WO2012010019A1

WO2012010019A1 - Method and system for realizing media anchoring

Info

Publication number: WO2012010019A1
Application number: PCT/CN2011/075608
Authority: WO
Inventors: 谢振华
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-07-23
Filing date: 2011-06-10
Publication date: 2012-01-26
Also published as: CN102340490A; CN102340490B

Abstract

The present invention provides a method and system for realizing media anchoring. The method includes the following steps: after receiving a session description protocol (SDP) request, an application layer gateway (ALG) makes the SDP request needing to be forwarded carry the media resource information of the received SDP request and the ALG allocated media resource information of a media process entity, and then forwards the SDP request; an application server (AS) receives the SDP request and determines whether the ALG needs to anchor the media; the AS transmits a session initiation protocol (SIP) message which carries an SDP response and a media anchoring indication denoting whether the ALG needs to anchor the media; the ALG determines whether to anchor the media according to the received SIP message. With the existing signaling in the call setup procedure, the AS realizes the determination whether the ALG needs to anchor the media without extra signaling. Thereby the signaling consumption is saved and the call setup time period is shortened.

Description

Method and system for realizing media anchoring

The present invention relates to a call technology in an IP Multimedia Core Subsystem (IMS), and more particularly to a method and system for implementing media anchoring. Background technique

IMS is an IP-based network architecture proposed by the 3rd Generation Partnership Project (3GPP) to build an open and flexible business environment. IMS supports multimedia applications and provides users with rich multimedia services.

In the IMS service system, the control layer and the service layer are separated. The control layer does not provide specific services, and only provides the necessary triggering, routing, and accounting functions to the service layer.

The service triggering and control functions in the control layer are performed by the Call Session Control Function (CSCF, Call Session Control Function). Call session control functions are divided into: proxy call session control function (P-CSCF, Proxy-CSCF), query call session control function (I-CSCF, Interrogating-CSCF) and service call session control function (S-CSCF, Serving-CSCF) ) Three types, of which I-CSCF is optional.

The service layer is composed of a series of application servers (AS, Application Server), which can provide specific service services. The AS can be an independent entity or exist in the S-CSCF.

The S-CSCF in the control layer controls the service trigger according to the subscription information of the user, and invokes the service on the AS to implement the service function.

There is also an application layer gateway (ALG) in the IMS network. The ALG includes a signaling processing entity and a media processing entity, which are used to implement control signaling and media interaction, topology hiding, media codec conversion, and media data between different networks. For functions such as address translation, if ALG decides to include its media processing entity in the media path, the media path between the two session terminals is split into two by ALG. Paragraph.

The end-to-end device in the session is called User Equipment (UE) and is responsible for interaction with the user. Some UEs have multiple access networks, including 3GPP packet switching (PS, Packet Switch) domain. Access the network, access the network through other non-3GPP PS domains, and even access the network through the circuit switched (CS, Circuit Switch) domain.

In the prior art, if the direction is transmitted along the Session Description Protocol (SDP), and the ALG is in front of the AS, then the ALG cannot determine whether to anchor the media according to the user subscription information of the SDP request initiator, for example, the calling user signs the contract. When multi-mode single-standby continuous service (network and terminal can realize that the voice service is not interrupted when the user switches from the PS domain to the CS domain), at this time, the ALG first decides to anchor the media or not to anchor the media according to the local policy. After the SDP request arrives at the AS, the AS determines, according to the SDP requesting the user's subscription information, that the anchor does not need to be anchored or needs to anchor the media. Then, the AS notifies the ALG again, and the ALG performs media resource renegotiation through the possible additional signaling interaction process. Achieve removal of anchor or anchor media. Obviously, the prior art in the anchor media method implemented in the call-up process consumes additional signaling, resulting in a call setup time that is too long. Summary of the invention

In view of this, the main object of the present invention is to provide a method and system for implementing media anchoring, which can save signaling consumption and shorten the call setup duration.

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

A method of implementing media anchoring, the method comprising:

After receiving the session description protocol SDP request, the application layer gateway ALG carries the media resource information in the SDP request received by the ALG and the media resource information of the media processing entity allocated by the ALG in the SDP request that needs to be forwarded, and Forward the SDP request;

The application server AS receives the SDP request, determines whether the ALG anchor media is needed, and sends a session initiation protocol SIP message carrying a media anchor indication and an SDP response indicating whether the ALG anchor media is required; The ALG determines whether to anchor the media based on the received SIP message.

