WO2006047957A1

WO2006047957A1 - The method of determining the occasion of initiating the selection service call controlling function entity

Info

Publication number: WO2006047957A1
Application number: PCT/CN2005/001846
Authority: WO
Inventors: Dongming Zhu; Yajuan Wu
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2004-11-05
Filing date: 2005-11-04
Publication date: 2006-05-11
Also published as: CN1770687A; CN100512106C

Abstract

Two kinds of method on realizing selection of service call controlling function entity, and one of them is HSS judging some public user identifier is not registered but provided service by S-CSCF, then sending the S-CSCF capability information of the user to the I-CSCF when the set condition of the selection S-CSCF is satisfied, otherwise sending the S-CSCF name providing service to the user to the I-CSCF without I-CSCF to select again. Another is performing the modification directly in local database by operation maintenance after HSS judging some S-CSCF is satisfied the set condition of the selection S-CSCF. In this way, the S-CSCF reselection course by the I-CSCF is not required. HSS returns the relative S-CSCF capability information only when the S-CSCF reselection is required by I-CSCF definitude. Applying the invention, the time of initiating S-CSCF selection is reduced, the Cx interface load is decreased, and the invalid S-CSCF selection initiated by the I-CSCF is avoided.

Description

Determining the method of initiating the timing of selecting a service call control function entity

Technical field

The present invention relates to techniques for initiating a Serving Call Control Function (S-CSCF) entity selection in an Internet Protocol (IP) Multimedia Subsystem (IMS) domain, and more particularly to a method of determining the timing of initiating a selective service call control function entity. Background of the invention

With the development of broadband networks, mobile communications are not limited to traditional voice communications, and a variety of media services, including audio, video, pictures and text, will gradually be developed. Multimedia services can meet the diverse needs of users through a combination of data services such as presence, short message, web browsing, location information, push service (PUSH) and file sharing.

Driven by various data service applications, the third generation mobile communication standardization partner project (3GPP) and the third generation mobile communication standardization partner project 2 (3GPP2) and other standards organizations have successively launched IP-based multimedia subsystem (IMS). The purpose of the architecture is to implement a variety of multimedia service applications in a mobile network using a standardized open architecture to provide users with more choices and richer experiences.

The IMS is superimposed on the packet domain network and consists of functional entities such as a Call State Control Function (CSCF) entity, a Media Gateway Control Function (MGCF) entity, a Media Resource Function (MRF) entity, and a Home Subscriber Server (HSS). The MGCF is used to implement interworking between the IMS network and other networks; the MRF is used to provide media resources, such as audio and video, codec, and multimedia conference bridges; the HSS is a user database for storing subscriber subscription data and configuration information.

CSCF can be divided into three logical entities: S-CSCF, Proxy CSCF (P-CSCF) and Query CSCF (I-CSCF). The S-CSCF is the service switching center of the IMS, and performs the session. Control, maintain session state, manage user information, generate billing information, etc.; P-CSCF is an access point for terminal users to access IMS, complete user registration, responsible for quality of service (QoS) control and security management, etc., I-CSCF Responsible for interworking between IMS domains, managing the allocation and selection of S-CSCFs, hiding network topology and configuration, and generating billing data.

In IMS, the Session Initiation Protocol (SIP) is used as the signaling control protocol for IP multimedia sessions; the HSS and I-CSCF and the Cx interface between the HSS and the S-CSCF use the Diameter protocol family for information exchange.

Since the implementation of IMS is independent of the type of terminal used by the user, IMS is not only applied to networks and applications related to 3GPP, and IMS can also be applied to packet networks, wireless local area networks (WLANs) or next generation networks defined in 3GPP2. (NGN).

When the user wants to access the IMS, the public user ID must be registered to the IMS network side for registration. The public user ID is used to identify the user in the IMS network. A subscriber terminal (UE) may have one or more subscribed public subscriber identities. All public user identifiers of a UE are separately registered, that is, the registration process of each public user identifier is independent, but since these public user identifiers belong to the same UE, the specification stipulates that when a certain UE uses a public user identifier After the registration is successful, after the S-CSCF allocated by the network side is obtained, when the UE registers with other public user identifiers, the network side must return to the same S-CSCF for use by the UE.

