A method for realizing session communication between the calling party and the called party

Method to establish a session between a caller and a caller

5 FIELD OF THE INVENTION

The present invention relates to the field of communications technology, more specifically to a method of establishing a session between a calling user and a calling user.

BACKGROUND OF THE INVENTION

The next generation network (NGN) is rapidly developing and introducing a large number of new services. In the field of voice and multimedia services, it has become a trend to control and provide NGN services based on flexible and extensible SIP (initial session protocol) signaling and other

fifteen auxiliary signals such as RTP (real-time transport protocol) and SDP (session description protocol), etc.

Many services currently coexist and, in order to meet the growing demands of users and take into account the repeatability of the characteristics of the services, it is necessary to combine the current services and perform the nesting of different service characteristics, which, in Consequently, it causes the problem of nesting between multi-services.

However, current NGN services only take into account the handling of call flows without nesting but cannot properly handle multi-service nested call flows. At the same time,

25 for example, when the hitch number, the shipping number or the door number changes, it is impossible to achieve the treatment when the called user's SDP changes. Taking as example the typical multiservice sending and nesting, when the user dials an intelligent service and activates the corresponding intelligent flow, it is necessary to send the call once and activate the application server twice and the detailed flow is illustrated in Figure 1 as follows:

The calling user dials the access code of the first service and sends the Invite message containing its own SDP to the AS1 application server of the calling user, which is activated to perform the first service flow.

The calling server's AS1 application server issues the routing number of the second service (it is

35 ie, the access code of the second service) for the logical switch according to the Invite message. And, according to the routing number, the logical switch activates the AS2 application server of the second service to implement the flow of the second service. Then, the AS2 application server calls the named named user.

Once the called user picks up, the AS2 application server sends the Update message containing an SDP of the called user to the calling user.

The SDP message of the called user is updated on the side of the calling user and the response message OK (correct answer) 200 is sent to the logical switch, which contains an SDP of the calling user.

Four. Five The called user transmits the Off-hook Response message and informs the AS1 application server of the calling user at level, and the calling server's AS2 application server returns the ACK (acknowledgment) message of the called user. And, thus, the session negotiation process is terminated since the number of the called user is issued.

During the previous session negotiation process, after picking up, the called user immediately sends the Update message containing its own SDP, and at this time the SDP of the user called in the Update message is the current SDP of the called user. The SDP can change according to the variation of the door number of the called user, so the calling user is required to send the Reinvi message

55 Take the called user after receiving the Update message from the called user to renegotiate in order to obtain the last SDP of the called user. The called user returns the OK 200 Response message that contains its own most recent SDP to the calling user and the renegotiation process of the called user is completed since he picked up. And the call is established between the calling user and the called user.

In addition, during the previous session negotiation process, if the called off-hook user (the original called user) is sent or hooked with the third called user, the real called user is the third called user whose SDP is different from the original SDP. The Update message sent by the called original user who picked up includes its own SDP but not the SDP of the real called user (the third called user). Therefore, after receiving the Update message from the original called user, the calling user is required to send the message Reinvitar the real called user for renegotiation in order to obtain the real called user SDP. The real called user returns the OK 200 Response message that contains its own SDP to the calling user and,

thus, the renegotiation process of the called user is completed since he picked up. Consequently, the call is established between the calling user and the real called user.

The above flows shown after updating the SDP of the called user on the side of the calling user

5 ma, when the renegotiation is carried out between the calling user and the called user using the Reinvitar signaling once after another, they will refer to many devices and it is difficult to achieve. In addition, in the B2B-based mode (the back-to-back mode in the SIP protocol), cross-treatment in Reinvitar signaling will lead directly to chaos. According to the previous flows, if the service or shipping flow nesting occurs many times, the number of Reinvitar signaling will be greater and will be more likely to lead to chaos, which may result in the single-pass state. In addition, many Reinvitar signaling will increase the signaling load on the network and will result in a higher probability of losing packets and transmission errors, which will include service performance and may even cause it to collapse. the net.

fifteen The US patent application 2005/0036492 A1 describes, in the event that there is no question of call redirection with the help of the message Reinvitar during the call state, how to solve the problem of controlling the redirection of a carrier connection, even in the call status, by having the first user called (subscriber B) request an offer from SDP to the second user called (subscriber C) through the SIP / SIP-T protocol using a corresponding parameter (header) "request for offer of SDP", etc.

