Patent Publication Number: US-7212519-B2

Title: Combining narrowband applications with broadband transport

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This U.S. Nonprovisional Application for Patent is a Continuation-in-Part of U.S. Nonprovisional application for patent Ser. No. 09/764,953, which was filed on Jan. 17, 2001, which is a Continuation-in-Part of U.S. Nonprovisional application for patent Ser. No. 09/353,135, which was filed on Jul. 14, 1999. U.S. Nonprovisional applications for patent Ser. Nos. 09/764,953 and 09/353,135 are also hereby incorporated by reference in their entirety herein. 
     This U.S. Nonprovisional application for patent is related by subject matter to U.S. Nonprovisional applications for patent Ser. Nos. 10/010,832, filed Dec. 6, 2001, 10/025,354, filed Dec. 18, 2001, 10/021,940, filed Dec. 12, 2001, and 10/028,176 filed Dec. 21, 2001. These U.S. Nonprovisional applications for patent Ser. Nos. 10/010,832, 10/025,354, 10/021,940 and 10/028,176 are hereby incorporated by reference in their entirety herein. 
     This U.S. Nonprovisional Application for Patent is further related by subject matter to U.S. Nonprovisional applications for patent Ser. Nos. 09/764,622, filed Jan. 17, 2001, 09/765,119, filed Jan. 17, 2001, 09/764,960, filed Jan. 17, 2001 and 09/866,135, filed May 25, 2001. These U.S. Nonprovisional applications for patent Ser. Nos. 09/764,622, 09/765,119, 09/764,960 and 09/866,135 are hereby incorporated by reference in their entirety herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates in general to the field of communications, and in particular, by way of example but not limitation, to using broadband transport for narrowband telephony and data communications. 
     2. Description of Related Art 
     The increasing interest for high band services such as multimedia applications, video on demand, video telephone, and teleconferencing has motivated development of the Broadband Integrated Service Digital Network (B-ISDN). B-ISDN is based on a technology known as Asynchronous Transfer Mode (ATM) and offers considerable extension of telecommunications capabilities. 
     ATM is a packet-oriented transfer mode which uses asynchronous time division multiplexing techniques. The packets are called cells and traditionally have a fixed size. A standard ATM cell comprises 53 octets, five of which form a header and 48 of which constitute a “payload” or information portion of the cell. The header of the ATM cell includes two quantities that are used to identify a connection in an ATM network over which the cell is to travel. These two quantities include the Virtual Path Identifier (VPI) and the Virtual Channel Identifier (VCI). In general, a virtual path is a principal path defined between two switching nodes of the network; a virtual channel is one specific connection on the respective principal path. 
     At its termination points, an ATM network is connected to terminal equipment, e.g., ATM network users. In between ATM network termination points, there are typically multiple switching nodes. The switching nodes have ports which are connected together by physical transmission paths or links. Thus, in traveling from an originating terminal equipment to a destination terminal equipment, ATM cells forming a message may travel through several switching nodes and the ports thereof. 
     Of the multiple ports of a given switching node, each may be connected via a link circuit and a link to another node. The link circuit performs packaging of the cells according to the particular protocol in use on the link. A cell that is incoming to a switching node may enter the switching node at a first port and exit from a second port via a link circuit onto a link connected to another node. Each link can carry cells for multiple connections, with each connection being, e.g., a transmission between a calling subscriber or party and a called subscriber or party. 
     The switching nodes each typically have several functional parts, a primary of which is a switch core. The switch core essentially functions like a cross-connect between ports of the switch. Paths internal to the switch core are selectively controlled so that particular ports of the switch are connected together to allow a message to travel from an ingress side/port of the switch to an egress side/port of the switch. The message can therefore ultimately travel from the originating terminal equipment to the destination terminal equipment. 
     While ATM, because of the high speed and bandwidth that it offers, is envisioned as the transport mechanism for more advanced services such as B-ISDN, it nevertheless must be recognized that the current narrowband networks (e.g., Public Switched Telephone Networks (PSTN), ISDN, etc.) will remain in use (at least in part) for quite some time. It has taken decades for the present voice switched telephony networks (e.g., PSTN, ISDN, etc.) to reach their present advanced functionalities. While ATM networks are being built, the ATM networks will likely not easily acquire all the functionalities of advanced voice communication. Therefore, at least initially, ATM networks/nodes will in some instances be added to parts or will replace parts of circuit switched telephony networks. In such instances, ATM will be used for transport and switching. ATM can actually be used as a single transport and switching mechanism for multiple other networks, including multiple other different types of networks. For example, a single ATM network can be used to transport and switch communications from mobile networks (e.g., Public Land Mobile Networks (PLMNs)), Internet protocol (IP)-based networks (e.g., the Internet), etc., as well as landline networks such as PSTNs and ISDNs. 
     U.S. Pat. Nos. 5,568,475 and 5,483,527 to Doshi et al., for example, incorporate ATM switches for routing telephony voice signals between Synchronous Transfer Mode (STM) nodes. The ATM switches use a signaling system No. 7 (SS#7) network to establish a virtual connection, rather than a circuit switched connection, as would be the case in a pure STM network. The signaling system No. 7 (SS#7) network of U.S. Pat. Nos. 5,568,475 and 5,483,527 includes signal transfer points (STPs) that are connected by special physical links to each of the ATM switch nodes. For call setup, for example, signaling messages are relayed through the signaling system No. 7 (SS#7) network. In such relaying, a non-ATM STP receives the signaling message and advises its associated ATM node of the call setup. The associated ATM node may then identify idle resources to be used for forwarding voice signals to the next ATM node once the call has been setup, and it may prepare its own signaling message to be used in the relay. 
     The signaling message for the relay that is prepared by the ATM node is returned to its associated STP, which forwards the signaling message via the signaling system No. 7 (SS#7) network to another STP associated with the next ATM node. Such relaying continues until the signaling message reaches an STP of an STM local exchange carrier (LEC). Once the call has been set up, the ensuing speech (or voice-band data) is transported via the ATM nodes. STM/ATM terminal adapters are situated between the STM network and the ATM network for packing samples of voice signals as received from the STM network into ATM cells for application to the ATM network, and for unpacking ATM cell payloads to obtain voice signals for application to the STM network from the ATM network. The incorporation of ATM into an STM network in the particular manner as described above thus involves a non-ATM signaling network alongside the ATM nodes. Furthermore, each STP node associated with an ATM node performs only call control functions in the network of Doshi et al. Otherwise and in general, call control and connection control is traditionally combined in conventional communication nodes. 
     With reference now to  FIG. 1A , a conventional unified communications node is illustrated at  100 . The conventional unified communications node  100  may represent any general purpose switching node in a telecommunications network such as a PSTN. Within the conventional communications node  100 , the call control  105  functions and the connection control  110  functions are united. The call control  105  and the connection control  110  functions together encompass the entire seven (7) layers of the Open System Interconnection (OSI) protocol. These seven (7) layers are denoted as the physical, data link, network, transport, session, presentation, and application layers. Accordingly, the conventional communications node  100  may perform all functions related to both switching intelligence and switching fabric. Conventional communication nodes  100  are not, however, capable of handling the interworking between (i) narrowband telephony and data communications and (ii) broadband communications using faster and higher bandwidth networks, such as ATM networks. 
     With reference now to  FIG. 1B , a conventional approach to separating functions of the conventional unified communications node of  FIG. 1A  is illustrated generally at  150 . Conventional approaches attempt to meet the stringent demands of interworking narrowband telephony and data communications with broadband networks using ATM by separating control functions. Specifically, call control  155  functions are separated from connection control  160  functions. The call control  155  functions are thereby made independent of any particular set of connection control  160  functions. This separation is typically accomplished by utilizing a conventional communications node (such as the conventional communications node  100  of  FIG. 1A ) that is stripped of its switching intelligence, leaving only the connection control  160 . In effect, a conventional communications node  100  is modified by removing or rendering inoperative the call control  105  functions, thus leaving only the connection control  110  functions. This modified conventional communications node is substituted as the connection control  160  part. The call control  155  part, on the other hand, is typically designed and created without relying on traditional telecommunications hardware or software. 
     With reference now to  FIG. 2 , an existing scheme for utilizing a broadband network in conjunction with nodes corresponding to separated functions of a conventional unified communications node is illustrated generally at  200 . Switching intelligence  205 A, 205 B parts are connected to switching fabric  210 A, 210 B parts. The switching fabric  210 A, 210 B parts are connected to the ATM network  215 , and they effect required emulation and cell packing for interworking a narrowband network (not shown) with the ATM network  215 . The switching intelligence  205 A, 205 B parts are usually realized with a UNIX-based server. The switching intelligence  205 A, 205 B parts are intended to provide the advanced calling services and features (e.g., those traditionally provided by the Intelligence Network (IN)). The switching intelligence  205 A, 205 B parts do not include any switching fabric resources, so they must rely on the switching fabric  210 A, 210 B parts for these resources. 
     Because the switching intelligence  205 A, 205 B parts do not have any of their own switching fabric resources, they are not directly connected to any transport mechanisms, nor do they include the requisite interface(s) for doing so. Incoming calls are therefore received at a switching fabric  210  part and managed by the associated switching intelligence  205  part. When an incoming call is received at a switching fabric  210  part, call signaling information is sent to the switching intelligence  205  part. The switching intelligence  205  part performs the appropriate call control functions and sends instructions (e.g., in the form of call signaling information) to the switching fabric  210  part. The switching fabric  210  part follows the instructions by making the appropriate connections (e.g., to/through the ATM network  215 , to/through a narrowband network (not shown), etc.) for forwarding the call data information for the incoming call. As such, no call data information is (or can be) sent to the switching intelligence  205  part, including from the switching fabric  210  part. 
