WO2007069819A1

WO2007069819A1 - Method and apparatus for distinguishing data in session based communications

Info

Publication number: WO2007069819A1
Application number: PCT/KR2006/004289
Authority: WO
Inventors: Kang-Suk Huh; Te-Hyun Kim; Sung-Mu Son
Original assignee: Lg Electronics Inc.
Priority date: 2005-12-12
Filing date: 2006-10-20
Publication date: 2007-06-21

Abstract

A method and apparatus for discriminating data in session-based communication are disclosed. A mobile terminal generates a unique value for discriminating a session, includes it in a session invitation message, and transmits it to a server, and other devices including the server include the unique value in data (or message) related to a particular session indicated by the unique value and transmit it. When the mobile terminal receives data from the server, it discriminates the data as to which session it belongs by comparing the unique value included in the received data and the unique value included in the session invitation message.

Description

METHOD AND APPARATUS FOR DISTINGUISHING DATA IN SESSION

BASED COMMUNICATIONS

TECHNICAL FIELD

The present invention relates to a session-based service and, more particularly, to a method and apparatus for discriminating/distinguishing data in session-based communication.

BACKGROUND ART

In general, a session-based service includes a PT (Push Talk) service. The PT service, which provides high speed communication to a service provider and a mobile communication user, is a half-duplex communication service for transmitting media data (talk burst) to one or more clients for which a session has been established. The PT service can be one of a PoC (PTT over Cellular) service for transmitting audio data, a PTV (Push To View) service for transmitting video data, and a PTD (Push To Data) service for transmitting data.

In the PT service, one client can invite another client to a PT session by clients or groups to which clients belong. Namely, when a particular (specific) PT client selects one or more PT clients and invites them to the PT session, a session is connected between the both clients through a PT server and media data is transferred therebetween.

In general, before transferring the media data, the PT client requests an authority to transmit the media data (referred to hereinafter as 'talk burst') from the PT server, acquires a talk burst (i.e., authority to speak) by the PT i server, and then transmits the media data. After the PT client obtains the talk burst from the PT server, it can return it.

In order to control the talk burst, a talk burst control protocol (TBCP) message is exchanged between the PT client and the PT server. The TBCP uses a UDP (User Datagram Protocol) as a transport protocol.

In general, the PT server may include a controlling function unit, a participating function unit, and both the controlling function unit and the participating function unit.

The controlling function unit provides a centralized session processing, a media distribution, controlling of the talk burst including an identifier of a speaker, a policy for participating in a group session, and information on a participant, etc. The participating function unit provides a policy for processing a corresponding session and inputting the session, and a media relay function and a TBCP message relay function between the PT client and the controlling function unit.

The general session establishing method will now be described. FIG. 1 is a session establishing method in a general session-based communication system, in which a case where a first PT client 1 invites second and third PT clients is taken as an example. When the first PT client 1 invites the second and third PT client by using a session previously established between the second PT server 2 and the first PT client 1 , the first PT client 1 transmits a first session invitation message to the first PT server 2 (step S1). The first PT server 2 starts a procedure for inviting the second and third PT clients. Herein, the first PT server 2 a PT server to which the first PT client 1 belongs, including the participating function unit. When the second and third PT clients accept the invitation of the third PT client later, the invitation procedure is proceeding for a long time (steps S2 and S3).

After the session invitation message is transmitted, when a first PT user of the first PT client wants to cancel inviting of the second and third PT clients before a response message with respect to the session invitation message is received, the first PT client 1 transmits a cancel message for canceling the invitation of the second and third PT clients to the first PT server according to a command of the first PT user (step S4). In this respect, the cancel message is transmitted by using a UDP

(user Datagram Protocol) transport protocol, so it is not guaranteed that the cancel message is successfully transferred.

Meanwhile, the first PT server 2 receives a response message (200 OK) informing that the second or third PT client has accepted the invitation so a PT session has been established from a second PT server 3 (step S5).

