AU2014397894B2

AU2014397894B2 - Method and system for media negotiation in voice call continuity service, and ATCF

Info

Publication number: AU2014397894B2
Application number: AU2014397894A
Authority: AU
Inventors: Shanbao CHENG; Yun DENG; Qiang Tu
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2014-06-20
Filing date: 2014-10-13
Publication date: 2018-02-08
Anticipated expiration: 2034-10-13
Also published as: CN105323217B; BR112016030033A2; WO2015192554A1; AU2014397894A1; CN105323217A; BR112016030033B1

Abstract

Disclosed is a method for media negotiation in a voice call continuity (VCC) service. The method comprises: when a received media modification request sent by a first call session control function (CSCF) carries an offer media, storing the offer media and not instructing an access transfer gateway (ATGW) to update a media; and when a received media modification response sent by a second CSCF carries an answer media, instructing the ATGW to update the media. Also disclosed are an access transfer control function (ATCF) and a system for media negotiation in a VCC service.

Description

Technical Field

The present invention relates to the field of mobile communications, in particular to a method and a system for media negotiation in a Voice Call Continuity (VCC) service, and an Access Transfer Control Functionality (ATCF).

Background of the Related Art

A Single Radio Voice Call Continuity (SRVCC) solution is a Voice over Long Term Evolution (VoLTE) service-based continuous solution proposed by the Third Generation Partnership Project (3GPP), and mainly solves the problem of how to ensure continuity of a voice call when a single radio frequency User Equipment (UE) moves between a Long Term Evolution (LTE)/Pre-LTE network and a Second Generation (2G)/3rd Generation (3G) Circuit Switch (CS) network, that is, ensure the smooth switching of the single radio frequency UE between a Voice over IP (VOIP) voice and a CS domain voice controlled by an IP Multimedia Subsystem (IMS). In the early phase of the construction of an LTE network, its coverage is limited, when a user moves to an area where LTE signals are weak but network signals of a Global System for Mobile communications Enhanced Data Rate for GSM Evolution radio access network (GERAN)/Universal Mobile Telecommunication System Radio Access Network (UTRAN) are well covered during a voice call executed by the user using the LTE network, in order to ensure VCC, it is necessary to switch a speech path from an LTE network to the GERAN/UTRAN.

A Voice over LTE (VoLTE) voice call in Enhanced Single-Radio Voice Call Continuity (eSRVCC) technology solves the problem of smooth voice evolution during 4G network upgrade, improves the switching speed, and provides end-to-end voice quality assurance for a VoLTE call. Here, eSRVCC technology is defined in 3GPPR10. Compared with SRVCC technology in 3GPP R8, eSRVCC technology efficiently shortens the media delay of voice

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- 2 switching and improves the user experience. The difference between technical solutions of eSRVCC and SRVCC is that the former adds a pair of functional entities in IMS: an Access Transfer Control Functionality (ATCF) and an Access Transfer Gateway (ATGW), which are used as anchor points of a VoIP call in a control plane and a user plane, respectively.

In the specifications of 3GPP TS 24.292, 3GPP TS 23.237, and 3GPP TS 24.237, the ATCF has already been used to realize signaling and procedures for performing the switching between Packet Switched (PS) and CS. However, the prior art has the following problems:

Session switching is faster when using eSRVCC technology, but the media negotiation of a session is executed according to the existing process, as a signaling interaction process between the ATCF and the ATGW has more signaling, the time delay thereof is significantly longer than that of SRVCC technology.

Summary of the Invention

To solve the technical problems present in the prior art, embodiments of the present invention provide a method and a system for media negotiation in a VCC service, and an ATCF.

An embodiment of the present invention provides a method for media negotiation in a voice call continuity (VCC) service, applied in an access transfer control functionality (ATCF), comprising:

storing an offer media and not instructing an access transfer gateway (ATGW) to update a media when a received media modification request sent by a first call session control function (CSCF) carries the offer media; and instructing the ATGW to update the media only when a received media modification response sent by a second CSCF carries an answer media.

In the above solution, when receiving the media modification response sent by the second CSCF, the method further comprises:

selecting to use the same coding and decoding manner for the offer media and the answer media.

determining that the offer media and the answer media have no intersection;

correspondingly, instructing the ATGW to update the media comprises:

instructing the ATGW to start transcoding.

In the above solution, the media modification request is an update request message, or a re-invite request message or a session switching request; correspondingly, the media modification response is a 200 OK response message; or the media modification request is a 200 OK response message; correspondingly, the media modification response is an ACK response message.

In the above solution, before receiving the media modification request sent by the first CSCF, the method further comprises:

storing a corresponding session and an anchored media of the ATGW;

correspondingly, before receiving the media modification response sent by the second CSCF, the method further comprises:

assembling the offer media and the stored corresponding anchored media of the ATGW to obtain an assembled media and sending the assembled media to the second CSCF.

In the above solution, assembling the offer media and the stored corresponding anchored media of the ATGW comprises:

replacing an IP address and a port of the offer media with an IP address and a port of the corresponding anchored media of the ATGW, and supplementing a coding and decoding capacity which is supported by the ATGW and not provided in the offer media.

In the above solution, the method further comprises:

not instructing the ATGW to update the media and retransmitting a received response message of a media negotiation failure to the first CSCF when receiving the response message of the media negotiation failure sent by the second CSCF.

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-4An embodiment of the present invention further provides an access transfer control functionality (ATCF), comprising: a first indicating module and a second indicating module; wherein the first indicating module is arranged to store an offer media and not to instruct an ATGW to update a media when a received media modification request sent by a first CSCF carries the offer media;

the second indicating module is arranged to instruct the ATGW to update the media only when a received media modification response sent by a second CSCF carries an answer media.

In the above solution, the second indicating module is further arranged to select to use the same coding and decoding manner for the offer media and the answer media when receiving the media modification response sent by the second CSCF.

In the above solution, the second indicating module is arranged to determine that the offer media and the answer media have no intersection, and instruct the ATGW to start transcoding.

In the above solution, the ATCF further comprises a memory module arranged to store a corresponding session and an anchored media of the ATGW:

the second indicating module is further arranged to assemble the offer media and the stored corresponding anchored media of the ATGW to obtain an assembled media and send the assembled media to the second CSCF before receiving the media modification response sent by the second CSCF.

