Method and apparatus for PSTN-based IP active call recovery and re-routing

1. A method for rerouting IP (Internet Protocol) telephony call information, said method comprising:

during an active IP telephony call made by a first IP telephony phone for originating IP telephony calls over an IP network, with a boundary element, actively detecting a network failure condition in the IP network which indicates a switchover to a PSTN (Public Switched Telephone Network) network and generating a failure notification; and

with a server for receiving the failure notification, generating a dynamic switchover instruction generated that is sent to the first IP telephony phone, the dynamic switchover instruction initiating automatic switchover of said active IP telephony call to a PSTN network.

2. The method of claim 1 , further comprising using a Session Initiation Protocol (SIP) for call signaling in the IP telephony network.

3. The method of claim 1 , wherein said first IP telephony phone comprises a Session Initiation Protocol phone.

4. The method of claim 1 , further comprising using H.323 protocol call signaling in the IP telephony network.

5. The method of claim 1 , further comprising, in response to said switchover instruction,

establishing an IP telephony connection between said first IP telephony phone and a first PSTN gateway communicatively linked to said first IP telephony phone;

establishing a PSTN connection from said first PSTN gateway to a second PSTN gateway; and

establishing an IP telephony connection between said second PSTN gateway and said second IP telephony phone communicatively linked to said second gateway.

6. The method of claim 1 , in which the dynamic switchover instruction comprises a notify signal to the first IP telephony phone, the method comprising, in response to the notify signal, initiating switchover logic in the first IP telephony phone.

7. The method of claim 1 , wherein the network comprises a Session Initiation Protocol (SIP) proxy on the server and SIP user agents in each boundary element, the method comprising using SIP NOTIFY and SUBSCRIBE methods between the SIP proxy and boundary elements.

8. The method of claim 7 , further comprising notifying the server of a network failure with a boundary element in communication with the SIP proxy by sending an SIP NOTIFY message to the SIP proxy from the boundary element.

9. The method of claim 1 , further comprising using heartbeat messages comprising a protocol for health monitoring between peer elements.

10. The method of claim 1 , in which the dynamic switchover instruction is generated by the server and sent to the first IP telephony phone, the first IP telephony phone generating a rerouted call which is connected through a PSTN network such that a call interruption is unnoticeable.

11. The method of claim 10 , in which the dynamic switchover instruction is distinguishable from call setup signaling for new calls.

12. The method of claim 11 , in which the dynamic switchover instruction is a Session Initiation Protocol (SIP) INVITE message, the method further comprising:

with the server, adding a replaces header to the SIP INVITE message; and

with the first IP telephony phone, replacing a current interrupted IP telephony call with a new call which is at least partially routed through the PSTN network.

13. A method for rerouting IP (Internet Protocol) telephony call information, said method comprising:

with a server, monitoring an IP network for route failures; and

with the server, generating a switchover instruction when an active IP telephony call is interrupted by a route failure,

the switchover instruction initiating automatic switchover of the active IP telephony call to a fallback call routed through a Public Switched Telephone Network (PSTN),

the switchover instruction including information which identifies the fallback call as a replacement for the active IP telephony call.

14. The method of claim 13 , further comprising, with an originating phone for originating IP telephony calls over the IP network, receiving the switchover instruction and making the fallback call.

15. The method of claim 14 , in which the server is a registrar for the originating phone and maintains IP client device identification and boundary element connection information for rapid rerouting decisions.

16. The method of claim 14 , wherein the originating phone comprises a Session Initiation Protocol phone.

17. The method of claim 1 , wherein the network comprises a Session Initiation Protocol (SIP) proxy on the server and SIP user agents in each of a plurality of boundary element, the method comprising using SIP NOTIFY and SUBSCRIBE methods between the SIP proxy and boundary elements.

18. The method of claim 17 , further comprising notifying the server of a network failure with a boundary element in communication with the SIP proxy by sending an SIP NOTIFY message to the SIP proxy from the boundary element.

19. The method of claim 13 , wherein said monitoring an IP network for route failures further comprises, with a first border element in communication with said server, monitoring the IP network through which the active IP telephony call is routed, the monitoring performed by said first border element comprising:

a heartbeat request sent through the network by the first border element to a peer border element;

a heartbeat response sent through the network by the peer border element to the first border element.

20. The method of claim 19 , further comprising, with the first border element, sending a failure notification to the server when the monitoring reveals a route failure.