Patent Publication Number: US-6704327-B1

Title: System and method for connecting a call

Description:
RELATED APPLICATIONS 
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     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     MICROFICHE APPENDIX 
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     FIELD OF THE INVENTION 
     The present invention relates to the field of telecommunications call control and transport. 
     BACKGROUND OF THE INVENTION 
     Broadband systems are being developed and implemented. Broadband systems provide telecommunications providers with many benefits, including greater bandwidth, more efficient use of bandwidth, and the ability to integrate voice, data, and video communications. These broadband systems provide callers with increased capabilities at lower costs. 
     Signaling systems are used to process call signaling and to select connections and processing options for calls. These types of signaling systems are generally comprised of broadband switches or other systems that have the ability to transport asynchronous transfer mode (ATM) formatted communications. These switches and systems have a processor component to process call signaling to select the connections and processing options and a switching or interworking component to connect the connections that are selected by the signaling processor and to interwork and process calls. 
     Generally, however, each processor component is either attached to, or directly linked to, the switching or interworking component so that the processor component may instruct or control the switching or interworking component. Thus, a more efficient way to control and transport calls over broadband systems using ATM is desirable so that the processor component is not attached to, or directly physically linked to, the switching or interworking component. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a system for connecting a call having user communications and call signaling. The system comprises a signaling processor that is adapted to receive the call signaling. The signaling processor processes the call signaling to select a connection. The signaling processor then transports a control message that designates the selected connection. The control message is transported in an asynchronous transfer mode format. The system further comprises an interworking unit that is adapted to receive the user communications in a communication format and to receive the control message from the signaling processor in the asynchronous transfer mode format. The interworking unit interworks the user communications between the communication format and asynchronous transfer mode cells that identify the selected connection. The interworking unit then transports the asynchronous transfer mode cells that contain the user communications over the selected connection. The system further comprises a virtual path that links the signaling processor to the interworking unit. The virtual path is adapted to carry the control message in the asynchronous transfer mode format between the signaling processor and the interworking unit. 
     Still further, the present invention comprises a system for connecting a call having user communications and call signaling The system comprises a signaling processor that is adapted to receive the call signaling. The signaling processor processes the call signaling to select a connection. The signaling processor then transports a control message that designates the selected connection. The system, further comprises an interworking unit that is adapted to receive the user communications in a communication format and to receive the control message that is transported by the signaling processor. The interworking unit interworks the user communications between the communication format and asynchronous transfer mode cells that identify the selected connection. The interworking unit then transports the asynchronous transfer mode cells that contain the user communications over the selected connection. Still further, the system comprises a cross connect that is adapted to provision a virtual path between the signaling processor and the interworking unit. The virtual path carries the control message between the signaling processor and the interworking unit. 
     In another aspect, the present invention is a system for connecting a call having user communications and call signaling. The system comprises a first communication device that is adapted to transport the call signaling and the user communications. The system comprises a second communication device that is adapted to receive the user communications. The system also has a signaling processor that is adapted to receive the call signaling and to process the call signaling to select a first connection and a second connection. The signaling processor transports a first control message that designates the selected first connection and a second control message that designates the selected second connection. 
     The system further comprises a first interworking unit that is adapted to receive the user communications in a first communication format and to receive the first control message that is transported by the signaling processor. The first interworking unit is adapted to interwork the user communications between the communication format and asynchronous transfer mode cells that identify the selected first connection and to transport the asynchronous transfer mode cells that contain the user communications over the selected first connection. 
     The system includes a second interworking unit that is adapted to receive the asynchronous transfer mode cells that contain the user communications and to receive the second control message that is transported by the signaling processor. The second interworking unit is adapted to interwork the user communications between the asynchronous transfer mode cells and the second communication format and to transport the user communications in the second communication format to the second communication device over the selected second connection. 
     The system also includes a cross connect that is adapted to provision a first virtual path between the signaling processor and the first interworking unit to carry the first control message from the signaling processor to the first interworking unit. The cross connect also is adapted to provision a second virtual path between the signaling processor and the second interworking unit to carry the second control message from the signaling processor to the second interworking unit. 
     In still another aspect, the present invention is a method for connecting a call having call signaling and user communications. The method comprises provisioning a virtual path to an interworking unit. The method includes receiving the call signaling in a signaling processor and processing the call signaling to determine a connection for the user communications. A control message is transported over the virtual path from the signaling processor to the interworking unit. The control message designates the selected connection. The control message is received in the interworking unit over the virtual path, and the user communications are received in the interworking unit. The user communications are interworked to asynchronous transfer mode cells that identify the selected connection. The asynchronous transfer mode cells then are transported from the interworking unit over the selected connection. 
     In yet another aspect, the present invention comprises a method for connecting a call having call signaling and user communications. The method comprises provisioning a virtual path to carry a control message. The call signaling is received and processes to determine a connection for the user communications. The control message is transported over the virtual path. The control message designates the selected connection. The control message is received over the virtual path. The user communications are interworked to asynchronous transfer mode cells that identify the selected connection that was designated in the control message. The asynchronous transfer mode cells are transported over the selected connection. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a control system that remotely controls an interworking unit. 
     FIG. 2 is a block diagram of a version of the control system of FIG.  1 . 
     FIG. 3 is a relational diagram of a protocol stack used to provide assured delivery of control messages between a signaling ‘processor’ and an interworking unit. 
     FIG. 4 is a block diagram of a version of the control system of FIG. 1 which includes a converter. 
     FIG. 5 is a block diagram a version of a control system in which user communications are transported outside of the control system. 
     FIG. 6 is a functional diagram of an asynchronous transfer mode interworking unit for use with a synchronous optical network system in accordance with the present invention. 
     FIG. 7 is a functional diagram of an asynchronous transfer mode interworking unit for use with a synchronous digital hierarchy system in accordance with the present invention. 
     FIG. 8 is a block diagram of a signaling processor constructed in accordance with the present system. 
     FIG. 9 is a block diagram of a data structure having tables that are used in the signaling processor of FIG.  8 . 
     FIG. 10 is a block diagram of additional tables that are used in the signaling processor of FIG.  9 . 
     FIG. 11 is a table diagram of a trunk circuit table used in the signaling processor of FIG.  9 . 
     FIG. 12 is a table diagram of a trunk group table used in the signaling processor of FIG.  9 . 
     FIG. 13 is a table diagram of an exception circuit table used in the signaling processor of FIG.  9 . 
     FIG. 14 is a table diagram of an automated number index table used in the signaling processor of FIG.  9 . 
     FIG. 15 is a table diagram of a called number table used in the signaling processor of FIG.  9 . 
     FIG. 16 is a table diagram of a routing table used in the signaling processor of FIG.  9 . 
     FIG. 17 is a table diagram of a treatment table used in the signaling processor of FIG.  9 . 
     FIG. 18 is a table diagram of a message table used in the signaling processor of FIG.  9 . 
     FIG. 19 is a table diagram of a routing table used in the signaling processes of FIG.  9 . 
    