In addition, the first PT server receives a talk burst granted message

(namely, a message for giving talk burst to the first PT client 1) from the second PT server 3 at approximately the same time as when the response message is received, and transmits it to the first PT client 1 (steps S6 and S7).

In this respect, it is assumed that the first PT client 1 entered a tunnel or the like or if a radio interface or a fixed line section was unstable due to various reasons, so the cancel message the first PT client 1 had transmitted to the first PT server 2 and the talk burst granted message the first PT server 2 had transmitted to the first PT client 1 were lost in the radio interface.

In this situation, the first PT user of the first PT client 1 determines to invite fourth and fifth PT clients, so the first PT client 1 generates a second session invitation message for inviting the fourth and fifth PT clients and transmits it to the first PT server 2 (step S8).

Meanwhile, the second PT server 3 transmits the data (media data (RTP data, RTCP data and TBCP data, etc.) related to the PT session (referred to hereinafter as 'the first PT session') generated by having invited the second and third PT clients to the first PT client 1 via the first PT server 2. With the data related to the first PT session received, because the first PT client 1 had transmitted the cancel message for canceling inviting of the second and third PT clients, transmitted the second session invitation message for inviting the fourth and fifth PT clients, and then received the data related to the first PT session, the first PT client 1 considers the data related to the PT session generated by having invited the fourth and fifth PT clients, so it processes the received data and outputs it to the first PT user (step S9).

DISCLOSURE OF THE INVENTION

Thus, in the general PT service system, the PT client cannot discriminate the PT session before the establishment of the PT session is completed, when the data related to a particular (specific) session is transmitted from the PT server, the PT client fails to discriminate the transmitted data as to which PT session it is related. Thus, the PT client erroneously processes and outputs the data.

Therefore, one exemplary feature of the present invention provides a method and apparatus in which a particular (specific) client generates a unique value for discriminating a particular session, adds it in a session invitation message and transmits the session invitation message to a network and the network adds the unique value in data related to the particular session and transmits it so that the particular client can discriminate a session to which the data belongs through the unique value. Another exemplary feature of the present invention provides a method and apparatus for discriminating data in session-based communication in which after a server transmits a talk burst granted message in order to give a talk burst (i.e., authority to speak) to a particular client, it re-transmits the talk burst granted message at prescribed intervals until it receives a corresponding response message, so that the particular client can properly recognize a particular session establishment state.

Still another exemplary feature of the present invention provides a method and apparatus for discriminating data in session-based communication in which a particular client, which has transmitted a cancel message for canceling a particular session invitation it had requested, re-transmits the cancel message at prescribed intervals until it receives a response message with respect to the cancel message, so that a server can properly recognize that the particular session invitation has been canceled.

Yet another exemplary feature of the present invention provides a method and apparatus for discriminating data in session-based communication in which a particular client checks a unique value for discriminating a session included in data received from a server, and if the data corresponds to a session desired to be canceled, the particular client discards the data and transmits a cancel message to the server. To implement at least the above feature in whole or in parts, the present invention provides a terminal that may include a client for generating a first unique value for discriminating a session, adding it in a session invitation message and transmits the message, and then comparing a second unique value included in data received through a server with the first unique value, and processing or discarding the data according to the comparison result.

To implement at least the above feature in whole or in parts, the present invention also provides a session-based communication system for discriminating data that may include: a terminal for transmitting a session invitation message for inviting at least one particular (specific) device; and a server for transmitting a talk burst granted message in order to give a talk burst (i.e., authority to speak) to the terminal and then re-transmitting it at prescribed intervals until it receives a corresponding response message.

To implement at least the above feature in whole or in parts, the present invention also provides a method for discriminating data in session-based communication that may include: generating, by a terminal, a first unique value for discriminating a session, adding it in a session invitation message, and transmitting the message to a server; comparing, by the terminal, a second unique value included in data transmitted from the server with the first unique value; and processing or discarding, by the terminal, the data according to the comparison result.