Another US patent application, 2005/0105511 A1 describes a method and system for establishing a media session, the method of which comprises: sending a media session invitation request from a first media communication device to a second media device. media communication; initiate a media session establishment from the second media communication device to a user equipment

25 destination; sending a first indication of media inactivity from the second media communication device to the first media communication device; and sending a first indication of media activity from the second media communication device to the first media communication device, in response to receiving an accepted session establishment response from the destination user equipment to the second communication device media.

The draft of the Internet document "Status during a SIP dialogue" (ELWELL SIEMENS V VENKATARAMANAN SYLANTRO SYSTEMS CORP J) examines the need to update status information, such as the identity of the remote party, during a SIP dialogue. Explore existing mechanisms that may be appropriate and propose minor clarifications to RFCs and existing drafts to achieve this.

35 In the document "Solutions to the implementation of services in SIP networks" (HILT V et al., BELL LABS TECHNICAL JOURNAL, WILEY, CA., USA), we evaluate common service models suitable for the desired services and the network environment of service manufacturers and the new cooperative service model is introduced.

SUMMARY OF THE INVENTION

The present invention provides a method for establishing a session between a calling user and a called user, with application to a next generation network, after said called user picks up, which com

Four. Five also turns on:

restarting a session negotiation with said called user first through a first application server corresponding to the called user; when obtaining a session description protocol of said called user, send an update request message containing said session description protocol of said called user to a second application server corresponding to the user calling through a logical switch to all levels;

renegotiate, through the second application server, a session with a calling user in accordance with said session description protocol of said called user;

55 once the calling user completes the session update, return a reply message containing a session description protocol of said user calling said called user, thus completing a two-way session negotiation between said calling user and said called user

According to one embodiment, when the session renegotiation is carried out with said called user, the application server of said called user sends to said called user a new request message without session description protocol.

According to one embodiment, after the application server of said called user carries out the

65 session renegotiation with said called user, said called user returns its own session description protocol to its application server by means of the reply message.

According to one embodiment, after the session update, said calling user returns a reply message containing a session description protocol of said user calling the said called user that specifically includes the steps of:

5 return said user who calls a reply message containing its own SDP to the application server of said calling user;

return the application server of said calling user a response message to the logical switch of said calling user;

return the logical switch of said user calling a response message to the logical switch of said called user, level by level;

fifteen return the logical switch of said user called a reply message to the application server of said called user; and

sending the application server of said user called an end confirmation response message containing a session description protocol of said user that calls said called user.

According to one embodiment, the method further includes:

after two-way session negotiation between said calling user and said called user, the application server of said called user transfers a message Off-hooked from said user called to the switch

25 logic of said user calling through the logical switch of said called user, level by level;

the logical switch of said calling user transmits a Off-hook message to the application server of said calling user; and

The application server of said calling user sends an end message to the media resource server on the side of said calling user in order to stop the reproduction of the call set tone for said calling user.

According to one embodiment, the method for establishing a session between a calling user and a calling user

35 mado, in which after a first called user picks up and sends or hooks to a second called user, it also includes:

restarting a session negotiation with said second called user through a first application server corresponding to said first called user and, upon obtaining a session description protocol of said second called user, sending an update request message with said session description protocol of said second user called to a second application server corresponding to said user calling through all levels of logical switches;

renegotiate by means of the second application server, a session with said user calling according to said session description protocol of said second called user;

once the calling user has completed the session update, return a reply message containing a session description protocol of said user calling said second called user, thereby completing a bidirectional session negotiation between said calling user and the second called user.

According to one embodiment, when the session renegotiation is carried out with said second called user, the application server of said first called user sends to said second user called a new request message without session description protocol.

55 According to one embodiment, after the application server of said first called user performs the session renegotiation with said second called user, said second called user returns its own session description protocol to its application server by means of the message of answer.

According to one embodiment, after the session is updated, said calling user returns a reply message containing a session description protocol of said user calling said second called user that specifically includes the steps of:

returning said user calling an answer message containing its own SDP to the application server 65 of said calling user;

return the application server of said caller to the logical switch of said caller;

returning the logical switch of said user calling a response message to the logical switch of said first called user, level by level;

returning the logical switch of said first user called a response message to the application server of said first user called; and

sending the application server of said first user called a final confirm reply message containing a session description protocol of said user calling said second called user.