The AS determines whether the ALG anchoring medium is required to include:

The AS determines whether the ALG anchoring medium is required according to one or any combination of the following: SDP requesting the user's subscription information of the initiator, the SDP requesting the initiator's roaming information, the SDP requesting the destination party's home information, and the SDP requesting the destination party's roaming Information, whether the SDP requests the originator's home network to anchor the media.

Whether the decision requires the ALG anchor media specifically includes:

The AS determines the anchoring information according to the SDP requesting the user's subscription information of the initiator, and determines that the subscription information indicates that the anchoring needs to be anchored;

If the signing information of the SDP requesting initiator indicates that the anchoring is recommended, the AS further determines whether the home network of the SDP requesting initiator anchors the media, and if not, further determines whether the SDP requests the initiator to roam, and if roaming, decides to anchor. ;

If the roaming is not roaming, the SDP requests the destination party's attribution information to determine whether the destination party is the carrier network user, and if not, decides to anchor;

If yes, determining whether the destination party roams according to the attribution information of the target party of the SDP, and determining the anchor if roaming;

In other cases, it is decided not to anchor.

After the AS determines whether the ALG is required to anchor the media, before sending the SIP message, the AS further includes:

When the anchor media is determined, the AS carries the ALG-related media resource information carried in the received SDP request in the forwarded SDP request.

When it is determined that the media is not anchored, the AS carries the media resource information related to the SDP request initiator that is carried in the received SDP request, and is carried in the forwarded SDP request.

The ALG determines, according to the received SIP message, whether to anchor the media, including:

The ALG sends an SDP response to the SDP requesting initiator, and if it is determined that the anchoring is required by the media anchoring indication in the SIP message, the SDP response carries the media allocated by the ALG. The media resource information of the entity is processed by the entity, otherwise the SDP response does not carry the media resource information of the media processing entity allocated by the ALG.

The method for implementing the media anchor indication for indicating whether the ALG anchor media is needed is: the media anchor indication uses a special SIP message header field identifier to indicate whether the ALG anchor media is needed; or

The media anchor indication is included in the SDP response carried by the SIP message.

When the media anchor indication is included in the SDP response carried by the SIP message, the implementation manner of the anchor indication is:

Use a special SDP attribute identifier to indicate whether ALG is required to anchor the media; or, to indicate whether a particular media line is valid or invalid.

When the media anchor indication is indicated by selecting whether a specific media line is valid or invalid, the anchor indication implementation method is:

When the media line corresponding to the media resource information associated with the ALG is valid, it indicates that the media needs to be anchored; or, when the media line corresponding to the media resource information related to the SDP request originator is invalid, it indicates that the media needs to be anchored.

A system for implementing media anchoring, including at least ALG and AS, wherein

The ALG is configured to forward a session description protocol (SDP request), where the forwarded SDP request carries the received media resource information and the media resource information allocated by the ALG;

The AS is configured to receive an SDP request, determine whether the ALG anchor media is required, and send an SIP message carrying the SDP response according to the determined result.

If the AS determines that the ALG anchoring medium is required, the media line corresponding to the media resource information related to the ALG in the SDP response is valid, or the media resource information related to the SDP request initiator in the SDP response is The corresponding media line is invalid.

It can be seen from the technical solution provided by the foregoing that, after the ALG receives the SDP request, the SDP request to be forwarded carries the media resource information in the received SDP request, and the media resource information of the media processing entity allocated by the ALG. And forward the SDP request; AS receives The SDP requests to determine whether the ALG anchor media is needed; the AS sends a Session Initiation Protocol (SIP) message carrying a media anchor indication and an SDP response indicating whether the ALG anchor media is required; the ALG determines according to the received SIP message. Whether to anchor the media. Through the existing signaling in the call setup process, the AS implements determining whether the ALG anchors the media, does not require additional signaling, and saves signaling consumption, thereby shortening the call setup duration. DRAWINGS

1 is a flow chart of a method for implementing media anchoring according to the present invention;

2 is a schematic structural diagram of a system for implementing media anchoring according to the present invention;

3 is a schematic flow chart of a first embodiment of implementing media anchoring according to the present invention;

4 is a schematic flow chart of a second embodiment of implementing media anchoring according to the present invention. detailed description

FIG. 1 is a flowchart of a method for implementing media anchoring according to the present invention. As shown in FIG. 1, the method includes the following steps:

Step 100: After receiving the SDP request, the ALG carries the media resource information in the SDP request and the media resource information of the media processing entity allocated by the ALG in the SDP request that needs to be forwarded, and forwards the SDP request.