In the above solution, the second indicating module is further arranged not to instruct the ATGW to update the media and retransmit a received response message of a media negotiation failure to the first CSCF when receiving the response message of the media negotiation failure sent by the second CSCF.

An embodiment of the present invention also provides a system for media negotiation in a voice call continuity (VCC) service, comprising a first CSCF, an ATCF, a second CSCF and an ATGW; wherein the first CSCF is arranged to send a media modification request to the ATCF; the ATCF is arranged to receive the media modification request sent by the first CSCF,

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-5and store an offer media and not to instruct the ATGW to update a media when the received media modification request sent by the first CSCF carries the offer media, and is further arranged to receive a media modification response sent by the second CSCF, and instruct the ATGW to update the media only when the received media modification response sent by the second CSCF carries an answer media;

the second CSCF is arranged to send the media modification response to the ATCF; the ATGW is arranged to update the media after receiving an instruction of the ATCF.

In the above solution, the ATCF is further arranged to select to use the same coding and decoding manner for the offer media and the answer media when receiving the media modification response sent by the second CSCF.

In the above solution, the ATCF is arranged to determine that the offer media and the answer media have no intersection, and instruct the ATGW to start transcoding.

In the above solution, the ATCF is further arranged to store a corresponding session and an anchored media of the ATGW to execute media negotiation and modification before receiving the media modification request sent by the first CSCF.

In the above solution, the ATCF is further arranged to assemble the offer media and the stored corresponding anchored media of the ATGW to obtain an assembled media and send the assembled media to the second CSCF before receiving the media modification response sent by the second CSCF;

correspondingly, the second CSCF is further arranged to receive the assembled media sent by the ATCF.

In the above solution, the second CSCF is further arranged to send a response message of a media negotiation failure to the ATCF;

the ATCF is further arranged not to instruct the ATGW to update the media but retransmit the received response message of the media negotiation failure to the first CSCF when receiving the response message of the media negotiation failure sent by the second CSCF;

the first CSCF is further arranged to receive the response message of the media negotiation failure retransmitted by the ATCF.

An embodiment of the present invention further provides a computer storage medium, comprising a group of instructions that when executed cause at least one processor to execute the above method for media negotiation in a VCC service.

In the method and the system for media negotiation in a VCC service and the ATCF provided by the embodiments of the present invention, an offer media is stored and an ATGW is not instructed to update a media when a received media modification response carries the offer media; the ATGW is instructed to update the media when the received media modification response carries an answer media; that is to say, the AGTW is notified to update the media only when the answer media of the media negotiation is received, in this way, it can solve the problem of an obvious time delay in media negotiation caused by the ATCF that has anchored the media interacting with the ATGW for many times during the media negotiation, that is to say, with the solutions of the embodiments of the present invention, as the AGTW is notified to update the media only when the answer media of the media negotiation is received, the signaling of the ATCF and the ATGW can be reduced by one half in a process of the media negotiation, thus greatly improving the media negotiation speed, that is, effectively reducing the time delay.

Brief Description of Drawings

In the drawings, which are not necessarily drawn to scale, like reference numerals may be used to describe like parts in different views. Similar reference numerals with different letter suffixes may represent different examples of similar components. The drawings illustrate, by way of example but not limitation, the various embodiments discussed herein in general.

Fig. 1 is a flow diagram of a method for media negotiation in a VCC service of embodiment 1 of the present invention;

Fig. 2 is a flow diagram of a method for media negotiation of embodiment 2 of the present invention;

Fig. 3 is a diagram of a connection situation of a media channel before media negotiation of an embodiment of the present invention;

Fig. 4 is a diagram of a connection situation of a media channel after media negotiation of an embodiment of the present invention;

Fig. 5 is a flow diagram of a method for media negotiation of embodiment 3 of the present invention;

Fig. 6 is a flow diagram of a method for media negotiation of embodiment 4 of the present invention;

Fig. 7 is a flow diagram of a method for media negotiation of embodiment 5 of the present invention;

Fig. 8 is a flow diagram of a method for media negotiation of embodiment 6 of the present invention;

FIG. 9 is a structural diagram of an ATCF of an embodiment of the invention;

Fig. 10 is a structural diagram of a system for media negotiation in a VCC service of an embodiment of the present invention.

Preferred Embodiments of the Invention

According to an existing process, when eSRVCC technology is used, due to more signaling in a signaling interaction process between an ATCF and an ATGW, the time delay thereof is significantly longer than that of SRVCC technology.

In addition, when an exception occurs in the media negotiation, according to the requirement of RFC3261, the media need to remain an unchanged state before modification. According to the existing process, when the eSRVCC technology is used, it is not easy for the anchored media to return to the state before the modification, so it is necessary for the ATCF to re-direct the ATGW to amend the anchored media into the media before the failure.

In addition, according to the existing process, the media is negotiated sectionally, this will result in inconsistent media negotiation on both sides, thus requiring the ATGW to transcode, this will waste transcoding resources of the ATGW.

Based on this, in various embodiments of the present application: when a received media modification request carries an offer media, the offer media is stored and the ATGW is not instructed to update a media; and when a received media modification response carries an answer media, the ATGW is instructed to update the media.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and the embodiments. It should be noted that, in the case of no conflict, the embodiments of the present application and the features of the embodiments may be combined with each other.

Embodiment 1

A method for media negotiation in a VCC service of embodiment 1 is shown in Fig. 1 and comprises the following steps:

In step 101, an offer media is stored and an ATGW is not instructed to update a media when a received media modification request sent by a first CSCF carries the offer media;

specifically, an ATCF stores the offer media and does not instruct the ATGW to update the media when the received media modification request sent by the first CSCF carries the offer media. At this time, the ATCF has anchored the media.

Here, the offer media is used for indicating a coding and decoding capacity of the media of the request.

Before executing the step, the method may further comprise:

a corresponding session and an anchored media of the ATGW are stored to execute the media negotiation and modification.

In practical application, the ATCF stores the session and the anchored media of the ATGW to execute the media negotiation and the modification.