     Furthermore, while UNIX-based servers, which realize the switching intelligence  205  parts, may be designed to operate at high speeds, they suffer from a number of deficiencies. First, significant research, design, and testing is required to produce appropriate software code to run the UNIX-based servers as switching intelligence  205  parts. Existing circuit-switched voice telephony networks include many advanced features that require many lines of code that have been gradually developed, tested, and implemented over many years. Duplicating the diverse number and types of features while maintaining the required level of reliability and service using newly written code on a UNIX server is not only a daunting task, but it is also virtually impossible to achieve quickly. Second, it is extraordinarily difficult to migrate gradually from traditional network architectures (e.g., those using the conventional unified communications node  100  of  FIG. 1A ) to next generation networks that rely on broadband transport mechanisms when deploying nodes with only the switching intelligence  205  part. System operators are essentially forced to simultaneously replace whole portions of their networks in large chunks. The consequential large capital expenditures are naturally undesirable to system operators. 
     SUMMARY OF THE INVENTION 
     The deficiencies of the prior art are overcome by the methods, systems, and arrangements of the present invention. For example, as heretofore unrecognized, it would be beneficial to re-use and/or extend the life of existing/legacy switches when combining narrowband networks with broadband transport mechanisms. In fact, it would be beneficial to utilize existing switches to enable a gradual migration from narrowband networks to broadband transport mechanisms via the implementation of hybrid switches. 
     The present invention is directed to a tri-level nodal architecture including a call control node having switching intelligence and narrowband switching fabric, at least one connection control node having broadband switching fabric and an intermediate node for interworking between the call control node and connection control node. The call control node further includes a load distribution function for distributing the load amongst a plurality of call processors. 
     In certain embodiments, the load distribution function assigns the call processors on a per call basis. The assigned call processor is used for encoding all messages transmitted from the call control node to a selected connection control node for the call. In further embodiments, a linked call processor has a transport link towards the selected connection control node, and all messages encoded by the assigned call processor are transmitted to the selected connection control node through the linked call processor. In still further embodiments, all messages transmitted from the selected connection control node to the call control node are received and decoded at the linked call processor before being transmitted to the call control node through the assigned call processor. 
     In one embodiment, the call control node may be realized by a legacy switch (LS), the intermediate node may be realized by mediation logic (ML) and the LS and ML combined form a media gateway controller (MGC). In addition, the connection control node may be realized by one or more media gateways (MGs). 
     The above-described and other features of the present invention are explained in detail hereinafter with reference to the illustrative examples shown in the accompanying drawings. Those skilled in the art will appreciate that the described embodiments are provided for purposes of illustration and understanding and that numerous equivalent embodiments are contemplated herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the methods, systems, and arrangements of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein: 
         FIG. 1A  illustrates a conventional unified communications node; 
         FIG. 1B  illustrates a conventional approach to separating functions of the conventional unified communications node of  FIG. 1A ; 
         FIG. 2  illustrates an existing scheme for utilizing a broadband network in conjunction with nodes corresponding to separated functions of a conventional unified communications node; 
         FIG. 3  illustrates an exemplary schematic view of a hybrid STM/ATM network according to an embodiment of the invention; 
         FIG. 3A  illustrates an exemplary schematic view of selected portions of the hybrid STM/ATM network of  FIG. 3 , and further showing various operational events; 
         FIG. 3B  illustrates an exemplary schematic view of a hybrid STM/ATM network according to another embodiment of the invention; 
         FIG. 3C  illustrates an exemplary schematic view showing a transit hybrid node pair of the invention connected between two local exchange hybrid node pairs of the invention; 
         FIG. 3D  illustrates a diagrammatic view of an exemplary protocol between two elements of the network of the embodiment(s) of the invention that include hybrid node pairs; 
         FIGS. 3E ,  3 F, and  3 G illustrate diagrammatic views of alternate exemplary protocols between two elements, a first of the network elements having a hybrid node pair in accordance with embodiment(s) of the invention and a second of the network elements being an access node with an additional ATM interface having circuit emulation; 
         FIG. 3H  illustrates an exemplary diagrammatic view showing gradual upgrading of a network from a traditional narrowband STM-transported-and-switched environment into an environment with a hybrid STM/ATM network in accordance with embodiment(s) of the invention; 
         FIG. 3I  illustrates an exemplary schematic view showing a multi-switch hybrid node according to yet another embodiment of the invention; 
         FIG. 4  illustrates another exemplary scheme for utilizing a broadband network in conjunction with nodes having partially separated functions in accordance with the present invention; 
         FIG. 5  illustrates yet another exemplary scheme for utilizing a broadband network in conjunction with nodes having partially separated functions in accordance with the present invention; 
         FIG. 6  illustrates another exemplary hybrid switch with multiple ports for switching a connection in accordance with the present invention; 
         FIG. 7  illustrates a simplified block diagram of an exemplary hybrid switch in accordance with the present invention; 
         FIG. 8  illustrates exemplary communications and connections between nodes in another simplified block diagram of an exemplary hybrid switch in accordance with the present invention; 
         FIG. 9  illustrates an exemplary method in flowchart form for communicating between nodes in a hybrid switch in accordance with the present invention; 
         FIGS. 10A–10E  illustrate a first set of exemplary traffic scenarios for a hybrid switch in accordance with the present invention; 
         FIGS. 10F–10K  illustrate a second set of exemplary traffic scenarios for a hybrid switch in accordance with the present invention; 
         FIG. 11  illustrates an exemplary outgoing communication format selection for a hybrid switch in accordance with the present invention; 
         FIG. 12  illustrates exemplary interactions between a hybrid switch and other telecommunications technology in accordance with the present invention; 
         FIG. 13  illustrates an exemplary traffic scenario migration for a hybrid switch in accordance with the present invention; 
         FIG. 14  illustrates an exemplary method in flowchart form for enabling a gradual migration from a primarily narrowband network to a primarily broadband network in accordance with the present invention; 
         FIG. 15  illustrates an exemplary tri-level nodal environment in accordance with the present invention; 
         FIG. 15A  illustrates a first exemplary tri-level nodal environment alternative in accordance with the present invention; 
         FIG. 15B  illustrates a second exemplary tri-level nodal environment alternative in accordance with the present invention; 
         FIG. 15C  illustrates an exemplary interworking function in accordance with the present invention; 
         FIG. 16  illustrates an exemplary tri-level nodal environment implementation in accordance with the present invention; 
         FIGS. 17A and 17B  illustrate two other exemplary tri-level nodal environment implementations in accordance with the present invention; 
         FIGS. 18A and 18B  illustrate two exemplary call setups in an exemplary tri-level nodal environment implementation in accordance with the present invention; 
         FIG. 19  illustrates exemplary communication path configuring in an exemplary tri-level nodal network in accordance with the present invention; 
         FIGS. 20A and 20B  illustrate exemplary mapping embodiments in an exemplary tri-level nodal environment implementation in accordance with the present invention; 
         FIG. 21  illustrates an exemplary tri-level nodal environment with exemplary functionality in accordance with the present invention; 
         FIG. 22  illustrates an exemplary load distribution embodiment in an exemplary tri-level nodal environment implementation in accordance with the present invention; 
         FIG. 23  illustrates an exemplary load assignment embodiment in an exemplary tri-level nodal environment implementation in accordance with the present invention; 
         FIG. 24  illustrates an exemplary message encoding and transmission embodiment in an exemplary tri-level nodal environment implementation in accordance with the present invention; 
         FIG. 25  illustrates an exemplary message decoding and transmission embodiment in an exemplary tri-level nodal environment implementation in accordance with the present invention; and 
         FIGS. 26A and 26B  illustrate an exemplary method in flowchart form for transmitting messages between nodes within a tri-level nodal environment in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular architectures, interfaces, circuits, information exchanges, logic modules (implemented in, for example, software, hardware, firmware, some combination thereof, etc.), techniques, etc. in order to provide a thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods, devices, logical code (e.g., hardware, software, firmware, etc.), etc. are omitted so as not to obscure the description of the present invention with unnecessary detail. It should be understood that the terms “module” and “logic module” as used herein embrace, subsume, and include, inter alia, object oriented programming techniques as well as so-called traditional programming techniques such as, for example, custom-developed applications. 
     Embodiment(s) of the present invention and advantages thereof are best understood by referring to  FIGS. 1A–26  of the drawings, like numerals being used for like and corresponding parts of the various drawings. 
     In certain embodiments in accordance with the invention (e.g., including embodiment(s) of the invention of the parent applications), ATM is used as a transport and switching mechanism in a hybrid STM/ATM network, while the signaling remains normal narrowband signaling. The narrowband signaling may be transported on permanent paths over ATM connections (e.g., permanent virtual connections (PVCs)), and the narrowband speech channels may be transported on ATM and switched on a “per call basis” (e.g., on-demand) through an ATM switch (e.g., a switched virtual connection (SVC)). 
     The hybrid STM/ATM network has an access node which services narrowband terminals and which generates a signaling message in connection with call setup. A translator formats the first signaling message into ATM cells so that the first signaling message can be routed through an ATM switch to a circuit switched (e.g., STM) node. The circuit switched node (e.g., PSTN/ISDN) sets up a physical connection for the call and generates a further signaling message for the call, the further signaling message pertaining to the physical connection. The ATM switch routes an ATM-cell-formatted version of the further signaling message to another ATM switch over an ATM physical interface. Thus, the ATM switch switches both narrowband traffic and signaling for the call over the ATM physical interface. The ATM physical interface thus carries an ATM-cell-formatted version of the further signaling message amidst ATM traffic cells. 
     In view of the fact that the circuit switched node and the ATM switch employ different parameters (e.g., b-channel, etc., for the STM node and VP/VC for the ATM switch), in one embodiment the STM node obtains global position numbers (GPN) for use in setting a path for the further signaling message through the ATM switch. In this regard, at the circuit switched node a translation is made from STM to GPN using an STM/GPN translation table; at the ATM node a translation is made from GPN to VP/VC/port using a GPN/ATM translation table. 
