number corresponding to the virtual number to a message body field of the first SIP message and generating trigger information for accessing the real number in a message header field; Confirming the actual number according to trigger information of the second SIP message; And And processing the second SIP message to a called party's network node using this actual number as a called number. A method for providing a virtual number service based on an IMS network, Receiving, at the calling network node, a first SIP message from the calling subscriber with the virtual number as the called number; Routing the first SIP message to an application server for providing a virtual number service according to trigger information of an Initial Filter Criteria (IFC) of a subscriber profile before an incoming call processing; In the application server, a real number corresponding to the virtual number is added to the message body field of the first SIP message by using an extensible Session Description Protocol (SDP) parameter of the message body field of the SIP message. Generating a second SIP message by generating trigger information for access in a message header field of the first SIP message and transmitting it to the originating network node; And Identifying, at the originating network node, the actual number according to the trigger information of the second SIP message and processing the second SIP message with the actual number as the called number; How to Provide Number Services. The method of claim 15, At a called network node, receiving the second SIP message from the calling network node; And And converting the SIP-URI of the start line field of the second SIP message by using the IP for the actual number. The method of claim 16, And the calling network node is a serving-call session control function (S-CSCF) of the calling IMS core network. The method of claim 16, And the called-side network node is a serving-call session control function (S-CSCF) of the called-side IMS core network. The method of claim 17 or 18, The real number is added to the message body field in the form of "a = svc-type: real number" virtual number service providing method. The method of claim 19, The trigger information is a virtual number service providing method, characterized in that generated in the message header field "User-Agent: svc-type" form. The method of claim 20, And the first and second SIP messages are SIP INVITE messages. The method of claim 21, And a virtual number is linked to a To tag of a message header field of the first and second SIP messages.

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