Apparatus and method for P-CSCF failure detection and processing

1. A method for checking status of Proxy-Call Session Control Function (P-CSCF) in an IP Multimedia Subsystem (IMS) network, the method comprising:

sending, by a serving-CSCF (S-CSCF), a message to the P-CSCF to check operability using a periodic timer;

marking, by the S-CSCF, in a list that the P-CSCF is unavailable if a negative response or no response is received from the P-CSCF;

setting, by the S-CSCF, a timer to recheck availability of the unavailable P-CSCF;

sending, by the S-CSCF to a device management system, a message to force a user device to reset from the unavailable P-CSCF to a different P-CSCF when a negative response or no response is received from the P-CSCF in response to the message to the P-CSCF to check availability sent by the S-CSCF;

checking, by the S-CSCF, operability of the unavailable P-CSCF upon earlier expiry of the timer or the periodic timer; and

removing, by the S-CSCF, the unavailable P-CSCF from the list when a positive response is received from the unavailable P-CSCF.

2. The method of claim 1 , the method further comprising:

sending, by the device management system to the user device, a message to register with the different P-CSCF.

3. The method of claim 2 , wherein the message to the device management system is a Hypertext Transfer Protocol (HTTP) request message.

4. The method of claim 2 , the method further comprising:

checking, by the S-CSCF, if the periodic timer has expired.

5. The method of claim 4 , the method further comprising:

checking, by the S-CSCF, of the unavailable P-CSCF upon expiry of the periodic timer if the unavailable P-CSCF is unavailable after expiry of the timer.

6. The method of claim 4 , wherein the periodic timer is configurable.

7. The method of claim 1 , wherein the timer is configurable.

8. The method of claim 1 , the method further comprising:

resetting, by the S-CSCF, the timer if the unavailable P-CSCF is unavailable after expiry of the timer.

9. The method of claim 8 , the method further comprising:

checking, by the S-CSCF, of the unavailable P-CSCF upon earlier expiration of the timer or the periodic timer if the unavailable P-CSCF is unavailable after expiry of the timer.

10. A method for checking status of Proxy-Call Session Control Function (P-CSCF), the method comprising:

sending, by a serving-CSCF (S-CSCF), a SIP OPTIONS message to a P-CSCF to check availability upon expiration of one of a periodic timer or a reset timer;

designating, by the S-CSCE, the P-CSCF as unavailable if a negative response or no response is received from the P-CSCF;

setting, by the S-CSCF, the reset timer to recheck availability of the unavailable P-CSCF;

sending, by the S-CSCF to a device management system, a message to force a requesting device to reset from the unavailable P-CSCF to a different P-CSCF if the user device is registered with the unavailable P-CSCF when a negative response or no response is received from the P-CSCF in response to the message to the P-CSCF to check availability sent by the S-CSCF; and

restoring, by the S-CSCF, use of the unavailable P-CSCF upon receipt of a positive response in response to a further SIP OPTIONS message.

11. The method of claim 10 , the method further comprising:

sending, by the device management system to the requesting device, a message to register with the different P-CSCF.

12. The method of claim 11 , wherein the message sent to the device management system is a Hypertext Transfer Protocol (HTTP) request message.

13. The method of claim 10 , wherein the sending of the SIP OPTIONS message is sent upon earlier expiration of the periodic timer or the reset timer.

14. The method of claim 10 , wherein the periodic timer is configurable and the reset time is configurable.

15. The method of claim 10 , the method further comprising:

resetting, by the S-CSCF, the timer if the unavailable P-CSCF is unavailable after expiry of timer.

16. A system comprising:

a device management system;

a Proxy-Call Session Control Function (P-CSCF); and

a serving-CSCF (S-CSCF) connected to the device management system and the P-CSCF, the S-CSCF configured to:

send a status inquiry to the P-CSCF;

isolate the P-CSCF from use if the P-CSCF provides a negative response or fails to respond;

set an isolation timer with respect to the isolated P-CSCF;

send a reset request message to the device management system to force user equipment using the isolated P-CSCF to another P-CSCF when a negative response or no response is received from the P-CSCF in response to the status inquiry to the P-CSCF sent by the S-CSCF; and

return to use the isolated P-CSCF upon receipt of a positive response in response to further status inquiries, wherein the P-CSCF and the S-CSCF are one or more servers.

17. The system of claim 16 , wherein the device management system is configured to:

send to the user equipment a registration message to register with the another P-CSCF.

18. The system of claim 16 , wherein the S-CSCF is configured to:

check the isolated P-CSCF upon expiry of the periodic timer if the isolated P-CSCF is unavailable after expiry of the isolation timer.

19. The system of claim 16 , wherein the S-CSCF is configured to:

reset the isolation timer if the isolated P-CSCF is unavailable after expiry of the isolation timer.

20. The system of claim 16 , wherein the S-CSCF is configured to:

check the isolated P-CSCF upon earlier expiration of the isolation timer or the periodic timer if the unavailable P-CSCF is unavailable after expiry of the isolation timer.