CN101291448A - Method, system and device for called routing - Google Patents

Abstract

The invention discloses a called routing method, system and device, which can insert a user agent network element into the call path after the DSF selects to connect to the CS domain to connect the session, and route the call request message to the user through the user agent network element. The method of the present invention includes: after the domain selection entity DSF selects to connect the session in the CS domain, add relevant information about routing the call request message to the user agent network element in the call request message delivered to the S-CSCF; the S-CSCF according to the The relevant information routes the call request message to the user agent network element; and the user agent network element routes the call request message to the original called user through the CS domain according to the obtained routing information.

Description

Method, system and device for called routing

technical field

The invention relates to the communication field, in particular to a method, system and device for called routing.

Background technique

IMS is the IP multimedia subsystem in the WCDMA network defined by the 3GPP R5/R6 standard. It is the target network for the 3G mobile network to realize packet voice and packet data and provide unified multimedia services and applications. The IMS uses the IP packet domain as the bearer channel for its control signaling and media transmission, and uses the SIP protocol as the call control signaling. In IMS, IMS user subscription data is centrally managed in HSS, the service is provided by the application server AS, and the session control is completed by the S-CSCF. The two are completely separated in the network structure, and the service is triggered by the S-CSCF to the AS for processing. Multiple ASs can work together. The user accesses the IMS through the proxy node P-CSCF at the current location, and the session and service control are completed by the home domain service node where the user is registered. Therefore, the user can always get the same service at different access points, realizing service management and session control. The separation of the three and the bearer access, as well as the provision of services independent of access and location.

IMS is a description of 3GPP and Tispan. In 3GPP2, there is also a similar multimedia subsystem called MMD (Multimedia Domain, Multimedia Domain), which has a similar structure to IMS. Therefore, for the sake of simplicity, the situation of MMD is not considered below. But obviously what is described below also applies to MMD.

[GRUU related background technology]

When calling, for the situation where multiple terminals share the IMPU, in order to prevent SIP REQUEST from forking to multiple UEs, IETF and 3GPP introduced the concept of GRUU. GRUU is composed of IMPU and UE's Instance ID. Among them, Instance ID is a globally unique ID used to identify UE Instance, so that GRUU can uniquely identify a UE. Even if the IMPU is shared by multiple UEs, using GRUU as the REQUEST URI can still ensure that the SIP message is sent to the only specified UE.

【Background technology related to feature tag】

This is an application mechanism added by IETF to SIP signaling (refer to RFC 3840), which is used to add various parameters after the contact header field to indicate various application capabilities of the terminal, such as audio capabilities, video capabilities, and mobility capabilities , supported languages, usage (commercial or personal), supported SIP methods, priority, etc. The other mechanism is "Caller Preferences" proposed by IETF in RFC 3841. This mechanism is used in conjunction with the above feature tag. The calling party can specify some applications that the called terminal should have according to the attributes of the session. characteristics, or application characteristics that should not have (carried in the Accept-contact header field), let the network search for the most suitable terminal to connect to according to the specified application capabilities among multiple terminals used by the called party.

【Introduction to DSAI】

DSAI is an identifier that identifies whether a certain service is activated or not, allowing the AS to dynamically set whether a certain service is activated or not. If activation is not required, set a service to Inactive through the SH interface, the HSS sets the iFC corresponding to the service to Inactive, and sends the updated iFC to the S-CSCF, so that the call will not be triggered in the corresponding AS. The essence of DSAI is that the AS can activate or deactivate one or some iFCs as needed.

[Background of ICS]

During the evolution of the network to IMS, there will be a situation where CS and IMS coexist for a period of time. At this time, users hope that there is a control point in the network that can centrally control their services in the two domains, so as to reduce deployment and management costs. Cost and providing a consistent service experience, this centralized control point is generally located in the IMS network and implemented by the AS. That is, when a user accesses through the CS network, services are also provided for the user on the IMS network. At present, this topic is involved in 3GPP's centralized service control and TISPAN. In the 3GPP's centralized service control research project, the ICS architecture is shown in Figure 1:

Among them, ICCF is called the IMS CS Control Function (IMS CS Control Function), which completes the adaptation between the CS domain signaling and the IMS domain SIP signaling, and as a user agent, realizes the user's service control in the IMS domain and interact. In this way, when the domain selection entity DSF in the VCC AS selects the CS to connect the session, in order to control subsequent services, the call needs to be routed to the ICCF, and then the ICCF routes the call to the user through the CS domain.