    
     DETAILED DESCRIPTION 
     Telecommunication systems have a number of communication devices in local exchange and interexchange environments that interact to provide call services, to customers. Both traditional services and resources and intelligent network (IN) services and resources are used to process, route, or connect a call to a designated connection. 
     A call has call signaling and user communications. The user communications contain the caller&#39;s information, such as a voice communication or data communication, and they are communicated over a connection. Call signaling contains information that facilitates call processing, and it is communicated over a link. Call signaling, for example, contains information describing the called number and the calling number. Examples of call signaling are standardized signaling, such as signaling system #7 (SS7), C7, integrated services digital network (ISDN), and digital private network signaling system (DPNSS), which are based on ITU recommendation Q.933. 
     A call can be transported to or from a communication device. A communication device can be, for example, customer premises equipment (CPE), a service platform, a switch, or any other device capable of initiating, handling, or terminating a call. Customer premises equipment can be, for example, a telephone, a computer, a facsimile machine, or a private branch exchange. A service platform can be, for example, a service platform or any other enhanced platform that is capable of processing calls. 
     Communications devices in both traditional and intelligent systems can use a variety of protocols and methods to achieve a connection for a call or to complete call processing. For example, CPE can be connected to a switch using a time division multiplex (TDM) format, such as super frame (SF) or extended superframe (ESF). The ESF connection allows multiple devices at the customer site to access the local switch and obtain telecommunication services. 
     Also, communication devices, such as telephones, are likely connected to a remote digital terminal, and the connection typically carries analog signals over twisted pair wires. The remote digital terminals provide a digital interface between the telephones and a local switch by converting the analog signals from the telephones into a multiplexed digital signal to be transferred to the local switch. A common standard for the connection between the remote digital terminal and the local switch is provided in Bellcore Reference GR-TSY-000303 (GR-303). 
     In addition, communications devices use broadband protocols, such as broadband-integrated services digital network (B-ISDN). Broadband systems provide greater bandwidth than narrowband systems for calls, in addition to providing digital processing of the calls. B-ISDN provides a communication device with a digital connection to a local switch or other device. The B-ISDN loop provides more bandwidth and control than a convention local loop. The European implementation of B-ISDN and other broadband protocols can also be used. 
     Communication devices use circuit-based connections for calls. For example, digital signal (DS) level communications, such as digital signal level 3 (DS3), digital signal level one (DS1), and digital signal level zero (DS0) are conventional circuit-based connections. European level four (E4), European level three (E3), European level one (E1), European level zero (E0), and other European equivalent circuit-based connections, also are used. 
     High speed electrical/optical transmission protocols also are used by communications devices for switching and signaling. The synchronous optical network (SONET) protocol, which is used primarily in North America, and the synchronous digital hierarchy, (SDH) protocol, which is used primarily in Europe, are examples of high speed electrical/optical protocols. The SONET and SDH protocols describe the physical media and transmission protocols through which the communications take place. 
     SONET includes optical transmission of optical carrier (OC) signals and electrical transmission of synchronous, transport signals (STSs). SONET signals transmit at a base rate of 51.84 Mega-bits per second (Mbps) for optical carrier level one (OC-1) and synchronous transport signal level one (STS-1). Also transmitted are multiples thereof, such as an STS level three (STS-3) and an OC level three (OC-3) at rates of 155.52 Mbps and an STS level twelve (STS-12) and an OC level 12 (OC-12) at rates of 622.08 Mbps, and fractions thereof, such as a virtual tributary group (VTG) at a rate of 6.912 Mbps. 
     SDH includes transmission of optical synchronous transport module (STM O) signals and electrical synchronous transport module (STM E) signals. SDH signals transmit at a base rate of 155.52 Mbps for synchronous transport module level one electrical and optical (STM-1 E/O). Also transmitted are multiples thereof, such as an STM level four electrical/optical (STM-4 E/O) at rates of 622.08 Mbps, and fractions thereof, such as a tributary unit group (TUG) at a rate of 6.912 Mbps. 
     Asynchronous transfer mode (ATM) is one technology that is being used in conjunction with SONET and SDH to provide broadband call switching and call transport for telecommunication services. ATM is a protocol that describes communication of user communications in ATM cells. Because the protocol uses cells, calls can be transported on demand for connection-oriented traffic or connectionless-oriented traffic, constant-bit traffic or variable-bit traffic, and between equipment that either requires timing or does not require timing. 
     Some ATM systems handle calls over switched virtual paths (SVPs) and switched virtual circuits (SVCs). The virtual nature of ATM allows multiple communication devices to use a physical communication line at different times. This type of virtual connection more efficiently uses bandwidth, and thereby provides more cost efficient transport for customer calls, than permanent virtual circuits (PVCs) or other dedicated circuits. 
     The ATM system is able to connect a caller from an origination point to a destination point by selecting a connection from the origination point to the destination point. The connection contains a virtual path (VP) and a virtual channel (VC). A VC is a logical connection between two end points for the transfer of ATM cells. A VP is a logical combination of VCs. The ATM system designates the selected connection by specifying a virtual path identifier (VPI) that identifies the selected VP and a virtual channel identifier (VCI) that identifies the selected VC within the selected VP. Because many ATM connections are uni-directional, bi-directional communications in an ATM system usually require companion VPIs/VCIs. 
     The control system of the present invention provides a more efficient way to link interworking units with a signaling processor by providing control messages to interworking units remotely. This allows one signaling processor to communicate control messages to multiple interworking units without having a separate and physical direct link to each interworking unit. 
     The control system can remotely control a plurality of interworking units. Preferably, this is accomplished by provisioning a VPI/VCI from each interworking unit or communication device to a signaling processor. 
     FIG. 1 illustrates a control system  102  that remotely transports control messages to system devices. The control system  102  is connected to a first communication device  104  and a second communication de vice  106 . The control system also is connected to a first interworking unit  108  and a second interworking unit.  110 . 
     The control system  102  is linked to the first communication device  104  through a link  112 , to the second communication device  106  through a link  114 , to the first interworking unit  108  through a link  116 , and to the second interworking unit  110  through a link  108 . The first interworking unit  108  is connected to the first communication device  104  through a, connection  120  and to the control system  102  through a connection  122 . The second interworking unit  110  is connected to the second communication device  106  through a connection  124  and to the control system  102  through a connection  126 . 
     Connections are used to transport user communications and other device information between communication devices and between the elements and devices of the processing system  102 . The term “connection” as used herein means the transmission media used to carry user communications between the first and second communication devices  104  and  106  and the processing system  102  or between the elements of the processing system  102 . For example, a connection could carry a user&#39;s voice, computer data, or other communication device data. A connection can be associated with either in-band communications or out-of-band communications. 
     Links are used to transport call signaling and control messages. The term “link” as used herein means a transmission media used to carry call signaling and control messages. For example, a link would carry call signaling or a device control message containing device instructions and data. A link can carry, for example, out-of-band signaling such as SS7, C7, ISDN, B-ISDN, GR-303, local area network (LAN), or data bus call signaling. A link can be, for example, an AAL5 data link, UDP/IP, ethernet, or DS0 over T1. In addition, a link, as shown in the figures, can represent a single physical link or multiple links, such as one link or a combination of links of ISDN, SS7, TCP/IP, or some other data link. The term “control message” as used herein means a control or signaling message, a control or signaling instruction, or a control or signaling signal, whether proprietary or standardized, that conveys information from one point to another. 
     The control system  102  remotely controls one or more interworking units  108  and  110 . The control system  102  processes call signaling; from the communication devices  104  and  106  to determine connections and processing options for calls. The control system  102  directs the interworking units  108  and  110  to make connections for calls and, in some instances, assists in routing user communications for calls. 
     The communication devices  104  and  106  each comprise CPE, a service platform, a switch, a remote digital terminal, or any other device capable of initiating, handling, or terminating a call. CPE can be, for example, a telephone, a computer, a facsimile machine, or a private branch exchange. A service platform can be, for example, a service platform or any other enhanced platform that is capable of processing calls. A remote digital terminal is a device that concentrates analog twisted pairs from telephones and other like devices and converts the analog signals to a digital format known as GR-303. 
     The first interworking unit  108  interworks traffic between various protocols. Preferably, the first interworking unit  108  interworks between ATM traffic and non-ATM traffic. The first interworking unit  108  operates in accordance with control messages received from the control system  102  over the link  116 . These control messages are typically provided on a call-by-call basis and typically identify an assignment between a DS0 and a VPI/VCI for which user communications are interworked. In some instances, the first interworking unit  108  may transport control messages which may include data to the control system  102 . 
     The second interworking unit  110  interworks traffic between various protocols. Preferably, the second interworking unit  110  interworks between ATM traffic and non-ATM traffic. The second interworking unit  110  operates in accordance with control messages received from the control system  102  over the link  118 . These control messages are typically provided on a call-by-call basis and typically identify an assignment between a DS0 and a VPI/VCI for which user communications are interworked. In some instances, the second interworking unit  110  may transport control messages which may include data to the control system  102 . 