     The ATM-cell-formatted version of the further signaling message is transported over the ATM physical link and ultimately reaches a destination access node which serves a destination terminal. A destination translator unpacks ATM cells carrying the ATM-cell-formatted version of the further signaling message to obtain the STM signaling information for use by the destination access node. The translators may be situated at the access node, for example. In illustrated embodiment(s), the ATM switches are situated at nodes distinct from the PSTN/ISDN nodes, but such need not be the case in other embodiment(s). The signaling messages can be in accordance with the signaling system no. 7 (SS#7) convention, and the further signaling message can be one of an ISUP or a TUP message, for example. 
     Referring now to  FIG. 3 , an exemplary hybrid STM/ATM network  320  according to an embodiment of the invention is illustrated. Narrowband terminal devices communicate with hybrid STM/ATM network  320  through access nodes, such as access node  322   O  and access node  322   D . For example,  FIG. 3  shows terminals  324   O  connected to access node  322   O , particularly ISDN terminal  324   O-I  and PSTN terminal  324   O-P . Similarly, access node  322   D  has access terminals  324   D  connected thereto, namely ISDN terminal  324   D-I  and PSTN terminal  324   D-P . Of course, a differing (and most likely greater) number of terminals can be connected to each access node  322 , but for simplicity only two such terminals are shown for exemplary purposes in  FIG. 3 . It should be noted that, as used herein, the term “access node” is not limited to a simple node used merely for connecting subscriber lines, for it may encompass other nodes such as a local exchange (LE) node, for example. 
     The hybrid STM/ATM network  320  of  FIG. 3  comprises one or more STM nodes, also known as PSTN/ISDN nodes  330 . While only two such PSTN/ISDN nodes  330   1  and  330   2  are shown in  FIG. 3  for sake of illustration, it should be understood that the invention is not limited to only two such nodes. The structure and operation of conventional PSTN/ISDN nodes  330  are well known; such as those typified by utilization of Ericsson AXE switches, for example. Therefore, only selected pertinent portions of conventional PSTN/ISDN nodes  330  are described herein with reference to PSTN/ISDN node  330   1 . For example, PSTN/ISDN node  330   1  has processor(s)  332  which execute, e.g., node application software including switch and resource control software  333 . Such software is used to control STM circuit switch  335  as well as signaling terminals  337  which comprise PSTN/ISDN node  330   1 . Other details of the structure and operation of a conventional PSTN/ISDN node are understood, for example, from U.S. patent application Ser. No. 08/601,964 for “Telecommunications Switching Exchange”, which is hereby incorporated by reference in its entirety herein. 
     The STM/ATM network  320  of certain embodiment(s) of the invention is considered a hybrid network in view of the fact that ATM nodes  340  are also included therein. As explained hereinafter, the ATM nodes  340  are used not only to route narrowband traffic between access nodes  322 , but also for transport of signaling in ATM cells over an ATM physical interface. In the illustrated example, the ATM network aspect includes two exemplary ATM nodes, particularly ATM node  340   1  and ATM node  340   2 , which are connected by ATM physical interface or link  341 . Again, it should be understood that the ATM component can (and typically does) comprise a greater number of ATM nodes, with the nodes being connected by ATM physical links. 
     In hybrid network  320 , a PSTN/ISDN node  330  and a ATM node  340  can be paired together in the manner illustrated in  FIG. 3 . With such a pair, the PSTN/ISDN node  330  and ATM node  340  are collectively referred to as hybrid node pair  330 / 340 . The network  320  of certain embodiment(s) of the invention thus can comprise any number of hybrid node pairs  330 / 340 . An ATM node such as ATM node  340  takes on differing configurations, but commonly has a main processor  342  or the like which executes application software including switch and resource control software as generally depicted by  343  in  FIG. 3 . The heart of an ATM node is usually the ATM switch core or switch fabric, which for the illustrated embodiment is shown as ATM cell switch  345  in  FIG. 3 . Further information regarding an exemplary ATM switch is provided by U.S. patent application Ser. No. 08/188,101, entitled “Asynchronous Transfer Mode Switch”, filed Nov. 9, 1998, which is hereby incorporated by reference in its entirety herein. ATM cell switch  345  has plural ingress ports and plural egress ports, with at least some of such ports having a device board attached thereto. 
     Each device board at ATM node  340  can have one or more different functions performed thereby or one or more different devices mounted thereon. For example, one of the device boards attached to a port of ATM cell switch  345  can, in one embodiment, have the main processor  342  mounted thereon. Other device boards may have other processors, known as “board processors”. Some device boards serve as extension terminals (ETs)  346  which may be used to connect the ATM node to other nodes. For example, the ATM physical link  341  shown in  FIG. 3  has a first end connected to an extension terminal ET  346   1  of ATM node  340   1 , while a second end of ATM physical link  341  is connected to an unillustrated extension terminal ET of ATM node  340   2 . The device boards connected to ATM cell switch  345  of ATM node  340  are not specifically illustrated in detail in  FIG. 3 , but the structure and operation of such device boards is understood with reference to (for example) the following United States patent applications, all of which are hereby incorporated by reference in their entirety herein: U.S. patent application Ser. No. 08/893,507 for “Augmentation of ATM Cell With Buffering Data”; U.S. patent application Ser. No. 08/893,677 for “Buffering of Point-to-Point and/or Point-to-Multipoint ATM Cells”; U.S. patent application Ser. No. 08/893,479 for “VPNC Look-Up Function”; U.S. patent application Ser. No. 09/188,097 for “Centralized Queuing For ATM Node”, filed Nov. 9, 1998. 
     As explained hereinafter, signaling (e.g., for call setup) is routed from an access node  322  through an ATM node  340  to an appropriate one of the PSTN/ISDN nodes  330 . Such being the case, a circuit emulation or translator  350  is provided for each access node  322  which communicates with an ATM node  340 . The translators  350  serve, e.g., to encapsulate signaling information from the access node  322  into ATM cells for signaling directed toward an ATM node  340 , and conversely unpack ATM payloads received from an ATM node  340  to extract signaling information for use by the access node  322 . In this particular illustrated embodiment, the translators  350  are preferably provided at or proximate to their associated access nodes  322 . That is, translator  350   O  may be situated at or included in access node  322   O ; translator  350   D  may be situated at or included in access node  322   D . A pair of physical links, shown as links  351 , are provided for connecting each access node  322  to a corresponding one of the ATM nodes  340 . 
     ATM node  340  is connected to a PSTN/ISDN node  330  by a physical link  360 . With reference to ATM node  340   1 , for example, a pair of switch-to-switch links  360  is employed to connect ATM cell switch  345  (through its circuit emulation board  370 ) to STM circuit switch  335  of PSTN/ISDN node  330 , for the carrying of signaling messages. One of the links in pair  360  carries messages from ATM cell switch  345  (after translation at circuit emulation board  370 ) to STM circuit switch  335 ; the other link of the pair  360  carries messages in the reverse direction. 
     In the illustrated embodiment, a dedicated VPI, VCI internal to ATM cell switch  345  is used for signaling. Thus, with reference to ATM node  340   1 , for example, link  351   O  is connected to extension terminal (ET)  346   2 , which in turn is connected to a first pair of dedicated ports of ATM cell switch  345 . Signaling messages received at ATM node  340   1  which are destined to PSTN/ISDN node  330   1  are routed on the dedicated internal VPI/VCI to a port of ATM cell switch  345  which ultimately connects (via circuit emulator  370 ) to switch-to-switch links  360 . However, since the signaling routed through ATM cell switch  345  is encapsulated in ATM cells, a translation to the STM signaling must be performed prior to transmitting the signaling information on switch-to-switch links  360 . For this reason, a device board connected to switch-to-switch links  360  has the circuit emulation (CE) or translator  370  mounted thereon. 
     The circuit emulation (CE) or translator  370  serves to unpack signaling information which is destined to PSTN/ISDN node  330 , but contained in ATM cells, so that the signaling information can be extracted from the ATM cells prior to application on switch-to-switch links  360 . Conversely, signaling information received from PSTN/ISDN node  330   1  on switch-to-switch links  360  at translator  370  is encapsulated into ATM cells for routing through ATM node  340   1 . From  FIG. 3  it can also be seen that a plurality of interfaces  300   a – 300   f  are utilized in the hybrid STM/ATM network  320  of certain embodiment(s) of the invention. These interfaces are described below, primarily with reference to the exemplary nodes (e.g., PSTN/ISDN node  330   1  and ATM node  340   1 ). 
     Interface  300   a  is a logical interface which exists between processor(s)  332  of PSTN/ISDN node  330   1  and main processor(s)  342  of ATM node  340   1 . Interface  300   a  enables PSTN/ISDN node  330  to control the ATM node  340  connected thereto. That is, with the signaling carried by interface  300   a , PSTN/ISDN node  330   1  can order physical connections which are to be set up in ATM node  340   1 . Interface  300   a  can be a proprietary interface or an open interface (such as a General Switch Management Protocol (GSMP) interface [see Request For Comments (RFC) 1987]). Logical interface  300   a  can be carried on any physical interface, such as interface  360  described below. Alternatively, interface  300   a  can be carried by a separate link (e.g., between processors  332  and  342 ), or carried on top of IP/Ethernet links. 
     Interface  300   b  is the signaling between the PSTN/ISDN nodes  330  and the access node  322  connected thereto. Interface  300   b  is carried on one or more semipermanent connections through the STM circuit switch  335 ; through the interworking unit with circuit emulation  370  into ATM cell switch  345 ; and over permanent virtual connections to access node  322  (particularly to translator  350  in access node  322 , where it is emulated back and terminated). As mentioned above, translator  350  is employed to encapsulate the narrowband signaling from an access node  322  in ATM cells for use by an ATM node  340 , and conversely for unpacking ATM cells with signaling information for use by an access node  322 . Each STM channel on the user side may have a corresponding VPI/VCI on interface  300   b.    
