Alternate network fallback for IP telephony

Details Alternate network fallback for IP telephony Alternate network fallback for IP telephony

1999-09-30

2003-01-21

Smith, Creighton (Department: 2742)

Telephonic communications

Plural exchange network or interconnection

With interexchange network routing

C379S900000, C370S354000

Reexamination Certificate

active

06510219

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to telephony and more particularly to customer premise switching equipment with the ability to route calls over unreliable networks such as the Internet and to transparently switch to an alternate route during a telephone call when a quality of service of the unreliable network falls below a predetermined threshold.
BACKGROUND OF THE INVENTION
Support for end-to-end voice calls using Internet Protocol (“IP”) networks such as the Internet as an alternative to traditional public switched telephone networks (“PSTN”) is well known. Unlike the PSTN, which is circuit-switched, the Internet is packet-switched (i.e., communication on the Internet is accomplished by transmitting and receiving packets of data). In addition to data, each packet contains a destination address to ensure that it is routed correctly. The format of these packets is defined by the IP. One type of allowable data is encoded, digitized voice, termed voice over IP (VoIP). VoIP is voice that is packetized as defined by IP, and communicated over the Internet for telephone-like communication. Individual VoIP packets may travel over different network paths to reach the final destination where the packets are reassembled in correct sequence to reconstruct the voice information.
While transmission over the Internet is inexpensive relative to transmission over the PSTN, the Internet poses problems which are not present in the PSTN. In particular, the transmission speed between any two users can change drastically due to the dynamic number of users sharing the common transmission medium, their bandwidth requirements, the capacity of the transmission medium, and the efficiency of the network routing and design. Other problems associated with VoIP are the variability of the quality of the signal received at the destination (i.e. the number of transmission errors such as packet loss, packet delay, corrupted packets, etc.). Thus, while the Internet may be a suitable medium for voice communications the suitability is not consistent. Thus, in the event a quality of service (QoS) of the transmission falls below acceptable levels it would be advantageous to be able to switch to a different network in a way that may be transparent to the parties speaking.
Many businesses employ customer premise switches (“CPS”) (e.g. Key Signaling Units (“KSU”), Private Branch Exchanges (“PBX”), Centrexes or the like) for routing calls. Further, with the growing popularity of the home office, many private homes are installing customer premise switches. In addition to routing calls through the PSTN, many of these CPS route calls through unreliable networks such as the Internet, Frame Relays, wireless networks and the like. When an end-user makes a call, the digits dialed are parsed based upon pre-configured tables which indicate which communication interfaces are to be employed for the call attempt (i.e. PSTN, Internet, wireless networks, other IP networks, etc.).
Systems currently exist which monitor the in-call QoS of an unreliable network to determine if an alternate communication path should be chosen. However, such systems either require the conversing parties to terminate the call and re-dial or they are slow and disrupt the call with voice prompts such as “please wait while your call is re-connected.”
Accordingly, there exists a need for a CPS for routing calls, which has access to multiple networks including at least one unreliable network, which can determine a QoS of the unreliable network while a call is in progress and transfer the call to a different network in a way that may be transparent to the call participants.
SUMMARY OF THE INVENTION
The present invention provides methods and apparatus for a CPS to transfer a telephone call which is taking place over an unreliable network to a different network.
An embodiment of the invention includes a method of rerouting a call over an alternate network including monitoring a Quality of Service (QoS) of a network connection between at least two points and establishing a network connection between the at least two points over an alternate network when the QoS of the network connection falls below a threshold. The method further includes switching to the alternate network connection subsequent to establishing the alternate network connection.
Another embodiment of the invention includes an apparatus for rerouting a call over an alternate network. The apparatus include a monitoring module for monitoring a Quality of Service (QoS) of a network connection between at least two points. It also includes a connection module for establishing a network connection between the at least two points over an alternate network in response to the monitoring module determining that the QoS has fallen below a threshold. The apparatus further includes a switching module for switching to the alternate network connection subsequent to the connection module establishing the alternate network connection.
Another embodiment of the invention includes a switching apparatus which includes a monitor configured to monitor a Quality of Service (QOS) of a connection between the switching apparatus and a remote switching apparatus. The apparatus also includes a routing table and a routing engine coupled to the monitor. The routing engine is capable of accessing the routing table and establishing an alternate path between the switching apparatus and the remote switching apparatus without disconnecting the original connection.


REFERENCES:
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patent: 6330316 (2001-12-01), Donak et al.
patent: 1035719 (2000-09-01), None
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A PACKET TELEPHONE GATEWAY FOR PUBLIC NETWORK OPERATORS Iss '97 World Telecommunications Congress (Internatioal Switching symposium) (Global Network Evolution convergence or Collision!Toronto -Sep. 21-26 1997 Iss./WORLD COMMUNICATIONS CONGRESS (INTERNATIONAL SWITCHING SYMPOSIUM) TORONTO, vol. 2, Sep. 21, 1997 pp. 34-44 XP0007/04453;p. 42, left-hand column; I. 19-right-hand column I. 27.

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