Method and System for Transmitting a Multimedia Stream

1. A method, wherein a gateway is capable of communicating with a first terminal and a second terminal, the method comprising: the gateway or the first terminal using a first protocol to exchange first multimedia session information between the first terminal and the gateway, wherein the exchange of the first multimedia session information establishes a first multimedia session between the first terminal and the gateway according to the first protocol and sets up a first media stream from the first terminal, and wherein the first multimedia session information includes a type of media; the second terminal using a second protocol to receive a trigger provided by the gateway or first terminal, wherein the trigger is to initiate an exchange of second multimedia session information between the gateway and the second terminal, and wherein the trigger serves to inform the second terminal of availability of a new multimedia stream; in response to receiving the trigger, the second terminal using a third protocol to initiate the exchange of the second multimedia session information between the gateway and the second terminal, wherein the exchange of the second multimedia session information establishes a second multimedia session according to the third protocol and sets up a second media stream to the second terminal in which the second terminal participates; and the second terminal receiving the second media stream, wherein the second media stream is associated with the first media stream, wherein the first protocol, the second protocol, and the third protocol are all different.

2. The method according to claim 1, wherein the exchange of the first multimedia session information comprises: the gateway providing to the first terminal at least part of the second multimedia session information.

3. The method according to claim 1, wherein the exchange of the second multimedia session information comprises: the gateway providing to the second terminal at least part of the first multimedia session information.

4. The method according to claim 1, wherein the exchange of the first multimedia session information comprises: the gateway receiving, from the first terminal, an identifier of the second terminal.

5. The method according to claim 4, further comprising: before using the second protocol to provide the trigger to the second terminal, the gateway resolving the identifier of the second terminal into a network address of the second terminal.

6. The method according to claim 5, wherein providing the trigger to the second terminal comprises the gateway transmitting the trigger to the resolved network address of the second terminal.

7. The method of claim 1, wherein the third protocol is different from the second protocol.

8. The method of claim 1, wherein the first multimedia stream is the second multimedia stream.

9. The method of claim 1, wherein the first protocol is a peer-to-peer protocol.

10. The method of claim 1, wherein the third protocol is a client-server protocol, and wherein the second receiving terminal has client capabilities of the third protocol and not server capabilities of the third protocol.

11. The method of claim 1, wherein the trigger comprises a network address of the gateway.

12. The method of claim 11, wherein the network address is a URI or a URI reference.

13. The method of claim 1, wherein the first protocol and the second protocol are identical.

14. The method of claim 13, wherein the first protocol and the second protocol are the Session Initiation Protocol (SIP).

15. The method of claim 1, wherein the gateway is configured to associate the first multimedia session information with the second multimedia session information.

16. An article of manufacture including a non-transitory computer-readable medium, having stored thereon software instructions that, if executed by a computing device, cause the computing device to perform operations comprising: using a first protocol to initiate an exchange of first multimedia session information between a first terminal and a gateway, wherein the exchange of the first multimedia session information establishes a first multimedia session between the first terminal and the gateway according to the first protocol and sets up a first media stream from the first terminal, and wherein the first multimedia session information includes a type of media; using a second protocol to provide a trigger to a second terminal, wherein the trigger is to initiate an exchange of second multimedia session information between the gateway and the second terminal, and wherein the trigger serves to inform the second terminal of availability of a new multimedia stream; using a third protocol to conduct the exchange of the second multimedia session information between the gateway and the second terminal, wherein the exchange of the second multimedia session information establishes a second multimedia session according to the third protocol and sets up a second media stream to the second terminal in which the second terminal participates; and using the first protocol to transmit a response to the first terminal, wherein the response causes the first terminal to begin transmission of the first media stream from the first terminal, wherein the second media stream to the second terminal is associated with the first media stream from the first terminal, wherein the first protocol, the second protocol, and the third protocol are all different.