According to one embodiment, the above method also includes:

fifteen after the two-way session negotiation between said calling user and said first called user, transmitting the application server of said first user called a Off-hook message of said first user called to the logical switch of said user calling through the logical switch of said user first user called, level by level;

sending the second logical switch of said user who calls a Off-hook message to the application server of said calling user; and

send the application server of said user calling an end message to the media resource server on the side of said user in order to stop the reproduction of the call set tone for

25 That caller user.

The present invention offers one or more of the following advantages:

<dl><dt>(1) </dt><dd>The present invention optimizes the SIP signaling flow in the case of step-by-step sending or nesting services and provides an activation method to send different multi-service flows or to send and nest different flows of a service, which can achieve the combination and integration of services. </dd></dl>

<dl><dt>(2)</dt><dd> In the signaling flow according to the method of the present invention, after picking up the first called user, the server of the first called user will carry out the session negotiation with a second user </dd></dl>

35 called to obtain the SDP of the second called user and then the calling user's server will carry out the session negotiation with a calling user to update the called user's SDP on the calling user's side. Thus, bidirectional session negotiation between the calling user and the second called user is guaranteed in order to ensure that the calling user and the called user can connect properly.

(3) In accordance with the present invention, it is not necessary to send the Reinvitar signaling many times and, in this way, the problem of the single pass state is solved due to the chaos of the signaling control.

BRIEF DESCRIPTION OF THE DRAWINGS

Four. Five Figure 1 is the diagram showing the treatment of call flow in the related art;

Figure 2 is the schematic diagram showing the related network entities in establishing communication between the calling user and the called user;

Fig. 3 is the process chart showing the method for achieving the establishment of communication between the calling user and the called user, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

55 Illustrative embodiments of the method of the present invention will be explained in detail with reference to the drawings.

Figure 2 is the schematic diagram showing the related network entities in establishing communication between the calling user and the called user.

The network elements are:

the application server, which is used to execute the service logic and call control of the logical switch;

65 the media resource server (MRS), which is used to provide voice interaction with a user, to perform voice reproduction and interaction in the language management flow and outgoing call flow, etc., and to achieve the play function of the call establishment tone change service and the voice service;

the logical switch, which is used to achieve the activation of the service, to receive the instructions from the application server in order to connect the call, report events and carry out the route traffic;

the database, which is used to store the data related to the service; and

Different kinds of user terminals.

A typical example of sending the call once and activating the application server twice is taken to illustrate the flows in the method of establishing communication between the calling user and the second called user according to an embodiment of the present invention, including the flow:

<dl><dt>1. </dt><dd>The caller dials service access code A with telephone 1 (telephone number N1) and passes the report of the call to logical switch 1. </dd></dl>

<dl><dt>2. </dt><dd>The logical switch determines if the access code belongs to service A; if so, the corresponding AS1 application server is activated.</dd></dl>

<dl><dt>3.</dt><dd> The application server AS1 carries out service flow A, which includes: interacting with an MRS, collecting the card number and authenticating the password of the calling user; operate together with a database to perform data comparison, etc.</dd></dl>

<dl><dt>4.</dt><dd> The application server AS1 issues a routing number of a service close to logical switch 1; for example, the routing number is the access code of service B.</dd></dl>

<dl><dt>5.</dt><dd> The logical switch 1 routes the call to the related logical switch 2 according to the service access code B. </dd></dl>

<dl><dt>6.</dt><dd> Logic switch 2 determines if the access code is the access code of service B; if so, the corresponding AS2 application server is activated.</dd></dl>

35 7. The AS2 application server performs the service B flow and issues the routing number N2 to the logical switch 2; Logic switch 2 judges that the routing number N2 is a terminal number and initiates a call to that terminal (telephone 2).

<dl><dt>8.</dt><dd> The telephone 2 corresponding to N2 rings and the message is returned. Sound the call signal to logic switch 2. </dd></dl>

<dl><dt>9.</dt><dd> Logic switch 2 returns the message to ring the call signal from telephone 2 to the logical switch </dd></dl>

1.

Four. Five 10. Logic switch 1 returns the message Ring the call signal from telephone 2 to the AS1 application server and the AS1 application server tells the MRS to play the call set tone for the calling user.