The media modification request may be an update request message, a re-invitation request message, a 200 OK response message, or a session switching request or the like. When the sent re-invitation request message does not carry the offer media, the returned 200 OK response message may carry the offer media, at this time, the CSCF of the returned 200 OK response message is the first CSCF.

In step 102, the ATGW is instructed to update the media when a received media modification response sent by a second CSCF carries an answer media.

Specifically, the ATCF instructs the ATGW to update the media when the received media modification response sent by the second CSCF carries the answer media.

Here, correspondingly, the answer media is used for indicating the coding and decoding capacity of the media in response to the media modification request.

Alternatively, the same coding and decoding manner is selected for the offer media and the answer media when the media modification response sent by the second CSCF is received. When the offer media and the answer media are determined to have no intersection, instructing the ATGW to update the media specifically comprises:

instructing the ATGW to start transcoding.

Before executing the step, the method may further comprise:

Specifically, the ATCF assembles the offer media and the stored corresponding anchored media of the ATGW to obtain the assembled media and sends the assembled media to the second CSCF.

Assembling the offer media and the stored corresponding anchored media of the ATGW specifically comprises: replacing an IP address and a port of the offer media with an IP address and a port of the corresponding anchored media of the ATGW, and supplementing the coding and decoding capacity which is supported by the ATGW and not provided in the offer media, so as to obtain the assembled media.

Correspondingly, the media modification response may be the 200 OK response message or an ACK response message. Specifically, when the media modification request carrying the offer media is the update request message, or the re-invitation request message or the session switching request, the media modification response is the 200 OK response message; when the media modification request carrying the offer media is the 200 OK response message, the media modification response is the ACK response message.

Determining the offer media and the answer media to have no intersection specifically comprises: determining the types and the coding and decoding capacities as well as related parameters of the offer media and the answer media to have no intersection, so the negotiation can not reach a consensus.

In practical application, the ATGW is not instructed to update the media and a received response message of media negotiation failure is retransmitted to the first CSCF when the response message of the media negotiation failure sent by the second CSCF is received.

In the method for media negotiation in the VCC service provided by embodiment 1 of the present invention, the offer media is stored and the ATGW is not instructed to update the media when the received media modification request sent by the first CSCF carries the offer media; the ATGW is instructed to update the media when the received media modification response sent by the second CSCF carries the answer media, that is to say, the AGTW is notified to update the media only when the answer media of the media negotiation is received, in this way, it may solve the problem of an obvious time delay in media negotiation caused by the ATCF that has anchored the media interacting with the ATGW for many times during the media negotiation, that is to say, with the solution of embodiment 1 of the present invention, as the AGTW is notified to update the media only when the answer media of the media negotiation is received, the signaling of the ATCF and the ATGW can be reduced by one half in a process of the media negotiation, thus greatly improving the media negotiation speed, that is, effectively reducing the time delay.

In addition, when the offer media and the answer media are determined to have no intersection, the ATGW is instructed to start transcoding. Therefore, transcoding resources of the ATGW may be effectively saved.

Besides, the ATGW is not instructed to update the media when the response message of the media negotiation failure sent by the second CSCF is received, at this time, as the ATGW does not update the media, the problem that the operation of the ATGW is difficult to be returned after the media negotiation failure during the media negotiation may be solved.

Embodiment 2

The application scenario of embodiment 2 is as follows: a media is anchored to an ATCF, a session is in a ringing state, an offer/answer media is balanced, the ATCF has stored a calling party and a called party as well as the media anchored by the ATGW.

Embodiment 2 uses an update session to execute media negotiation, a method for media negotiation in embodiment 2 is shown in Fig. 2 and comprises the following steps:

In step 201, the ATCF receives an update request message from a first CSCF;

here, the update request message from the first CSCF carries a first media (sdpl).

The update request message is used for executing the media negotiation.

In step 202, the ATCF stores the sdpl in the received update request message from the first CSCF and uses the sdpl to assemble the stored corresponding anchored media of the ATGW to obtain a second media (sdp2);

specifically, the ATCF replaces an IP address and a port of the sdpl with an IP address and a port of the corresponding anchored media of the ATGW, and supplements a coding and decoding capacity which is supported by the ATGW and not provided in the sdpl, so as to obtain the sdp2.

Here, the purpose of the assembly is: replacing the IP and the port of the sdpl as well as the coding and decoding capacity of the media to obtain the sdp2.

The sdp2 may be considered to represent the corresponding coding and decoding capacity of the media of the ATGW.

In step 203, the ATCF retransmits the update request message to a second CSCF;

here, the retransmitted update request message carries the sdp2.

The update request message retransmitted to the second CSCF by the ATCF is used for executing the media negotiation.

After step 203 is completed, it is indicated that the offer media is completely processed, that is: the offer media carried by a media modification request is completely processed.

It may be appreciated from the above description that the ATCF does not instruct the ATGW to update the media when the offer media is being processed.

Fig. 3 is a connection situation of a media channel before negotiation, as shown in Fig. 3, before the media negotiation, the media channel is established by a media (i.e. an old media (sdp-old)) before the negotiation among the first CSCF, the ATCF and the second CSCF.

Here, in practical application, the first CSCF is a proxy CSCF (P-CSCF), and the second CSCF is also the P-CSCF, at this time, the interaction between the second CSCF and the ATCF may be retransmitted through inquiring the CSCF (I-CSCF), in other words, the second CSCF may not be connected directly with the ATCF. Therefore, the interaction may be realized only through the retransmission of an II-CSCF.

In step 204, the second CSCF returns a 200 OK response message to the ATCF;

here, the returned 200 OK response message carries a third media (sdp3).

In step 205, the ATCF stores the sdp3 in the received 200 OK response message returned from the second CSCF, executes the media negotiation according to the stored sdpl and sdp3 and then executes step 206;

here, in the practical application, generally, the sdpl carries a plurality of coding and decoding capacities of the media, while the sdp3 only carries one coding and decoding capacity, so when the media negotiation is executed, the coding and decoding capacity of the media being the same as one corresponding to the sdp3 is alternatively selected.

When the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and sdp3 are determined to have no intersection, so the negotiation can not reach a consensus, transcoding is started.

