Optimum routing of calls over the public switched telephone...

Telephonic communications – Plural exchange network or interconnection – Interexchange signalling

Reexamination Certificate

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Details

C379S221010, C370S352000, C370S389000

Reexamination Certificate

active

06324280

ABSTRACT:

TECHNICAL FIELD
This invention relates to arrangements for switching calls from central offices switches to the public switched telephone network, or to a fast packet network such as the Internet, in such a way as to incur lowest costs for a call.
PROBLEM
The Internet has made it possible to use a radically different network for carrying voice calls. This network is becoming cost competitive with the public switched telephone network.
SOLUTION
Applicants have recognized that a problem with the prior art is that it is difficult to assign individual calls served by a central office switching system to a choice of the Internet and the public switched telephone network. The problem is especially aggravated by the difficulty of making extensive changes in the call routing arrangements because of the widespread use of different standard protocols for use with the public switched telephone network, and for use with the Internet.
The above problem is solved and an advance is made over the prior art in accordance with this invention wherein a decision is initially made in an originating switching system to select a public switched telephone network trunk, or an Internet connection; if an Internet connection is selected, an interoffice signaling message such as the CCS7 initial address message, (IAM), contains both a call identification, and an Internet Protocol (IP), address of the originating switch. The terminating switch in its acknowledgment, returns an Internet Protocol address of the terminating switch for a communication session. The originating office then sends an identification of the call, in this embodiment the prior art PSTN (Public Switched Telephone Network) circuit identifier code, and of the far end IP address in a real time protocol/IP (RTP/IP) packet over the Internet to the terminating switch. The terminating switch then is able to associate the Internet connection with the type of information that has been received in the IAM over the CCS7 network; the terminating switch is able to complete the connection from the terminating switch to the called customer using the information in the IAM in the standard way. The voice packets sent and received over the Internet are then interfaced in the originating switch and the terminating switch with a Vocoder which converts these Internet packets into a PCM (pulse code modulation) bit stream for transmission to the calling and called customers' switches, thence, as an analog signal or PCM digital telephone signal to the customers. Advantageously, even though the call is being served by Internet facilities, the call set-up operations can be performed in basically the same way that they are performed using only the public switched telephone network, (PSTN), so that the effect on the call processing program is minimized. In addition, the path across the Internet is verified by an exchange of call identifications and Internet addresses in both directions.
The changes in the call processing program and procedures include:
1. Internet Protocol (IP) address administration is required.
2. Vocoders must be connected to calls routed over the Internet.
3. Matching Vocoders must be selected in the two switches terminating an Internet connection.
4. The IP address is validated to secure the Internet against intrusion by unauthorized users (hackers).
5. Call identification numbers and IP addresses of the two ends are bonded.
6. An IP address field must be added to the IAM (Initial Address Message) and ACK (Acknowledgment) messages.
7. A new class of service is added for Internet connections.
8. New billing options can be provided for Internet connections.
However, advantageously, by using procedures that are linked to the type of call setup used with the PSTN (Public Switched Telephone Network), the existing array of Operations Support Systems can continue to be used for operations, administration, maintenance, installation, traffic measurements, and provisioning. For example, the “no circuit available” counts maintained for most trunk groups can be used as they are today, to request the addition of trunks, or, in this case, addition of Internet network capacity.


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