     Interface  300   c  is the non-broadband signaling that is carried through and between the nodes. Interface  300   c  thus carries the normal signaling system No. 7 (SS#7) interface (e.g., TUP or ISUP) which is transparently carried in ATM-cell-formatted versions of signaling messages over ATM physical link  341 . In PSTN/ISDN node  330 , the signaling terminals  337  are used for common channel signaling. In at least one embodiment, signaling terminals  337  can be pooled devices situated at STM circuit switch  335 . Alternatively, the signaling terminals  337  can be connected directly to the interfaces between the STM and ATM switches. 
     Interface  300   d  is the physical interface provided by switch-to-switch link  360 . Interface  300   d  can be used to carry speech for a call to and from an STM network, and also to carry the signaling of interface  300   b  and interface  300   c  as described herein. In addition, interface  300   d  can also be used to link-in special equipment that is to be connected to a normal circuit switch (e.g., conference equipment, answering machines, etc.). Interface  300   d  can be realized by any standard physical media, such as E1, for example; it being understood that STM-1 or similar speeds may be suitable. The physical interface  300   d  can also carry the voice data for a conversation between any of the terminals shown in  FIG. 3  and an unillustrated terminal connected to the circuit switched network, in which situation the hybrid node pair  330 / 340  acts as a gateway. 
     Interface  300   e  is the ATM physical link  341  to other ATM nodes. Any standard link for ATM may be employed for interface  300   e . A dedicated VP/VC is employed to transparently transfer the signaling system No. 7 (SS#7) signaling between PSTN/ISDN nodes  330  over interface  300   e . Interface  300   f , shown in  FIG. 3  as connecting each access node  322  with its terminals, is a typical user-network interface (e.g., ISDN, BA/BRA, PRA/FRI, two-wire PSTN, etc.). 
     For two traditional circuit switched PSTN/ISDN nodes to communicate with one another using protocols such as ISUP or TUP, it is preferable that ISUP entities in both PSTN/ISDN nodes have coordinated data tables. In this regard, each of the two PSTN/ISDN nodes has a table which translates a CIC value onto a same timeslot in a same physical interface connecting the two PSTN/ISDN nodes. Thus, a CIC value (together with a point code) represents a particular timeslot on a particular physical link. One specific CIC preferably points out the same time slot in the tables of both PSTN/ISDN nodes. In other words, the data tables of the two PSTN/ISDN nodes are preferably coordinated. 
     The need to coordinate the data tables of PSTN/ISDN node  330   1  and PSTN/ISDN node  330   2  for ISUP/TUP similarly exists in certain embodiment(s) of the invention. If two hybrid nodes  330   1 / 340   1  and  330   2 / 340   2  have a communication channel set up between them, by means of a semipermanent connection carrying SS#7 signaling for example, the translation tables  339  in both hybrid nodes are preferably coordinated from the standpoint of using CIC. This typically means that in both hybrid nodes  330   1 / 340   1  and  330   2 / 340   2  a certain CIC points at the same VP and VC (and possibly AAL2 pointer) identifying cells on a certain physical link (e.g., link  341 ) connecting the two hybrid nodes. Alternatively, the same objective may be accomplished by other suitable means such as a cross-connected-ATM switch positioned between the hybrid nodes that switches packets and gives the packets the VP and VC value understood by the other node. 
     Referring now to  FIG. 3A , an exemplary structure of hybrid STM/ATM network  320 , having omitted therefrom various items including the interfaces, is illustrated.  FIG. 3A  also provides an example of signal processing for a call originating at terminal  324   O-P  for which the called party number (destination) is terminal  324   D-P . As shown by the arrow labeled E- 1 , at event E- 1  a SETUP message is sent from terminal  324   O-P  to access node  322   O . In the illustrated embodiment, the SETUP message is an IAM message for an ISUP network interface, and is for a 30B+D PRA and for VS.x carried on a 64 kb/s bit stream in a circuit switched timeslot. 
     At the translator  350   O  associated with the access node  322   O , at event E- 2  the signaling from terminal  324   O-P  is converted from STM to ATM by packing the signaling information into ATM cell(s) In this regard, after the circuit emulation a table is employed to translate from a 64 kb/s speech channel from terminal  324   O-P  to a corresponding ATM address (VP/VC). The signaling of the SETUP message, now encapsulated in ATM cell(s), is applied to link  351   O  and transmitted to ATM cell switch  345  of ATM node  340   1  as indicated by event E- 3 . As further indicated by event E- 4 , the ATM cell(s) containing the SETUP message signaling is routed through the ATM cell switch  345  in accordance with a switch internal VP/VC dedicated for STM-originated signaling. Upon egress from ATM cell switch  345 , the signaling information for the SETUP message is retrieved from the ATM cell(s) by translator  370  (event E- 5 ), and it is reconverted at translator  370  from ATM to STM format, so that the SETUP message signaling information can be applied in STM format at event E- 6  to switch-to-switch link  360 . The SETUP message, now again in STM format, is routed through STM circuit switch  335  (as indicated by event E- 7 ) to an appropriate one of the signaling terminals  337 . Upon receipt of the SETUP message signaling information at the appropriate signaling terminal  337 , the signaling information is forwarded to processor(s)  332  of PSTN/ISDN node  330 , which engage in STM traffic handling (as indicated by event E- 8 ). 
     In its traffic handling, the processor  332  of PSTN/ISDN node  330  realizes that the incoming side of the call and the outgoing side of the call have physical connections through an ATM node. In this regard, when the access points of the connection were defined (subscriber or network interface), a bearer type was associated with the connection and stored in application software. In the present scenario, when the SETUP message (e.g., an IAM message in the case of an ISUP network interface) was received at PSTN/ISDN node  330 , the stored bearer type data was checked in order to determine what switch was on the incoming side to PSTN/ISDN node  330 . Further, the bearer type data stored for the outgoing point (e.g., based on B-Subscriber number) is similarly checked, and if the stored data indicates that both incoming and outgoing sides have an ATM bearer, the PSTN/ISDN node  330  can conclude that ATM node  340  is to be operated (e.g., utilized). In addition, data received in the SETUP message (particularly the B-subscriber number) is analyzed to determine that the called party (destination) terminal  324   D-P  can be reached by contacting PSTN/ISDN node  330   2 . The PSTN/ISDN node  330   1  realizes that it has an SS#7 signaling interface  300   c  to PSTN/ISDN node  330   2 , and therefore selects a free CIC (e.g., a CIC not used by any other call) for use toward PSTN/ISDN node  330   2 . 
     If, on the other hand, the stored bearer type data had indicated an STM bearer, both PSTN/ISDN node  330  and ATM node  340  have to be operated. Thus, PSTN/ISDN node  330  and ATM node  340  collectively function as a gateway between the STM and ATM worlds. Upon realizing that further signaling for the call will be routed through ATM nodes, in the embodiment(s) of the invention shown in  FIG. 3  and  FIG. 3A , the PSTN/ISDN node  330   1  makes reference to an STM/GPN translation table  339  maintained by processor(s)  332  (see event E- 9 ). Two translations are performed using the STM/GPN translation table  339 . As a first translation, the information (e.g., b-channel and access information in the case of ISDN or CIC plus signaling system #7 point codes in the case of PSTN) contained in the SETUP message is translated to a global position number (GPN). As a second translation, the CIC and destination point code for a circuit leading to hybrid node pair  330 / 340  is translated to another global position number (GPN). 
     In connection with the foregoing, the global position number (GPN) is a common way to identify the connection points, and as such is understood by the pair of nodes (PSTN/ISDN node  330  and ATM node  340 ). In other words, the GPN is an address, or reference, or system internal pointer known by both PSTN/ISDN node  330  and ATM node  340 , and used to translate between port/VP/VC and circuit switch address. Usage of GPN in the embodiment of  FIG. 3  and  FIG. 3A  thereby obviates the sending of real addresses between PSTN/ISDN node  330  and ATM node  340 . Advantageously, GPN can be shorter, meaning that there is less data to send. For traditional PSTN, the GPN uniquely corresponds to the 64 kbit voice on a two-wire line, but for ISDN, the GPN corresponds to a b-channel (which may be used by several subscribers). 
     Then, as event E- 10 , the PSTN/ISDN node  330  generates an ATM switch control message intended to setup a physical connection in ATM node  340 . This message of event E- 10  contains the two global position numbers (GPNs) obtained from STM/GPN translation table  339  at event E- 9 , together with an order for the ATM node  340  to connect the two GPN addresses in ATM switch fabric  345 . The PSTN/ISDN node  330  sends the switch control message generated at event E- 10  to processor  342  of ATM node  340  over interface  300   a , as shown by event E- 11 . 
     Upon reception of the switch control message sent as event E- 11  to ATM node  340   1 , as indicated by event E- 12 , main processor  342  consults GPN/ATM translation table  349  in order to translate the two global position numbers (GPNs) contained in the event E- 10  switch control message into VP/VC/port information understood by ATM node  340   1 . That is, the two global position numbers (GPNs) are used to obtain VP/VC/port information for ultimately reaching both the origination terminal ( 324   O-P ) and the destination terminal ( 324   D-P ). Upon successful translation of GPN to ATM, and assuming sufficient resources, processor  342  of ATM node  340   1  sets up a path through ATM Switch  345  and reserves resources on the port (trunk or link  341 ) for the call from terminal  324   O-P  to terminal  324   D-P . The path set up and resource reservation activities are accomplished using switch/reservation control  343  and are collectively illustrated as event E- 13  in  FIG. 3 . 
     Since PSTN/ISDN node  330  preferably knows whether ATM node  340   1  was successful in performing a GPN/ATM translation, a successful translation message is sent over interface  300   a  as event E- 14  from ATM node  340   1  to PSTN/ISDN node  330   1 . If the GPN/ATM translation is not successful at ATM node  340   1 , or if there are no available resources at ATM node  340   1 , a call rejection message is sent back to the originating terminal. After PSTN/ISDN node  330  receives the confirmatory message of event E- 14  (that ATM switch  345  has been setup and link reservations made (in accordance with event E- 13 )), at event E- 15  the PSTN/ISDN node  330   1  prepares and sends its further signaling message (e.g., ISUP or TUP) toward the PSTN/ISDN node at the other end (e.g., PSTN/ISDN node  330   2 ). This further signaling message is shown as event E- 15  in  FIG. 3A . The signaling of event E- 15  (e.g., an ISUP or TUP message) includes a message transfer part (MTP), and can be sent out on a timeslot (e.g., 64 kb/s) which carries the SS#7 signaling. 