     The control system  102  of FIG. 1 operates as follows when the first communication device  104  transports a call to the second communication device  106 . The first communication device  104  transports call signaling to the control system  102 . Typically the call signaling is SS7 call signaling. The first communication device  104  also transports user communications to the first interworking unit  108 . Typically, the user communications are TDM formatted user communications, such as a DS0. 
     The control system  102  processes the call signaling to select a first connection  122  and a second connection  124 . The selected first connection  122  is a VPI/VCI and the selected second connection  124  is a DS0. The control system  102  sends a control message to the first interworking unit  108  identifying the selected first connection  122  for the user communications. The control system  102  also sends a control message to the second interworking unit  110  identifying the selected second connection  124 . In addition, the control system  102  provisions a virtual path between the first interworking unit  108  and the second interworking unit  110  over the connection  122  and the connection  126 . 
     The first interworking unit  108  receives the user communications from the first communication device  104  and the control message from the control system  102 . The first interworking unit  108  interworks the user communications between the TDM format and the ATM format. Therefore, the first interworking unit  108  converts the user communications into ATM cells that identify the selected first connection  122 . The first interworking unit  108  then transports the ATM cells over the selected first connection  122 . 
     The control system  102  receives the ATM cells and routes them over the provisioned VPI(VCI connection  126  of the provisioned virtual path to the second interworking unit  110 . The second interworking unit  110  receives the ATM cells containing the user communications from the control system  102  over the connection  126 . In addition, the second interworking unit  110  receives the control message from the control system  102  that identifies the selected second connection  124 . 
     The second interworking unit  110  interworks the ATM cells from the VPI/VCI connection  126  to the selected second connection  124  identified in the control message from the control system  102 . The second interworking unit  110  converts the ATM cells to user communications having a TDM, format for the DS0. The second interworking unit  110  then transports the user communications over the selected second connection  124  to the second communication device  106 . 
     A call also may be transported from the second communication  106  device to the first communication device  104  in the manner described above. However, after receiving and processing the call signaling from the second communication device  106 , the signaling processor  202  transports a first control message that identifies a selected first connection  126  to the second interworking unit  110  over the link  118 . In addition, the signaling processor  202  transports a second control message that identifies a selected second connection  120  to the first interworking unit  108  over the link  116 . 
     The second interworking unit  110  receives the user communications from the second communication device  106  and interworks the user communications from a communication format, such as TDM, to the ATM format. The second interworking unit  110  then transports the ATM cells over the selected first connection. The control system  102  receives the ATM cells and routes them over the connection  122  to the first interworking unit  108 . The first interworking unit  102  receives the ATM cells and interworked them from the ATM format to user communications with a communication format, such as TDM. The first interworking unit  108  then transports the user communications to the first communication device  104 . 
     FIG. 2 illustrates an expanded control system  102 . The control system  102  comprises a signaling processor  202  and a cross connect  204  with a link  206  between the signaling processor and the cross connect. The signaling processor  202  is linked to the first communication device  104  through the link  112  and to the second communication device  106  through the link  114 . The cross connect  204  is connected to the first interworking unit  108  through the connection  122  and to the second interworking unit  110  through the connection  126 . The cross connect  204  is linked to the first interworking unit  108  through the link  116  and to the second interworking unit  110  through the link  118 . 
     It will be appreciated that the cross connect  204  may be connected to other communication devices in addition to, or in place of, the first and second interworking units  108  and  110 . In such a configuration, the cross connect  204  will provision VPIs/VCIs to the other communication devices for connections to carry user communications or for links to carry call signaling and control messages. 
     The signaling processor  202  is a signaling platform that can receive and process signaling. Based on the processed signaling, the signaling processor  202  selects processing options for the user communications and generates and transmits control messages that identify the communication device, processing option, service, or resource that is to be used. The signaling processor  202  also selects virtual connections and circuit-based connections for call routing and generates and transports control messages that identify the selected connections. The signaling processor  202  can process various forms of signaling, including ISDN, SS7, and C7. A preferred signaling processor is discussed below. 
     The cross connect  204  is any device, such as an ATM cross connect, that provides a plurality of ATM virtual connections between the first interworking unit  108  and the second interworking unit  110 , between the first and second interworking units  108  and  110  and other communication devices (not shown), or between other communication, devices. The cross connect  204  also provides a link  406  that has virtual connections to the signaling processor  202 . In ATM, virtual connections and, in the present case, links can be designated by the VPI/VCI in the cell header. An example of an ATM cross connect is the NEC Model 20. 
     The cross connect  204  is configured to provide a provisioned virtual path having VPI/VCI links  116  and  118  for signaling. The VPI/VCI links are provisioned from the signaling processor  202  to one or more interworking units, such as, for example the first and second interworking units  108  and  110 . The VPI/VCI links carry control messages from the signaling processor  202  to the first and second interworking  108  and  110  units so that the interworking units are remotely controlled and direct links do not have to be linked between the signaling processor and each interworking unit. 
     Because VPI/VCI links are used, an interworking unit may be added to the ATM system without adding a new direct connection between the signaling processor  202  and the new interworking unit. Instead, a new VPI/VCI is provisioned to link the signaling processor  202  to the new interworking unit. This provides flexibility so that a signaling processor and an interworking unit may be placed anywhere in the ATM system. 
     FIG. 3 illustrates a protocol stack  302  that is used to govern call transport so that signaling is reliably transported between the signaling processor  202  and the first interworking unit  108  with minimal errors. Although the second interworking unit  110  is not shown, the protocol stack  302  also is used to govern call transport for reliable signaling between the signaling processor  202  and the second interworking unit of FIG.  2 . Thus, the description of FIG. 3 is applicable to signaling between the signaling processor  202  and the second interworking unit  110 . 
     The protocol stack  302  has an ATM layer  304 , a signaling ATM adaptation layer (SAAL)  306 , and a call control layer  308 . The protocol stack  302  is used for point-to-point and point-to-multipoint peer-to-peer call control. Software to support the protocol stack  302  is known in the art and may be acquired, for example, from the Trillium Company. 
     The ATM layer  304  supports call signaling and user communications for multiplex and demultiplex functions, VPI/VCI translation, ATM cell header generation and extraction, and flow control. In the transport direction, the ATM layer multiplexes cells from VPs and VCs into a composite cell flow. In the receive direction, the ATM layer  308  demultiplexes a composite cell flow to direct cells to the appropriate VP and VC VPI/VCI fields in an incoming cell may require mapping to a new VPI/VCI. The ATM layer  308  also generates an ATM header and attaches it to a payload in the transport direction or extracts the payload from a received call and passes the payload to the next layer in the receive direction. In addition, the ATM layer  308  may generate cells to carry generic flow control information. 
     The SAAL  306  protocol and procedures define how to transport control messages reliably within the cells of the ATM layer  304  on VCs used for call signaling. The SAAL  306  is used as the delivery mechanism for the remote call signaling between the signaling processor  202  and one or more interworking units. 
     Referring still to FIG. 3, the SAAL  306  includes a common part and a service specific part. The common part identifies functions common to all users that require a connection-oriented, variable-bit rate transport. The common part provides information transfer, segmentation and reassembly, and information corruption detection in the SAAL frames. The service specific part identifies the protocol and procedures required at the user-network interface (UNI). In addition, the service specific part provides for recovery of lost, misinserted, or corrupted SAAL frames. 
     The service specific part includes a device-specific connection-oriented. protocol sublayer (SSCOP) and a service-specific coordination function sublayer (SSCF). The SSCOP is used for flow control and error correction. The SSCOP transfers service data units (SDUs) between SSCOP users and provides for the recovery of SDUs. The SSCF maps the service of SSCOP to the needs of the SSCF user. The common part is defined by ITU-T I.363, the SSCF by ITU-T Q.2130, and the SSCOP by ITU-T Q.2110, each of which is incorporated herein by reference. 
     The call control layer  308  is used to dynamically establish, maintain, and clear virtual connections between ATM interfaces. The call control layer  308  controls aspects such as call routing, determination of resource availability, subscription parameter procedures, and calling party addressing delivery. 
     Communication with a remote peer, such as between the first interworking unit  108  and the signaling processor  202 , at the same layer involves exchanging primitives. A primitive represents a logical exchange of information between a layer and the adjacent layers. Thus, for example, a primitive may be generated by the SAAL  306  and passed to the call control layer  308 . 
     Referring back to FIG. 2, the control system  102  is configured so that the cross connect  204  provisions a first virtual path between the signaling processor  202  and the first interworking unit  108 . The first virtual path is provisioned from the link  116  that is between the first interworking unit  108  and the cross connect  204 , and the first path extends through a VPI/VCI in the link  206  that is between the signaling processor  202  and the cross connect. The signaling processor  202  transports a first control message in ATM cells to the cross connect  204  over a VPI/VCI in the link  206 . The control message is routed in the ATM cells by the cross connect  204  over the link  116  in the provisioned first path. Thus, the first control message is transported from the signaling processor  202  to the first interworking unit  108  over the provisioned first path. 