<dl><dt>11. </dt><dd>After the user of telephone 2 picks up the telephone, the call is transferred to telephone 3 with the number N3; or the N2 is set to send the call to the N3 number.</dd></dl>

<dl><dt>12.</dt><dd> The user of telephone 3 picks up the telephone and the application server AS2 initiates a request to telephone 3 to negotiate on the repurchase of the SDP of the second called user, the second user being called telephone 3. </dd></dl>

<dl><dt>13. </dt><dd>Telephone 3 responds to the request and sends the Response message containing its own SDP to achieve bidirectional session negotiation with a calling user. </dd></dl>

<dl><dt>14.</dt><dd> The user of telephone 1 communicates with a user of telephone 3. </dd></dl>

The procedure for performing SIP signaling in the previous flows is shown in Figure 3, which specifically includes:

1. The caller dials the access code of the A service and uses the Invite signaling contained in their pro

65 pio SDP to request the activation of the service flow A, and the request is sent to the AS1 application server of the calling user to control the service flow A.

two. The AS1 application server executes the corresponding service logic, sends the Invite message that contains an SDP of the calling user to the MRS of the calling user and requests to collect the card number and the password of the calling user.

<dl><dt>3.</dt><dd> The MRS returns the OK 200 Response message that contains its own SDP to the AS1 application server. </dd></dl>

<dl><dt>4.</dt><dd> The AS1 application server transmits the OK 200 Response message containing an MRS SDP to the calling user and prepares to reproduce the corresponding warning tone and to pick up the card number and the password of the calling user. </dd></dl>

<dl><dt>5. </dt><dd>After authenticating the service initiated by the calling user, the AS1 application server interacts with a database and issues the routing number of a service near logical switch 1 according to the service initiated by the calling user, for example the routing number is the code </dd></dl>

fifteen of access of the next intelligent service B.

6. The logical switch 1 acquires the logical switch 2 corresponding to the service according to the fact that the routing number issued is the access code of the service B (for simplicity, the logical switch 1 and the logical switch 2 are combined as the switch logic of Figure 3), and sends the Invite message containing an SDP of the user calling through logical switch 2 to inform, and then activate, the AS2 application server and then the procedure continues until the treatment flow of the intelligent service B of the first called user.

7. The AS2 application server processes the internal service flow and sends the Request invitation message to the final office.

<dl><dt>8. </dt><dd>After connecting with the first called user, the final office returns the message Ringing the call signal 180 containing an SDP of the first called user; the message Ringing the call signal may also not include the SDP of the first called user; If you do not include it, the SDP of the first called user will be included in the last Reply Off-hook message.</dd></dl>

<dl><dt>9.</dt><dd> Application server AS2 returns message 180 Ringing the call signal to logical switch 2, which will return it to logical switch 1. </dd></dl>

35 10. Logic switch 1 transmits the message 180 Sounding the call signal to the application server AS1; then, the AS1 sends the PRACK message (the reliable transmission response message in SIP protocol) to the logical switch 1, and the logical switch 1 returns the OK 200 response message of the PRACK message.

<dl><dt>11.</dt><dd> The AS1 application server sends the Request invitation message that contains an SDP of the calling user to the MRS of the calling user and requests to play the call set tone for the calling user. </dd></dl>

<dl><dt>12.</dt><dd> The MRS of the calling user returns the OK 200 Response message that contains its own SDP to the AS1 application server. </dd></dl>

Four. Five 13. The AS1 application server sends to the caller the message Invite that contains an MRS SDP on the side of the calling user, performs the session negotiation with a caller and reproduces the call set tone for the caller

<dl><dt>14.</dt><dd> The first user called picks up and returns the OK 200 Response message that contains an SDP of the first user called to the AS2 application server. </dd></dl>

<dl><dt>15.</dt><dd> After receiving the Off-hook message from the first called user, the AS2 application server sends the Reinvitar message without its own SDP to the second called user for session renegotiation with the second called user; at this time, the call is sent to another terminal by the first called user that has</dd></dl>

55 hung up, the real called user (that is, the second called user) is the first one after sending, so that through the renegotiation process the SDP of the second called user can be obtained.

<dl><dt>16.</dt><dd> The second called user returns the OK 200 Response message that contains its own SDP. </dd></dl>

<dl><dt>17.</dt><dd> The AS2 application server sends the Update message to logical switch 2 which then returns the Update message that contains an SDP of the second user called to logical switch 1. </dd></dl>

<dl><dt>18.</dt><dd> The logical switch returns the Update message that contains an SDP of the second user called to the server.</dd></dl>

AS1 applications dor. 65

<dl><dt>19. </dt><dd>The AS1 application server sends the Reinvitar message that contains an SDP of the second user called to the </dd></dl>

Calling user and carry out session negotiation with the calling user in order to update the called SDP of the called user on the side of the calling user.