     As the signaling of event E- 15  arrives at ATM node  340   1 , the ATM node  340   1  prepares its ATM cell-formatted version of the signaling. In particular, the translator  370  puts the signaling information of the signaling of event E- 15  into the payload of one or more ATM cells. For example, the translator  370  is configured to take the 64 kb/s signaling information bit stream and to pack it into ATM cells with a predefined VP, VC, and a physical port. As also indicated as event E- 15 , the ATM cell-formatted version of the further signaling message is routed through ATM cell switch  345  and onto a link indicated by the VP/VC/port information obtained from the translation. In particular, in  FIG. 3A  the ATM cell-formatted version of the further signaling message is transported on ATM physical link  341 , as shown by event E- 16 . 
     Upon reaching ATM node  340   2 , the ATM cell-formatted version of the further signaling messages obtains a new internal VPI/VCI for the ATM cell switch  345  of ATM node  340   2 , and is routed (as indicated by event E- 17 ) through ATM cell switch  345  of ATM node  340   2  to a circuit emulator (not explicitly shown) in ATM node  340   2 , which is analogous to circuit emulator  370  in ATM node  340   1 . The circuit emulator of ATM node  340   2  performs the conversion from ATM to STM format in like manner as circuit emulator  370  in ATM node  340   1 , and then passes the signaling message to PSTN/ISDN node  330   2  as event E- 18 . 
     In PSTN/ISDN node  330   2 , the ISUP message is received together with the CIC value (from the message transfer part (MTP)) and the B-subscriber number (which is included in the ISUP message). As indicated by event E- 19 , the second hybrid node  330   2 / 340   2  also performs an analysis of the B-subscriber number and concludes that the B-subscriber number is associated with terminal  324   D-P , which involves B channels. The PSTN/ISDN node  330   2  then selects a B-channel which can be used to reach terminal  324   D-P , or negotiates with the terminal  324   D-P  as to which B-channel to use (depending on the terminal type and protocol type ISDN or PSTN). The PSTN/ISDN node  330   2  also signals terminal  324   D-P  to activate a ringing signal (as indicated by event E- 20 ). When an answer is received from terminal  324   D-P  (or during or before receiving an answer), the PSTN/ISDN node  330   2  consults its STM/GPN translation table  339  (not explicitly shown) using a CIC value and a B-channel. The PSTN/ISDN node  330   2  then operates the ATM switch  345  (not explicitly shown) of ATM node  340   2  in the same manner as described for ATM node  340   1 , as indicated by event E- 21 . 
     Operation of ATM switch  345  of ATM node  340   2  allows in-band data (e.g., voice data) carried in ATM packets to be passed through the ATM switch. Such operation is accomplished in like manner as described previously hereinabove (e.g., by consulting a table such as table  339 , by sending an ATM switch control message, by consulting a table such as table  349 , and by setting up of a path in the ATM switch). When an ATM switch is operated as described above, the resulting path through both ATM switches (carrying in-band information) has to be set up in the same way at both ends. This implies that encapsulation of in-band information (which is controlled by circuit emulation (e.g., circuit emulation  370 )) at the two end points of the path is preferably set up in the same way. To minimize delay, AAL2 is preferably utilized by circuit emulation  370  for the encapsulation, although other types of protocols may be alternatively used. 
     As noted hereinabove, a bearer type is associated with a connection and stored in the application software of the PSTN/ISDN node  330 . It is presumed that the PSTN/ISDN node  330  already is able to handle traditional access points (subscriber or network interfaces) connected to STM circuit switches. In so doing, the PSTN/ISDN node  330  has logical representations of these existing access points in a static data structure of the PSTN/ISDN node  330 . In accordance with certain embodiment(s) of the invention, the PSTN/ISDN node  330  additionally handles access points connected to the ATM switch. In this regard, see (for example) interface  341  of  FIG. 3C  (hereinafter described). Thus, for certain embodiment(s) of the invention, the PSTN/ISDN node  330  has logical representations of these additional access points in its static data structure. Therefore, the bearer type data may be employed in the prior discussion as a way of distinguishing the logical representation of the additional access points (e.g., ATM-related access points) in the static data structure from the logical representation of the traditional access points. 
     It was also noted hereinabove that encapsulation of in-band information is preferably set up the same way at both ends. More specifically, a same type of cell filling is preferably employed by two circuit emulation devices that are connected together. For example, if on a link connecting two circuit emulation devices an ATM cell is packed with only one voice sample by a first of the circuit emulation devices, the second of the circuit emulation devices preferably packs ATM cells in a similar manner. Alternatively, another emulation and/or bridging mechanism or scheme may be employed. 
     In the above regard, filling only part of an ATM cell with information is a technique for reducing delays, although it may increase overhead. Another way of reducing delay is employment of the AAL2 protocol. As understood by those skilled in the art, AAL2 is a protocol layer on top of ATM, and it allows transport of mini-cells within ATM cells. Usage of the smaller AAL2 cells helps address bandwidth and delay problems in the air interface. Certain embodiment(s) of the invention may be utilized with AAL2 switching as an alternative to ATM switching. If one implements AAL2 in certain embodiment(s) of the invention, the switch  345  operates as an AAL2 switch and GPN/ATM translation table  349  in ATM node  340  preferably also includes an AAL2 pointer. Whenever the ingress and egress point is referenced, it can alternately include an AAL2 pointer. Thus, as used herein and in the appended claims, ATM encompasses ATM-related protocols on top of ATM, such as AAL1, AAL2 , AAL5, etc. It should also be understood that the term “broadband”, as used herein and in the appended claims, embraces and encompasses packet-switched technologies in general (e.g., IP, VoIP, Frame-relay, ATM, etc.). 
     Referring now to  FIG. 3B , an exemplary hybrid STM/ATM network  320 ′ according to another embodiment of the invention is illustrated. The embodiment of  FIG. 3B  primarily differs from the embodiment of  FIG. 3  in that the embodiment of  FIG. 3B  does not employ global position numbers (GPNs). Rather, the embodiment of  FIG. 3B  uses an ATM/STM translation table  339 ′ in processor  332  of PSTN/ISDN node  330   1  instead of an GPN/ATM translation table. In the embodiment of  FIG. 3B , the translation tables in the circuit emulation  350   0  translate the SETUP message from a 64 kb/s speech channel to an ATM address (VP and VC) in a manner similar to that of event E- 2  in the embodiment(s) of  FIG. 3  and  FIG. 3A . After routing of the translated SETUP message through ATM switch  345   1 , the circuit emulation  370  translates the SETUP message to the STM format as occurred at event E- 5  of the embodiment(s) of  FIG. 3  and  FIG. 3A . 
     The embodiment of  FIG. 3B  also differs from that of the embodiment(s) of  FIG. 3  and  FIG. 3A  in that processor  332  of PSTN/ISDN node  330  terminates the narrowband signaling by translating a narrowband reference point (e.g., b-channel if an ISDN connection) to a corresponding ATM address for use by ATM node  340 . Thus, for the  FIG. 3B  embodiment, the switch control message of event E- 11  sends the ATM VP/VC/port information understood by ATM node  340   1 . Thus, the translation of event E- 12  of the FIG.  3 / FIG. 3A  embodiment is unnecessary in the  FIG. 3B  embodiment. Rather, upon receiving the ATM VP/VC/port information in the switch control message of event E- 11 , the embodiment of  FIG. 3B  proceeds to the path set up and resource reservation operations denoted as event E- 13 . 
     The principles as illustrated in the embodiments hereof are also applicable to the carrying of other types of signaling messages in ATM cells. Included among such other types of signaling messages are those destined for the originating terminal (e.g., a call completion signaling message), in which case some of the events described herein are performed essentially in reverse order. 
     Referring now to  FIG. 3C , an exemplary illustration of how hybrid node pairs  330 / 340  of the invention may be arranged in an exemplary hybrid STM/ATM network  320 ″ is presented. Network  320 ″ has three node pairs  330 / 340 , including a transit exchange hybrid node pair  330 / 340   TX  between two local exchange hybrid node pairs  330 / 340   1  and  330 / 340   2 .  FIG. 3C  shows provision of a “#7 signaling system”  393 , which is a logical system carried in the ATM network on an ATM AAL layer as described above. As an alternative embodiment, the “#7 signaling system”  393  may be provided with its own physical network. 
     Referring now to  FIG. 3D , a diagrammatic view of an exemplary protocol usable between two elements of a network in accordance with embodiment(s) of the invention that include hybrid node pairs is illustrated. The ATM node  340  with its ATM switch  345  terminates the ATM and AAL1 (circuit emulation part) layers; the PSTN/ISDN node  330  terminates the MTP and ISUP layers. 
     Referring now to  FIGS. 3E ,  3 F, and  3 G, diagrammatic views of alternate exemplary protocols between two elements, a first of the network elements having a hybrid node pair in accordance with embodiment(s) of the invention, and a second of the network elements being an access node with an additional ATM interface with circuit emulation is illustrated. In the first network element, the ATM switch  345  terminates the ATM and AAL1 (circuit emulation part) layers, while the layers above are terminated by the PSTN/ISDN node  330 . In the second network element, the ATM interface and circuit emulation addition to the access node terminates the ATM and AAL 1  layers, while the layers above are terminated by the connected terminal and the access node part. The exemplary protocols of  FIGS. 3E ,  3 F, and  3 G can be used, for example, on the interface  300   b.    