In this step, the SDP request received by the ALG carries the media resource information of the SDP request initiator, and the ALG allocates the media resource information (ie, the media resource related to the ALG) used to connect the media processing entity of the SDP request destination. Information). The SDP request forwarded by the ALG is forwarded to the AS via the S-CSCF.

The SDP request can be carried by the SIP INVITE message.

Step 101: The AS receives the SDP request to determine whether the ALG anchor media is needed.

In this step, the AS according to the SDP request or the INVITE message originator's user subscription information, SDP request or INVITE message initiator's roaming information, SDP request or INVITE message purpose Whether the party's attribution information, the SDP request or the INVITE message's destination party's roaming information, the SDP request, or the INIVTE message originator's home network is one of the anchor media or any combination, decide whether to forward the ALG-related media resource information to anchor or Do not anchor the media. such as:

If the SDP request or the signing information of the initiator of the INIVTE message indicates suggestion anchoring, the AS further determines whether the SDP request or the home network of the initiator of the INIVTE message anchors the media, and if not anchored, further determines the SDP request or the INVITE message initiator. Whether roaming, if roaming, decides to anchor; if not roaming, further determines whether the destination party is the operator network user according to the SDP request or the attribution information of the destination party of the INIVITE message, and if not, decides to anchor; if yes, decides to anchor; Then, according to the SDP request or the attribution information of the destination party of the INIVITE message, it is determined whether the destination party roams, and if it roams, it decides to anchor; otherwise, it decides not to anchor.

In this step, when determining the anchor media, the method further includes: the AS carrying the ALG-related media resource information carried in the received SDP request, and carrying the information in the SDP request forwarded to the SDP request or the INVITE message destination party, and sending When it is determined that the media is not anchored, the AS carries the media resource information related to the SDP request initiator carried in the received SDP request, and carries the information in the SDP request forwarded to the SDP request or the INVITE message destination party.

Step 102: The AS sends a SIP message carrying a media anchor indication and an SDP response indicating whether the ALG anchor media is needed.

In this step, the SIP message is forwarded to the ALG via the S-CSCF.

There are two ways to implement media anchor indications for indicating whether ALG anchor media is required: One way is to use a special SIP message header field identifier to indicate whether ALG anchor media is needed; another way is The media anchor indication is included in the SDP response carried by the SIP message. At this time, the anchor indication implementation method is: using a special SDP attribute identifier to indicate whether the ALG anchor media is required; or The specific media line is valid or invalid to indicate, specifically: when the media line corresponding to the media resource information related to the ALG is valid (carrying), indicating that the media needs to be anchored; or, when the media resource related to the SIP request originator is related Information When the corresponding media line is invalid, it indicates that the media needs to be anchored.

Step 103: The ALG determines whether to anchor the media according to the received SIP message. The method includes: the ALG sends an SDP response to the SDP request or the INVITE message initiator, and if it is determined that the anchoring is required by the media anchor indication in the SIP message, the SDP response carries the media processing media resource information allocated by the ALG.

In this step, if the media anchoring indication uses a special identifier, the identifier is displayed as requiring anchor timing; or, if the media anchoring indication is indicated by the media line, the media corresponding to the ALG-related media resource information When the line is valid, or the media line corresponding to the media resource information related to the SDP request or the INVITE message originator is invalid: The ALG carries the ALG-assigned connection SDP request in the SDP response forwarded to the SDP request or the INVITE message initiator. Or the media resource information of the media processing entity of the INVITE message originator. At this point, the SDP request or the INVITE message initiator negotiates the media resource with the ALG, and the ALG negotiates the media resource with the SDP request or the INVITE message destination party; the ALG controls the media processing function entity to forward the media data to implement the call between the two parties, and implements the anchor. The function of the media (ie in the media path);

If the media anchor indication indicates that a special identifier is used, the identifier is displayed as not requiring anchor timing; or, if the media anchor indication indicates that the media line corresponding to the ALG-related media resource information is invalid, Or when the media line corresponding to the media resource information related to the SDP request or the INVITE message originator is valid: the ALG does not carry the ALG allocated for connecting the SDP request or the INVITE in the SDP response forwarded to the SDP request or the INVITE message initiator. The media resource information of the media processing entity of the initiator. At this point, the SDP request or the INVITE message originator negotiates the media resource with the SDP request or the INVITE message destination. The ALG is not included in the call media path of both parties, that is, the media is not anchored.

