Methods and systems for facilitating transfer of sessions between user devices

1. A method of facilitating transfer of an existing session from a first user device to a second user device, the method comprising:

the existing session being established between the first user device and a remote party and the existing session including a first leg between the first user device and a server and a second leg between the server and the remote party, the server storing a first association between a user address and the first user device and a second association between the user address and the second user device, the user address comprising a Session Initiation Protocol (SIP) Uniform Resource Identifier (URI), the first user device having a first Globally Routable User Agent URI (GRUU) based on the SIP URI, and the second user device having a second GRUU based on the SIP URI;

receiving, at the server, a session invitation message from the second user device containing a reference to the existing session with an instruction to replace the first user device;

verifying from the stored first and second associations that the GRUU of the second user device is based on a same SIP URI as that included in the user address associated with the first user device, said verifying performed by the server without further communication with the remote party;

accepting the session invitation message from the second user device to establish a new leg between the second user device and the server;

joining the new leg with the second leg of the existing session to enable an exchange of media between the second user device and the remote party; and

terminating the first leg of the existing session.

2. The method claimed in claim 1 , wherein the reference to the existing session comprises a dialog ID for the first leg of the existing session.

3. The method claimed in claim 1 , wherein the first user device is registered with one or more SIP registrars for GRUU information associated with the user address.

4. The method claimed in claim 3 , wherein session invitation message is received from the second using device after a device switch message from the first user device is received at the second user device, the device switch message including information identifying the existing session and being addressed to the second user device using the second GRUU.

5. The method claimed in claim 4 , wherein the reference to the existing session comprises a dialog ID for the first leg of the existing session.

6. The method claimed in claim 5 , wherein the device switch message comprises a SIP REFER message referencing the server, and wherein the session invitation message comprises a SIP INVITE message containing a Replaces header.

7. The method claimed in claim 4 , wherein the device switch message comprises a SIP REFER message referencing the server, and wherein the session invitation message comprises a SIP INVITE message containing a Replaces header.

8. The method claimed in claim 1 , wherein session invitation message is received from the second using device after a device switch message from the first user device is received at the second user device, the device switch message including information identifying the existing session and being addressed to the second user device using the second GRUU.

9. The method claimed in claim 8 , wherein the device switch message comprises a SIP REFER message referencing the server, and wherein the session invitation message comprises a SIP INVITE message containing a Replaces header.

10. A system for facilitating transfer of an existing session from a first user device to a second user device, the system comprising:

the first user device;

the second user device;

and the server;

wherein the existing session is established between the first user device and a remote party and wherein the existing session includes a first leg between the first user device and a server and a second leg between the server and the remote party, wherein the first user device and the second user device are each associated with a user address and the user address comprises a Session Initial Protocol (SIP) Uniform Resource Identifier (URI), wherein the first user device has a first Globally Routable User Agent URI (GRUU) based on the SIP URI, and wherein the second user device has a second GRUU based on the SIP URI;

wherein the first user device is configured to send a device switch message to the second user device using the second GRUU, and wherein the device switch message includes information identifying the existing session;

and wherein the server comprises:

an IP communications interface for sending and receiving IP-based communications over a network;

a user data entity containing user information including a first association between the user address and the first user device, and a second association between the user address and the second user device; and

a control subsystem for controlling sessions, the control subsystem including a device swap component configured to:

receive from the second user device a session invitation message containing a reference to the existing session with an instruction to replace the first user device,

verify from the first and second associations that the GRUU of the second user device is based on a same SIP URI as that included in the user address associated with the first user device, said verifying performed by the server without further communication with the remote party,

accept the session invitation message from the second user device to establish a new leg between the second user device and the server,

join the new leg with the second leg of the existing session to enable an exchange of media between the second user device and the remote party, and

terminate the first leg of the existing session.

11. The system claimed in claim 10 , wherein the reference to the existing session comprises a dialog ID for the first leg of the existing session.

12. The system claimed in claim 11 , wherein the device switch message comprises a SIP REFER message referencing the server, and wherein the session invitation message comprises a SIP INVITE message containing a Replaces header.

13. The system claimed in claim 10 , wherein the device switch message comprises a SIP REFER message referencing the server, and wherein the session invitation message comprises a SIP INVITE message containing a Replaces header.

14. The system claimed in claim 10 , wherein the first user device is further configured to register with one or more SIP registrars for GRUU information associated with the user address and to receive from the one or more SIP registrars the second GRUU.

15. The system claimed in claim 14 , wherein the reference to the existing session comprises a dialog ID for the first leg of the existing session.

16. The system claimed in claim 14 , wherein the device switch message comprises a SIP REFER message referencing the server, and wherein the session invitation message comprises a SIP INVITE message containing a Replaces header.

17. A server for facilitating transfer of an existing session from a first user device to a second user device, the server comprising:

an IP communications interface for sending and receiving IP-based communications over a network;

a user data entity containing user information including a first association between the user address and the first user device, and a second association between the user address and the second user device; and

a control subsystem for controlling sessions;

wherein the existing session is established between the first user device and a remote party and wherein the existing session includes a first leg between the first user device and a server and a second leg between the server and the remote party, wherein the first user device and the second user device are each associated with a user address and the user address comprises a Session Initiation Protocol (SIP) Uniform Resource Identifier (URI), wherein the first user device has a first Globally Routable User Agent URI (GRUU) based on the SIP URI, and wherein the second user device has a second GRUU based on the SIP URI; and

wherein the control subsystem includes a device swap component configured to:

receive from the second user device a session invitation message containing a reference to the existing session with an instruction to replace the first user device;

verify from the stored association that the GRUU of the second user device is based on a same SIP URI as that included in the user address associated with the first user device, said verifying performed by the server without further communication with the remote party;

accept the session invitation message from the second user device to establish a new leg between the second user device and the server;

join the new leg with the second leg of the existing session to enable an exchange of media between the second user device and the remote party; and

terminate the first leg of the existing session.

18. The server claimed in claim 17 , wherein the reference to the existing session comprises a dialog ID for the first leg of the existing session.

19. The server claimed in claim 17 , wherein the first user device is registered with one or more SIP registrars for GRUU information associated with the user address.

20. The server claimed in claim 17 , wherein the session invitation message is received from the second using device after a device switch message from the first user device is received at the second user device, the device switch message including information identifying the existing session and being addressed to the second user device using the second GRUU.