     Referring now to  FIG. 3H , an exemplary gradual upgrade of a network from a traditional narrowband STM-transported-and-switched environment into the environment (e.g., hybrid STM/ATM network  320 ) of certain embodiment(s) of the invention is illustrated. In  FIG. 3H , the circuit emulation equipment (translator)  395  separates the hybrid environment from the pure STM environment. If node B (PSTN/ISDN node  330   N+1 ) is upgraded with ATM switching and (signaling and traffic) transport according to certain embodiment(s) of the invention, the node C (PSTN/ISDN node  330   N+2 ) is not disturbed if the circuit emulation equipment (translator)  395  is moved in between nodes B and C in the manner illustrated by the dotted-dashed line  396  as shown in  FIG. 3H . 
     Referring now to  FIG. 3I , certain embodiment(s) of the invention permit the possibility of one logical node to include many switches, with switching logic within the node coordinating the setting up of paths through the switches. This logic also inserts interworking functions (IWFs) between switches (if needed), and makes it possible to use resources independent on which switch they are allocated to. For example, the multi-switch node  397  of certain embodiment(s) of the invention includes the PSTN/ISDN node  330  with its STM switch  335 , connected by interface  300   d  to ATM node  340   7-1 . Specifically, connection is made through IWF  344   7-1  to ATM switch  345   7-1  of ATM node  340   7-1 . The ATM switch  345   7-1  of ATM node  340   7-1  is connected by interface  300   e  to an ATM network, as well as to ATM node  340   7-2  and ATM node  340   7-3  included in the multi-switch node  397 . The ATM node  340   7-2  has a switch  345   7-2  and an IWF  344   7-2 , through which connection can be made with access node  322   7-1 . The ATM node  340   7-3  has an ATM AAL2 switch  345   7-3 , which connects to ATM nodes  340   7-1  and  340   7-2  through IWF  344   7-3  of ATM node  340   7-3 . Access nodes  322   7-2  and  322   7-3  are connected to ATM AAL2 switch  345   7-3  of ATM node  340   7-3 . 
     Certain embodiment(s) of the invention advantageously reuse PSTN and ISDN software in the PSTN/ISDN nodes  330  in a fairly simple way. That is, already-developed narrowband application software residing in the PSTN/ISDN nodes  330  can be utilized, while on-demand ATM connections are used as traffic bearers. The invention thus allows a PSTN/ISDN node such as PSTN/ISDN node  330  to control the call, which facilitates use of well-proven software for various services and functions (e.g., subscriber services, intelligent network (IN) services, Centrex, Charging Customer Care systems, etc.). 
     ATM is thus used as a transport and switching mechanism in certain embodiment(s) of the invention, while the signaling remains normal narrowband signaling. The narrowband signaling is transported on permanent paths over ATM connections, and the narrowband speech channels are transported on ATM, and switched on a “per call basis” (e.g., on-demand) through an ATM switch. 
     The narrowband application software executed by processor(s)  332  of PSTN/ISDN nodes  330  thus acts as if operating on its STM circuit switched transport, when in fact it is actually operating on an ATM cell switch. It should be understood that the ATM switch may reside in a separate ATM node or may be integrated in the same node as the STM switch. On a “per call basis”, the switching logic in the PSTN/ISDN nodes  330  requests the switching mechanism in the ATM nodes  340  to be set up and disconnected through an ATM cell switch. 
     It should be understood that variations of the foregoing are within the scope of the embodiments of the invention. For example, the circuit emulation  370  is shown (e.g., in  FIG. 3 ) as being provided on a device board of ATM node  340 . Alternatively, circuit emulation  370  may be located elsewhere, such as (for example) on link  360  between PSTN/ISDN node  330  and ATM node  340 , or even included in PSTN/ISDN node  330  (e.g., at either end of interface  300   d ). While various processors, such as processors  332  and  342 , have been illustrated as single processors, it should be understood that the functionality of such processors may be situated or distributed in different ways (e.g., distributed over several processors to achieve, e.g., scalability in respect to processing capacity and reliability), for example. 
     In the foregoing examples, the SETUP message (received at the STM node in STM format) is routed through STM circuit switch  335  as indicated by the event E- 8  to signaling terminals  337 . It should be understood, however, that depending upon implementation in an PSTN/ISDN node, signaling may take another way to reach a signaling terminal (e.g., other than through a switch). The invention also describes a system with one STM switch and one ATM switch associated with one another. This particular configuration is advantageous in that resources which take care of certain kinds of signals (e.g., in-band signals) may be situated in the STM switch and be used also for the ATM transported calls. This is also a way of reusing the installed base, if such exists. Also, certain embodiment(s) of the invention can perform switching on various levels, such as the AAL2 level and with mini-cells, which tends to reduce any delay/echo problems. 
     The invention thus pertains to the telecommunications world and an attempt to introduce ATM to a telecommunications network. The invention addresses the situation in which a circuit switched telephony network pre-exists, and it is to be augmented or partially replaced by parts that employ ATM for transport and switching. Certain embodiment(s) of the invention need not employ broadband signaling, but rather narrowband signaling with the bearer part of the call following the signaling to the same extent as in a traditional narrowband circuit switched network. 
     As described herein, ATM may be used as a transport and switching mechanism in a hybrid STM/ATM network, while the signaling remains normal narrowband signaling. The narrowband signaling may be transported on permanent paths over ATM connections, and the narrowband speech channels may be transported on ATM and switched on a “per call basis” (e.g., on-demand) through an ATM switch. The hybrid STM/ATM network may include an access node that services narrowband terminals and which generates a signaling message in connection with call setup. A translator formats the first signaling message into ATM cells so that the first signaling message may be routed through an ATM switch to a circuit switched (e.g., STM) node. The circuit switched node (e.g., PSTN/ISDN) sets up a physical connection for the call and generates a further signaling message for the call, the further signaling message pertaining to the physical connection. The ATM switch routes an ATM cell-formatted version of the further signaling message to another ATM switch over an ATM physical interface. Thus, the ATM switch switches both narrowband traffic and signaling for the call over the ATM physical interface. 
     Referring now to  FIG. 4 , another exemplary scheme for utilizing a broadband network in conjunction with nodes having partially separated functions in accordance with the present invention is illustrated generally at  400 . The nodes  405 A, 405 B are connected to the nodes  410 A,  410 B. The nodes  405 A, 405 B each include both call control functions and connection control functions. In effect, each of the nodes  405 A, 405 B (e.g., which may correspond to, for example, PSTN/ISDN nodes  330  of the embodiment(s) of  FIG. 3  et seq.) include both switching intelligence (e.g., which may correspond to, for example, one or more of processor(s)  332 , switch and resource control software  333 , signaling terminals  337 , and STM/GPN translation table  339  of the embodiment(s) of  FIG. 3  et seq.) and switching fabric (e.g., which may correspond to, for example, an STM circuit switch  335  of the embodiment(s) of  FIG. 3  et seq.). While the nodes  410 A, 410 B include connection control functions, they rely on the call control functions of the nodes  405 A, 405 B to which they are respectively connected. In effect, each of the nodes  410 A, 410 B (e.g., which may correspond to, for example, ATM nodes  340  of the embodiment(s) of  FIG. 3  et seq.) include switching fabric (e.g., which may correspond to, for example, an ATM cell switch  345  of the embodiment(s) of  FIG. 3  et seq.). The nodes  410 A, 410 B, which are also connected to an ATM network  215 , effect required emulation and cell packing for interworking a narrowband network (not shown) with the ATM network  215 . 
     Generally, and in certain embodiment(s), call control involves features, functions, responsibilities, etc. pertaining to one or more of the following: routing a call; signaling between narrowband nodes; providing subscriber services; implementing charging; determining the connection and/or activation of tone senders, answering machines (e.g., voice mail), echo cancelers, and other types of telephony resources and/or equipment; ascertaining the desirability and/or necessity of utilizing an IN service; etc. Connection control, on the other hand, involves features, functions, responsibilities, etc. pertaining to setting up/establishing a connection between two (or among/across multiple) physical points within a switch and/or over a network responsive to call control, for example. The connection control, to effectuate such a connection, may rely on some type of signaling of the bearer network (e.g., UNI, PNNI, B-ISUP, etc.) 
     In accordance with certain embodiment(s) of the present invention, the nodes  405 A, 405 B may be advantageously realized using, at least partly, a modified version of an existing/legacy telecommunications switch. Using an existing telecommunications switch advantageously obviates any need to create code “from scratch” for the myriad of advanced calling features that are already supported by the existing telecommunications switch. Furthermore, in accordance with certain principles of the present invention, using an existing telecommunications switch enables a gradual migration to a broadband transport mechanism such as ATM. A call/connection control node  405 A, 405 B and a respective connection control node  410 A, 410 B pair together form a hybrid switch  420 A/ 420 B. 
     Referring now to  FIG. 5 , yet another exemplary scheme for utilizing a broadband network in conjunction with nodes having partially separated functions in accordance with the present invention is illustrated generally at  500 . The two hybrid switches  420 A, 420 B are illustrated as being connected to the ATM network  215  by ATM links  505  (e.g., which may correspond to, for example, one or more of interface  300   c , interface  300   e , and ATM physical link  341  of the embodiment(s) of  FIG. 3  et seq.), e.g., via a connection control node  410 . Each of the call/connection control node  405 A and the connection control node  410 A are connected to a Time Division Multiplexed (TDM) network  515  by TDM links  510  (e.g., which may correspond to, for example, interface  300   d  of embodiment(s) of  FIGS. 3  et seq. [including alternative embodiment(s) of  FIGS. 3  et seq. as described hereinabove with reference to the interface  300   d  of  FIG. 3 ]; as well as interface  300   b /link  351 , interfaces  300   b ,  300   c , and/or interface  300   d /switch-to-switch link  360 ). The TDM network  515  may correspond to any of many so-called narrowband networks such as PSTN, PLMN, ISDN, etc. As indicated within the hybrid switch  420 A, the call/connection control node  405 A is connected to the connection control node  410 A via a TDM link  510  (e.g., which may correspond to, for example, interface  300   b , interface  300   c , interface  300   d , switch-to-switch link  360 , etc. of  FIG. 3  et seq.) and an ethernet link  520  (e.g., which may correspond to, for example, interface  300   a , interface  300   b , interface  300   c , switch-to-switch link  360 , etc. of  FIG. 3  et seq.). 