In the current VCC standard, when the domain selection entity DSF chooses to connect to the CS domain, it will determine the routing number (CSRN) to the CS domain, and the VCC AS will modify the Request-uri to CSRN, thereby routing the call to CS Domain, so that the call will not trigger to other AS again. The specific process is shown in Figure 2, including a series of steps:

1. The S-CSCF receives a call request message directed to the user.

2. The S-CSCF triggers the call request message to the DSF according to the trigger rule of the iFC.

3-4. The DSF performs domain selection, selects the CS domain to connect to the session according to its own domain selection rules, and then determines the CSRN.

5. The DSF delivers the call to the S-CSCF;

6. The S-CSCF finds that the Request-uri is CSRN, and routes the call request message to the MGCF (the interaction with the BGCF is omitted).

7-9. The MGCF determines the MSRN according to the CSRN, and then routes the call request message to the original called user.

The inventor believes that it can be seen from Figure 2 that after the DSF chooses to connect to the CS domain, it will change the Request-uri to CSRN, so that the call will be routed directly to the CS domain through the S-CSCF, but in the ICS project, it is necessary to Insert ICCF in the call path between DSF and S-CSCF, so that ICCF can participate in the control of subsequent services.

Contents of the invention

Embodiments of the present invention provide a method, system and device for called routing. After the DSF is selected to connect to the CS domain to connect the session, a user agent network element can be inserted in the call path, and the call request message can be routed through the user agent network element to user.

The called routing method according to the embodiment of the present invention includes: after the domain selection entity DSF selects the CS domain to connect the session, adding the relevant information of routing the call request message to the user agent network element in the call request message sent to the S-CSCF information; the S-CSCF routes the call request message to the user agent network element according to the relevant information; and the user agent network element routes the call request message to the original called user through the CS domain according to the obtained routing information.

The domain selection entity in the embodiment of the present invention includes: a domain selection unit, configured to select a connection session to the CS domain or a connection session to the PS domain; a first adding unit, configured to, when the domain selection unit selects a connection session to the CS domain, Relevant information about routing the call request message to the user agent network element is added to the call request message to be sent; the sending unit is configured to send the call request message processed by the first adding unit to the S-CSCF.

The user agent network element in the embodiment of the present invention includes: a receiving unit, configured to receive a call request message;

The obtaining unit is used to obtain the routing information of the original called user number or the CS domain; the determining unit is used to determine the routing information according to the routing information of the original called user number or the CS domain obtained by the obtaining unit; the routing unit is used to determine the routing information according to the The routing information determined by the determining unit routes the call request message to the original called user via the CS domain.

The called routing system in the embodiment of the present invention includes: DSF, S-CSCF, user agent network element and the original called user terminal; the DSF is used to select the CS domain to connect the session, and sends it to the S-CSCF Add relevant information about routing the call request message to the user agent network element in the call request message; S-CSCF is used to route the call request message to the user agent network element according to the relevant information; the user agent network element uses Based on the obtained routing information, the call request message is routed to the original called user terminal through the CS domain.

Another called routing method in the embodiment of the present invention includes: when the user is attached in the CS domain and not registered in the PS domain, the user agent network element will trigger the iFC activation to the user agent network element through the DSAI mechanism; then the DSF When choosing to connect to the CS domain, send the call request message to the S-CSCF; the S-CSCF triggers the call request message to the user agent network element according to the iFC; and the user agent network element sends the The call request message is routed to the original called user through the CS domain.

In the embodiment of the present invention, after the DSF selects the CS domain to connect the session, it adds relevant information about routing the call request message to the user agent network element in the call request message sent to the S-CSCF, so the S-CSCF can according to the The above related information routes the call request message to the user agent network element; then the user agent network element routes the call request message to the original called user through the CS domain according to the obtained routing information. Therefore, after the DSF chooses to connect to the CS domain to connect the session, the user agent network element can be inserted into the call path, and the call request message can be routed to the user through the CS domain through the user agent network element, which meets the requirements of the ICS project.