FIG. 1 is a flow chart of implementing the S-CSCF selection when registering in the IMS in the prior art, and the specific steps are as follows:

Step 100: The UE initiates a registration (REGISTER) message carrying the public user identifier of the user to the I-CSCF.

Step 101: The I-CSCF receives the message, and sends a query request carrying the public user identifier to the HSS, and queries the current registration status of the public user identifier.

Step 102: The HSS determines the public user identifier according to the stored user configuration information. If the current registration status is the registered status, step 103 is performed, if it is the unregistered status, step 104 is performed, and if it is the logout status, step 105 is performed.

There are three types of user registration status: registered status, unregistered status, and logout status. The registered status refers to a public user ID that successfully completes the registration (REGISTER) process, the S-CSCF to which the service is assigned; the logout status refers to a public user ID that has not initiated the REGISTER process at all; the unregistered status refers to A public user ID does not initiate a REGISTER procedure, but acts as the S-CSCF to which the called service is assigned.

Step 103: The HSS directly returns the name of the S-CSCF serving the user to the I-CSCF, and the I-CSCF directly selects the S-CSCF, and continues the subsequent interaction with the S-CSCF, and ends.

Step 104: The HSS returns, to the I-CSCF, S-CSCF capability information that meets the strictest service subscription requirement of the user, and an S-CSCF that has been allocated to the UE, to notify the I-CSCF to perform reselection, and the I-CSCF according to the foregoing information. Decide whether to initiate the process of selecting the S-CSCF, and continue the subsequent interaction with the selected S-CSCF, ending.

Step 105: The HSS returns, to the I-CSCF, the S-CSCF capability information that meets the strictest service subscription requirement of the user, to notify the I-CSCF to perform the selection, and the I-CSCF initiates the process of selecting the S-CSCF according to the S-CSCF capability information. And continue the subsequent interaction with the selected S-CSCF, and the end.

The above is the process when the first registration is not performed. When a public user identifier is registered for the first time (according to the received query message, the HSS can distinguish whether it is the process when the first registration is performed), the registration status of the public user identifier. It can only be an unregistered state or a logout state. Therefore, the HSS determines the returned information by determining whether it holds the name of the S-CSCF that has been allocated for the UE, that is, if it has saved the S that has been allocated for the UE. The name of the -CSCF is considered to be in the unregistered state, and step 104 is performed. If not, the identifier is currently in the logout state, and step 105 is performed. Similarly, when the user is the object to be accessed, the I-CSCF sends an inquiry request to the HSS after receiving the access request carrying the public user identifier of the user, and the HSS determines the user according to the public user identifier carried by the request. The registration status of the public user identifier is determined and the corresponding information is returned. The specific process is the same as that shown in FIG. 1, and the description is not repeated here.

The existing timing for determining the selection of the S-CSCF is problematic, mainly in the case where a certain public user identifier of a UE has been assigned an S-CSCF for its service, whether it is allocated due to an active application. Or passively assigned as an access object, when the I-CSCF carries the public user identity to query the HSS, if the state of the public user identity queried by the I-CSCF in the HSS is unregistered, the HSS will satisfy The S-CSCF capability information required by the user's most strict service subscription and the name of the saved S-CSCF are sent to the I-CSCF, regardless of whether the S-CSCF selected by the current I-CSCF may be the S-CSCF that satisfies the condition, It needs to be re-selected once; for the I-CSCF, according to the processing of the existing specification, when the S-CSCF capability information and the S-CSCF name are received at the same time, the S-CSCF selection is performed, according to the selection result and received. The names of the S-CSCFs are compared to determine which S-CSCF to use, thus making it very likely that the I-CSCF will initiate an invalid selection of the S-CSCF.