To implement at least the above feature in whole or in parts, the present invention also provides a method for discriminating data in session-based communication that may includes: transmitting, by a terminal, a first session invitation message including a first unique value for discriminating a session, and then transmitting a session invitation cancel message including a first invitation value to a server; and re-transmitting, by the terminal, the session invitation cancel message at every certain intervals until it receives a response message with respect to the session invitation cancel message.

To implement at least the above feature in whole or in parts, the present invention also provides a method for discriminating data in session-based communication that may include: receiving, by a server, a first session invitation message including a first unique value for discriminating a session from a terminal and performing an invitation procedure; and transmitting, by the server, a talk burst granted message including the first unique value to the terminal, and then, re-transmitting the talk burst granted message at certain intervals until the server receives a corresponding response message.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a view illustrating a method for establishing a session in a general session-based communication system;

FIG. 2 is a view illustrating a method for discriminating data in a session-based communication system according to a first exemplary embodiment of the present invention; FIG. 3 is a view illustrating a method for discriminating data in a session-based communication system according to a second exemplary embodiment of the present invention;

FIG. 4 is a view illustrating a method for discriminating data in a session-based communication system according to a third exemplary embodiment of the present invention; and

FIG. 5 is a view illustrating a method for discriminating data in a session-based communication system according to a fourth exemplary embodiment of the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to the accompanying drawings.

In order to provide a session-based service in a communication system including a server for controlling a session and a terminal, in the present invention, the terminal generates a unique (particular) value for discriminating a session and allocates it to the session. Accordingly, data corresponding to the same session have the same unique value.

According to a first exemplary embodiment of the present invention, a mobile terminal includes a client for generating a unique value for discriminating a session and allocating it to the session. Namely, the client of the mobile terminal generates the unique value for discriminating a particular (specific) session, adds it in a session invitation message, and transmits the message to a network. Then, elements of the network include the unique value in data related to the particular session and transmit it. Then, the client checks the unique value included in the data received from the network elements and discriminates a session.

According to a second exemplary embodiment of the present invention, after the server transmits a talk burst granted message in order to give a talk burst (i.e., authority to speak) to the client of the mobile terminal, it re-transmits the talk burst granted message at every certain intervals until it receives a corresponding response message. If the server fails to receive the response message, it does not transmit data related to a particular session to the client.

The talk burst granted message may include a unique value for discriminating the particular session, and the response message may include the unique value.

According to a third exemplary embodiment of the present invention, the mobile terminal, which has transmitted a cancel message for canceling an invitation to a particular session that it had requested to the server, re-transmits the cancel message at every certain intervals until it receives a response message with respect to the cancel message from the server. If the mobile terminal fails to receive the response message, it does not transmit a session invitation message for inviting a different session.

The cancel message may include a unique value for discriminating the particular session, and the response message may also include the unique value.

According to a fourth exemplary embodiment of the present invention, the client of the mobile terminal checks the unique value for discriminating a session included in the data received from the server, and if the data corresponds to a session desired to be canceled, the client discards the data and transmits a cancel message for canceling the invitation to the session to the server.

The cancel message includes a unique value for discriminating the session.

A communication system for providing the session-based service using an SIP (Session Initiation Protocol) will be described by taking an example that the mobile terminal is a PT client and the server is a PT server.

First, a method for establishing a PT session according to the first exemplary embodiment of the present invention will now be described.

FIG. 2 is a view illustrating a method for discriminating data in the session-based communication system according to the first exemplary embodiment of the present invention.

The first mobile terminal is an inviter and includes a first PT client. Herein, only the first PT client 10 of the first mobile terminal is shown for the sake of brevity. The first PT server 20 includes a participating function unit and a second PT server 30 includes a controlling function unit. The first and second PT servers 20 and 30 may belong to each different network or to the same network. The first and second severs 20 and 30 can be implemented as a single device.

