Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
1998-12-28
2001-12-25
Nguyen, Chau (Department: 2663)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C370S410000, C370S352000
Reexamination Certificate
active
06333931
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to telecommunications. The invention relates more specifically to interconnecting a circuit-switched telephone network to a packet-switched data network, and methods of using the interconnected networks.
BACKGROUND OF THE INVENTION
The public switched telephony network (PSTN) is made up of carriers who have agreements to interconnect with one another and switch calls to among one another. The PSTN comprises numerous switching systems, which are stored program controlled computers comprising line terminations. The switching systems connect to other switching systems, forming indirect links from customer premises to customer premises around the world.
In a common channel signaling (CCS) network, switching systems interconnect using bearer channels and signaling channels. Bearer channels generally are 64 kbit/second channels that carry voice traffic such as modem calls. Signaling channels carry call information in a separate network; this is known as out-of-band signaling because call signaling information is communicated outside the audible voice band of calls. ITU Recommendation Q.700 describes this type of PSTN in detail.
Only carriers may connect to the signaling network. However, as a result of national and international deregulation of telephone systems, many new carriers are entering or are about to enter the field. For example, in the United States, in the past there have been approximately seven (7) major signaling carriers and numerous independent carriers, but in the future, there will be many new local exchange carriers. Internet Service Providers (ISPs), for example, are expected to rush into the local exchange switching market.
In a regulated environment, the major signaling carriers could establish common standards and rely on trust of one another to ensure that proper signals were carried in the signaling network. In a deregulated environment, the signaling network is perceived as a less trustworthy environment. In particular, in the past, the physical security of SS7 switching facilities provided the primary overall security of an SS7 switching network. Now, there is less assurance that new carriers will maintain the same level of physical facility security that the major carriers have enforced in the past.
Further, in the deregulated environment, a carrier cannot be trusted to connect to the network and use it in a proper manner. For example, a carrier could generate calls for no reason. A carrier could claim to have reachability to another location when in fact it doesn't have that capability. A carrier could express state information about its circuits incorrectly. A carrier could generate Initial Address Messages to distant switches and then wait for them to time out. All these operations are improper and potentially harmful to other network elements and to the private data networks that are connected to such network elements.
In data networks, firewalls are available that are based on UNIX computer systems, and may operate in standalone fashion or are integrated into routers. Firewalls can be used to selectively admit or deny data packets based on rules or policies. Such firewalls, however, cannot be used in SS7 telephone networks or their component systems because their hardware and software is incompatible. For example, lower SS7 messaging layers require unique firmware and hardware for terminating trunks. Further, SS7 is a message-oriented protocol that requires the use of special messages for graceful startup and shutdown of links. These messages are not supported in available firewalls.
Accordingly, there is a need to improve signaling security and data channel security between signaling network entities.
In particular, there is a need to protect internetworks, LANs and WANs from undesirable, undefined, or malicious signals and messages originating in local exchange carriers or other carriers outside such data networks.
There is also a need for a system and method that can interconnect a data network, and servers thereof, to a circuit-switched telephony network that uses time-division multiplexed signaling, for a variety of purposes. In particular, there is a need for a system and method that can interconnect a data network to a circuit-switched telephony network that uses Signaling System 7 protocols for signaling.
SUMMARY OF THE INVENTION
The foregoing needs and objects, and other needs and objects that will become apparent from the following description, are fulfilled by the present invention, which comprises, in one aspect a telecommunications apparatus that can interconnect a circuit-switched telephone network and a packet-switched data network to enable communication among the networks. The apparatus has a first server coupled to a signaling trunk of the telephone network to interchange call signaling messages therewith, and coupled to a control network. One or more second servers each are coupled to a voice trunk of the telephone network to communicate voice-band information thereon, and coupled to receive instructions from the first server through the control network, and coupled to the data network to communicate data thereon. First and second software components are executed by and controlling the first server and the second server, respectively, and interact cooperatively to establish a call originating in the telephone network and containing voiceband information and terminating in the data network, based on call signaling information received from the signaling trunk by the first server.
One feature of this aspect is that the first and second software components interact cooperatively to establish a call originating at one of the second servers and containing voiceband information and terminating in the telephone network, based on call signaling information generated by the first server and provided on the signaling trunk.
Another feature is that the second servers are coupled to the data network by an Internet Protocol (IP) backbone apparatus, and the second servers are coupled to the first server and to a management network by the control network, and the control network, the management network, the first server, and the second server communicate using IP.
In another feature, the signaling trunk and the voice trunk originate in a Common Channel Signaling telephone network. Another feature is that the signaling trunk is a Signaling System 7 (SS7) trunk, and the data network is a global, packet-switched network that operates using Internet Protocol (IP) and Transmission Control Protocol (TCP). According to another feature, the signaling trunk is coupled to a Signal Transfer Point of the telephone network and each of the second servers is coupled to receive the voiceband information from a switch of the telephone network.
In yet another feature, the signaling trunk is coupled from the first server to a digital cross connect apparatus that is coupled to the telephone network, and each of the second servers is coupled by an associated voice trunk to the digital cross connect apparatus to receive the voiceband information therefrom. Still another feature is that the apparatus includes a cross-connect apparatus logically coupled between the telephone network and both the signaling trunk and the voice trunk, and means, coupled between the signaling trunk and the first server, for communicating call routing signals from the digital cross-connect apparatus through the signaling trunk and to the first server. The software components are configured to receive call signaling messages from the means for communicating and over the control network, and to communicate the call signaling messages back over the control network to the second servers.
Still another feature is that the software components comprise instructions which, when executed by the first server, cause the first server to carry out the steps of receiving a call setup message from the telephone network that contains a master telephone number; sending a responsive message to the telephone network that contains a specific t
Adamian Andrew
Gouda Khaled A.
LaPier David C.
Neighbors Clay H.
Oran David R.
Cisco Technology Inc.
Hickman Palermo & Truong & Becker LLP
Kwoh Jasper
Nguyen Chau
Palermo Christopher J.
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