PSTN BYPASS FOR IP MEDIA

• US 20090238194A1
• Filed: 03/24/2008
• Published: 09/24/2009
• Est. Priority Date: 03/24/2008
• Status: Active Grant

• Current Assignee: ShoreTel Incorporated (Mitel Networks Corporation)
• Original Assignee: ShoreTel Incorporated (Mitel Networks Corporation)
• Inventors: Sueoka, Greg T., Basart, Edwin J.
• Granted Patent: US 8,451,714 B2
• Time in Patent Office: Days
• US Class Current: 370/401
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways

Abstract

A system and method for falling back to a secondary network when there is insufficient quality on a primary network is disclosed. The present invention uses a PSTN as a fallback for the IP media when the IP network cannot pass the media acceptably and while continuing to use the IP network for call control and other features. In one embodiment, a call controller has a media monitoring module, a bypass module and a PSTN control module. Once a call has been established between endpoints using a primary IP network, the media monitoring module monitors for degradation in call quality. If degradation in call quality is detected, the bypass module is activated to transfer the data communication to a secondary network such as a PSTN while the call control continues to be over the primary network. The present invention also includes a variety of methods including a method for falling back to a secondary network and a method for dynamically switching between a primary and a secondary network to ensure call quality.

Claims

1. A method for falling back from a primary network to a secondary network to ensure call quality in a distributed telephony system, the method comprising:

initiating a call from a first endpoint to a second endpoint;

using the primary network for call control;

determining whether the primary network can be used for data transmission;

using the primary network for data transmission if it is determined that the primary network can be used for data transmission; and

using the secondary network for data transmission if it is determined that the primary network cannot be used for data transmission.

2. The method of claim 1 wherein the secondary network is a PSTN.

3. The method of claim 1 wherein the call control includes one from the group of transfer, conference, directory listing, callee status, a graphical interface, voice messaging, instant messaging and text messaging.

4. The method of claim 1 wherein the primary network is used for call control when the secondary network is used for data transmission.

5. The method of claim 1 further comprising determining whether any network preferences are stored, and wherein determining whether the primary network can be used for data transmission includes determining whether there is a preference for the secondary network.

6. The method of claim 5 wherein the network preferences include class of service, a preference for important calls, conference calls or collaboration calls.

7. The method of claim 1 wherein determining whether the primary network can be used for data transmission includes determining whether the quality of service on the primary network is above a predetermined threshold.

8. The method of claim 1 wherein determining whether the primary network can be used for data transmission includes determining whether the primary network has sufficient quality.

9. The method of claim 1 wherein using the secondary network for data transmission includes initiating a call between a first gateway and a second gateway over a PSTN.

10. The method of claim 9 further comprising sending a signal to the first gateway to include an identifier in the call over the PSTN and sending a signal to the second gateway including the identifier to disambiguate the call from other PSTN calls.

11. The method of claim 1 wherein the call is between three or more endpoints.

12. A method for dynamically switching between a first and a second network in a distributed telephony system, the method comprising:

establishing a call from a first endpoint to a second endpoint using the first network;

monitoring the first network for a quality of service;

determining whether the quality of service is below a predefined threshold;

if the quality of service is below a predefined threshold,

using the first network for call control; and

using the second network for data transmission;

continuing to monitor the first network for the quality of service;

if the quality of service is above a predefined threshold, switching the data transmission to the first network.

13. The method of claim 12 wherein the second network is a PSTN.

14. The method of claim 12 wherein monitoring the first network for a quality of service includes monitoring for an availability of the first network, monitoring for a quality of service over the first network or monitoring for a stored preference.

15. The method of claim 12 wherein the call is between three or more endpoints.

16. An apparatus for switching a call from a first network to a second network of an distributed IP telephony system, the apparatus comprising:

a first gateway coupled to the first network and the second network for interconnecting with the first network and the second network;

a second gateway coupled to the first network and the second network for interconnecting with the first network and the second network; and

a first controller for setting up and controlling calls, the first controller sending control signals to the first gateway and the second gateway, the controller for determining an availability of the first network and establishing the call on the second network if the first network is not available, the first controller coupled to the first gateway, the second gateway and the first network.

17. The apparatus of claim 16, wherein the first network is an IP network and the second network is a PSTN network.

18. The apparatus of claim 16, wherein the first controller uses the first network for call control when the call is established on the second network.

19. The apparatus of claim 16, wherein the first controller is part of the first gateway, the second gateway, an IP phone, a server, or other device coupled to the distributed IP telephony system

20. The apparatus of claim 16 further comprising a second controller, the second controller coupled to the first controller and the second gateway, the second controller adapted to cooperate with the first controller to establish the call on the second network if the first network is not available.

21. The apparatus of claim 20 wherein the first controller, a first IP phone and the first gateway are part of a first site, and the second controller, a second IP phone and the second gateway are part of a second site.

22. The apparatus of claim 20 wherein the first controller and the second controller use a SIP protocol to communicate with each other.

23. The apparatus of claim 16 further comprising:

a third gateway_coupled to the first network and a third network for interconnecting with the first network and the third network;

a fourth gateway_coupled to the first network and the third network for interconnecting with the first network and the third network; and

wherein the first controller sets up and controls calls over the third network if the first network is not available, the first controller coupled to the third gateway and the fourth gateway.

24. The apparatus of claim 16 wherein first controller comprises an admission control module for determining whether the first network has sufficient bandwidth for the call.

25. The apparatus of claim 16 wherein first controller comprises a bypass module for switching the data communication (media transmission) from being on the first network to being on the second network.

26. The apparatus of claim 16 wherein first controller comprises a resumption module for switching of data communication from being on the second network to being on the first network.

27. The apparatus of claim 16 wherein first controller comprises an optimization module for managing switching between the first network and the second network, and between the second network and the first network, the optimization module controlling switching to occur adaptively to ensure a predetermined quality of service.

28. A device comprising:

an IP phone having a display, an input device, a speaker, a microphone, a processor, a memory and a first communication interface to a first network;

a second communication interface to a second network; and

a controller for switching between communicating using the first communication interface to communicating using the second communication interface.

29. The device of claim 28 wherein the controller is also for setting up calls and controlling calls, the controller coupled to the first network, the controller sending control signals to the second network, the controller for determining an availability of the first network and establishing a call on the second network if the first network is not available.

30. The device of claim 28, wherein the first network is an IP network and the second network is a PSTN.

31. The device of claim 28, wherein the controller uses the first network for call control when the call is established on the second network.

32. The device of claim 28, wherein the controller comprises an optimization module for managing switching between the first network and the second network, and between the second network and the first network, the optimization module controlling switching to occur adaptively to ensure a predetermined quality of service.

33. The device of claim 28, wherein the controller determines if the first network is available, and if the first network is not available, the controller sets up the call on the second network.