The present invention will be described by taking an example of a case where the first PT client 10 establishes a PT session by using a previously established session, after inviting a different PT client. Herein, the previously established session is a PT session established between the inviter PT client and the PT server without a PT client of the other party (namely, an invitee). When the inviter invites an invitee by using the previously established session, once the inviter designates the invitee, the PT session is established between the inviter and the invitee, so the establishment of the PT session can be quickly and easily made, advantageously.

The first PT client 10 generates a first unique value for discriminating the PT session.

The first PT client 10 includes the first unique value in a session invitation message (a first session invitation message), for example, a first TB reference (Talk Burst_Refer) message, for inviting second and third PT clients, and transmits the message to the first PT server 20 (Herein, the first TB reference message is one of talk burst control protocol (TBCP) messages, which is transmitted from the inviter to the PT server without passing through an IMS server (step S11 ). The first PT server 20 transmits an invitation message (INVITE) for inviting the second and third PT clients to the second PT server 30, and in this case, the first PT server 20 includes the first unique value in the invitation message and transmits it (step S12). Then, the second PT server 30 performs a general procedure for inviting the second and third PT clients (detailed description for the general invitation procedure will be omitted) (step S13).

If the second and third PT clients accept the invitation in a belated time, the invitation process may proceed for a long time, i.e., 30 seconds or longer. After the session invitation message (the first TB_Refer message) is transmitted, when the first PT user of the first PT client 10 wants to cancel the inviting of the second and third clients before receiving a response message therefrom, the first PT client 10 can transmit a cancel message (e.g., a TB-Cancel message) to the first PT server 20 in order to cancel the invitation of the second and third PT clients according to a command of the first PT user (step S 14). At this time, the first PT client 10 adds the first unique value included in the first TB_Refer message also in the cancel message and transmits it.

The cancel message is transmitted by using a UDP (User Datagram Protocol) transport protocol, so a success of the transfer of the cancel message is not guaranteed. When the second or third PT client accepts the invitation, the second

PT server 30 transmits a response message (200 OK) with respect to the INVITE message to the first PT client 10 via the first PT server 20 (In this case, the second PT server 30 adds the first unique value in the response message and transmits it) (step S15). The first PT server 20 receives a talk burst granted message from the second PT server 30 at approximately the same time as when the response message is received, and transmits it to the first PT client 10. The talk burst granted message is a message for giving a talk burst (i.e., authority to speak) to the first PT client 10, and can be, for example, a TB-granted message. The talk burst granted message includes the first unique value (steps S16 and S17).

When a radio interface or a fixed line section becomes unstable as the first PT client 10 enters a tunnel or the like or for other various reasons, the cancel message which has been transmitted by the first PT client 10 to the first PT server 20 and the talk burst granted message which has been transmitted by the first PT server 20 to the first PT client 10 may be lost in the radio interface.

Meanwhile, the first PT user requests the first PT client 10 to invite fourth and fifth PT clients. Thus, the first PT client 10 transmits a second TB_Refer message (one of session invitation messages) in order to invite the fourth and fifth clients according to the request of the first PT user. In this case, the first PT client 10 generates a second unique (particular) value for discriminating a PT session, adds it in the second TB_Refer message, and transmits it (step S18).

Accordingly, the first PT user of the first PT client 10 recognizes that the invitation of the second and third PT clients was canceled and a procedure for inviting the fourth and fifth client is ongoing.

When the first PT server 20 fails to receive the cancel message (TB_Cancel) from the first PT client 10, it recognizes that the first PT session generated upon inviting the second and third PT clients is ongoing (maintained), and when data related to the first PT session (PT service data) is transmitted from the second PT server 30, the first PT server 20 transmits the data to the first PT client 10. The data related to the first PT session includes the first unique value for discriminating the first PT session (step S19). The first PT client 10 checks the unique value for discriminating the PT session included in the data transmitted from the first PT server 20. If the checked unique value is identical to the first unique value for the first PT session (namely, the PT session generated upon inviting the second and third PT clients), the first PT client 10 determines that the data is related to the first PT session which has been requested to be canceled, and discards it, rather than processing it (herein, the data is PT service data and includes at least one of RTP data, RTCP data and TBCP data.