     The control system  102  is configured so that the cross connect  204  provisions a second virtual path between the signaling processor  202  and the second interworking unit  110 . The second virtual path is provisioned from the link  118  that is between the second interworking unit  110  and the cross connect  204 , and the second path extends through a VPI/VCI in the link  206  that is between the signaling processor  202  and the cross connect. The signaling processor  202  transports a second control message in, ATM cells to the cross connect  204  over a VPI/VCI in the link  206 . The control message is routed in the ATM cells by the cross connect  204  over the link  118  in the provisioned second path. Thus, the second control message is transported from the signaling processor  202  to the second interworking unit  110  over the provisioned second path. 
     Referring still to FIG. 2, the control system  102  operates as follows. A first path is provisioned from the signaling processor  202  through the cross connect.  204  and to the first interworking unit  108 . The first path connects the VPI/VCI link  116  with VPI/VCI in the link  206  leading to the signaling processor  202 . A second path is provisioned from the signaling processor  202  through the cross connect  204  and to the second interworking unit  110 . The second path connects the VPI/VCI link.  118  with another VPI/VCI in the link  206  leading to the signaling processor  202 . Paths are also provisioned for transport for user communications over the connections  122  and  126  from the cross connect  204  to the first and second interworking units  108  and  110 , respectively. 
     The first communication device  104  transports a call. The first communication device  104  transports the call signaling to the signaling processor  202  over the link  112  and the user communications to the first interworking unit  108  over the connection  120 . 
     The signaling processor  202  receives the call signaling and processes the call signaling to select a processing option for the call, such as a first connection  122  and a second connection  124 . In addition, the signaling processor  202  may select other processing options, such as echo cancellation to be performed by the first interworking unit  108 , or service processing to be performed by a service platform (not shown). 
     The signaling processor  202  transports a first control message to the first interworking unit  108  identifying the selected first connection  122 . The first control message is transported from the signaling processor  202  to the first interworking unit  108  over the provisioned first path, including the link  206  and the connected link  116 . The signaling processor  202  transports a second control message to the second interworking unit  110  identifying the selected second connection  124 . The second control message is transported over the provisioned second path, including the link  206  and the connected link  118 . The control system  102  uses the SAAL  306  to assure delivery of the first and second control messages. (See FIG. 3.) 
     The first interworking unit  108  receives the user communications from the first communication device  104  and the first control message from the signaling processor  202 . The first interworking unit  108  interworks the user communications from the communication format in which they are received to ATM cells that identify the selected first connection  122  over which they will be transported. The first interworking unit  108  then transports the ATM cells over the selected first connection  122  to the cross connect  204 . 
     At the cross connect  204 , a path is provisioned that connects the connection  122  from the first interworking unit  108  to the connection  126  leading to the second interworking unit  110 . Thus, the cross connect  204  receives the ATM cells and routes them over the connection  126  to the second interworking unit  110 . 
     The second interworking unit  110  receives the ATM cells over the provisioned connection  126  and the second control message over the provisioned link  118  of the provisioned second path. The second interworking unit  110  uses the second control message to identify the selected second connection  124 . The second interworking unit  110  interworks the user communications between the ATM cells and user communications with a communication format that is compatible with the second communication device  106 . Typically, the ATM cells are converted to TDM formatted user communications. The second interworking unit  110  then transports the user communication to the second communication device  106  over the selected second connection  124 . 
     Referring still to FIG. 2, the control system.  102  also may operate to connect a call from the second communication device  106  to the first communication device  104 . The control system  102  operates in the reverse of that described above. 
     The second communication device  106  transports a call. The second communication device  106  transports the call signaling to the signaling processor  202  over the link  114  and the user communications to the second interworking unit  110  over the connection  124 . 
     The signaling processor  202  receives the call signaling and processes the call signaling to select a processing option for the call, such as a first connection  126  and a second connection  120 . In addition, the signaling processor  202  may select other processing options, such as echo cancellation to be performed by the second interworking unit  110 , or service processing to be performed by a service platform (not shown). 
     The signaling processor  202  transports a first control message to the second interworking unit  110  identifying the selected first connection  126 . The first control message is transported from the signaling processor  202  to the second interworking unit  110  over the provisioned second path, including a VPI/VCI in the link  206  and the connected link  118 . The signaling processor  202  transports a second control message to the first interworking unit  108  identifying the selected second connection  120 . The second control message is transported over the provisioned first path, including a VPI/VCI in the link  206  and the connected link  116 . The control system  102  uses the SAAL  306  to assure delivery of the first and second control messages. (See FIG. 3.) 
     The second interworking unit  110  receives the user communications from the second communication device  106  and the first control message from the signaling processor  202 . The second interworking unit  110  interworks the user communications from the communication format in which they are received to ATM cells that identify the selected first connection  126  over which they will be transported. The second interworking unit  110  then transports the ATM cells over the selected- first connection  126  to the cross connect  204 . 
     At the cross connect  204 , a path is provisioned that connects the connection  126  from the second interworking unit  110  to the connection  122  leading to the first interworking unit  108 . Thus, the cross connect  204  receives the ATM cells and routes them over the provisioned connection  122  to the first interworking unit  108 . 
     The first interworking unit  108  receives the ATM cells over the connection  122  and the second control message over the link  116  of the provisioned first path. The first interworking unit  108  uses the second control message to identify the first selected connection  120 . The first interworking unit  108  interworks the user communications between the ATM cells and user communications with a communication format that is compatible with the first communication device  104 . Typically, the ATM cells are converted to TDM formatted user communications. The first interworking unit  108  then transports the user communications to the first communication device  104  over the selected second connection  120 . 
     As illustrated in FIG. 4, the control system  102 A may be configured so that the signaling processor  202  transports control messages in an internet protocol (IP) format. The control system  102 A of that configuration has a converter  402  that is linked to the signaling processor  202  through a link  404  and to the cross connect  204  through a link  406 . The link  404  to the signaling processor  202  may be, for example, an ethernet link. The link  406  to the cross connect  204  has one or more VPIs/VCIs. 
     The converter  402  converts control messages between the IP format and the ATM format. For example, a first path may be provisioned with a VPI/VCI in the link  406 . A second path may be provisioned with another VPI/VCI in the link  406 . The converter  402  encapsulates an IP formatted control message that is received from the link  404  and transports the control message over a VPI/VCI in the link  406  to the cross connect  204  in ATM cells that identify the VPI/VCI. In addition, the converter  402  converts ATM cells that contain control messages and that are received over the link.  406  from the cross connect  204  to IP formatted control messages and transports the control messages to the signaling processor  202 . 
     The control system  112 A of FIG. 4 operates as follows. Either the first communication device  104  or the second communication device  106  transports a call. The call signaling is transported to the signaling processor  202  and the user communications to the respective first interworking unit  108  or second interworking unit.  110 . 
     The signaling processor  202  receives the call signaling and processes the call signaling to select a processing options for the call, such as one or more connections. In addition, the signaling processor  202  may select other processing options, such as echo cancellation to be performed by the first or second interworking units  108  or  110 , or service processing to be performed by a service platform (not shown). 
     The signaling processor  202  transports a first control message to the first interworking unit  108  identifying a selected connection. The first control message is transported from the signaling processor  202  to converter  402  in the IP format. The converter  402  converts the first control message to ATM cells and transports the ATM cells to the cross connect  406  over a VPI/VCI in the link  406 . Because the path has been provisioned from the converter  402  to the first interworking unit  108  through the VPI/VCI in the link  406  and through the link  116 , the cross connect  204  routes the first control message to the first interworking unit  108  over the link  116 . 
     The signaling processor  202  also transports a second control message to the second interworking unit  110  identifying a selected connection. The second control message is transported from the signaling processor  202  to the converter  402  in the IP format. The converter  402  converts the second control message to ATM cells and transports the ATM cells to the cross connect  406  over another VPI/VCI in the link  406 . Because the path from the converter  402  to the second interworking unit  110  has been provisioned through the VPI/VCI in the link  406  and through the link  118 , the cross connect  204  routes the second control message to the second interworking unit  110  over the link  118 . 
     The connections for user communications are connected as discussed above for either calls that are transported from the first communication device  104  to the second communication device  110  or calls that are transported from the second communication device to the first communication device. In addition, interworking by the first interworking unit  108  and the second interworking unit  110  proceeds as described above. 
     It will be appreciated that the control system may have other configurations. For example, as illustrated in FIG. 5, call signaling or control messages may be routed through the cross connect  204  over a provisioned path from the signaling processor  202  to the first interworking unit  108  over a VPI/VCI in the link  206  and the link  116 . In addition, call signaling or control messages may be routed through the cross connect  204  over a provisioned path from the signaling processor  202  to an ATM system  502  over a VPI/VCI in the link  206  and the link  506 . However, user communications may be transported directly between the first interworking unit  108  and the ATM system  502 , or a communication device, over a connection  504 , without being routed by the cross connect  204 . 