In the embodiment of the present invention, when the user is attached in the CS domain and not registered in the PS domain, the user agent network element will trigger the iFC activation of the user agent network element through the DSAI mechanism; therefore, according to the existing process, it can be realized After the DSF chooses to connect to the CS domain, it can insert a user agent network element in the call path, and route the call request message to the user through the CS domain through the user agent network element, which meets the requirements of the ICS project.

Description of drawings

Figure 1 is a schematic diagram of the ICS architecture in the existing 3GPP centralized service control research project;

Fig. 2 is the routing flowchart after the existing DSF selects to connect the session to the CS domain;

Fig. 3 is a flow chart of method steps of a called routing method according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a domain selection entity according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a user agent network element according to an embodiment of the present invention;

FIG. 6 is a flowchart of Embodiment 1 of the present invention;

FIG. 7 is a flowchart of Embodiment 2 of the present invention;

FIG. 8 is a flowchart of Embodiment 3 of the present invention;

FIG. 9 is a flowchart of Embodiment 4 of the present invention;

FIG. 10 is a flowchart of Embodiment 5 of the present invention;

FIG. 11 is a flowchart of steps of another called routing method according to an embodiment of the present invention;

Fig. 12 is a flow chart of Embodiment 6 of the present invention.

Detailed ways

In order to realize that after the DSF selects the CS domain to connect the session, a user agent network element may be inserted in the call path, and the call request message is routed to the user via the user agent network element.

Embodiments of the present invention provide a method for called routing, as shown in FIG. 3 , including the following steps:

S11. The DSF selects to continue the session in the CS domain.

S12. The DSF adds relevant information about routing the call request message to the user agent network element in the call request message delivered to the S-CSCF.

Wherein, the relevant information may be the PSI of the user agent network element; then the DSF obtaining the PSI of the user agent network element includes the following steps: the DSF sends signaling to the HSS to obtain the MSRN of the original called user; the user agent network element performs signaling interception , and return the PSI of the user agent network element in a response message of the intercepted signaling; and the DSF obtains the PSI of the user agent network element from the response message. or,

The relevant information is the PSI of the user agent network element; the DSF obtains the relevant information from the locally statically configured PSI of the user agent network element. or,

The relevant information is the calling preference information, and the DSF obtaining the calling preference information includes the following steps: when the user agent network element registers on behalf of the user, it carries the user's Feature tag in the registration request message; the S-CSCF reports the user's Feature tag to DSF. The caller preference information added by the DSF is the information reported by the user in the Feature tag. or,

The related information is the GRUU of the user agent network element; then the DSF obtains the GRUU of the user agent network element including the following steps: when the user agent network element registers on behalf of the user, it carries the instance-id in the registration request message; The instance-id in the received registration request message allocates a GRUU for the user agent network element, and reports the GRUU to the DSF. or,

The relevant information is the information that triggers the initial filtering rule iFC, and the S-CSCF performs iFC matching according to the relevant information added by the DSF in the call request message, and triggers the call request message to the user agent network element according to the matched iFC .

S13. The S-CSCF routes the call request message to the user agent network element according to the relevant information.

S14. According to the obtained routing information, the user agent network element routes the call request message to the original called user (that is, the called user originally targeted by the call request message) via the CS domain.

An embodiment of the present invention also provides a domain selection entity, as shown in FIG. 4 , which includes: a domain selection unit, a first adding unit, and a sending unit; further includes: an acquiring unit and a second adding unit.

The domain selection unit is used for selecting to connect the session to the CS domain or to connect the session to the PS domain.

The acquiring unit is configured to acquire relevant information about routing the call request message to the user agent network element, and hand it over to the first adding unit for processing.

The first adding unit is configured to add relevant information about routing the call request message to the user agent network element in the call request message to be delivered when the domain selection unit selects to connect to the CS domain to connect the session.

The second adding unit is configured to add the original called user number or the routing information of the CS domain to the call request message to be delivered.