It can be seen from the method of the present invention that the AS determines whether the ALG anchors the media through the existing signaling in the call setup process, does not require additional signaling, and saves signaling consumption, thereby shortening the call setup duration. A method for implementing media anchoring is provided for the method of the present invention, including at least ALG and AS, wherein

Those skilled in the art will appreciate that the information interaction between the ALG and the AS is forwarded through the S-CSCF (shown in Figure 2).

The method of the present invention will be described in detail below with reference to the embodiments.

FIG. 3 is a schematic flowchart of a first embodiment of implementing media anchoring according to the present invention. As shown in FIG. 3, in the first embodiment, UE-1 initiates a call as a calling party to the called party UE-2, and UE-1 establishes a call. During the IMS session with the UE-2, the session signaling is forwarded by the ALG and the AS, and the information exchanged between the AS and the ALG is forwarded by the S-CSCF. The specific steps include the following steps:

Step 300: The UE-1 sends a Session Description Protocol (SDP) request to the UE-2: SDP1 to establish a media connection with the UE-2, for example, by sending an Invite INVITE message of the Session Initiation Protocol SIP, where the SDP1 includes the UE-1. Media resource information.

Step 301: The SDP request or the INVITE message carrying the SDP request passes through the ALG, and the ALG allocates a media resource used to connect to the media processing entity at the UE-2 end.

Step 302: The ALG generates a new SDP request: SDP2, in SDP2, the media resource information in the received SDP request, and the media resource information of the media processing entity allocated by the ALG in step 301 (indicated by ALG1 in FIG. 3) ), and then forward the INVITE message carrying SDP2.

There may be other processing entities between UE-1 and ALG, which may be modified by these processing entities. After receiving the SDP request, the SDP request is forwarded, so that the SDP request received by the ALG may not be SDP1, but the modified SDP request is still used to establish a media connection with the UE-1, so the media resource information may still be regarded as UE-1 related.

ALG includes ALG1 in SDP2. For example, if ALG1 contains voice media resource information, then the voice media resource information related to UE-1 is in front, ALG1 voice media resource information is behind or vice versa, or ALG1 voice media resource. The attribute of the message is "inactive";

Step 303: The SDP request or the INVITE message carrying the SDP request arrives at the S-CSCF, and the S-CSCF forwards the SDP request or the INVITE message carrying the SDP request.

Step 304: The SDP request or the INVITE message carrying the SDP request arrives at the AS, and the AS according to the SDP request or the INVITE message originator's user subscription information, the SDP request or the INVITE message initiator's roaming information, the SDP request or the INVITE message destination party's attribution information. Whether the SDP request or the INVITE message destination party's roaming information, the SDP request, or the INIVTE message originator's home network anchors one or any combination of media, whether the decision requires ALG anchoring or no anchoring. Than ^ mouth:

In the first embodiment, it is assumed that the judgment result of the AS is that anchoring is required. In this embodiment, if the AS does not anchor the media, the subsequent steps 305-306 are performed. If the AS anchors the media, the steps 305-306 are performed in a standard anchoring manner, and are not related to the present invention and will not be described again.

It should be noted that there may be other processing entities between the ALG and the AS. The entity may modify the received SDP request and forward it out, so that the SDP request received by the AS may not be SDP2, but the modified SDP request is still used to establish a media connection with the media processing entity controlled by UE-1 and ALG. Therefore, the media resource information therein can still be regarded as related to UE-1 or ALG.

Step 305: The AS generates a new SDP request: SDP3, which includes ALG-related media resource information (represented by ALG1 in FIG. 3) in SDP3, and does not include the same media type in the media resource information related to ALG1 included in UE-1. The media resource information, for example, ALG1 includes voice media resource information, and the SDP3 does not include the UE-1 related voice media resource information.

Step 306: The SDP request or the INVITE message carrying the SDP request arrives at the UE-2, and the UE-2 uses the media resource information in the received SDP request to negotiate the media, and sends a SIP message, where the message carries an SDP response (English translation: Answer) SDP4, for example, the SIP message is a 200 OK message, and the SDP4 carries the media resource information of the UE-2.