In step 206, the ATCF instructs the ATGW to update the anchored media of the calling party and the called party on the ATGW and then executes step 207;

here, when the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and sdp3 are determined to have no intersection, so the negotiation can not reach a consensus, transcoding is started, that is, the ATGW is instructed to start the transcoding.

In practical application, the ATCF may instruct the ATGW to update the anchored media of the calling party and the called party through two signaling interactions respectively, and may also instruct the ATGW to update the anchored media of the calling party and the called party through one signaling interaction at the same time.

It is assumed that the media corresponding to the sdpl is a fourth media (sdp4) and the media corresponding to the sdp3 is a fifth media (sdp5) after the anchored media is updated, the ATGW sends the updated anchored media (the sdp4 and the sdp5) to the ATCF.

In step 207, the ATCF stores the received anchored media from the ATGW and uses the sdp3 and the stored sdp5 to perform assembly to obtain a sixth media (sdp6);

specifically, the ATCF replaces an IP address and a port of the sdp3 with the IP address and the port of the corresponding anchored media of the ATGW, and supplements the coding and decoding capacity which is supported by the ATGW and not provided in the sdp3, so as to obtain the sdp6.

Here, the purpose of the assembly is: replacing the IP and the port of the sdp3 as well as the coding and decoding capacity of the media to obtain the sdp6.

The sdp6 may be considered to represent the corresponding coding and decoding capacity of the media of the ATGW.

In step 208, the ATCF retransmits the 200 OK response message to the first CSCF.

Here, the retransmitted 200 OK response message carries the sdp6.

After this step is completed, it is indicated that the answer media is completely processed, that is, the answer media carried by the media modification response is completely processed.

It can be appreciated from the description of the steps 204-208 that the ATGW is instructed to update the media only when the answer media is received. Therefore, the media negotiation speed is greatly increased and the time delay is effectively reduced. When the ATCF executes the media negotiation, the coding and decoding capacity of the media being the same as one corresponding to the sdp3 is alternatively selected,. When the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and sdp3 are determined to have no intersection, so the negotiation can not reach a consensus, transcoding resources of the ATGW start to be used. That is, the ATGW is instructed to start transcoding, saving the transcoding resources of the ATGW.

The connection situation of the media channel after the negotiation is completed is shown in Fig. 4, after the media negotiation is completed, the media channel is established by the media (i.e. a new media (sdp-new)) after the negotiation among the first CSCF, the ATCF and the second CSCF.

Here, in the practical application, the first CSCF is a P-CSCF, and the second CSCF is also the P-CSCF, at this time, the interaction between the second CSCF and the ATCF may be retransmitted through the I-CSCF, in other words, a connection may not be directly established between the second CSCF and the ATCF. Therefore, the interaction may be realized only through the retransmission of the II-CSCF.

Embodiment 3

The application scenario of embodiment 3 is as follows: a media is anchored to an ATCF, a session is in a ringing state, an offer/answer media is balanced, the ATCF has stored a calling party and a called party as well as the media anchored by the ATGW.

Embodiment 3 uses a re-invitation session to execute media negotiation. A method for media negotiation of embodiment 3 is shown in Fig. 5 and comprises the following steps:

In step 501, the ATCF receives a re-invitation request message from a first CSCF;

here, the re-invitation request message from the first CSCF carries an sdpl.

The re-invitation request message is used for executing the media negotiation.

In step 502, the ATCF stores the sdpl in the received re-invitation request message from the first CSCF, and uses the sdpl and the stored corresponding anchored media of the ATGW to perform assembly to obtain an sdp2;

specifically, the ATCF replaces an IP address and a port of the sdpl with an IP address and a port of a corresponding anchored media of the ATGW, and supplements a coding and decoding capacity which is supported by the ATGW and not provided in the sdpl, so as to obtain the sdp2.

In step 503, the ATCF retransmits the re-invitation request message to the second CSCF;

here, the retransmitted re-invitation request message carries the sdp2.

After this step is completed, it is indicated that the offer media is completely processed, that is, the offer media carried by a media modification request is completely processed.

It can be appreciated from the above description that the ATCF does not instruct the ATGW to update the media when the offer media is being processed.

Fig. 3 shows a connection situation of a media channel before the negotiation. As shown in Fig. 3, before the media negotiation, the media channel is established by a media (i.e. an old media (sdp-old)) before the negotiation among the first CSCF, the ATCF and the second CSCF.

Here, in practical application, the first CSCF is a P-CSCF, and the second CSCF is also the P-CSCF, at this time, the interaction between the second CSCF and the ATCF may be retransmitted through an I-CSCF, in other words, a connection may not be directly established between the second CSCF and the ATCF. Therefore, the interaction may be realized only through the retransmission of an II-CSCF.

In step 504, the second CSCF returns a 200 OK response message to the ATCF;

here, the returned 200 OK response message carries the sdp3.

In step 505, the ATCF stores the sdp3 in the received 200 OK response message returned from the second CSCF, executes the media negotiation according to the stored sdpl and sdp3 and then executes step 506;

here, in the practical application, generally, the sdpl carries a plurality of coding and decoding capacities of the media while the sdp3 only carries one coding and decoding capacity, so when the media negotiation is executed, the coding and decoding capacity of the media being the same as one corresponding to the sdp3 is alternatively selected.

When the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and the sdp3 are determined to have no intersection, so the negotiation can not reach a consensus, transcoding is started.

In step 506, the ATCF instructs the ATGW to update the anchored media of the calling party and the called party on the ATGW and then executes step 507;

It is assumed that the media corresponding to the sdpl is an sdp4 and the media corresponding to the sdp3 is an sdp5 after the anchored media is updated, the ATGW sends the updated anchored media (sdp4 and sdp5) to the ATCF.

In step 507, the ATCF stores the received anchored media from the ATGW and uses the sdp3 and the stored sdp5 to perform assembly to obtain an sdp6;

specifically, the ATCF replaces an IP address and a port of the sdp3 with the IP address and the port of the corresponding anchored media of the ATGW, and supplements the coding and decoding capacity which is supported by the ATGW and not provided in the sdp3, so as to obtain an sdp6.

In step 508, the ATCF retransmits the 200 OK response message to the first CSCF.

here, the retransmitted 200 OK response message carries the sdp6.

