Telephonic communications – Call or terminal access alarm or control – At switching center
Reexamination Certificate
1999-03-12
2001-12-11
Matar, Ahmad (Department: 2642)
Telephonic communications
Call or terminal access alarm or control
At switching center
C379S201010, C379S265010, C370S351000, C370S260000, C370S236000
Reexamination Certificate
active
06330316
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to customer premise switching equipment and more particularly to customer premise switching equipment with the ability to route calls over unreliable networks such as the Internet and to select an alternate route for a telephone call intended for the unreliable network when the 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; 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.
Many businesses employ customer premise switches (“CPS”)(e.g. Key Signaling Units (“KSU”), Private Branch Exchanges (“PBX”), Centrexes or the like) for routing calls, inter alia, from the business equipment to destination telephone equipment. 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, other IP networks, etc.). The choice of which route to take may be based upon cost or quality of the connection or other well known attributes. In addition to routing calls through the PSTN, many of these CPS route calls through unreliable networks such as the Internet, Frame Relays and the like.
Systems currently exist which monitor the quality of service (QoS) of an unreliable network to determine if an alternate communication path should be chosen. However, such systems either disable the gateway to the network when the QoS falls below a predetermined threshold, the call manager associated with the network routes the call back to the routing engine to be rerouted therefrom or the call manager routes the call to an alternate network.
Disabling the gateway entirely is illogical since the QoS of the network is specific to a destination. Thus while the QoS of the network with regard to one destination may not be acceptable, the QoS of the network with regard to other destinations may be acceptable. Thus, disabling the entire gateway shuts off a relatively inexpensive route for all calls when only a single destination may be unusable. With regard to either routing the call from the call manager back to the routing engine or routing the call from the call manager to another network, this wastes valuable resources (e.g. communication channels, etc.).
Accordingly, there exists a need for a customer premise switch (“CPS”), having access to an unreliable network for routing calls, which can determine the QoS of the unreliable network for a particular call prior to routing the call to the call manager for that network.
Accordingly, it is an object of this invention to provide a CPS, having access to an unreliable network for routing calls, which can determine the QoS of the unreliable network for a particular call prior to routing the call to the call manager for that network.
This and other objects of the invention will become apparent to those skilled in the art from the following description thereof.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, this and other objects may be accomplished by the present invention, which provides methods and apparatus for determining whether a CPS should employ a standard telephone interface or an unreliable network for routing telephone calls.
An embodiment of the invention includes a telephone call switching apparatus. The switching apparatus includes a memory for storing a routing table and a routing engine connected to the memory. The routing engine is configured to receive a telephone call including a destination code. It is also configured to determine an unreliable network route for the telephone call from the routing table, based upon said destination code. It is configured to provide a message, including the destination code, for receipt by a call manager associated with the unreliable network route. The routing engine is also configured to receive a response from the call manager; and route the call over the unreliable network route if the response indicates that a QoS of the unreliable network is sufficient for routing the telephone call.
Another embodiment of the invention includes a method of routing telephone calls. The method includes a routing engine receiving a telephone call including a destination code. The routing engine determines a route for the telephone call which includes an unreliable network. The routing engine sends a message, which includes the destination code, for receipt by a call manager associated with the unreliable network and routes the telephone call over the unreliable network if the routing engine receives an acknowledgment to the message.
Still another embodiment of the invention includes a telephone call switching apparatus. The telephone switching apparatus includes a receiving module for receiving a telephone call from a terminal. The telephone call includes a destination code. The apparatus further includes a module for determining a route for the telephone call which is connected to the module for receiving. The route includes an unreliable network. The apparatus also includes a module for determining if a quality of service of the unreliable network is sufficient for routing the telephone call over the unreliable network. The module for determining a route, routes the telephone call over the unreliable network if the module for determining if a quality of service is sufficient determines that the quality of service is sufficient and communicates this determination to the module for determining a route.
REFERENCES:
patent: 5446730 (1995-08-01), Lee et al.
patent: 5825869 (1998-10-01), Brooks et al.
patent: 5892754 (1999-04-01), Kompella et al.
patent: 5903558 (1999-05-01), Jones et al.
patent: 5995490 (1999-11-01), Shaffer et al.
patent: 5995606 (1999-11-01), Civanlar et al.
Donak John R.
Meijer Frank P.
Solar Christopher R.
Cobrin & Gittes
Knowlin Thjuan P
Matar Ahmad
Nortel Networks Limited
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