17. A gateway comprising: a communication interface; and memory that stores software instructions that, when executed by the gateway, cause the gateway to: (i) exchange first multimedia session information with a first terminal using a first protocol, wherein the exchange of the first multimedia session information establishes a first multimedia session according between the first terminal and the gateway to the first protocol and sets up a first media stream from the first terminal, and wherein the first multimedia session information includes a type of media, (ii) provide a trigger to a second terminal, wherein the trigger is provided using a second protocol, in response to which the second terminal is able to initiate exchange of second multimedia session information with the gateway, and wherein the trigger serves to inform the second terminal of availability of a new multimedia stream, and (iii) exchange second multimedia session information with the second terminal, using a third protocol, wherein the third protocol is different from the first protocol, wherein the exchange of the second multimedia session information establishes a second multimedia session according to the third protocol and sets up a second media stream to the second terminal in which the second terminal participates, wherein the first protocol, the second protocol, and the third protocol are all different.

18. The gateway of claim 17, wherein the gateway is further configured to connect to a the first terminal supporting a the first protocol and to a the second terminal supporting a the second protocol, wherein the first protocol is Session Initiation Protocol (SIP) and the second protocol is Real Time Streaming Protocol (RTSP), wherein, in relation to the first protocol, the first terminal is an originating user-side SIP client, wherein the gateway acts as a terminating SIP client, wherein the gateway is further configured to confirm that the gateway is able to receive a multimedia session from the user the first terminal and to provide the first terminal with multimedia session information, wherein, in relation to the second protocol, the second terminal is an RTSP client, wherein the gateway acts as an RTSP server on behalf of the user, and wherein the second terminal uses RTSP for session control, and wherein the gateway is further configured to inform the second terminal that an incoming session is pending and notify the RTSP client to connect to an RTSP server function of the gateway.

19. The gateway of claim 17, wherein the gateway is further configured to transmit a notification message to the second terminal in response to an invitation of the first terminal, in order to activate the second terminal to set up a second multimedia session between the second terminal and the gateway.

20. The gateway of claim 17, wherein the gateway is embedded further configured to operate in an IP Multi-Media Subsystem (IMS) network architecture, wherein the first protocol is Session Initiation Protocol (SIP), wherein the third protocol is Real Time Streaming Protocol (RTSP), the IMS network architecture comprising a service-control-function component and a media-function component, wherein the memory of the gateway is distributed in the IMS network architecture, such that: exchanging the first multimedia session information is handled by the a service-control-function component within the IMS network architecture; triggering the second terminal is controlled by the a service-control-function component within the IMS network architecture; and exchanging second multimedia session information is handled by the a media-function component within the IMS network architecture.

21. The gateway of claim 17, wherein the gateway is further configured to associate the first multimedia session information and the second multimedia session information with each other.

22. The gateway of claim 17, wherein the gateway further comprises Session Initiation Protocol (SIP) client functionality and Real Time Streaming Protocol (RTSP) server functionality.

23. A system comprising a gateway, a first terminal, and a second terminal, configured for communicating with the gateway, and wherein: the gateway or the first terminal using a first protocol to exchange first multimedia session information between the first terminal and the gateway, wherein the multimedia session information between the first terminal and the gateway, wherein the exchange of the first multimedia session information establishes a first multimedia session between the first terminal and the gateway according to the first protocol and sets up a first media stream from the first terminal, and wherein the first multimedia session information includes a type of media; the second terminal using a second protocol to receive a trigger provided by the gateway or first terminal, wherein the trigger is to initiate an exchange of second multimedia session information between the gateway and the second terminal, and wherein the trigger serves to inform the second terminal of availability of a new multimedia stream: in response to receiving the trigger, the second terminal using a third protocol to initiate the exchange of the second multimedia session information between the gateway and the second terminal, wherein the exchange of the second multimedia session information establishes a second multimedia session according to the third protocol and sets up a second media stream to the second terminal in which the second terminal participates; and the second terminal receiving the second media stream, wherein the second media stream is associated with the first media stream, wherein the first protocol, the second protocol, and the third protocol are all different.

24. The system of claim 23, wherein at least one of the first terminal and the second terminal is one of a personal computer, a PDA, or a mobile phone with multimedia capabilities.