The sending unit is configured to send the call request message processed by the first adding unit, or the first adding unit and the second adding unit, to the S-CSCF.

The embodiment of the present invention also provides a user agent network element, as shown in FIG. 5 , which includes: a receiving unit, an obtaining unit, a determining unit, and a routing unit.

The receiving unit is used for receiving the call request message.

The obtaining unit is used to obtain the routing information of the original called user number or CS domain.

The determining unit is configured to determine the routing information according to the original called party number or the routing information of the CS domain obtained by the obtaining unit.

The routing unit is configured to route the call request message to the original called user via the CS domain according to the routing information determined by the determining unit.

The embodiment of the present invention also provides a called routing system, including: DSF (that is, the DSF in the embodiment of the present invention), S-CSCF, a user agent network element (that is, the user agent network element in the embodiment of the present invention) and the original The called user terminal.

The DSF is used to select the CS domain to connect the session, and add relevant information about routing the call request message to the user agent network element in the call request message delivered to the S-CSCF.

The S-CSCF is configured to route the call request message to the user agent network element according to the relevant information.

The user agent network element is configured to route the call request message to the original called user terminal via the CS domain according to the obtained routing information.

Describe in detail below through 5 embodiments.

[Embodiment 1] The PSI of the ICCF is returned by means of signaling interception, and the call request message is routed to the user through the CSRN. See shown in Figure 6, including the following steps:

1. The S-CSCF receives a call request message directed to the user.

2. The S-CSCF triggers the call request message to the DSF according to the trigger rule of the iFC.

3. The DSF performs domain selection, selects the CS domain to connect the session according to its own domain selection rules, and sends an SRI command to the HSS to obtain the MSRN of the original called user.

4. The ICCF intercepts the signaling, and returns its own PSI in the response message of the SRI message.

5. The DSF fills the PSI of the ICCF obtained from the response message into the Request-uri of the call request message, and fills in the CSRN of the original called user (converted from the MSRN in the response message) into the call request message. P-Called-Party-ID header field (or fill in the CSRN of the original called user in the History-info header field, or other header fields), and then send the call request message to the S-CSCF.

6. The S-CSCF routes the call request message to the ICCF according to the PSI of the ICCF in the Request-uri of the call request message.

7. The ICCF determines the CSRN of the original called user, fills the CSRN into the Request-uri of the call request message, and then sends the call request message to the S-CSCF.

8. The S-CSCF finds that the Request-uri in the call request message is CSRN, and routes the call request message to the MGCF (the interaction with the BGCF is omitted).

9. The MGCF determines the MSRN according to the CSRN, and then routes the call request message to the original called user.

[Embodiment 2] The PSI of the ICCF is statically configured in the DSF, and the call request message is routed to the user through the CSRN. Referring to shown in Figure 7, including the following steps:

1. The S-CSCF receives a call request message directed to the user.

2. The S-CSCF triggers the call request message to the DSF according to the trigger rule of the iFC.

3. The DSF performs domain selection, and according to its own domain selection rules, selects the CS domain to connect to the session, and fills in the configured PSI of the ICCF in the Request-uri of the call request message, and fills in the number information of the original called user into the P-Called-Party-ID header field of the call request message (or fill in the number information of the original called user in the History-info header field, or other header fields), and then send the call request message to S -CSCF.

4. The S-CSCF routes the call request message to the ICCF according to the PSI of the ICCF in the Request-uri of the call request message.

5. ICCF determines the CSRN of the original called user (converted from the number information of the original called user), fills the CSRN into the Request-uri of the call request message, and then sends the call request message to the S-CSCF .

6. The S-CSCF finds that the Request-uri in the call request message is CSRN, and routes the call request message to the MGCF (the interaction with the BGCF is omitted).

7. The MGCF determines the MSRN according to the CSRN, and then routes the call request message to the original called user.

[Embodiment 3] The call request message is routed to the ICCF through the caller preference mechanism, and the call request message is routed to the user through the CSRN. Shown in Fig. 8, comprise the following steps:

1. The S-CSCF receives a call request message directed to the user (the Request-uri of the call request message carries the number information of the original called user).