     As illustrated in FIG. 6, call signaling may be transmitted in-band. The control system  102 C of FIG. 6 includes the signaling processor  202  and the cross connect  204  that are described above. Also included is the link  206  that links the signaling processor  202  to the cross connect  204 . 
     However, the control system  102 C interacts with a system which includes a first communication device  602  and a second communication device  604  that transport call signaling in-band, such as in the ESF format. The first communication device  602  transmits user communications and call signaling in-band to the first interworking unit  606  via a connection  608 . The second communication device  604  transmits user communications and call signaling in-band to the second interworking unit  610  via a connection  612 . 
     The cross connect  204  is linked to the first interworking unit  606  through a link  614  and to the second interworking unit  610  through a link  616 . The cross connect  204  is connected to the first interworking unit  606  through a connection  618  and to the second interworking unit  610  through a connection  610 . 
     The first and second communication devices  602  and  604  are the same as the first and second communication devices  104  and  106  of FIG. 2, respectively, except that the first and second communication devices  602  and  604  of FIG. 6 only transport call signaling in-band. The first and second interworking units  606  and  610  of FIG. 5 are the same as the first and second interworking units  108  and  110  of FIG. 2, respectively. 
     However, in the control system  102 C of FIG. 6, a virtual path is provisioned by the cross connect  204  from each of the first and second interworking units  606  and  610  to the signaling processor  202 . These virtual paths are used by the first and second interworking units  606  and  610  to transport the call signaling to the signaling processor  202 . 
     Therefore, companion VPIs/VCIs are connected for the link  614  from the first interworking unit  606  to the cross connect  204  and for the link  206  from the cross connect to the signaling processor  202 . This provides a bi-directional virtual path for call signaling and control messages to be transported between the signaling processor  202  and the first interworking unit  606 . 
     Likewise, companion VPIs/VCIs are connected for the link  616  from the second interworking unit  610  to the cross connect  204  and for the link  206  from the cross connect to the signaling processor  202 . This provides a bi-directional virtual path for call signaling and control messages to be transported between the signaling processor  202  and the second interworking unit  610 . 
     The system of FIG. 6 operates as follows. The cross connect  204  provisions a first virtual path from the signaling processor  202  to the first interworking unit  606 . The first virtual path is bi-directional and connects companion VPIs/VCIs for the link  616  to a first set of companion VPIs/VCIs in the link  206 . 
     The cross connect  204  provisions a second virtual path from the signaling processor  202  to the second interworking unit  610 . The second virtual path is bi-directional and connects companion VPIs/VCIs for the link  618  to a second set of companion VPIs/VCIs in the link  206 . 
     The first communication device  602  transports user communications and call signaling in-band to the first interworking unit  606 . The first interworking unit  606  may detect the in-band call signaling and convert the in-band call signaling to call signaling that may be transported to the signaling processor  202  separate from the user communications. The first interworking unit  606  then transports the call signaling to the signaling processor  202  via the cross connect  204  over the first virtual path. 
     The signaling processor  202  processes the call signaling to determine a first connection  618  and a second connection  612  for the call. The signaling processor  202  transports a first control message via the first virtual path to the first interworking unit  606 . The first control message designates the first connection  618 . The signaling processor  202  also transports a second control message via the second virtual path to the second interworking unit  610 . The second control message designates the second connection  620 . 
     The first interworking unit  606  receives the first control message over the first virtual path and receives the user communications from the first communication device  602 . The first interworking unit  606  interworks the user communications to ATM cells that identify the selected first connection  618 . The first interworking unit  606  then transports the ATM cells over the selected first connection  618 . The cross connect  204  receives the ATM cells and routes them to the second interworking unit  610  via the connection  620  which had been provisioned for the selected first connection  618 . 
     The second interworking unit  610  receives the ATM cells from the connection  618  and the second control message over the second virtual path. The second interworking unit  610  interworks the ATM cells to user communications in a communication format, such as a PCM format, that is processable by the second communication device  604 . The second interworking unit  610  then transports the user communications, together with any required call signaling in-band, to the second communication device  604 . 
     The system of FIG. 6 also transports a call from the second communication device  604  to the first communication device  602  in a like manner. It will be appreciated that other configurations also may exist. 
     The ATM Interworking Unit 
     FIG. 9 shows one embodiment of an interworking unit which is an ATM interworking unit  902  suitable for the present invention for use with a SONET system, but other interworking units that support the requirements of the invention are also applicable. The ATM interworking unit  902  may receive and transmit in-band and out-of-band calls. 
     The ATM interworking unit  902  has a control interface  904 , an OC-N/STS-N interface  906 , a DS 3  interface  908 , a DS1 interface  910 , a DS0 interface  912 , a signal processor  914 , an ATM adaptation layer (AAL)  916 , an OC-M/STS-M interface  918 , and an ISDN/GR-303 interface  920 . As used herein in conjunction with OC or STS, “N” refers to an integer, and “M” refers to an integer. 
     The control interface  902  accepts control messages from the signaling processor  922 . In particular, the control interface  904  identifies DS0 connections and virtual connection assignments in the control messages from the signaling: processor  922 . These assignments are provided to the AAL  916  for implementation. 
     The OC-N/STS-N interface  906 , the DS3 interface  908 , the DS1 interface  910 , the DS0 interface  912 , and the ISDN/GR-303 interface  920  each can accept calls, including user communications, from a communication device  924 . Likewise, the OC-M/STS-M interface  918  can accept calls, including user communications, from a communication device  926 . 
     The OC-N/STS-N interface  906  accepts OC-N formatted calls and STS-N formatted calls and converts the calls from the OC-N or STS-N formats to the DS3 format. The DS3 interface  908  accepts calls in the DS3 format and converts the calls to the DS1 format. The DS3 interface  908  can accept DS3s from the OC-N/STS-N interface  906  or from an external connection. The DS1 interface  910  accepts the calls in the DS1 format and converts the calls to the DS0 format. The DS1 interface  910  can accept DS1s from the DS3 interface  908  or from an external connection. The DS0 interface  912  accepts calls in the DS0 format and provides an interface to the AAL  916 . The ISDN/GR-303 interface  920  accepts calls in either the ISDN format or the GR-303 format and converts the calls to the DS0 format. In addition, each interface may transmit signals in like manner to the communication device  924 . 
     The OC-M/STS-M interface  918  is operational to accept ATM cells from the AAL  916  and to transmit the ATM cells over the connection to the communication device  926 . The OC-M/STS-M interface  918  may also accept ATM cells in the OC or STS format and transmit them to the AAL  916 . 
     The AAL  916  comprises both a convergence sublayer and a segmentation and reassembly (SAR) sublayer. The AAL  916  is operational to accept communication device information in the DS0 format from the DS0 interface  912  and to convert the communication device information into ATM cells. AALs are known in the art and information about AALs is provided by International Telecommunications. Union (ITU): document I.363, which is incorporated fully herein by reference. An AAL for voice calls is described in U.S. patent application Ser. No. 08/395,745, which was filed on Feb. 28, 1995, and entitled “Cell Processing for Voice Transmission,” and which is incorporated herein by reference. 
     The AAL  916  obtains from the control interface  904  the virtual path identifier (VPI) and the virtual channel identifier (VCI) for each DS0 for each call connection. The AAL  916  also obtains the identity of the DS0 for each call (or the DS0s for an Nx64 call). The AAL  916  then transfers the communication device information between the identified DS0 and the identified ATM virtual connection. An acknowledgment that the assignments have been implemented may be sent to the signaling processor  922  if desired. Calls with multiple 64 Kilo-bits per second (Kbps) DSOs are known as Nx64 calls. If desired, the AAL  916  can be configured to accept control messages through the control interface  904  for Nx64 calls. 
     As discussed above, the ATM interworking unit  902  also handles calls in the opposite direction, that is, in the direction from the OC-M/STS-M interface  918  to the DS0 interface  912 , including calls exiting from the DS1 interface.  910 , the DS3 interface  908 , the OC-N/STS-N interface  906 , and the ISDN/GR-303 interface  920 . For this traffic, the VPI/VCI has been selected already and the traffic has been routed through the cross-connect (not shown). As a result, the AAL  916  only needs to identify the pre-assigned DS0 for the selected VPI/VCI. This can be accomplished through a look-up table. In alternative embodiments, the signaling processor  922  can provide this DSO-VPI/VCI assignment through the control interface  904  to the AAL  916 . 
     A technique for processing VPI/VCIs is disclosed in U.S. patent application Ser. No. 08/653,852, which was filed on May 28, 1996, and entitled “Telecommunications System with a Connection Processing System;” and which is incorporated herein by reference. 
     DS0 connections are bi-directional and ATM connections are typically uni-directional. As a result, two virtual connections in opposing directions typically will be required for each DS0. Those skilled in the art will appreciate how this can be accomplished in the context of the invention. For example, the cross-connect can be provisioned with a second set of VPI/VCIs in the opposite direction as the original set of VPI/VCIs. For each call, ATM interworking multiplexers would be configured to invoke automatically this second VPI/VCI to provide a bi-directional virtual connection to match the bi-directional DS0 on the call. 
     In some embodiments, it may be desirable to incorporate digital signal processing capabilities at the DS0 level. It may also be desired to apply echo cancellation to selected DS0 circuits. In these embodiments, a signal processor  914  would be included either separately (as shown) or as a part of the DS0 interface  912 . The signaling processor  922  would be configured to send control messages to the ATM interworking unit  902  to implement particular features on particular DS0 circuits. Alternatively, lookup tables may be used to implement particular features for particular circuits or VPIs/VCIs. 
     FIG. 10 shows another embodiment of an interworking unit which is an ATM interworking unit  1002  suitable for the present invention. The ATM interworking unit  902  may receive and transmit in-band and out-of-band calls. 