If, however, the checked unique value (namely, unique value included in the data) is not identical to the first unique value for the first PT session, the first PT client 10 determines that the data is related to the proceeding PT session and processes it. Accordingly, the data is outputted to the first PT user (in a visual and/or audible manner) (step S20).

Thus, although the erroneous PT session data is transmitted to the first

PT client 10 due to an unstable situation of the radio interface, the first PT client 10 can properly determine which session the data is related and discards or processes it, to thus prevent outputting of erroneous data or unnecessary data to the first PT user.

A method for establishing a PT session according to the second exemplary embodiment of the present invention will now be described.

FIG. 3 is shows the method for establishing a PT session according to the second exemplary embodiment of the present invention.

Steps S21 to S26 are performed in the same manner as the steps S11 to S16.

After the first PT server 20 transmits a talk burst granted message

(TB_Granted) (namely, a message for giving talk burst (i.e., authority to speak) to the first PT client) to the first PT client 10, it waits for receiving a corresponding response message, e.g., a TB_Ack message. Herein, the talk burst granted message includes the same value as the unique value for discriminating a session which has been added in the session invitation message for inviting the second and third PT clients by the first PT client 10. If the unique value is 'x', the talk burst granted message includes 'x'.

If the first PT server 20 fails to receive the response message (TB_Ack message), it re-transmits the talk burst granted message at every certain time intervals.

If the response message is not received even after a certain time lapses, the first PT server 20 does not perform the step S30 of transmitting data (including at least one of RTP data, RTCP data and TBCP data) corresponding to the first PT session to the first PT client 10 (Herein, the first PT session is a PT session for inviting the second and third PT clients). Thus, when the first PT server 20 fails to receive the cancel message (namely, a message for canceling the invitation of the second and third PT clients) which has been transmitted by the first PT client 10, transmission of unnecessary data to the first PT client 10 can be prevented.

Meanwhile, upon receiving the talk burst granted message according to its repeated re-transmission, the first PT client 10 adds the same value (x) as the unique value for discriminating the session included in the talk burst granted message in the response message (TB_Ack) and transmits it to the first PT server 20. Thus, upon receiving the response message, the first PT server 20 determines that the PT session (first PT session) indicated by the unique value (x) included in the response message, which was generated upon inviting the second and third PT clients is ongoing (maintained). When the first PT server 20 has data to be transmitted to the first PT client 10 (namely, data corresponding to the first PT session), it normally transmits the data to the first PT client 10. In this case, the data includes the 'x' value (step S30).

The second embodiment of the present invention can be also applicable to a case where each message does not include a unique value for discriminating a session as shown in FIG. 2. A method for establishing a PT session according to a third embodiment of the present invention will now be described.

FIG. 4 shows the method for establishing a PT session according to a third embodiment of the present invention. Steps S31 to S33 are performed in the same manner as the steps S11 to S13 shown in FIG. 2.

After the first PT client 10 transmits the cancel message, i.e.,

TB_Cancel message, for canceling the request for inviting the second and third PT clients, to the first PT server 20, it re-transmits the TB_Cancel message at prescribed intervals until it receives a response message with respect to the TB_Cancel message (step S34).

If a response message is not received even when a certain time lapses, the first PT client 10 does not transmit a second session invitation message for inviting a different PT client. Also, when the first PT server 20 receives the messages related to the first PT session, namely, the 200 OK message in the step S35 or the TB_Granted message in the step S37, from the second PT server 30, it does not transmit the received messages to the first PT client 10.

When a response message with respect to the TB_Cancel message is received, the first PT client 10 transmits a second session invitation message (i.e., the TB_Refer message) for inviting different PT clients (e.g., fifth and sixth PT clients) to the first PT server 20 (step S38).