In step 509, the ATCF transparently transmits to the second CSCF an ACK response message without media sent by the first CSCF.

After this step is completed, it is indicated that an answer media is completely processed, that is, the answer media carried by a media modification response is completely processed.

It can be appreciated from the description of the steps 504-509 that the ATGW is instructed to update the media only when the answer media is received. Therefore, the media negotiation speed is greatly improved and the time delay is significantly reduced. When the ATCF executes the media negotiation, the coding and decoding capacity of the media being the same as one corresponding to the sdp3 is alternatively selected, when the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and sdp3 are determined to have no intersection, so the negotiation can not reach a consensus, transcoding resources of the ATGW start to be used, that is, the ATGW is instructed to start the transcoding, saving the transcoding resources of the ATGW.

A connection situation of the media channel after the negotiation is completed is shown in Fig. 4, after the media negotiation is completed, the media channel is established by the media (i.e. a new media (sdp-new)) after the negotiation among the first CSCF, the ATCF and the second CSCF.

Here, in the practical application, the first CSCF is the P-CSCF, and the second CSCF is also the P-CSCF, at this time, the interaction between the second CSCF and the ATCF may be retransmitted through the I-CSCF, in other words, a connection may not be directly established between the second CSCF and the ATCF. Therefore, the interaction may be realized only through the retransmission of the II-CSCF.

Embodiment 4

The application scenario of embodiment 4 is as follows: a media is anchored to an ATCF, a session is in a ringing state, an offer/answer media is balanced, the ATCF has stored a calling party and a called party as well as the media anchored by the ATGW.

Embodiment 4 uses a re-invitation session to execute media negotiation. A method for media negotiation of embodiment 4 is shown in Fig. 6 and comprises the following steps:

In step 601, the ATCF transparently transmits to a second CSCF a re-invitation request message from a first CSCF;

here, the re-invitation request message does not carry any media.

In step 602, the second CSCF returns a 200 OK response message to the ATCF;

here, the returned 200 OK response message carries an sdpl.

In step 603, the ATCF stores the sdpl in the received 200 OK response message returned from the second CSCF, and uses the sdpl and the stored corresponding anchored media of the ATGW to obtain an sdp2;

The sdp2 may be considered to represent the corresponding coding and decoding capacity media of the ATGW.

In step 604, the ATCF retransmits the 200 OK response message to the first CSCF;

here, the retransmitted 200 OK response message carries the sdp2.

After this step is completed, it is indicated that an offer media is completely processed, that is: the offer media carried by a media modification request is completely processed.

It can be appreciated from the above description that the ATCF does not instruct the

ATGW to update the media when the offer media is being processed.

Fig. 3 is a connection situation of a media channel before media negotiation, as shown in Fig. 3, before the media negotiation, the media channel is established by a media (i.e. an old media (sdp-old)) before the negotiation among the first CSCF, the ATCF and the second CSCF.

In step 605, the first CSCF sends an ACK response message to the ATCF;

here, the ACK response message carries an sdp3.

The ACK response message is used for executing the media negotiation.

In step 606, the ATCF stores the sdp3 in the received ACK response message sent from the first CSCF, executes the media negotiation according to the stored sdpl and sdp3 and then executes step 606;

here, in the practical application, generally, the sdpl carries a plurality of coding and decoding capacities of the media while the sdp3 only carries one coding and decoding capacity, so when the media negotiation is executed, the coding and decoding capacity of the media being the same as that corresponding to the sdp3 is alternatively selected.

When the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and sdp3 are determined to have no intersection, so the negotiation can not reach a consensus,, transcoding is started.

In step 607, the ATCF instructs the ATGW to update the anchored media of the calling party and the called party on the ATGW and then executes step 607;

here, when the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and sdp3 are determined to have no intersection, so the negotiation can not reach a consensus, transcoding is started, that is, the ATGW is instructed to start transcoding.

It is assumed that the media corresponding to the sdpl is an sdp4 and the media corresponding to the sdp3 is an sdp5 after the anchored media is updated, the ATGW sends the updated anchored media (the sdp4 and the sdp5) to the ATCF.

In step 608, the ATCF stores the received anchored media from the ATGW and uses the sdp3 and the stored sdp5 to perform assembly to obtain an sdp6;

specifically, the ATCF replaces an IP address and a port of the sdp3 with the IP address and the port of a corresponding anchored media of the ATGW, and supplements the coding and decoding capacity which is supported by the ATGW and not provided in the sdp3, so as to obtain the sdp6.

In step 609, the ATCF retransmits the ACK response message to the second CSCP;

here, the retransmitted ACK response message carries the sdp6.

After this step is completed, it is indicated that the answer media is completely processed, that is: the answer media carried by a media modification response is completely processed.

It can be appreciated from the description of the steps 605-609 that the ATGW is instructed to update the media only when the answer media is received. Therefore, the media negotiation speed is greatly improved and the time delay is effectively reduced. When the ATCF executes the media negotiation, the coding and decoding capacity of the media being the same as that corresponding to the sdp3 is alternatively selected. When the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and sdp3 are determined to have no intersection, so the negotiation can not reach a consensus,, transcoding resources of the ATGW start to be used, that is, the ATGW is instructed to start transcoding. Therefore, the transcoding resources of the ATGW are saved.

Embodiment 5

The application scenario of embodiment 5 is as follows: a media is anchored to an ATCF, a session is in a ringing state, an offer/answer media is balanced, the ATCF has stored a calling party and a called party as well as the media anchored by an ATGW.

Embodiment 5 uses a re-invitation session to execute media negotiation, a method for media negotiation of embodiment 5 is shown in Fig. 7 and comprises the following steps:

In step 701, the ATCF receives a re-invitation request message from a first CSCF;

here, the re-invitation request message from the first CSCF carries an sdpl.

The re-invitation request message is used for executing the media negotiation.

In step 702, the ATCF stores the sdpl in the received re-invitation request message from the first CSCF and uses the sdpl and the stored corresponding anchored media of the ATGW to perform assembly to obtain an sdp2;

In step 703, the ATCF retransmits the re-invitation request message to a second CSCF;

here, the retransmitted re-invitation request message carries the sdp2.