This is because > according to the specification, only one S-CSCF can provide services for one UE at a time, and the S-CSCF selected according to the requirements of the services subscribed by multiple public user IDs of the UE and returned by the HSS is in the absolute In most cases, it is able to meet the requirements of business services, because the change of contracted service requirements is still relatively small. It can be seen that the reselection by I-CSCF is likely to be redundant, which not only increases the Cx interface load, but also High demands are placed on the processing power of the I-CSCF.

In addition, when the HSS responds to the inquiry request of the I-CSCF, it only considers the status of the public user identifier carried in the current query request, and does not consider the registration status of other public user identifiers owned by the UE. In this way, when the query is carried in the request When the common user identity is in the logout state, if the other public user identity of the UE has actively or passively obtained the S-CSCF for its service, the HSS still only returns the S- that satisfies the strictest service subscription requirement of the user. CSCF capability information, without any measures to effectively prevent the I-CSCF from selecting the S-CSCF. At this time, the I-CSCF still has to reselect the S-CSCF, and the S-CSCF reselected by the I-CSCF at this time is likely. That is, the S-CSCF that has provided services for other public user identities of the UE. It can be seen that the reselection operation performed by the I-CSCF is redundant operation in most cases, which not only increases the load of the Cx interface, but also imposes high requirements on the processing capability of the I-CSCF. Summary of the invention

In view of this, the main object of the present invention is to provide two methods for implementing the timing of selecting a service call control function entity to prevent an invalid S-CSCF selection from being initiated, reduce the Cx interface load, and reduce the processing capability of the I-CSCF.

In order to achieve the above object, the technical solution of the present invention is achieved as follows:

A method for determining an opportunity to initiate a selection of a service call control function entity, the method comprising:

A. After receiving the query request for carrying the public user identifier from the querying call control function I-CSCF entity, the home subscriber server HSS determines whether the public subscriber identity is the first registration, and if yes, performs step C, otherwise, Step B;

B. The HSS determines the user according to the public user identifier carried in the request, and determines, according to the stored user configuration information, whether the current registration status of the public user identifier is a registered state, and if yes, stores the stored service for the user. The name of the call control function S-CSCF is sent to the I-CSCF to notify the I-CSCF to select and end; otherwise, step C is performed;

C. The HSS determines whether the assigned name of the S-CSCF that provides the service for the user is stored, and if yes, performs step D; otherwise, the HSS is from the stored subscription data of the user. Obtaining the S-CSCF capability information that meets the strictest service subscription requirement of the user, and sending the information to the I-CSCF to notify the I-CSCF to select and end;

D. The HSS determines whether the set S-CSCF selection condition is not met, and if not, sends the assigned name of the S-CSCF that provides the service to the I-CSCF; if satisfied, the HSS stores from the The user subscription data obtains the S-CSCF capability information that meets the strictest service subscription requirement of the user and the assigned name of the S-CSCF that provides the service for the user, and sends the name to the I-CSCF to notify the I-CSCF to select.

Preferably, the HSS in step C determines whether to store the name of the allocated S-CSCF serving the user, including the following steps:

The C HSS determines the registration status of the public user identifier carried in the query request. If it is an unregistered state, the HSS determines that the name of the assigned S-CSCF serving the user is stored; if it is the logout state, the step is performed. C2;

C2: The HSS determines whether there is an unregistered state of the public user identifier corresponding to the common user identifier carried in the query request corresponding to the user, and if yes, the HSS determines that the allocated S- serving for the user is stored. The name of the CSCF.

Preferably, before step C2, the method further includes:

C3. The HSS determines whether the public user identifier corresponding to the public user identifier other than the public user identifier carried in the query request has a registered status, and if yes, stores the stored public user identifier that is in the registered state. - The name of the CSCF is sent to the I-CSCF and ends; otherwise, step C2 is executed.