FIG. 4 shows that each message includes the unique value for discriminating the session. The third embodiment of the present invention can be applicable for a case where each message includes the unique value for discriminating the session or for a case where each message does not include the unique value for discriminating the session.

A method for establishing a PT session according to a fourth embodiment of the present invention will now be described. FIG. 5 shows a method for establishing a PT session according to a fourth embodiment of the present invention.

Steps S41 to S48 are performed in the same manner as the steps S11 to S18.

The first PT client 10 receives data (e.g., at least one of RTP data, RTCP data and TBCP data) related to a particular (specific) PT session from the first PT server 30 (step S49), checks a unique value for discriminating a session included in the received data and processes or discharges the data.

Namely, if the checked unique value is identical to the unique value indicating the PT session which is currently ongoing, the first PT client 10 processes the data and outputs it to the first PT user (in a visible and/or audible manner).

If, however, the checked unique value is not identical to the unique value indicating the PT session recognized as being currently ongoing, the first PT client 10 determines that the received data is data corresponding to the PT session (Namely, the PT session generated upon inviting the second and third PT clients) desired to be canceled, and discards it. At the same time, the first PT client transmits the cancel message (TB_Cancel) for canceling the invitation of the second and third PT clients to the first PT server 20. In this case, the first PT client 10 includes the checked unique value in the cancel message and transmits it. In FIG. 5, the checked unique value is the same as the unique value included in the session invitation message for inviting the second and third PT clients (steps S50 and S51).

The first PT client 10 can repeatedly perform the steps S49 to S51 whenever the data is received from the first PT server 20.

Accordingly, even when the cancel message (TB_Cancel) transmitted by the first PT client is failed to reach the PT server 20 due to some problems in the radio interface or the fixed line section so the PT server 20 transmits the data (or message) related to the PT session which was requested to be canceled to the first PT client 10, because the first PT client 10 repeatedly transmits the cancel message, the PT server can perform the procedure for canceling the established session.

The present invention may be applied to all other situations, with respect to the RTP, RTCP, TBCP data that is received by a particular PT client, where it is necessary to distinguish the particular PT session to which the RTP, RTCP, TBCP data corresponds to, among many PT sessions that the particular PT client intended to generate but failed or successfully generated.

As so far described, when the entirety or a portion of the PT session establishing request (TB_Refer) or establishing cancel (TB_Cancel) message using the TBCP message or other TBCP message is lost due to the problems in the radio interface of the fixed line section, the successfully established PT session recognized by the PT client and that recognized by the PT server may be different. In this situation, upon receiving the RTP, RTCP and TBCP, etc., the PT client can check the unique value included in the received data and determines whether the received data is related to the successfully established PT session as recognized by the PT client. If the received data is not related to the successfully established PT session recognized by the PT client, the PT client does not process and discard it. And the PT client transmits the establishment canceling (TB_Cancel) message including the unique value (namely, unique value for discriminating the session) included in the received data to the PT server. Therefore, although the cancel messages for canceling the session requested to be first established are lost, the PT client can normally process only the message and/or data corresponding to the PT session recognized to have been currently requested to be established and outputs them to the user. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.

Claims

1. A terminal comprising: a client which generates a first unique value for discriminating a session, adds the first unique value in a session invitation message and transmits the session invitation message, compares a second unique value included in data received through a server with the first unique value, and processes or discards the data according to the comparison result.

2. The terminal of claim 1 , wherein if the second unique value is the same as the first unique value, the client processes the data and outputs the processed data to a user.

3. The terminal of claim 1 , wherein if the second unique value is different from the first unique value, the client discards the data.

4. The terminal of claim 3, wherein the client transmits a cancel message including the second unique value to the server.

5. The terminal of claim 1 , wherein the session invitation message is a

TB_Refer message.