2. The S-CSCF triggers the call request message to the DSF according to the trigger rule of the iFC.

3. The DSF performs domain selection, and selects the CS domain to connect to the session according to its own domain selection rules, and then fills in the CS connection session information Accept-Contact in the Accept-Contact header field of the call request message: Access-type=CS . And the routing information (CSRN) of the CS domain is carried in the P-Called-Party-ID header field or the History-info header field of the call request message. Then send the call request message to the S-CSCF.

4. According to the requirements in the Accept-Contact of the call request message, the S-CSCF finds that the connection of the ICCF meets the requirements (when the ICCF registers on behalf of the user, the access network type has been reported, so the S-CSCF will record that the user is in the ICCF The registration at the location is in the CS domain, so according to Access-type=CS, the ICCF is located), so the call request message is routed to the ICCF.

5. ICCF directly fills the CSRN carried in the P-Called-Party-ID header field or History-info header field of the call request message into the Request-uri of the call request message, and then sends the call request message to the S- CSCF; or determine the CSRN (converted) according to the original called party number information carried in the Request-uri of the call request message, and fill in the CSRN in the Request-uri of the call request message, and then send the call request message to S-CSCF.

6. The S-CSCF finds that the Request-uri in the call request message is CSRN, and routes the call to the MGCF (the interaction with the BGCF is omitted).

7. The MGCF determines the MSRN according to the CSRN, and then routes the call to the original called user.

【Note】

1. In this embodiment, ICCF is required to use the Feature tag mechanism to report that the user's access network type is CS when registering on behalf of the user.

2. In step 3 of FIG. 8, the DSF may also fill in the information of rejecting PS access, for example: Reject-Contact: Access-type=PS. It is equivalent to the information Accept-Contact: Access-type=CS to connect to the CS.

[Embodiment 4] The call request message is routed to the ICCF through the GRUU. Shown in Fig. 9, comprise the following steps:

1. The S-CSCF receives a call request message directed to the user.

2. The S-CSCF triggers the call request message to the DSF according to the trigger rule of the iFC.

3. The DSF performs domain selection. According to its own domain selection rules, it selects the CS domain to connect the session, and fills the GRUU of the ICCF into the Request-uri of the call request message, and puts the number information of the original called user into the P -Called-Party-ID header field or History-info header field. Then send the call request message to the S-CSCF.

4. The S-CSCF locates the connection to the ICCF according to the GRUU in the Request-uri of the call request message, and then routes the call request message to the ICCF.

5. ICCF finds the number of the original called user from the P-Called-Party-ID header field or History-info header field of the call request message, and changes the Request-uri to the number of the original called user, and then calls The request message is sent to MGCF.

6. The MGCF routes the call to the user according to the normal call flow.

【Note】

In this embodiment, the ICCF is required to logically generate an instance-id when registering on behalf of the user, so that the S-CSCF can use the instance-id to assign a GRUU to the ICCF, and report the GRUU to the DSF.

[Embodiment 5] The information added by the DSF triggers the iFC, and the call request message is routed to the ICCF according to the iFC, and the call request message is routed to the user through the CSRN. Shown in Fig. 10, comprise the following steps:

1. The S-CSCF receives a call request message directed to the user. (The Request-uri of the call request message carries the original called user number information).

2. The S-CSCF triggers the call request message to the DSF according to the trigger rule of the iFC.

3. The DSF performs domain selection, selects the CS domain to connect to the session according to its own domain selection rules, and adds an indication S in the Accept-Contact header field of the call request message, or in the History-info header field or other header fields - The CSCF routes the call request message to the iFC trigger information of the ICCF, and then sends the call request message to the S-CSCF.

4. The S-CSCF routes the call request message to the ICCF according to the triggered iFC.

5. ICCF determines the CSRN (converted) according to the original called party number information carried in the Request-uri of the call request message, and fills the CSRN into the Request-uri of the call request message, and then sends the call request message to S-CSCF.

6. The S-CSCF finds that the Request-uri is CSRN, and routes the call request message to the MGCF (the interaction with the BGCF is omitted).

7. The MGCF determines the MSRN according to the CSRN, and then routes the call request message to the original called user.

