Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
2000-01-27
2004-10-19
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S252000, C370S352000, C370S401000
Reexamination Certificate
active
06807150
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to telephony systems and more particularly to a system and method for controlling a telephony communication session.
BACKGROUND OF THE INVENTION
Telephony systems provide connectivity between subscribers for communicating voice, data, video, or image signals. These systems must provide quality real-time connections on demand for a large volume of subscriber calls. A primary goal of telephony systems is to provide high quality voice connections at the least cost to users. This has been accomplished by digitizing and multiplexing multiple connections on a single line. Multiple digitized connections are traditionally transmitted along a single line using time division multiplexing (TDM). TDM provides fixed timeslots for each connection on the line to ensure quality, but the dedicated timeslot results in an inefficient use of bandwidth.
Packet-based communication protocols offer an attractive alternative to TDM networks. For example, voice over Internet protocol (VoIP) techniques support voice services with high compression and shared bandwidth. However, a major roadblock to the widespread acceptance of VoIP is a concern over the quality of connections. IP was designed for the transport of data that can tolerate delays, dropped packets, and the need for retransmissions. Voice connections, however, are necessarily delay-sensitive and cannot tolerate excessive dropped packets or retransmissions.
SUMMARY OF THE INVENTION
In accordance with the present invention, a system and method for controlling a telephony communication session is provided which substantially eliminates or reduces disadvantages and problems associated with previous systems and methods. In a particular embodiment, the present invention satisfies a need for high quality, low cost telephony service using a packet network and a TDM network.
According to one embodiment of the invention, a telephony system includes a first switch coupled to a first telephony device and a second switch coupled to a second telephony device. The first switch and the second switch establish a telephony communication session connecting the first telephony device and the second telephony device on a first path between the first switch and the second switch, wherein the first path communicates information using a first transmission protocol. The first switch and the second switch also switch the communication session from the first path to a second path between the first switch and the second switch, wherein the second path communicates information using a second transmission protocol.
In accordance with another embodiment of the present invention, a method for controlling a telephony communication session establishes a telephony communication session with a remote device on a first network communicating information using a first transmission protocol, and switches the communication session from the first network to a second network communicating information using a second transmission protocol without disrupting the communication session. The method may also monitor a quality metric of the communication session and switch the communication session from the first network to the second network responsive to the quality metric.
The invention provides a number of technical advantages. The system controls a telephony communication session to allow for mid-call adjustments between available networks to provide low cost connections without sacrificing the quality of service. The quality of service of a connection can be guaranteed by switching from low cost, less reliable networks to more reliable networks, such as TDM networks, if the quality of service deteriorates. The system also allows for more effective marketing of IP telephony networks, since the system guarantees a minimum quality of service by allowing degraded connections to switch mid-call to higher quality connections. The system can also reduce the cost of telephone calls, by switching between different telephony networks mid-call in order to find the least cost connection.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, description, and claims.
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Druce Cedric H.
McNiff Bradley J.
Baker & Botts L.L.P.
Cisco Technology Inc.
Hsu Alpus H.
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