6. The terminal of claim 1 , wherein the data is one of RTP data, RTCP data and TBCP data.

7. The terminal of claim 1 , wherein the client includes a PT client and the server includes a PT server.

8. The terminal of claim 1 , wherein the second unique value is added in the data by a device that generates the data.

9. A session-based communication system for discriminating data comprising: a terminal for transmitting a session invitation message for inviting at least one particular device; and a server for transmitting a talk burst granted message in order to give a talk burst to the terminal and then re-transmitting it at every certain intervals until it receives a corresponding response message.

10. The system of claim 9, wherein if the server fails to receive the response message during a predetermined time, the server does not transmit data related to a particular session to the particular terminal.

11. The system of claim 9, wherein the talk burst granted message is a TB_Granted message.

12. The system of claim 9, wherein when the session invitation message comprises a unique value for discriminating a session, the talk burst granted message and the response message comprise the same value as the unique value, respectively.

13. The system of claim 12, wherein the unique value is generated by the terminal.

14. The system of claim 9, wherein the terminal transmits a cancel message for canceling the invitation to the server, and re-transmits the cancel message at prescribed intervals until the terminal receives a response message with respect to the cancel message.

15. The system of claim 14, wherein when the response message is not received during a certain time, the terminal does not transmit another session invitation message for inviting a different terminal.

16. The system of claim 14, wherein if the session invitation message includes a unique value for discriminating a session, the cancel message and the response message include the same value as the unique value, respectively.

17. The system of claim 14, wherein the terminal includes a PT client and the server includes a PT server.

18. A method for discriminating data in session-based communication comprising: generating, by a terminal, a first unique value for discriminating a session, adding the first unique value in a session invitation message, and transmitting the message to a server; comparing, by the terminal, a second unique value included in data transmitted from the server with the first unique value; and processing or discarding, by the terminal, the data according to the comparison result.

19. The method of claim 18, wherein when the second unique value is the same as the first unique value, the terminal processes the data and outputs it to a user.

20. The method of claim 18, wherein when the second unique value is different from the first unique value, the terminal discards the data.

21. The method of claim 20, wherein the terminal transmits a cancel message including the second unique value to the server.

22. The method of claim 18, wherein the data is one of RTP data, RTCP data and TBCP data.

23. The method of claim 18, wherein the second unique value is added to the data by a device that generates the data.

24. The method of claim 18, wherein the terminal includes a PT client and the server includes a PT server.

25. A method for discriminating data in session-based communication comprising: transmitting, by a terminal, a first session invitation message including a first unique value for discriminating a session, and then transmitting a session invitation cancel message including the first unique value to a server; and re-transmitting, by the terminal, the first session invitation cancel message at every certain intervals until the terminal receives a response message with respect to the session invitation cancel message.

26. The method of claim 25, wherein when the terminal receives the response message from the server, the terminal compares a second unique value for discriminating a session included in the response message and the first unique value included in the session invitation cancel message, and transmitting a second session invitation message including a third unique value for discriminating a session when the first and second unique values are the same.

27. The method of claim 25, further comprising: not transmitting, by the terminal, the second session invitation message including the third unique value if the terminal fails to receive the response message within a certain time.

28. The method of claim 25, wherein the terminal includes a PT client and the server includes a PT server.

29. A method for discriminating data in session-based communication comprising: receiving, by a server, a first session invitation message including a first unique value for discriminating a session from a terminal and performing an invitation procedure; and transmitting, by the server, a talk burst granted message including the first unique value to the terminal, and then, re-transmitting the talk burst granted message at certain intervals until the server receives a corresponding response message.

30. The method of claim 29, wherein when the response message is received from the terminal, the server compares a second unique value included in the response message and the first unique value included in the talk burst granted message, and transmitting data including the first unique value to the terminal if the first and second unique values are the same.

31. The method of claim 29, further comprising: not transmitting, by the server, the data including the first unique value to the terminal if the response message is not received within a certain time.

32. The method of claim 29, wherein the terminal includes a PT client and the server includes a PT server.