The embodiment of the present invention also provides another called routing method, as shown in FIG. 11 , including the following steps:

S21. When the user attaches to the CS domain, the user agent network element triggers iFC activation to the user agent network element through the DSAI mechanism.

S22. When the DSF chooses to connect to the CS domain to connect the session, it sends the call request message to the S-CSCF.

S23. The S-CSCF triggers the call request message to the user agent network element according to the iFC.

S24. The user agent network element routes the call request message to the original called user through the CS domain according to the obtained routing information.

The following is a specific description through an embodiment.

[Embodiment 6] Triggered by the DSAI mechanism, the call request message is routed to the ICCF, and the call request message is routed to the user through the CSRN. Shown in Fig. 12, comprise the following steps:

1. The S-CSCF receives a call request message directed to the user.

2. The S-CSCF triggers the call request message to the DSF according to the trigger rule of the iFC.

3. The DSF performs domain selection, and according to its own domain selection rules, selects the CS domain to connect to the session, and can carry the route of the CS domain in the P-Called-Party-ID header field or History-info header field of the call request message information, and then send the call request message to the S-CSCF.

4. The S-CSCF triggers the call request message to the ICCF according to the iFC trigger rule.

5. ICCF obtains the MSRN of the original called user through HSS/HLR to VLR query, then determines the CSRN of the original called user according to the MSRN, and fills the CSRN into the Request-uri of the call request message, and then sends the call request message Send it to the S-CSCF. The CSRN of the originally called user may also be determined by using the routing information of the CS domain carried in the P-Called-Party-ID header field or the History-info header field of the call request message.

6. The S-CSCF finds that the Request-uri is CSRN, and routes the call request message to the MGCF (the interaction with the BGCF is omitted).

7. The MGCF determines the MSRN according to the CSRN, and then routes the call request message to the original called user.

【Note】

1. In this embodiment, the ICCF is required to use the DSAI mechanism to activate the iFC routed to the ICCF, and then send it to the S-CSCF for use in step 4. When the user logs out in the CS domain, the call request message does not need to be routed to the ICCF. At this time, the user agent network element triggers the iFC deactivation of the user agent network element through the DSAI mechanism.

2. In step 5 of this embodiment, ICCF obtains the MSRN of the original called user through HSS/HLR to VLR query, and then determines the CSRN process of the original called user according to the MSRN, which is also applicable in embodiments 1 to 5; embodiment The ways in which the ICCF obtains routing information from items 1 to 5 are also applicable in this embodiment.

In summary, in the embodiment of the present invention, after the DSF selects the CS domain to connect the session, it adds relevant information about routing the call request message to the user agent network element in the call request message sent to the S-CSCF, so S - The CSCF can route the call request message to the user agent network element according to the relevant information; then the user agent network element routes the call request message to the original called user through the CS domain according to the obtained routing information. Therefore, after the DSF chooses to connect to the CS domain to connect the session, the user agent network element can be inserted into the call path, and the call request message can be routed to the user through the CS domain through the user agent network element, which meets the requirements of the ICS project.

Further, the above embodiments 1 to 5 respectively describe different situations in which the call request message is routed to the relevant information of the user agent network element.

In the embodiment of the present invention, when the user is attached in the CS domain and not registered in the PS domain, the user agent network element will trigger the iFC activation of the user agent network element through the DSAI mechanism; therefore, according to the existing process, it can be realized After the DSF chooses to connect to the CS domain, it can insert a user agent network element in the call path, and route the call request message to the user through the CS domain through the user agent network element, which meets the requirements of the ICS project.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (18)