Fig. 3 is a connection situation of a media channel before negotiation, as shown in Fig. 3, before the media negotiation the media channel is established by the media (i.e. an old media (sdp-old)) before the negotiation among the first CSCF, the ATCF and the second CSCF.

Here, in practical application, the first CSCF is a P-CSCF, and the second CSCF is also the P-CSCF, at this time, the interaction between the second CSCF and the ATCF may be retransmitted through the I-CSCF, in other words, a connection may not be directly established between the second CSCF and the ATCF. Therefore, the interaction may be realized only through the retransmission of an II-CSCF.

In step 704, the second CSCF returns to the second CSCF a 4xx or 5xx response message indicating a media negotiation failure;

In step 705, the ATCF transparently transmits to the first CSCF the 4xx or 5xx response message indicating the media negotiation failure.

After this step is completed, the media negotiation failure is indicated, at this time, since the connection of the media channel is not changed and is still as the connection of the media channel shown in Fig. 3, it is not necessary to notify the ATGW to return, that is: it is not necessary for the ATCF to send a returning indication to the ATGW.

Embodiment 6

The application scenario of embodiment 6 is as follows: a processing process of session switching is initiated by an Enhanced Mobile Switch Center (eMSC) server, that is, media negotiation is initiated by the eMSC Server, a method for media negotiation of embodiment 6 is shown in Fig. 8 and comprises the following steps:

In step 801, an ATCF receives a session switching request message from the eMSC Server;

here, the session switching request message carries an sdpl.

The session switching request message is used for executing the media negotiation.

In step 802, the ATCF stores the sdpl carried in the session switching request message and executes the media negotiation according to the sdpl and a stored media for an end user and then executes step 803;

Here, in practical application, generally, the sdpl carries a plurality of coding and decoding capacities of the media while the media of the end user only carries one coding and decoding capacity, so when the media negotiation is executed, the coding and decoding capacity of the media being the same as that corresponding to the media of the end user is alternatively selected.

When the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and to the media of the end user are determined to have no intersection, so the negotiation can not reach a consensus, transcoding is started.

In step 803, the ATCF instructs an ATGW to update an anchored media of a user side on the ATGW and then executes step 804;

here, when the types and the coding and decoding capacities as well as related parameters of the media corresponding to the sdpl and to the media of the end user are determined to have no intersection, so the negotiation can not reach a consensus, the transcoding is started, that is, the ATGW is instructed to start the transcoding.

It is assumed that the media corresponding to the sdpl is an sdp2 after the anchored media is updated, the ATGW sends the updated anchored media (the sdp2) to the ATCF.

In step 804, the ATCF returns a 200 OK response message to the eMSC Server;

here, the 200 OK response message carries the sdp2.

In step 805, the eMSC Server sends an ACK response message to the ATCF, and a switching process is complete.

To realize the above method, an embodiment of the present invention further provides an ATCF, as shown in Fig. 9, the ATCF comprises a first indicating module 91 and a second indicating module 92; wherein the first indicating module 91 is arranged to store an offer media and not to instruct an ATGW to update a media when a received media modification request sent by a first CSCF carries the offer media.

the second indicating module 92 is arranged to instruct the ATGW to update the media when a received media modification response sent by a second CSCF carries an answer media.

At this time, the ATCF has anchored the media.

The offer media is used for indicating the coding and decoding capacity of the media of the request; correspondingly, the answer media is used for indicating the coding and decoding capacity of the media in response to the media modification request.

The second indicating module 92 alternatively selects to use the same coding and decoding manner for the offer media and the answer media when receiving the media modification response sent by the second CSCF. When the offer media and the answer media are determined to have no intersection, instructing the ATGW to update the media specifically comprises:

the second indicating module 92 instructing the ATGW to start transcoding.

The ATCF may also comprise a memory module arranged to store a corresponding session and the anchored media of the ATGW to execute the media negotiation and modification.

The media modification request may be an update request message, or a re-invitation request message, or a 200 OK response message or a session switching request. When the sent re-invitation request message does not carry the offer media, the returned 200 OK response message may carry the offer media, at this time, the CSCF of the returned 200 OK response message is the first CSCF.

The second indicating module 92 is further arranged to assemble the offer media and the stored corresponding anchored media of the ATGW to obtain an assembled media and send the assembled media to the second CSCF before receiving the media modification response sent by the second CSCF.

Here, assembling the offer media and the stored corresponding anchored media of the ATGW specifically comprises: replacing an IP address and a port of the offer media with an IP address and a port of the corresponding anchored media of the ATGW, and supplementing the coding and decoding capacity which is supported by the ATGW and not provided in the offer media, so as to obtain the assembled media.

Correspondingly, the media modification response may be the 200 OK response message or the ACK response message; specifically, when the media modification request carrying the offer media is the update request message, or the re-invitation request message or the session switching request, the media modification response is the 200 OK response message; when the media modification request carrying the offer media is the 200 OK response message, the media modification response is the ACK response message.

Determining the offer media and the answer media to have no intersection specifically comprises: determining the types as well as the coding and decoding capacities and related parameters of the offer media and the answer media to have no intersection, so the negotiation can not reach the consensus.

In practical application, the second indicating module 92 does not instruct the ATGW to update the media and retransmits the received response message of media negotiation failure to the first CSCF when receiving the response message of the media negotiation failure sent by the second CSCF.

In practical application, the first indicating module 91 and the second indicating module 92 may be realized by a Central Processing Unit (CPU), a Digital Signal Processor (DSP) or a Field-Programmable Gate Array (FPGA) in the ATCF in combination with a transceiver; the memory module may be realized by a memory in the ATCF.

In the ATCF provided by the embodiment of the present application, the first indicating module stores the offer media and does not instruct the ATGW to update the media when the received media modification request sent by the first CSCF carries the offer media; the second indicating module instructs the ATGW to update the media when the received media modification response sent by the second CSCF carries the answer media. That is to say, the AGTW is notified to update the media only when the answer media of the media negotiation is received, in this way, it may solve the problem of an obvious time delay in media negotiation caused by the ATCF that has anchored the media interacting with the ATGW for many times during the media negotiation.That is to say, with the solution of the embodiment of the present invention, as the AGTW is notified to update the media only when the answer media of the media negotiation is received, the signaling of the ATCF and the ATGW can be reduced by one half in a process of the media negotiation, thus greatly improving the media negotiation speed, that is, effectively reducing the time delay.