Preferably, the S-CSCF selection condition set in step D is: the user subscription data change stored in the HSS causes the S-CSCF capability information to change, or the S-CSCF configuration change causes the S-CSCF capability information to change; or, when The configuration of the S-CSCF changes and the original S-CSCF support capability is not a subset of the updated S-CSCF support capabilities.

Preferably, the HSS sets a selection flag for a user who satisfies the condition for selecting the S-CSCF; The process of determining whether the S-CSCF selection condition is not satisfied in step D is: determining whether the S-CSCF has a selection flag, and if so, conforming to the set S-CSCF selection condition; otherwise, Set the S-CSCF selection condition;

Step S: After the HSS obtains the S-CSCF capability information that meets the user subscription requirement and sends the information to the I-CSCF for S-CSCF selection, the method further includes: the HSS clearing the selection flag bit corresponding to the S-CSCF.

Preferably, the query request in step A is a registration status query request (Cx-Query or Cx-Select-Pull) or a user location query request (Cx-Location-Query).

A method for determining the timing of initiating the selection of the service call control function entity, the HSS saves the reselected S-CSCF by means of local operation and maintenance when the S-CSCF selection condition is met; the method further includes:

a. After receiving the query request from the I-CSCF entity that carries the public user identifier, the HSS determines the user according to the public user identifier carried in the request, and determines whether the allocated S-CSCF serving the user is stored. The name, if yes, perform step b; otherwise, obtain the S-CSCF capability information that meets the strictest service subscription requirement of the user, and send the capability information to the I-CSCF, and end;

The HSS determines whether the request carries the indication information that is desired to reselect the S-CSCF. If yes, the HSS obtains the S-CSCF capability information and the allocated information that meets the strictest service subscription requirement of the user from the stored user subscription data. The name of the S-CSCF is sent to the I-CSCF to inform the I-CSCF to make a selection; otherwise, the stored name of the S-CSCF serving the user is directly sent to the I-CSCF.

Preferably, the HSS determines whether to store the name of the allocated S-CSCF serving the user, including the following steps:

Al, the HSS determines the registration status of the public user identifier carried in the query request, and if it is unregistered and registered, the HSS determines that the allocated service for the user is stored. The name of the S-CSCF; if it is the logout state, proceed to step a2;

A2: The HSS determines whether there is an unregistered state or a registered state other public user identifiers other than the public user identifier carried in the query request corresponding to the user, and if yes, the HSS determines that the allocated user is stored. The name of the S-CSCF that provides the service.

Preferably, the set S-CSCF selection condition is: the user subscription data change stored in the HSS causes the S-CSCF capability information to change, or the S-CSCF configuration change causes the S-CSCF capability information to change; or, when S The configuration of the -CSCF changes and the original S-CSCF support capability is not a subset of the updated S-CSCF support capabilities.

Preferably, the query request in step A is a registration status query request (Cx-Query or Cx-Select-Pull), or a user location query request (Cx-Location-Quer).

It can be seen from the above solution that when the HSS receives the query request containing the public user identity sent by the I-CSCF, if it is determined that the current registration status of the public user identity is not the registered state, the S-CSCF already has If the service is provided, the S-CSCF capability information of the user is not directly sent to the I-CSCF as in the prior art, but is determined according to the condition that the S-CSCF is selected in the HSS in advance, and if the condition is met, The I-CSCF sends the S-CSCF capability information of the user. Otherwise, the name of the already assigned S-CSCF serving the user is sent to the I-CSCF without the I-CSCF to select. Therefore, since the S-CSCF condition can be set as needed, the method provided by the present invention can reduce the number of times the S-CSCF is initiated, prevent the initiating invalid S-CSCF selection, reduce the Cx interface load, and reduce the processing of the I-CSCF. Ability requirements.