     The ATM interworking unit  1002  is for use with an SDH system and has a control interface  1004 , an STM-N electrical/optical (E/O) interface  1006 , an E3 interface  1008 , an E1 interface  1010 , an E0 interface  1012 , a signal processor  1014 , an ATM adaptation layer (AAL)  1016 , an STM-M electrical/optical (E/O) interface  1018 , and a digital private network signaling system (DPNSS) interface  1020 . As used herein in conjunction with STM, “N” refers to an integer, and “M” refers to an integer. 
     The control interface  1004  accepts control messages from the signaling processor  1022 . In particular, the control interface  1004  identifies E0 connections and virtual connection assignments in the control messages from the signaling processor  1022 . These assignments are provided to the AAL  1016  for implementation. 
     The STM-N E/O interface  1006 , the E3 interface  1008 , the E1 interface  1010 , the E0 interface  1012 , and the DPNSS interface  1020  each can accept calls, including user communications, from a second communication device  1024 . Likewise, the STM-M E/O interface  1018  can accept calls, including user communications, from a third communication device  1026 . 
     The STM-N E/O interface  1006  accepts STM-N electrical or optical formatted calls and converts the calls from the STM-N electrical or STM-N optical format to the E3 format. The E3 interface  1008  accepts calls in the E3 format and converts the calls to the E1 format. The E3 interface  1008  can accept E3s from the STM-N E/O interface  1006  or from an external connection. The E1 interface  1010  accepts the calls in the E1 format and converts the calls to the E0 format. The E1 interface  1010  can accept E1s from the STM-N E/O interface  1006  or the E3 interface  1008  or from an external connection. The E0 interface  1012  accepts calls in the E0 format and provides an interface to the AAL  1016 . The DPNSS interface  1020  accepts calls in the DPNSS format and converts the calls to the E0 format. In addition, each interface may transmit signals in a like manner to the communication device  1024 . 
     The STM-M E/O interface  1018  is operational to accept ATM cells from the AAL  1016  and to transmit the ATM cells over the connection to the communication device  1026 . The STM-M E/O interface  1018  may also accept ATM cells in the STM-M E/O format and transmit them to the AAL  1016 . 
     The AAL  1016  comprises both a convergence sublayer and a segmentation and reassembly (SAR) sublayer. The AAL  1016  is operational to accept communication device information in the E0 format from the E0 interface  1012  and to convert the communication device information into ATM cells. 
     The AAL  1016  obtains from the control interface  1004  the virtual path identifier and the virtual channel identifier for each call connection. The AAL  1016  also obtains the identity of each call. The AAL  1016  then transfers the communication device information between the identified E0 and the identified ATM virtual connection. An acknowledgment that the assignments have been implemented may be sent back to the signaling processor  1022  if desired. If desired, the AAL  1016  can be configured to accept control messages through the control interface  1004  for Nx64 calls. 
     As discussed above, the ATM interworking unit  1002  also handles calls in the opposite direction, that is, in the direction from the STM-M E/O interface  1018  to the E0 interface  1012 , including calls exiting from the E1 interface  1010 , :the E3 interface  1008 , the STM-N E/O interface  1006 , and the DPNSS interface  1020 . For this traffic, the VPI/VCI has been selected already and the traffic has been routed through the cross-connect (not shown). As a result, the AAL  1016  only needs to identify the pre-assigned E0 for the selected VPI/VCI. This can be accomplished through a look-up table. In alternative embodiments, the signaling processor  1022  can provide this VPI/VCI assignment through the control interface  1004  to the AAL  1016 . 
     E0 connections are bi-directional and ATM connections typically are uni-directional. As a result, two virtual connections in opposing directions typically will be required for each E0. Those skilled in the art will appreciate how this can be accomplished in the context of the invention. For example, the cross-connect can be provisioned with a second set of VPI/VCIs in the opposite direction as the original set of VPI/VCIs. For each call, ATM interworking multiplexers would be configured to automatically invoke this second VPI/VCI to provide a bi-directional virtual connection to match the bi-directional E0 on the call. 
     In some instances, it may be desirable to incorporate digital signal processing capabilities at the E0 level. Also, it may be desirable apply echo cancellation. In these embodiments, a signal processor  1014  would be included either separately (as shown) or as a part of the E0 interface  1012 . The signaling processor  1022  would be configured to send control messages to the ATM interworking unit  1002  to implement particular features on particular circuits. Alternatively, lookup tables may be used to implement particular features for particular circuits or VPIs/VCIs. 
     The Signaling Processor 
     The signaling processor is referred to as a call/connection manager (CCM), and it receives and processes telecommunications call signaling and control messages to select connections that establish communication paths for calls. In the preferred embodiment, the CCM processes ISDN, GR-303, and SS7signaling to select connections for a call. CCM processing is described in a U.S. Patent Application Ser. No. 08/754,349, which is entitled “Telecommunication System,” which is assigned to the same assignee as this patent application, and which is incorporated herein by reference. 
     In addition to selecting connections, the CCM performs many other functions in the context of call processing. It not only can control routing and select the actual connections, but it also can validate callers, control echo cancelers, generate billing information, invoke intelligent network functions, access remote databases, manage traffic, and balance network loads. One skilled in the art will appreciate how the CCM described below can be adapted to operate in the above embodiments. 
     FIG. 11 depicts a version of the CCM. Other versions also are contemplated. In the embodiment of FIG. 11, the CCM  1102  controls an ATM interworking unit, such as an ATM interworking multiplexer (mux) that performs interworking of DS0s and VPI/VCIs. However, the CCM may control other communications devices and connections in other embodiments. 
     The CCM  1102  comprises a signaling platform  1104 , a control platform  1106 , and an application platform  1108 . Each of the platforms  1104 ,  1106 , and  1108  is coupled to the other platforms. 
     The signaling platform  1104  is externally coupled to the signaling systems—in particular to SS7 signaling systems having a message transfer part (MTP), an ISDN user part (ISUP), a signaling connection control part (SCCP), an intelligent network application part (INAP), and a transaction capabilities application part (TCAP). The control platform  1106  is externally coupled to an interworking unit control, an echo control, a resource control, billing, and operations. 
     The signaling platform  1104  preferably is an SS7 platform that comprises MTP levels 1-3, ISUP, TCAP, SCCP, and INAP functionality and is operational to transmit and receive the SS7 messages. The ISUP, SCCP, INAP, and TCAP functionality use MTP to transmit and receive the SS7 messages. Together, this functionality is referred as an “SS7 stack,” and it is well known. The software required by one skilled in the art to configure an SS7 stack is commercially available, for example, from the Trillium company. 
     The control platform  1106  is comprised of various external interfaces including an interworking unit interface, an echo interface, a resource control interface, a billing interface, and an operations interface. The interworking unit interface exchanges messages with at least one interworking unit. These messages comprise DS0 to VPI/VCI assignments, acknowledgments, and status information. The echo control interface exchanges messages with echo control systems. Messages exchanged with echo control systems might include instructions to enable or disable echo cancellation on particular DS0s, acknowledgments, and status information. 
     The resource control interface exchanges messages with external resources. Examples of such resources are devices that implement continuity testing, encryption, compression, tone detection/transmission, voice detection, and voice messaging. The messages exchanged with resources are instructions to apply the resource to particular DS0s, acknowledgments, and status information. For example, a message may instruct a continuity testing resource to provide a loopback or to send and detect a tone for a continuity test. 
     The billing interface transfers pertinent billing information to a billing system. Typical billing information includes the parties to the call, time points for the call, and any special features applied to the call. The operations interface allows for the configuration and control of the CCM  1102 . One skilled in the art will appreciate how to produce the software for the interfaces in the control platform  1106 . 
     The application platform  1108  is functional to process signaling information from the signaling platform  1104  in order to select connections. The identity of the selected connections are provided to the control platform  1106  for the interworking unit interface. The application platform  1108  is responsible for validation, translation, routing, call control, exceptions, screening, and error handling. In addition to providing the control requirements for the interworking unit, the application platform  1108  also provides requirements for echo control and resource control to the appropriate interface of the control platform  1106 . In addition, the application platform  1108  generates signaling information for transmission by the signaling platform  1104 . The signaling information might be ISUP, INAP, or TCAP messages to external network elements. Pertinent information for each call is stored in a call control block (CCB) for the call. The CCB can be used for tracking and billing the call. 
     The application platform  1108  operates in general accord with the Basic Call Model (BCM) defined by the ITU. An instance of the BCM is created to handle each call. The BCM includes an originating process and a terminating process. The application platform  1108  includes a service switching function (SSF) that is used to invoke the service control function (SCF). Typically, the SCF is contained in a service control point (SCP). The SCF is queried with TCAP or INAP messages. The originating or terminating processes will access remote databases with intelligent network (IN) functionality via the SSF function. 
     Software requirements for the application platform  1108  can be produced in specification and description language (SDL) defined in ITU-T Z. 100. The SDL can be converted into C code. Additional C and C++ code can be added as required to establish the environment. 
     The CCM  1102  can be comprised of the above-described software loaded onto a computer. The computer can be an Integrated Micro Products (IMP) FT-Sparc 600 using the Solaris operating system and conventional database systems. It may be desirable to utilize the multi-threading capability of a Unix operating system. 
     From FIG. 11, it can be seen that the application platform  1108  processes signaling information to control numerous systems and facilitate call connections and services. The SS7 signaling is exchanged with external components through the signaling platform  1104 , and control information is exchanged with external systems through the control platform  1106 . Advantageously, the CCM  1102  is not integrated into a switch central processing unit (CPU) that is coupled to a switching matrix. Unlike an SCP, the CCM  1102  is capable of processing ISUP messages independently of TCAP queries. 
     SS7 Message Designations 
     SS7 messages are well known. Designations for various SS7 messages commonly are used. Those skilled in the art are familiar with the following message designations: 
     