In addition, when the second indicating module determines the offer media and the answer media to have no intersection, the ATGW is instructed to start transcoding. Therefore, transcoding resources of the ATGW may be effectively saved.

In addition, the second indicating module does not instruct the ATGW to update the media when receiving the response message of the media negotiation failure sent by the second CSCF, at this time, since the ATGW does not update the media, the problem that the operation of the ATGW is difficult to be returned after the media negotiation failure during the media negotiation may be solved.

An embodiment of the present invention further provides a system for media negotiation in a VCC service, as shown in Fig. 10, the system comprises a first CSCF 101, an ATCF 102, a second CSCF 103 and an ATGW 104; wherein the first CSCF 101 is arranged to send a media modification request to the ATCF 102;

the ATCF 102 is arranged to receive the media modification request sent by the first CSCF 101, and store an offer media and does not instruct the ATGW 104 to update the media when the received media modification request sent by the first CSCF carries the offer media; and is further arranged to receive a media modification response sent by the second CSCF 103, and instruct the ATGW 104 to update the media when the received media modification response sent by the second CSCF carries an answer media;

the second CSCF 103 is arranged to send the media modification request to the ATCF

102;

the ATGW 104 is arranged to update the media after receiving an instruction from the ATCF 102.

The ATCF 102 has anchored the media.

In practical application, a first indicating module of the ATCF 102 receives the media modification request sent by the first CSCF 101, and stores the offer media and does not instruct the ATGW 104 to update the media when the received media modification request sent by the first CSCF carries the offer media, a second indicating module of the ATCF 102 receives the media modification response sent by the second CSCF 103, and instruct the ATGW 104 to update the media when the received media modification response sent by the second CSCF 103 carries the answer media.

Here, the ATCF 102 is further arranged to alternatively select to use the same coding and decoding manner for the offer media and the answer media when receiving the media modification response sent by the second CSCF; and to instruct the ATGW to start transcoding when the ATGW is instructed to update the media, when the offer media and the answer media are determined to have no intersection.

In practical application, the second indicating module of the ATCF 102 alternatively selects to use the same coding and decoding manner for the offer media and the answer media when receiving the media modification response sent by the second CSCF; when the offer media and the answer media are determined to have no intersection, the ATGW is instructed to start transcoding when the ATGW is instructed to update the media.

The ATCF 102 is further arranged to store a corresponding session and an anchored media of the ATGW 104 to execute the media negotiation and modification before receiving the media modification request sent by the first CSCF.

In practical application, a memory module of the ATCF 102 may store the corresponding session and the anchored media of the ATGW.

The ATCF 102 is further arranged to assemble the offer media and the stored corresponding anchored media of the ATGW to obtain an assembled media and send the assembled media to the second CSCF 103 before receiving the media modification response sent by the second CSCF 103;

correspondingly, the second CSCF is further arranged to receive the assembled media sent by the ATCF 102.

Herein, assembling the offer media and the stored corresponding anchored media of the ATGW specifically comprises: replacing an IP address and a port of the offer media with an IP address and a port of the corresponding anchored media of the ATGW, and supplementing the coding and decoding capacity which is supported by the ATGW and not provided in the offer media, so as to obtain the assembled media.

Correspondingly, the media modification response may be the 200 OK response message or an ACK response message; specifically, when the media modification request carrying the offer media is the update request message, or the re-invitation request message or the session switching request, the media modification response is the 200 OK response message; when the media modification request carrying the offer media is the 200 OK response message, the media modification response is the ACK response message.

Determining the offer media and the answer media to have no intersection specifically comprises: determining the types as well as the coding and decoding capacities and related parameters of the offer media and the answer media to have no intersection, so the negotiation can not reach a consensus.

In practical application, the ATCF 102 does not instruct the ATGW to update the media and retransmits a received response message of media negotiation failure to the first CSCF 101 when receiving the response message of the media negotiation failure sent by the second CSCF 103.

In the system for media modification in the VCC service of the embodiment of the present invention, the ATCF stores the offer media and does not instruct the ATGW to update the media when the received media modification request sent by the first CSCF carries the offer media; the ATCF instructs the ATGW to update the media when the received media modification response sent by the second CSCF carries the answer media, that is to say, the ATCF notifies the AGTW to update the media only when the answer media of the media negotiation is received, in this way, it may solve the problem of an obvious time delay in media negotiation caused by the ATCF that has anchored the media interacting with the ATGW for many times during the media negotiation, that is to say, with the solution of the embodiment of the present invention, since the ATCF notifies the AGTW to update the media only when the answer media of the media negotiation is received, the signaling of the ATCF and the ATGW can be reduced by one half in a process of the media negotiation, thus greatly improving the media negotiation speed, that is, effectively reducing the time delay.

In addition, when the ATCF determines the offer media and the answer media to have no intersection, the ATGW is instructed to start transcoding. Therefore, transcoding resources of the ATGW may be effectively saved.

In addition, the ATCF does not instruct the ATGW to update the media when receiving the response message of the media negotiation failure sent by the second CSCF, at this time, as the ATGW does not update the media, the problem that the operation of the ATGW is difficult to be returned after the media negotiation failure during the media negotiation may be solved.

It will be appreciated by one skilled in the art that embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware. Moreover, the invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to a magnetic disk storage, an optical storage, etc.) containing a computer-usable program code therein.

The present invention is described with reference to a flow chart and/or a block diagram of a method, an apparatus (a system), and a computer program product according to the embodiments of the present invention. It is to be understood that each process and/or block in the flow chart and/or the block diagram, as well as a combination of the process and/or the block in the flow chart and /or the block diagram, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, a special purpose computer, an embedded processor, or other programmable data processing apparatuses to produce a machine such that the instructions executed by a processor of a computer or other programmable data processing apparatuses produce a device for implementing a function specified in one or more processes of the flow chart and/or one or more blocks of the block diagram.

The computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing apparatuses to operate in a particular manner, such that the instructions stored in the computer readable memory produce a manufacture article comprising an instruction device, the instruction device realizes the function specified in one or more processes of the flow chart and/or one or more blocks of the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatuses such that a series of steps are performed on the n:\ci<;fUnlerwovei]\NRPc,rtbl\r>C'C\L5ER\i617616^,Ll .dnoi-14/12/2017

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-31 computer or other programmable apparatuses to produce a computer-implemented process. Therefore, the instruction executed on the computer or other programmable apparatuses provide steps for implementing the functions specified in one or more processes of the flow chart and/or one or more blocks of the block diagram.

The above description is only for the preferred embodiments of the present invention and is not intended to limit the scope of the present invention.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word comprise, and variations such as comprises and comprising, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

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Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for media negotiation in a voice call continuity (VCC) service, applied in an access transfer control functionality (ATCF), comprising:

storing an offer media and not instructing an access transfer gateway (ATGW) to update a media when a received media modification request sent by a first call session control function (CSCF) carries the offer media; and instructing the ATGW to update the media only when a received media modification response sent by a second CSCF carries an answer media.
2. The method according to claim 1, wherein when receiving the media modification response sent by the second CSCF, the method further comprises:

selecting to use the same coding and decoding manner for the offer media and the answer media.
3. The method according to claim 1, wherein when receiving the media modification response sent by the second CSCF, the method further comprises:

determining that the offer media and the answer media have no intersection; correspondingly, instructing the ATGW to update the media comprises: instructing the ATGW to start transcoding.
4. The method according to claim 1, wherein the media modification request is an update request message, or a re-invite request message or a session switching request; correspondingly, the media modification response is a 200 OK response message; or the media modification request is the 200 OK response message; correspondingly, the media modification response is an ACK response message.
5. The method according to claim 1, wherein before receiving the media modification request sent by the first CSCF, the method further comprises:

storing a corresponding session and an anchored media of the ATGW; correspondingly, before receiving the media modification response sent by the second CSCF,

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-33 the method further comprises:

assembling the offer media and the stored corresponding anchored media of the ATGW to obtain an assembled media and sending the assemble media to the second CSCF.
6. The method according to claim 5, wherein assembling the offer media and the stored corresponding anchored media of the ATGW comprises:

replacing an IP address and a port of the offer media with an IP address and a port of the corresponding anchored media of the ATGW, and supplementing a coding and decoding capacity which is supported by the ATGW and not provided in the offer media.
7. The method according to claim 1, wherein the method further comprises:

not instructing the ATGW to update the media and retransmitting a received response message of a media negotiation failure to the first CSCF when receiving the response message of the media negotiation failure sent by the second CSCF.
8. An access transfer control functionality (ATCF), comprising: a first indicating module and a second indicating module; wherein the first indicating module is arranged to store an offer media and not to instruct an ATGW to update a media when a received media modification request sent by a first CSCF carries the offer media;

the second indicating module is arranged to instnict the ATGW to update the media only when a received media modification response sent by a second CSCF carries an answer media.
9. The ATCF according to claim 8, wherein the second indicating module is further arranged to select to use the same coding and decoding manner for the offer media and the answer media when receiving the media modification response sent by the second CSCF.
10. The ATCF according to claim 8, wherein the second indicating module is arranged to determine that the offer media and the answer media have no intersection, and instruct the ATGW to start transcoding.

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-3411. The ATCF according to claim 8, wherein the ATCF further comprises a memory module arranged to store a corresponding session and an anchored media of the ATGW;

the second indicating module is further arranged to assemble the offer media and the stored corresponding anchored media of the ATGW to obtain an assembled media and send the assembled media to the second CSCF before receiving the media modification response sent by the second CSCF.
12. The ATCF according to claim 8, wherein the second indicating module is further arranged not to instruct the ATGW to update the media but retransmit a received response message of a media negotiation failure to the first CSCF when receiving the response message of the media negotiation failure sent by the second CSCF.
13. A system for media negotiation in a voice call continuity (VCC) service, comprising a first CSCF, an ATCF, a second CSCF and an ATGW; wherein the first CSCF is arranged to send a media modification request to the ATCF; the ATCF is arranged to receive the media modification request sent by the first CSCF, and to store an offer media and not to instruct the ATGW to update the media when the received media modification request sent by the first CSCF carries the offer media; and is further arranged to receive a media modification response sent by the second CSCF, and instruct the ATGW to update the media only when the received media modification response sent by the second CSCF carries an answer media;

the second CSCF is arranged to send the media modification response to the ATCF; the ATGW is arranged to update the media after receiving an indication of the ATCF.
14. The system according to claim 13, wherein the ATCF is further arranged to select to use the same coding and decoding manner for the offer media and the answer media when receiving the media modification response sent by the second CSCF.
15. The system according to claim 13, wherein the ATCF is arranged to determine that the offer media and the answer media have no intersection, and instruct the ATGW to start transcoding.

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-35 16. The system according to claim 13, wherein the ATCF is further arranged to store a corresponding session and an anchored media of the ATGW to execute the media negotiation and modification before receiving the media modification request sent by the first CSCF.
17. The system according to claim 13, wherein the ATCF is further arranged to assemble the offer media and stored corresponding anchored media of the ATGW to obtain an assembled media and send the assembled media to the second CSCF before receiving the media modification response sent by the second CSCF, correspondingly, the second CSCF is further arranged to receive the assembled media sent by the ATCF.
18. The system according to claim 13, wherein the second CSCF is further arranged to send a response message of a media negotiation failure to the ATCF;

the ATCF is further arranged not to instruct the ATGW to update the media but retransmit the received response message of the media negotiation failure to the first CSCF when receiving the response message of the media negotiation failure sent by the second CSCF;

the first CSCF is further arranged to receive the response message of the media negotiation failure retransmitted by the ATCF.
19. A computer storage medium comprising a group of instructions that when being executed causes at least one processor to execute the method for media negotiation in a VCC service according to any one of claims 1-7.

Store a proposed media when a received media modification request sent by a first CSCF carries the proposed media.

101 instruct an ATGW to update a media when a received media modification response sent by a second CSCF carries a response media.

FIG. 1

FIG. 2

EIG.

. 5

FIG. 10