<dl><dt>20. </dt><dd>The calling user updates the SDP of the called user, changes the SDP of the original connected MRS of the user</dd></dl>

5 It calls the SDP of the second user called and, after the success of the update, returns the message Answer OK 200 containing its own SDP to the AS1 application server.

<dl><dt>21.</dt><dd> The application server AS1 returns the message Answer OK 200 that contains an SDP of the user calling the logical switch 1 which then sends the message to the logical switch 2. </dd></dl>

<dl><dt>22. </dt><dd>Logic switch 2 returns the OK 200 Response message that contains an SDP of the user calling the AS2 application server. </dd></dl>

<dl><dt>23.</dt><dd> The AS2 application server sent the final ACK message containing an SDP of the user calling the</dd></dl>

fifteen A large called user and only then is a full session renegotiation terminated between the second called user and the calling user.

24. The AS2 application server returns the OK 200 Response message for the first called user that has picked up logical switch 2; then, the logical switch 2 sends the message to the logical switch 1, the logical switch 1 transmits it to the application server AS1 and, after receiving the Off-hook message from the first called user, the application server AS1 sends the message Goodbye (terminating call signal playback) to the MRS of the calling user to stop playing the call set tone to the calling user.

25 25. The AS1 application server returns the final ACK message to the calling user.

26. The AS2 application server returns the final ACK message through logical switches 1 and 2 to the AS2 application server and communication is established between the calling user and the second called user.

From the above procedure, it can be seen that in the multi-service nesting flow established by the calling of the calling user, after the first called user picks up, the AS2 application server of the first called user sends the Reinvitar message without its SDP to a second called user and performs session renegotiation with the second called user, then the second called user returns the message

35 Answer OK 200 that contains its own SDP to the AS2 application server of the first called user, and the AS2 application server of the first called user sends the Update message containing an SDP of the second user called to the application server AS1 of the calling user with in order to carry out the update of the called user SDP on the calling user side and, consequently, ensure that communication is established between the calling user and the second called user.

The above illustrates the embodiments of the present invention with a typical example of sending the call once and activating the application server twice. Embodiments of the present invention can also be applied to the case in which only the shipment exists.

Four. Five Furthermore, when only multi-service nesting occurs but without sending, as shown in Figure 3, an embodiment of the method of the present invention for carrying out communication between the calling user and the called user, includes the following flows :

<dl><dt>1. </dt><dd>The calling user dials the access code of service A and uses the Invite signaling that contains their own SDP to request activation of service flow A and the request is sent to the AS1 application server of the calling user to control the flow of service A. </dd></dl>

<dl><dt>2. </dt><dd>The AS1 application server executes the corresponding service logic to send the message Invite that </dd></dl>

It contains an SDP of the user that calls the MRS of the calling user and to request the collection of the card number and the password of the calling user.

<dl><dt>3.</dt><dd> The MRS returns the OK 200 Response message that contains its own SDP to the AS1 application server. </dd></dl>

<dl><dt>4.</dt><dd> The AS1 application server transmits the Ok 200 Response message that contains an MRS SDP to the calling user and prepares to reproduce the corresponding warning tone and to pick up the card number and the password. </dd></dl>

<dl><dt>5.</dt><dd> After performing authentication for the service initiated by the calling user, the AS1 application server interacts with a database and issues the routing number of a service near the switch </dd></dl>

65 logical 1 according to the service initiated by the calling user, for example, the routing number is the access code of the next intelligent service B.

6. The logical switch 1 acquires the logical switch 2 corresponding to the service according to the fact that the routing number issued is the access code of the service B, and sends the message Invite through the logical switch 2 to activate the application server AS2 and then the procedure continues for the flow

5 of treatment of the intelligent service B of the called user.

<dl><dt>7.</dt><dd> The AS2 application server executes the internal service flow processing and sends the Request invitation message to the final office. </dd></dl>

<dl><dt>8.</dt><dd> After connecting with the called user, the final office returns the message Ringing the call signal 180 containing an SDP of the called user. Alternatively, the message Ringing the call signal may also have a structure lacking the SDP of the called user; if it lacks it, the SDP of the called user will be included in the last Reply Off-hook message.</dd></dl>

fifteen 9. The AS2 application server returns the message Ringing call signal 180 to logical switch 2, which then returns it to logical switch 1.