Step 307: The SIP message arrives at the AS, and the AS carries an anchor indication to indicate the ALG anchor media when forwarding the SIP message, and includes a new SDP response in the message body: SDP5, which includes the received media resource information in the SDP4 in the SDP5. .

Specifically, for example, the header field of the SIP message is used to indicate whether ALG anchor media is required, or the anchor indication is included in SDP5, using "a=" attribute line to indicate whether ALG anchor media is required; or, the anchor indication is included in SDP5 The SDP5 includes the same number and type of media lines as the SDP2, and the media line portion corresponding to the ALG1 in the SDP2 in the SDP5 contains the media resource information in the received SDP4, that is, the ALP related to the ADP in the SDP5. The media line corresponding to the media resource information is valid; the port in the media line corresponding to the media resource information related to UE-1 in SDP2 in SDP5 is set to 0, that is, the media resource information related to UE-1 in SDP5 corresponds. The media line is invalid.

Step 308: The SIP message arrives at the S-CSCF, and the S-CSCF forwards the SIP message.

Step 309: The ALG receives the SIP message, and determines that the media anchor indication carried in the SIP message is indicated as requiring anchoring; or determining the media related to the ALG in the SDP response in the SIP message. If the media line corresponding to the resource information is valid (or the media line corresponding to the media resource information related to the UE-1 is invalid), the media resource for connecting to the media processing entity at the UE-1 end is allocated (indicated by ALG2 in FIG. 3) ).

Step 310: When forwarding the SIP message, the ALG includes a new SDP response in the message body: SDP6, where the SDP6 includes the media resource information allocated by the ALG in step 309 for connecting to the media processing entity of the UE-1 end (in FIG. 3 Expressed as ALG2).

So far, UE-1 negotiates media resources with ALG, ALG negotiates media resources with UE-2, and ALG controls media processing function entity to forward media data to realize UE-1 and UE-2 calls, and realizes the function of anchoring media. (ie in the media path).

4 is a schematic flowchart of a second embodiment of implementing media anchoring according to the present invention. As shown in FIG. 4, in the second embodiment, UE-1 initiates a call as a calling party to the called party UE-2, and UE-1 establishes a call. During the IMS session with the UE-2, the session signaling is forwarded by the ALG and the AS, and the information exchanged between the AS and the ALG is forwarded by the S-CSCF. The specific steps include the following steps:

Steps 400 to 403 are identical to the implementations of steps 300 to 303 in the first embodiment, and are not described herein again.

Step 404: The SDP request or the INVITE message carrying the SDP request arrives at the AS, and the AS according to the SDP request or the INVITE message originator's user subscription information, the SDP request or the INVITE message initiator's roaming information, the SDP request or the INVITE message destination party's attribution information. Whether the SDP request or the INVITE message destination party's roaming information, SDP request (INVITE message) originator's home network anchors one or a combination of media, and decides whether ALG anchor or non-anchor media is required. Than ^ mouth:

If the signing information of the initiator of the SDP request (INVITE message) indicates suggestion anchoring, the AS further determines whether the home network of the initiator of the SDP request (INVITE message) anchors the media, and further determines the SDP request or the INVITE message if not anchored. Whether the initiator is roaming, if roaming, determining anchoring; if not roaming, further determining whether the destination party is the carrier network user according to the SDP request or the attribution information of the destination party of the INIVITE message, if not Determining anchoring; if yes, further determining whether the destination party is roaming according to the SDP request or the attribution information of the destination party of the INIVITE message, and determining anchoring if roaming; otherwise determining not to anchor.

In the second embodiment, it is assumed that the judgment result of the AS is that anchoring is not required. In this embodiment, if the AS does not anchor the media, the subsequent steps 305-306 are performed. If the AS anchors the media, the steps 305-306 are performed in a standard anchoring manner, and are not related to the present invention and will not be described again.

It should be noted that there may be other processing entities between the ALG and the AS. The processing entities may modify the received SDP request and forward them out. Therefore, the SDP request received by the AS may not be SDP2, but the modified SDP. The request is still used to establish a media connection with the UE-1 and ALG controlled media processing entities, so the media resource information therein can still be considered to be related to UE-1 or ALG.

Step 405: The AS generates a new SDP request: SDP3, and only the UE-1 related media resource information is included in the SDP3.