     The hybrid switch  420  advantageously enables an existing switch in conjunction with an associated switch to facilitate the transport of call connections at least partly across a broadband network, such as the ATM network  215 . As illustrated in the scheme  500 , the existing switch may be realized using, for example, an AXE switch (available from Ericsson Inc.), and the associated switch may be realized using, for example, an AXD  301  switch (also available from Ericsson Inc.). Thus, the hybrid switches  420 A, 420 B may be realized using, for example, an Ericsson Hybrid Switch (also available from Ericsson Inc.). 
     Referring now to  FIG. 6 , another exemplary hybrid switch with multiple ports for switching a connection in accordance with the present invention is illustrated generally at  420 . The hybrid switch  420  includes a call/connection control node  405  and a connection control node  410  that are connected by linkage  605  (e.g., which may correspond to, for example, one or more of interface  300   a , interface  300   b , interface  300   c , interface  300   d , and switch-to-switch link  360  of the embodiment(s) of  FIGS. 3  et seq.). It should be noted that the thick line representing the linkage  605  indicates that the linkage  605  may be composed of more than one link. Information exchange across linkage  605  permits the call/connection control node  405  to switch narrowband calls across the switching fabric of the connection control node  410 . Such information exchange enables 64 kbit/sec, narrowband calls originating and terminating in narrowband networks (e.g., one or more TDM networks  515 ) to be trunked over broadband networks (e.g., one or more ATM networks  215 ) between hybrid switches  420 . It should be noted that TDM as used herein, including the claims, encompasses and embraces time-division multiplexed protocols in general, and it is not limited to any particular TDM protocol. 
     The call/connection control node  405  includes input/outputs (I/Os) for two TDM links  510 . Each TDM link  510  terminates at exchange termination (ET) equipment  610 . Each ET equipment  610  is connected to a group switch (GS)  615  (e.g., which may correspond to, for example, the STM circuit switch  335  of the embodiment(s) of  FIGS. 3  et seq.). Each ET equipment  610  receives from the GS  615  data samples taken from multiple calls and multiplexes this data into a stream of data sent out over a TDM link  510  that connects the hybrid switch  420  to another node. The ET equipment  610  also receives data from other nodes over the TDM link  510  and de-multiplexes this data into samples from separate calls to be transferred to the GS  615 . The GS  615  is also connected to one or more signaling terminals (STs)  620  (e.g., which may correspond to, for example, the signaling terminals  337  of the embodiment(s) of  FIG. 3  et seq.). The linkage  605  may include a TDM link  510  (not explicitly shown in  FIG. 6 ) that connects an ET equipment  610  of the call/connection control node  405  with a circuit emulation-ET (CE-ET) equipment  625  (e.g., which may correspond to, for example, the circuit emulation/translator  370  of the embodiment(s) of  FIG. 3  et seq.) of the connection control node  410 . 
     The connection control node  410  includes I/Os for two TDM links  510 . Each TDM link  510  terminates at CE-ET equipment  625  (e.g., which may correspond to, for example, the extension terminal ET  346   2  (optionally in conjunction with the circuit emulation/translator  350 ) of the embodiment(s) of  FIG. 3  et seq.). Each CE-ET equipment  625  is connected to an ATM switch  630  (e.g., which may correspond to, for example, the ATM switch  345  of the embodiment(s) of  FIG. 3  et seq.). The CE-ET equipment  625  terminates a TDM link  510  for the ATM switching fabric of the connection control node  410  by using circuit emulation. The circuit emulation, e.g., hardware on a CE-ET equipment  625  maps time slots from an E1 line into, for example, single streams of ATM adaptation layer 1 (AAL1) cells. The CE-ET equipment  625  maps successive octets from a single time slot to a single stream of AAL 1  cells. The ATM switch  630  is also connected to one or more ATM-ET equipments  635  (e.g., which may correspond to, for example, the extension terminal ET  346   1  of the embodiment(s) of  FIG. 3  et seq.). Each ATM-ET equipment  635  terminates an ATM link  505  to the ATM switching fabric of the connection control node  410 . 
     The various ports/interfaces of the call/connection control node  405  and the connection control node  410  enable the establishment of various connection paths in the hybrid switch  420 . Connection paths may be established across the following exemplary points as enumerated in Table 1: 
                     TABLE 1               Connection Paths Establishable for FIG. 6                                            (1) point A - (I, J) - G           (2) point A - (I, J) - H           (3) point D - (J, I) - B           (4) point E - (J, I) - B           (5) point C - (I, J) - G           (6) point C - (I, J) - H           (7) point D - (J, I) - F           (8) point D - G           (9) point D - H           (10) point E - (J, I) - F           (11) point E - G           (12) point E - H                        
Taking connection path “(6) point C-(I, J)-H”, for example, a connection may be established from point “C” at the TDM link  510 , through two ET equipments  610  and the GS  615 , to point “I”. The connection continues from point “I” across the linkage  605  to point “J”. The connection continues further from point “J” through a CE-ET equipment  625 , the ATM switch  630 , and the ATM-ET equipment  635  to point “H” at the ATM link  505 .
 
     Referring now to  FIG. 7 , a simplified block diagram of an exemplary hybrid switch in accordance with the present invention is illustrated generally at  700 . The hybrid switch at  700  includes a call/connection control node  405 , which is shown connected to a TDM network  515  via a TDM link  510 , and a connection control node  410 , which is shown connected to a TDM network  515  via a TDM link  510  and an ATM network  215  via an ATM link  505 . The call/connection control node  405  is connected to the connection control node  410  via the linkage  605 , which may include one or more links. The connection control node  410  includes connection control logic  705  and the ATM switch  630 . The connection control logic  705  may be composed of, for example, hardware, software, firmware, some combination thereof, etc. 
     The ATM switch  630  is connected via link  710  to the GS  615  of the call/connection control node  405 . The link  710  may be utilized to transfer data information between the ATM switch  630  and the GS  615 . The call/connection control node  405  also includes connection control logic  715  to enable the call/connection control node  405  to switch calls (e.g., to or through the TDM network  515  directly connected thereto via the TDM link  510 ) without the aid of the connection control node  410 . The connection control logic  715  may also be composed of, for example, hardware, software, firmware, some combination thereof, etc. The call/connection control node  405  further includes call control logic  720 , which provides call control functions for the connection control node  410  as well as the call/connection control node  405 . The call control logic  720  may also be composed of, for example, hardware, software, firmware, some combination thereof, etc. 
     The call control logic  720  may provide call control functions to the connection control node  410  by exchanging signaling information over a link  725 . (It should be noted that either or both of the links  710  and  725  may be composed of more than one link.) For example, for a call incoming to the connection control node  410  over the TDM link  510  from the TDM network  515 , signaling information may be forwarded to the call control logic  720  from the connection control logic  705  over the link  725 . The switching intelligence of the call control logic  720  executes applicable call control functions and ascertains relevant call control information (e.g., as explained further hereinabove with reference to  FIG. 3  et seq.). This signaling information is sent from the call control logic  720  over the link  725  to the connection control logic  705 , which may thereafter switch the call data information of the incoming call to/through the appropriate network (e.g., the ATM network  215 ). The call control functions of existing (e.g., STM) switches can therefore be advantageously utilized by newer and faster (e.g., ATM) switches to thereby avoid needing to completely reprogram call control functionality for the newer switches. 
     It should be emphasized that the call/connection control node  405  is capable of connecting directly to the TDM network  515  over the TDM link  510  via the GS  615 . Consequently, a hybrid switch architecture in accordance with the present invention, by combining a call/connection control node  405  with a connection control node  410 , enables this logical node to communicate (i) with an existing TDM network  515  (e.g., a PSTN network) using the GS  615  (e.g., an STM switch) and (ii) with a broadband network (e.g., the ATM network  215 ) over a broadband link (e.g., the ATM link  505 ) using a broadband switch (e.g., the ATM switch  630 ). Providing such dual connectivity advantageously enables a network to gradually migrate from a first network protocol (e.g., a narrowband network protocol) to a second network protocol (e.g., a broadband network protocol) while utilizing both existing call control logic (e.g., software, etc.) and existing connections to and within the first network (e.g., a narrowband network). 
     Referring now to  FIG. 8 , exemplary communications and connections between nodes in another simplified block diagram of an exemplary hybrid switch in accordance with the present invention are illustrated generally at  800 . In the exemplary hybrid switch  420 , the call/connection control node  405  is connected to the connection control node  410  via the linkage  605  at points I and J. The linkage  605  may be composed of multiple links. In this exemplary embodiment  800 , a signaling information link  805  (e.g., which may correspond to, for example, interface  300   a , interface  300   b , interface  300   c , switch-to-switch link  360 , etc. of  FIG. 3  et seq.) and a data information link  810  (e.g., which may correspond to, for example, interface  300   b , interface  300   c , interface  300   d , switch-to-switch link  360 , etc. of  FIG. 3  et seq.) are illustrated as connecting the call/connection control node  405  to the connection control node  410 . The signaling information link  805  may carry signaling communications between the call/connection control node  405  and the connection control node  410 , and the data information link  810  may carry data communications between the call/connection control node  405  and the connection control node  410 . Such data communications may include voice or data calls, for example. 