       
         
           
               
               
             
               
                   
                   
               
             
            
               
                   
                 ACM—Address Complete Message 
               
               
                   
                 ANM—Answer Message 
               
               
                   
                 BLO—Blocking 
               
               
                   
                 BLA—Blocking Acknowledgment 
               
               
                   
                 CPG—Call Progress 
               
               
                   
                 CRG—Charge Information 
               
               
                   
                 CGB—Circuit Group Blocking 
               
               
                   
                 CGBA—Circuit Group Blocking Acknowledgment 
               
               
                   
                 GRS—Circuit Group Reset 
               
               
                   
                 GRA—Circuit Group Reset Acknowledgment 
               
               
                   
                 CGU—Circuit Group Unblocking 
               
               
                   
                 CGUA—Circuit Group Unblocking Acknowledgment 
               
               
                   
                 CQM—Circuit Group Query 
               
               
                   
                 CQR—Circuit Group Query Response 
               
               
                   
                 CRM—Circuit Reservation Message 
               
               
                   
                 CRA—Circuit Reservation Acknowledgment 
               
               
                   
                 CVT—Circuit Validation Test 
               
               
                   
                 CVR—Circuit Validation Response 
               
               
                   
                 CFN—Confusion 
               
               
                   
                 COT—Continuity 
               
               
                   
                 CCR—Continuity Check Request 
               
               
                   
                 EXM—Exit Message 
               
               
                   
                 INF—Information 
               
               
                   
                 INR—Information Request 
               
               
                   
                 IAM—Initial Address 
               
               
                   
                 LPA—Loop Back Acknowledgment 
               
               
                   
                 PAM—Pass Along 
               
               
                   
                 REL—Release 
               
               
                   
                 RLC—Release Complete 
               
               
                   
                 RSC—Reset Circuit 
               
               
                   
                 RES—Resume 
               
               
                   
                 SUS—Suspend 
               
               
                   
                 UBL—Unblocking 
               
               
                   
                 UBA—Unblocking Acknowledgment 
               
               
                   
                 UCIC—Unequipped Circuit Identification Code. 
               
               
                   
                   
               
            
           
         
       