Further, if the HSS determines that an S-CSCF satisfies the condition for selecting the S-CSCF, it can be modified directly in the local database by operation and maintenance to update the S-CSCF. In this way, when the I-CSCF queries the HSS for the S-CSCF currently serving the user, the direct result is the name of the S-CSCF that can meet the requirements of the subscription service, and thus the subsequent S-CSCF reselection process is not required. When using this method, only HSS The HSS returns the relevant S-CSCF capability information when the I-CSCF explicitly requires S-CSCF reselection. Applying this method also avoids transferring a large amount of redundant information on the Cx interface, preventing the I-CSCF from initiating invalid S-CSCF selection and reducing the burden on the device. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of implementing the S-CSCF selection when registering in the IMS in the prior art; FIG. 2 is a flow chart of determining the timing of initiating the selection of the S-CSCF when the user first registers in the present invention;

Figure 3 is a flow chart showing the timing of initiating the selection of the S-CSCF in the process of non-first registration or as the object to be accessed. Mode for carrying out the invention

In order to make the objects, technical solutions and advantages of the present invention more comprehensible, the present invention will be further described in detail with reference to the accompanying drawings.

2 is a flow chart of determining the timing of initiating the selection of the S-CSCF when the user first registers, the specific steps of which are:

Step 200: The I-CSCF receives a first registration message that is sent by the user and carries a public user identifier.

Step 201: The I-CSCF sends a query request that carries the public user identifier to the HSS, and the message indicates that the first public registration is based on the public user identifier.

Step 202: The HSS determines the user according to the public user identifier carried in the request, and determines whether the S-CSCF for the user has been allocated for the user, that is, determines the status of the public user identifier, and if it is not registered, executes Step 203; If it is the logout state, go to step 206;

Step 203: The HSS determines whether the S-CSCF meets the set initiated S-CSCF selection. The condition, if yes, perform step 204; otherwise, perform step 205;

Step 204: According to the prior art, the HSS queries the subscription data of the user according to the stored user configuration information, and carries the S-CSCF capability information that meets the strictest service subscription requirement of the user and has been allocated in the message that returns the query request. The name of the S-CSCF serving the user to notify the I-CSCF to make a selection, and the I-CSCF determines whether to initiate the S-CSCF selection of the user according to the above information, and continues the subsequent interaction with the selected S-CSCF; End;

Step 205: The HSS carries the name of the S-CSCF that has been allocated to provide the service to the I-CSCF, and the I-CSCF directly selects the S-CSCF, and continues with the S-CSCF. Subsequent interaction; end;

Step 206, the HSS determines the registration status corresponding to the other public user IDs of the user, if it is the unregistered state, step 203; if it is the registered state, step 205; if it is the logout state, step 207;

Step 207: According to the prior art, the HSS queries the subscription data of the user according to the stored user configuration information, and carries the S-CSCF capability information that meets the strictest service subscription requirement of the user in the message that returns the query request, to notify the I. - The CSCF makes a selection, and the I-CSCF decides whether to initiate the S-CSCF selection of the user according to the above information, and continues the subsequent interaction with the selected S-CSCF.

How do I make an S-CSCF selection when the user is in the process of registration other than the first registration, or when it is accessed as an access object? As shown in FIG. 3, the specific steps are as follows: Step 300: The I-CSCF receives a user initiated registration message (REGESITE) or accesses the user's message (INVITE), and sends a query request carrying the user's public user identity to the HSS. Query the current registration status of the user;

Step 301: The HSS determines the user according to the public user identifier carried in the request, and determines the current registration status of the public user identifier. If the status is already registered, the step is performed. 302, if it is an unregistered state, step 303 is performed, if it is a logout state, step 306 is performed;

Step 302: The HSS directly returns the name of the S-CSCF that provides the service to the I-CSCF, and the I-CSCF directly selects the S-CSCF to continue the subsequent interaction with the S-CSCF;

Step 303: The HSS determines whether the S-CSCF currently serving the user satisfies the set condition for initiating the S-CSCF selection, and if yes, step 304 is performed; otherwise, step 305 is performed;