1. A method for called routing, characterized in that, comprising the following steps: After the domain selection entity DSF selects the CS domain to connect the session, it adds relevant information about routing the call request message to the user agent network element in the call request message sent to the S-CSCF; The S-CSCF routes the call request message to the user agent network element according to the relevant information; and The user agent network element routes the call request message to the original called user through the CS domain according to the obtained routing information. 2. The method according to claim 1, wherein the relevant information is the PSI of the user agent network element; Obtaining the PSI of the user agent network element by the DSF includes the following steps: DSF sends signaling to the HSS to obtain the MSRN of the original called user; the user agent network element intercepts the signaling, and returns to the user agent network element in the response message of the intercepted signaling. The PSI of the element; and the DSF obtains the PSI of the user agent network element from the response message. 3. The method according to claim 1, wherein the relevant information is the PSI of the user agent network element; and the DSF obtains the relevant information from the locally statically configured PSI of the user agent network element. 4. The method according to claim 1, wherein the relevant information is caller preference information; The DSF obtains the calling preference information including the following steps: when the user agent network element registers on behalf of the user, it carries the user's Feature tag in the registration request message; the S-CSCF reports the user's Feature tag to the DSF. 5. The method according to claim 1, wherein the relevant information is a GRUU pointing to a user agent network element; The DSF obtains the GRUU of the user agent network element including the following steps: when the user agent network element registers on behalf of the user, it carries the instance-id in the registration request message; The proxy network element allocates the GRUU and reports the GRUU to the DSF. 6. The method according to claim 1, wherein the S-CSCF performs iFC matching according to the relevant information added by the DSF in the call request message, and triggers the call request message to the user agent according to the matched iFC network element. 7. The method according to claim 2, 3 or 5, wherein the relevant information is carried in the Request-uri of the call request message. 8. The method according to claim 7, wherein the DSF also carries the original information in the P-Called-Party-ID header field or History-info header field of the call request message sent to the S-CSCF. routing information of the called subscriber number or CS domain; and The user agent network element searches the P-Called-Party-ID header field or the History-info header field of the call request message for the routing information of the original called party number or CS domain, and determines the routing information accordingly. 9. The method according to claim 4, wherein the related information is carried in the Accept-contact header field or the Reject-contact header field of the call request message. 10. The method according to claim 6 or 9, wherein the DSF also carries the CS field in the P-Called-Party-ID header field or History-info header field of the call request message sent to the S-CSCF routing information for ; and The user agent network element obtains the routing information of the original called user number or CS domain in the call request message, and determines the routing information accordingly. 11. A domain selection entity, characterized by comprising: The domain selection unit is used to select the connection session to the CS domain or the connection session to the PS domain; The first adding unit is used to add the relevant information of routing the call request message to the user agent network element in the call request message to be issued when the domain selection unit selects to connect to the CS domain; The sending unit is configured to send the call request message processed by the first adding unit to the S-CSCF. 12. The entity of claim 11, further comprising: The acquiring unit is configured to acquire the relevant information and hand it over to the first adding unit for processing. 13. The entity of claim 11, further comprising: The second adding unit is configured to add the original called user number or the routing information of the CS domain to the call request message to be delivered. 14. A user agent network element, comprising: a receiving unit, configured to receive a call request message; An acquisition unit, configured to acquire the routing information of the original called user number or CS domain; A determining unit, configured to determine the routing information according to the original called user number or the routing information of the CS domain obtained by the obtaining unit; The routing unit is configured to route the call request message to the original called user via the CS domain according to the routing information determined by the determining unit. 15. A called routing system, comprising: DSF, S-CSCF, user agent network element and original called user terminal; The DSF is used to select the CS domain to connect the session, and add relevant information about routing the call request message to the user agent network element in the call request message sent to the S-CSCF; S-CSCF, configured to route the call request message to the user agent network element according to the relevant information; The user agent network element is configured to route the call request message to the original called user terminal via the CS domain according to the obtained routing information. 16. A called routing method, comprising the following steps: When the user attaches to the CS domain, the user agent network element will trigger the iFC activation to the user agent network element through the DSAI mechanism; after that When the DSF chooses to connect to the CS domain to connect the session, it sends the call request message to the S-CSCF; S-CSCF triggers the call request message to the user agent network element according to iFC; and The user agent network element routes the call request message to the original called user through the CS domain according to the obtained routing information. 17. The method according to claim 16, wherein when the user logs out in the CS domain, the user agent network element triggers the deactivation of the iFC of the user agent network element through the DSAI mechanism. 18. The method according to claim 16, wherein the DSF carries routing information of the CS domain in the P-Called-Party-ID header field or the History-info header field of the call request message sent to the S-CSCF as well as The user agent network element obtains the routing information of the original called user number or CS domain in the call request message, and determines the routing information accordingly.

Images