     
     CCM Tables 
     Call processing typically entails two aspects. First, an incoming or “originating” connection is recognized by an originating call process. For example, the initial connection that a call uses to enter a network is the originating connection in that network. Second, an outgoing or “terminating” connection is selected by a terminating call process. For example, the terminating connection is coupled to the originating connection in order to extend the call through the network. These two aspects of call processing are referred to as the originating side of the call and the terminating side of the call. 
     FIG. 12 depicts a data structure used by the application platform  1108  to execute the BCM. This is accomplished through a series of tables that point to one another in various ways. The pointers are typically comprised of next function and next index designations. The next function points to the next table, and the next index points to an entry or a range of entries in that table. The data structure has a trunk circuit table  1202 , a trunk group table  1204 , an exception table  1206 , an ANI table  1208 , a called number table  1210 , and a routing table  1212 . 
     The trunk circuit table  1202  contains information related to the connections. Typically, the connections are DS0 or ATM connections. Initially, the trunk circuit table  1202  is used to retrieve information about the originating connection. Later, the table is used to retrieve information about the terminating connection. When the originating connection is being processed, the trunk group number in the trunk circuit table  1202  points to the applicable trunk group for the originating connection in the trunk group table  1204 . 
     The trunk group table  1204  contains information related to the originating and terminating trunk groups. When the originating connection is being processed, the trunk group table  1204  provides information relevant to the trunk group for the originating connection and typically points to the exception table  1206 . 
     The exception table  1206  is used to identify various exception conditions related to the call that may influence the routing or other handling of the call. Typically, the exception table  1206  points to the ANI table  1208 . Although, the exception table  1206  may point directly to the trunk group table  1204 , the called number table  1210 , or the routing table  1212 . 
     The ANI table  1208  is used to identify any special characteristics related to the caller&#39;s number. The caller&#39;s number is commonly known as automatic number identification (ANI). The ANI table  1208  typically points to the called number table  1210 . Although, the ANI table  1208  may point directly to the trunk group table  1204  or the routing table  1212 . 
     The called number table  1210  is used to identify routing requirements based on the called number. This will be the case for standard telephone calls. The called number table  1210  typically points to the routing table  1212 . Although, it may point to the trunk group table  1204 . 
     The routing table  1212  has information relating to the routing of the call for the various connections. The routing table  1212  is entered from a pointer in the exception table  1206 , the ANI table  1208 , or the called number table  1210 . The routing table  1212  typically points to a trunk group in the trunk group table  1204 . 
     When the exception table  1206 , the ANI table  1208 , the called number table  1210 , or the routing table  1212  point to the trunk group table  1204 , they effectively select the terminating trunk group. When the terminating connection is being processed, the trunk group number in the trunk group table  1204  points to the trunk group that contains the applicable terminating connection in the trunk circuit table  1204 . 
     The terminating trunk circuit is used to extend the call. The trunk circuit is typically a VPI/VCI or a DS0. Thus, it can be seen that by migrating through the tables, a terminating connection can be selected for a call. 
     FIG. 13 is an overlay of FIG.  12 . The tables from FIG. 12 are present, but for clarity, their pointers have been omitted. FIG. 13 illustrates additional tables that can be accessed from the tables of FIG.  12 . These include a CCM ID table  1302 , a treatment table  1304 , a query/response table  1306 , and, a message table  1308 . 
     The CCM ID table  1302  contains various CCM SS7 point codes. It can be accessed from the trunk group table  1204 , and it points back to the trunk group table  1204 . 
     The treatment table  1304  identifies various special actions to be taken in the course of call processing. This will typically result in the transmission of a release, message (REL) and a cause value. The treatment table  1304  can be accessed from the trunk circuit table  1202 , the trunk group table  1204 , the exception table  1206 , the ANI table  1208 , the called number table  1210 , the routing table  1212 , and the query/response table  1306 . 
     The query/response table  1306  has information used to invoke the SCF. It can be accessed by the trunk group table  1204 , the exception table  1206 , the ANI table  1208 , the called number table  1210 , and the routing table  1212 . It points to the trunk group table  1204 , the exception table  1206 , the ANI table  1208 , the called number table  1210 , the routing table  1212 , and the treatment table  1304 . 
     The message table  1308  is used to provide instructions for messages from the termination side of the call. It can be accessed by the trunk group table  1204  and points to the trunk group table  1204 . 
     FIGS. 14-21 depict examples of the various tables described above. FIG. 14 depicts an example of the trunk circuit table. Initially, the trunk circuit table is used to access information about the originating circuit. Later in the processing, it is used to provide information about the terminating circuit. For originating circuit processing, the associated point code is used to enter the table. This is the point code of the switch or CCM associated with the originating circuit. For terminating circuit processing, the trunk group number is used to enter the table. 
     The table also contains the circuit identification code (CIC). The CIC identifies the circuit which is typically a DS0 or a VPI/VCI. Thus, the invention is capable of mapping the SS7 CICs to the ATM VPI/VCI. If the circuit is ATM, the virtual path (VP) and the virtual channel (VC) also can be used for identification. The group member number is a numeric code that is used for terminating circuit selection. The hardware identifier identifies the location of the hardware associated with the originating circuit. The echo canceler (EC) identification (ID) entry identifies the echo canceler for the originating circuit. 
     The remaining fields are dynamic in that they are filled during call processing. The echo control entry is filled based on three fields in signaling messages: the echo suppresser indicator in the IAM or CRM, the echo control device indicator in the ACM or CPM, and the information transfer capability in the LAM. This information is used to determine if echo control is required on the call. The satellite indicator is filled with the satellite indicator in the IAM or CRM. It may be used to reject a call if too many satellites are used. The circuit status indicates if the given circuit is idle, blocked, or not blocked. The circuit state indicates the current state of the circuit, for example, active or transient. The time/date indicates when the idle circuit went idle. 
     FIG. 15 depicts an example of the trunk group table. During origination processing, the trunk group number from the trunk circuit table is used to key into the trunk table. Glare resolution indicates how a glare situation is to be resolved. Glare is dual seizure of the same circuit. If the glare resolution entry is set to “even/odd,” the network element with the higher point code controls the even circuits, and the network element with the lower point code controls the odd circuits. If the glare resolution entry is set to “all,” the CCM controls all of the circuits. If the glare resolution entry is set to “none,” the CCM yields. The continuity control entry lists the percent of calls requiring continuity tests on the trunk group. 
     The common language location identifier (CLLI) entry is a Bellcore standardized entry. The satellite trunk group entry indicates that the trunk group uses a satellite. The satellite trunk group entry is used in conjunction with the satellite indicator field described above to determine if the call has used too many satellite connections and, therefore, must be rejected. The service indicator indicates if the incoming message is from a CCM (ATM) or a switch (TDM). The outgoing message index (OMI) points to the message table so that outgoing messages can obtain parameters. The associated number plan area (NPA) entry identifies the area code. 
     Selection sequence indicates the methodology that will be used to select a connection. The selection sequence field designations tell the trunk group to select circuits based on the following: least idle, most idle, ascending, descending, clockwise, and counterclockwise. The hop counter is decremented from the IAM. If the hop, counter is zero, the call is released. Automatic congestion control (ACC) active indicates whether or not congestion control is active. If automatic congestion control is active, the CCM may release the call. During termination processing, the next function and index are used to enter the trunk circuit table. 
     FIG. 16 depicts an example of the exception table. The index is used as a pointer to enter the table. The carrier selection identification (ID) parameter indicates how the caller reached the network and is used for routing certain types of calls. The following are used for this field: spare or no indication, selected carrier identification code presubscribed and input by the calling party, selected carrier identification code presubscribed and not input by the calling party, selected carrier identification code presubscribed and no indication of input by the calling party, and selected carrier identification code not presubscribed and input by the calling party. The carrier identification (ID) indicates the network that the caller wants to use. This is used to route calls directly to the desired network. The called party number nature of address differentiates between 0+ calls, 1+ calls, test calls, and international calls. For example, international calls might be routed to a pre-selected international carrier. 
     The called party “digits from” and “digits to” focus further processing unique to a defined range of called numbers. The “digits from” field is a decimal number ranging from 1-15 digits. It can be any length and, if filled with less than 15 digits, is filled with 0s for the remaining digits. The “digits to” field is a decimal number ranging from 1-15 digits. It can be any length and, if filled with less than 15 digits, is filled with 9s for the remaining digits. The next function and next index entries point to the next table which is typically the ANI table. 
     FIG. 17 depicts an example of the ANI table. The index is used to enter the fields of the table. The calling party category differentiates among types of calling parties, for example, test calls, emergency calls, and ordinary calls. The calling party charge number entry nature of address indicates how the ANI is to be obtained. The following is the table fill that is used in this field: unknown, unique subscriber numbers, ANI not available or not provided, unique national number, ANI of the called party included, ANI of the called party not included, ANI of the called party includes national number, non-unique subscriber number, non-unique national number, non-unique international number, test line test code, and all other parameter values. 
     The “digits from” and “digits to” focus further processing unique to ANI within a given range. The data entry indicates if the ANI represents a data device that does not need echo control. Originating line information (OLI) differentiates among ordinary subscriber, multiparty line, ANI failure, station level rating, special operator handling, automatic identified outward dialing, coin or non-coin call using database access, 800\888 service call, coin, prison/inmate service, intercept (blank, trouble, and regular), operator handled call, outward wide area telecommunications service, telecommunications relay service (TRS), cellular services, private paystation, and access for private virtual network types of service. The next function and next index point to the next table which is typically the called number table. 
     FIG. 18 depicts an example of the called number table. The index is used to enter the table. The called number nature of address entry indicates the type of dialed number, for example, national versus international. The “digits from” and “digits to” entries focus further processing unique to a range of called numbers. The processing follows the processing logic of the “digits from” and “digits to” fields in FIG.  16 . The next function and next index point to the next table which is typically the routing table. 
     FIG. 19 depicts an example of the routing table. The index is used to enter the table. The transit network selection (TNS) network identification (ID) plan indicates the number of digits to use for the CIC. The transit network selection “digits from” and “digits to” fields define the range of numbers to identify an international carrier. The circuit code indicates the need for an operator on the call. The next function and next index entries in the routing table are used to identify a trunk group. The second and third next function/index entries define alternate routes. The third next function entry can also point back to another set of next functions in the routing table in order to expand the number of alternate route choices. The only other entries allowed are pointers to the treatment table. If the routing table points to the trunk group table, then the trunk group table typically points to a trunk circuit in the trunk circuit table. The yield from the trunk circuit table is the terminating connection for the call. 
     It can be seen from FIGS. 14-19 that the tables can be configured and relate to one another in such a way that call processes can enter the trunk circuit table for the originating connection and can traverse through the tables by keying on information and using pointers. The yield of the tables is typically a terminating connection identified by the trunk circuit table. In some cases, treatment is specified by the treatment table instead of a connection. If, at any point during the processing, a trunk group can be selected, processing may proceed directly to the trunk group table for terminating circuit selection. For example, it may be desirable to route calls from a particular ANI over a particular set of trunk groups. In this case, the ANI table would point directly to the trunk group table, and the trunk group table would point to the trunk circuit table for a terminating circuit. The default path through the tables is: trunk circuit, trunk group, exception, ANI, called number, routing, trunk group, and trunk circuit. 
     Those skilled in the art will appreciate that variations from the specific embodiments disclosed above are contemplated by the invention. The invention should not be restricted to the above embodiments, but should be measured by the following claims.