Step 304: According to the prior art, the HSS queries the subscription data of the user, and carries the S-CSCF capability information that meets the strictest service subscription requirement of the user and the assigned information for the user in the query request message returned by the I-CSCF. The name of the S-CSCF providing the service to notify the I-CSCF to make a selection, and the I-CSCF determines whether to initiate the S-CSCF selection of the user according to the above information, and continues the subsequent interaction with the selected S-CSCF;

Step 305: The HSS carries the name of the S-CSCF that has been allocated for the user in the message that returns the query request, and sends the message to the I-CSCF, and the I-CSCF directly selects the S-CSCF to continue the subsequent interaction with the S-CSCF. End;

Step 306, the HSS determines the registration status corresponding to the other public user IDs of the user, if it is unregistered, step 303; if it is the registered state, step 305; if it is the logout state, step 307;

Step 307: The HSS queries the subscription data of the user, and carries the S-CSCF capability information that meets the strictest service subscription requirement of the user in the return query request message, to notify the I-CSCF to select, and the I-CSCF receives the received information according to the The capability information selects the S-CSCF according to the existing manner, and continues the subsequent interaction with the selected S-CSCF, and the HSS saves the name of the S-CSCF selected by the I-CSCF;

In the flow shown in Figures 2 and 3, the set S-CSCF selection condition that has been set can be The operator is configured in the HSS when the network is configured, and the set S-CSCF selection information may be: When the user subscription data stored in the HSS changes, the S-CSCF capability information selected according to the user subscription data is caused. If there is a change, then the HSS considers that it satisfies the condition of the initiated S-CSCF selection; when the configuration of the S-CSCF changes and the original S-CSCF support capability is not a subset of the updated S-CSCF support capability, then the HSS considers It is a condition that satisfies the set S-CSCF selection. Similar conditions can be added based on the operator's network configuration and operational conditions.

After the HSS considers that an S-CSCF satisfies the set S-CSCF selection condition, the flag corresponding to the S-CSCF may be further set, so that the next time the user accepting the S-CSCF service initiates registration, or When re-registering, or as an unregistered accessed object, the HSS determines whether the S-CSCF currently providing the user with the monthly service satisfies the set condition of initiating the S-CSCF selection to determine the status of the flag bit, thereby According to the flag bit, the information returned to the I-CSCF is determined. After the S-CSCF selected by the I-CSCF is re-saved in the HSS, the flag is cleared, thus ensuring that the S-CSCF currently serving the user must be able to satisfy. The S-CSCF required by the user for all contracted data.

In addition to the above method for determining when to perform the selection process of the S-CSCF, the present invention can also determine by the operator when to perform the selection process of the S-CSCF. The process is as follows: When the settings in the HSS are changed, such as the user's subscription data update, or the S-CSCF configuration upgrade, etc., the S-CSCF needs to be re-selected for the user. The HSS can be directly operated and maintained. Make changes in the local database. When the next time the I-CSCF queries the HSS for the S-CSCF currently serving the user, the direct result is the S-CSCF that can meet the contracted service requirements, so the subsequent S-CSCF selection process is not needed.

When using the operator's own method of determining when to perform S-CSCF selection, it is usually not necessary for the HSS to notify the I-CSCF to reselect, but only when the I-CSCF requires S-CSCF selection, ie I- CSCF is registering status query requests (Cx-Query or When the Cx-Select-Pull) or the Cx-Location-Query carries the indication information that wants to reselect the S-CSCF, the HSS returns the S-CSCF capability information and the allocated service for the user. The name of the S-CSCF for the I-CSCF to decide whether to make an S-CSCF selection. That is, after receiving the inquiry request of the I-CSCF, the HSS determines whether the S-CSCF has been allocated to the user, and if not, the HSS returns the S-CSCF capability information that satisfies the strictest contracting requirement of the user to the I-CSCF. If the S-CSCF has been allocated to the user, the name of the saved S-CSCF is directly returned to the I-CSCF without determining whether the condition for initiating the S-CSCF selection is met.