<dl><dt>10.</dt><dd> Logic switch 1 transmits the message Ringing call signal 180 to application server AS1; then, the AS1 sends the PRACK message (the reliable transmission response message in SIP protocol) to the logical switch 1, and the logical switch 1 returns the OK 200 response message of the PRACK message.</dd></dl>

<dl><dt>11.</dt><dd> The AS1 application server sends the request request message that contains an SDP of the calling user to the MRS of the calling user and requests that the call establishment tone be played for the calling user. </dd></dl>

<dl><dt>12.</dt><dd> The MRS of the calling user returns the OK 200 Response message that contains its own SDP to the AS1 application server. </dd></dl>

<dl><dt>13.</dt><dd> The AS1 application server sends the Invite message that contains an MRS SDP on the user side that calls the calling user, performs session negotiation with a calling user and plays the call set tone for the user What is it calling? </dd></dl>

<dl><dt>14.</dt><dd> The called user picks up and returns the OK 200 Answer message that contains a user's SDP called</dd></dl>

do to the AS2 application server. 35

<dl><dt>15.</dt><dd> After receiving the Off-hook message from the called user, the AS2 application server sends the Reinvitar message without its own SDP to the called user for the session renegotiation with the called user in order to obtain the last SDP of the called user. </dd></dl>

<dl><dt>16.</dt><dd> The called user returns the OK 200 Response message that contains their own SDP. </dd></dl>

<dl><dt>17.</dt><dd> The AS2 application server sends the Update message to logical switch 2 which then returns the Update message containing a more recent SDP of the user called to logical switch 1. </dd></dl>

Four. Five 18. Logic switch 1 returns the Update message that contains an SDP of the user called to the AS1 application server.

<dl><dt>19.</dt><dd> The AS1 application server sends the Reinvitar message that contains an SDP of the called user to the calling user and performs the session negotiation with a calling user in order to update the SDP of the called user on the side of the calling user . </dd></dl>

<dl><dt>20.</dt><dd> The calling user performs the SDP update of the called user, changes the SDP of the original connected MRS of the calling user to the most recent SDP of the called user and, after the success of the update, returns the message Answer OK 200 containing its SDP itself to the AS1 application server. </dd></dl>

<dl><dt>21.</dt><dd> The application server AS1 returns the message Answer OK 200 that contains an SDP of the user calling the logical switch 1 which then sends the message to the logical switch 2. </dd></dl>

<dl><dt>22. </dt><dd>Logic switch 2 returns the OK 200 Response message that contains an SDP of the user calling the AS2 application server. </dd></dl>

<dl><dt>23.</dt><dd> The AS2 application server sends the final ACK message containing an SDP of the calling user to the called user and, only then, is a full session renegotiation terminated between the called user and the calling user. </dd></dl>

24. The AS2 application server returns the OK 200 Response message for the called user who has picked up the logical switch 2; logical switch 2 then sends the message to logical switch 1; Logic switch 1 transmits it to the AS1 application server and, after receiving the Off-hook message from the called user, the AS1 application server sends the Goodbye message (which ends with the reproduction of the call signal sound) to the user's MRS calling to stop playing the flame setting tone

5 It gives to the caller.

<dl><dt>25.</dt><dd> The AS1 application server returns the final ACK message to the calling user. </dd></dl>

<dl><dt>26.</dt><dd> The AS2 application server returns the final ACK message through logical switches 1 and 2 to </dd></dl>

10 AS2 application server and the communication between the calling user and the called user is established accordingly.

From the above procedure, it can be seen that in the multiservice nesting flow established by the calling of the calling user, after the called user is picked up, the AS2 application server of the called user 15 sends the Reinvitar message without its own SDP to the called user for session renegotiation with the called user, the called user then returns the OK 200 Answer message containing its own SDP to the AS2 application server of the called user's server, and the AS2 application server of the called user's server sends the Update message containing an SDP of the called user to the server of AS1 applications of the calling user in order to perform the SDP update of the called user on the user side

twenty which calls and, consequently, ensure that communication is established between the calling user and the called user.

The above embodiments illustrate in detail the activation of the multiservice by means of an example of activation of two service flows (in relation to two logical switches and two application servers). The principle of

25 realization to activate the nesting of more than two services or flows is the same as to activate two flows or services and the only difference is that it can relate to more logical switches and application servers to transmit the previous signaling level by level.

Obviously, those skilled in the art can make improvements and modifications to the present invention without leaving

30 of the scope of the present invention. It is intended that the present invention cover the modifications and variations of this invention provided they fall within the scope of the appended claims and their equivalents.