Step 406: The SDP request or the INVITE message carrying the SDP request arrives at the UE-2, and the UE-2 uses the media resource information in the received SDP request to negotiate the media, and sends a SIP message, where the message carries an SDP response: SDP4, for example, the SIP message is 200 OK message, SDP4 carries the media resource information of UE-2.

Step 407: The SIP message arrives at the AS, and the AS carries an anchor indication when forwarding the SIP message to indicate that the ALG does not anchor the media, and includes a new SDP response in the message body: SDP5, which includes the received media resource in the SDP4 in the SDP5. information.

Specifically, for example, the header field of the SIP message indicates whether the ALG anchor media is required, or the anchor indication is included in the SDP 5, and the "a=" attribute line indicates whether the ALG anchor media is required; or the anchor indication is included in the SDP5. The SDP 5 includes the same number and type of media lines as the SDP2, and the media line portion corresponding to the media resource information related to the UE-1 in the SDP2 includes the media resource information in the received SDP4. That is, the media line corresponding to the media resource information related to UE-1 in SDP5 is valid, and SDP5 is related to ALG1 in SDP2. The port in the corresponding media line is set to 0, that is, the media line corresponding to the media resource information related to the ALG in SDP5 is invalid.

Step 408: The SIP message arrives at the S-CSCF, and the S-CSCF forwards the call SIP message.

Step 409: The ALG receives the SIP message, and determines that the media anchor indication carried in the SIP message is not required to be anchored; or determines that the media line corresponding to the ALG-related media resource information in the SDP response in the SIP message is invalid. (or determining that the media line corresponding to the media resource information related to UE-1 is valid), then releasing the media resource of the media processing entity allocated in step 401 for connecting the destination of the SDP request or the INVITE message.

Step 410: When forwarding the SIP message, the ALG includes a new SDP response in the message body: SDP6, in SDP6, the valid media resource information received in step 408 is included (the media with port number 0 is invalid).

So far, UE-1 negotiates media resources with UE-2, and ALG is not included in the call media path of UE-1 and UE-2, that is, the media is not anchored.

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

Claims

Claim

A method for implementing media anchoring, the method comprising:

The application server AS receives the SDP request, determines whether the ALG anchor media is needed, and sends a session initial protocol SIP message carrying a media anchor indication and an SDP response indicating whether the ALG anchor media is required;

The ALG determines whether to anchor the media based on the received SIP message.

2. The method according to claim 1, wherein the determining, by the AS, whether the ALG anchoring medium is required comprises:

The method according to claim 2, wherein the determining whether the ALG anchoring media is required comprises:

If yes, the destination party is further determined according to the attribution information of the target party of the SDP. Whether to roam, if roaming, decide to anchor;

In other cases, it is decided not to anchor.

The method according to claim 1, wherein the AS determines whether the ALG anchor media is required, and before sending the SIP message, the AS further includes:

The method according to claim 1, wherein the ALG determines whether to anchor the media according to the received SIP message, including:

The ALG sends an SDP response to the SDP requesting initiator, and if it is determined that the anchoring is required by the media anchoring indication in the SIP message, the SDP response carries the media resource information of the media processing entity allocated by the ALG, otherwise The SDP response does not carry the media resource information of the media processing entity allocated by the ALG.

The method according to claim 1, wherein the media anchor indication implementation method for indicating whether an ALG anchoring medium is required is:

The media anchoring indication uses a special SIP message header field identifier to indicate whether the ALG anchor media is required; or

The method according to claim 6, wherein when the media anchor indication is included in the SDP response carried by the SIP message, the anchor indication implementation method is: using a dedicated SDP The attribute identifier indicates whether the ALG anchor media is required; or, the indication is to select whether a particular media line is valid or invalid.

The method according to claim 7, wherein when the media anchor indication is indicated by selecting whether a specific media line is valid or invalid, the anchor indication implementation method is:

When the media line corresponding to the ALG-related media resource information is valid, it indicates that anchoring is required. Media; or, when the media line corresponding to the media resource information related to the SDP request originator is invalid, it indicates that the media needs to be anchored.

9. A system for implementing media anchoring, characterized in that it comprises at least an ALG and an AS, wherein

The system according to claim 9, wherein if the AS determines that an ALG anchoring medium is required, the media line corresponding to the media resource information related to the ALG in the SDP response is valid, or The media line corresponding to the media resource information related to the SDP request originator in the SDP response is invalid.