By determining the real timing of initiating the S-CSCF selection, the present invention realizes that the HSS notifies the I-CSCF to initiate the S-CSCF selection only when the conditions for initiating the S-CSCF selection set by the operator are met, thereby avoiding a large number of transmissions on the Cx interface. Redundant information, causing equipment burden and wasting processing power.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the present invention. Within the scope of protection.

Claims

Claim

A method for determining an opportunity to initiate a selective service call control function entity, the method comprising:

C, the HSS determines whether the assigned name of the S-CSCF that provides the service for the user is stored, and if yes, performs step D; otherwise, the HSS obtains the most stringent service contracting requirement from the stored user subscription data. The S-CSCF capability information is sent to the I-CSCF to notify the I-CSCF to select and end;

D. The HSS determines whether the set S-CSCF selection condition is not met, and if not, sends the assigned name of the S-CSCF that provides the monthly service to the I-CSCF; if satisfied, the HSS is stored. The user subscription data obtains the S-CSCF capability information that meets the strictest service subscription requirement of the user and the assigned name of the S-CSCF that provides the service for the user, and sends the name to the I-CSCF to notify the I-CSCF to make a selection.

2. The method according to claim 1, wherein the step S: the HSS determining whether to store the assigned name of the S-CSCF serving the user comprises the following steps:

The C HSS determines the registration status of the public user identifier carried in the query request. If it is an unregistered state, the HSS determines that the allocated service for the user is stored. The name of the S-CSCF; if it is the logout state, step C2 is performed;

3. The method of claim 2, wherein before step C2, the method further comprises:

C3. The HSS determines whether the public user identifier other than the public user identifier carried in the query request corresponding to the user has a registered status, and if yes, stores the stored public user identifier that is in the registered state. - The name of the CSCF is sent to the I-CSCF and ends; otherwise, step C2 is executed.

The method according to claim 1, wherein the S-CSCF selection condition set in step D is: the user subscription data change stored in the HSS causes the S-CSCF capability information to change, or the S-CSCF configuration change. Causes the S-CSCF capability information to change; or, when the configuration of the S-CSCF changes and the original S-CSCF support capability is not a subset of the updated S-CSCF support capabilities.

5. The method of claim 1 wherein the HSS sets a selection flag for a user who satisfies the selection of the S-CSCF condition;

The process of determining whether the S-CSCF selection condition is not satisfied in step D is: determining whether the S-CSCF has a selection flag, and if so, conforming to the set S-CSCF selection condition; otherwise, Set the S-CSCF selection condition;

6. The method according to claim 1, wherein the query request in step A is a registration status query request (Cx-Query or Cx-Select-Pull), or a user location query. Request ( Cx-Location-Query ).

7. A method for determining a timing of initiating a selective service call control function entity, wherein the HSS saves the reselected S-CSCF by means of local operation and maintenance when the set S-CSCF selection condition is met; The method also includes:

After receiving the query request from the I-CSCF entity that carries the public user identifier, the HSS determines the user according to the public user identifier carried in the request, and determines whether the assigned name of the S-CSCF that provides the service for the user is stored. If yes, perform step b; otherwise, obtain S-CSCF capability information that meets the strictest service subscription requirement of the user, and send the capability information to the I-CSCF, and end;

8. The method according to claim 7, wherein the HSS determines whether to store the assigned name of the S-CSCF that provides the user with the service includes the following steps:

Al, the HSS determines the registration status of the public user identifier carried in the query request, and if it is an unregistered and registered state, the HSS determines that the name of the allocated S-CSCF serving the user is stored; if it is the logout state, Then performing step a2;

The method according to claim 7, wherein the set S-CSCF selection condition is: the user subscription data change stored in the HSS causes the S-CSCF capability information to change, or the S-CSCF configuration change causes S-CSCF capability information changes; or, when S-CSCF The configuration changes and the original S-CSCF support capability is not a subset of the updated S-CSCF support capabilities.

10. The method according to claim 7, wherein the query request in step A is a registration status query request (Cx-Query or Cx-Select-Pull), or a user location query request (Cx-Location-Query). .