     In an exemplary embodiment, the signaling information link  805  is realized using two ethernet links. One ethernet link may be used for transmitting signaling information from the call/connection control node  405  to the connection control node  410  while the other ethernet link may be used for transmitting signaling information from the connection control node  410  to the call/connection control node  405 . It should be understood that ethernet links are typically duplex in nature and that any ethernet links employed in any particular embodiment(s) in accordance with the present invention may also be duplex. The data information link  810  may be realized using a TDM link. For example, the data information link  810  may be composed of one or more E1 lines. Communications necessary and/or beneficial to establishing the various connections described hereinabove with reference to  FIGS. 6 and 7 , for example, may be effectuated across the signaling information link  805  and the data information link  810 . Advantageously, because separate links are employed between the nodes  405  and  410 , signaling information and data information may be transferred therebetween across links  805  and  810 , respectively, without needing to specify whether the transmitted information pertains to signaling or to data. 
     As illustrated generally at  800 , the call/connection control node  405  is connected to two TDM networks  515 , and the connection control node  410  is connected to two TDM networks  515  as well as two ATM networks  215 . It should be noted that the number of networks to which the nodes  405  and  410  are connected is exemplary only. The flexibility of the hybrid node  420  advantageously enables calls to be incoming at either of the nodes  405  and  410  and to be forwarded via a connection of either of the nodes  405  and  410 . In other words, a narrowband call incoming to the connection control node  410  (at point D) or a broadband call (e.g., a narrowband call being carried by a broadband transport mechanism, etc.) incoming to the connection control node  410  (at point E) may be forwarded from the connection control node  410  (as a narrowband or broadband call at point G or point H, respectively) or from the call/connection control node  405  as a narrowband call (e.g., at point F). Furthermore, a narrowband call incoming to the call/connection control node  405  (at point C) may be forwarded from the call/connection control node  405  as a narrowband call (at point F) or from the connection control node  410  (e.g., as a narrowband or broadband call at point G or point H, respectively). It should be noted that other combinations of ingress and egress (e.g., other connection paths) are possible. 
     By way of a first example but not limitation, assume that a call (or, more generally, a communication) is incoming to the connection control node  410  from a TDM network  515  at point D. The signaling information related to the call (e.g., an ISUP Initial Address Message (IAM)) is encapsulated into ATM cells (e.g., at the CE-ET equipment  625  at point D) and passed to the ATM switch  630 . Advantageously, the signaling information may therefore be piped through the connection control node  410  and over the signaling information link  805  without reformatting after being de-packaged from ATM cells (e.g., at the CE-ET equipment  625  at point J). The signaling information therefore need not be modified inasmuch as it may be transported through “transparent” pipes across the ATM switching fabric of the connection control node  410  (e.g., using a permanent virtual path connection (PVPC) pipe or similar, etc.). 
     When the GS  615  and associated call control logic (not explicitly shown in  FIG. 8 ) receive the signaling information of the incoming call, the signaling information is analyzed (e.g., by an ST  620  at point A or point B). The traffic call handling is performed by, for example, performing a B-number analysis, accessing an interactive voice response system, contacting an Intelligence Network (IN) node  815  (e.g., for “(800)” call routing, etc.), consulting a database of bearer capabilities for destination and/or transit nodes, etc. If, in contradistinction to the example described hereinabove with reference to  FIG. 3A , the call/connection control node  405  determines that the call should not or can not be routed through a broadband ATM transport mechanism, then the call/connection control node  405  instructs the connection control node  410  (e.g., over the signaling information link  805 ) to route the data information of the call to (and through) the call/connection control node  405 . 
     The data information of the call is routed through the connection control node  410  from point D to point J (e.g., by piping the data information via a semi-permanent connection through the switching fabric of the ATM switch  630 ). It should be noted that the data information may be propagated through the connection control node  410  without reformatting by, for example, encapsulating the data information in ATM cells. Thereafter, the data information is forwarded from point J to point I over the data information link  810  in, for example, a TDM format. The ET equipment  610  receives the data information of the call, and the GS  615  switches it toward the appropriate TDM network  515  (e.g., through an ET equipment  610  to a point C or a point F) in accordance with the earlier traffic call analysis. 
     By way of a second example but not limitation, assume that a call is incoming to the call/connection control node  405  from a TDM network  515  at point C. The call/connection control node  405  performs a traffic call analysis based on signaling information of the call. If the analysis indicates that the call can (and optionally should) be sent over a broadband transport mechanism, the call/connection control node  405  can direct the incoming call through the connection control node  410  and then to an ATM network  215 , instead of directing the call to a TDM node in a TDM network  515  (e.g., through the ET equipment  610  at the point F). In this regard, the GS  615  may switch the call signaling information to the ATM switch  630  via the signaling information link  805  and the call data information to the ATM switch  630  via the data information link  810  (and appropriate ET equipment  610  and CE-ET equipment  625  at point I and point J, respectively). The ATM switch  630  may thereafter send the signaling information of the call over permanent connections set up in the broadband ATM network  215  and the data information of the call over, e.g., call-specific connections in the broadband ATM network  215  (via an ATM-ET equipment  635  at point E or point H). 
     Referring now to  FIG. 9 , an exemplary method in flowchart form for communicating between nodes in a hybrid switch in accordance with the present invention is illustrated generally at  900 . In the exemplary method of flowchart  900 , an incoming call is initially received at a first node (step  905 ). The first node sends signaling information related to the incoming call to a second node via a first link (step  910 ). The second node, which may provide call control for the first node, processes the signaling information (step  915 ) to determine how and to where the incoming call is to be routed. The second node sends instructions to the first node (e.g., via the first link) (step  920 ) directing the first node on how/where to route the incoming call. Assuming that the second node determined that the incoming call should be routed as an outgoing call from the second node (at step  915 ) and that the instructions sent to the first node (at step  920 ) so indicated, data information related to the incoming call is sent from the first node to the second node via a second link (step  925 ). 
     Alternatively, an incoming call can be received at a node capable of processing the corresponding signaling information. Accordingly, both signaling information and data information corresponding to the incoming call may be sent to an associated node via first and second links, respectively, if the node receiving the incoming call determines that it is appropriate to do so (e.g., as described hereinabove in the second example referencing  FIG. 8 ). The call control functions of existing (e.g., STM) switches can therefore be advantageously utilized by newer and faster (e.g., ATM) switches to thereby avoid needing to completely reprogram the call control functionality for the newer switches. Furthermore, hybrid switches including both narrowband and broadband switches enable greater versatility for switching communications between broadband and narrowband transport mechanisms. For example, a hybrid switch may receive a communication that is being transported in a narrowband format and forward the communication in a broadband format, or vice versa. This ability is particularly advantageous for enabling a gradual migration in a network from being primarily or entirely narrowband to being primarily or entirely broadband. 
     Referring now to  FIGS. 10A–10E , a first set of exemplary traffic scenarios for a hybrid switch in accordance with the present invention is illustrated. In  FIG. 10A , a hybrid switch  420  is illustrated as being connected to two local exchange/transit exchange (LE/TE) nodes via TDM links, which may operate using an “N-ISUP” protocol, for example. The hybrid switch  420  is illustrated as receiving and forwarding a communication  1000 . It should be understood that the detailed traffic scenarios illustrated in  FIGS. 10B–10E  are also applicable to other instances besides when a hybrid switch  420  is directly connected to a local exchange/transit exchange node on both sides of a communication  1000 . For instance, the traffic scenarios of  FIGS. 10B–10E  are applicable whenever both the incoming and the outgoing side of a communication are transported on a narrowband transport mechanism such as TDM. 
     In  FIG. 10B , the communication  1010  (which represents a particular traffic scenario and/or portion of the communication  1000 ) may be terminated and switched entirely within the narrowband portion of the hybrid switch  420 . In  FIG. 10C , the incoming side of a communication  1020  is terminated in the narrowband portion of the hybrid switch  420  while the outgoing side is terminated at the broadband portion (e.g., using a circuit emulation (CE) board). The switching occurs partly within the narrowband portion and partly within the broadband portion of the hybrid switch. In  FIG. 10D , both of the incoming and the outgoing sides of a communication  1030  are terminated in the broadband portion of the hybrid switch  420 . In this scenario, a, e.g., circuit emulation board is utilized on both the ingress and the egress sides of the, e.g., TDM connection. The switching may be effectuated entirely within the switching fabric of the broadband portion. In  FIG. 10E , the incoming side of a communication  1040  is terminated by the broadband portion of the hybrid switch  420  whereas the outgoing side is terminated at the narrowband portion. Switching of the communication  1040  is therefore effectuated partly within the broadband portion (e.g., using an ATM switch  630 ) and partly within the narrowband portion (e.g., using a GS  615 ) of the hybrid switch  420 . 
     Referring now to  FIGS. 10F–10K , a second set of exemplary traffic scenarios for a hybrid switch in accordance with the present invention is illustrated. In  FIG. 10F , multiple hybrid switches  420  are illustrated as being connected to each other and ultimately to two local exchange/transit exchange nodes. The hybrid switches  420  are illustrated as receiving and forwarding a communication  1000 . A connection between two hybrid switches  420  may be realized using an ATM link, which may carry an “N-ISUP” protocol thereon, for example. A connection between a hybrid switch  420  and a local exchange/transit exchange may be realized using a TDM link, which may operate using an “N-ISUP” protocol, for example. 
     It should be understood that the detailed traffic scenarios illustrated in  FIGS. 10G–10J  are also applicable to other instances besides when a hybrid switch  420  is directly connected to a local exchange/transit exchange node on a single side of a communication  1000 . For instance, the traffic scenarios of  FIGS. 10G–10J  are applicable whenever one side of a communication is transported on a narrowband transport mechanism such as TDM and the other side of the communication is transported on a broadband transport mechanism such as ATM. Likewise, it should be understood that the detailed traffic scenario illustrated in  FIG. 10K  is also applicable to other instances besides when a hybrid switch  420  is directly connected to hybrid switches  420  on both sides of a communication  1000 . For instance, the traffic scenario of  FIG. 10K  is applicable whenever both sides of a communication are transported on a broadband transport mechanism such as ATM. 
     In  FIG. 10G , a communication  1050  is terminated at the incoming (e.g., TDM) side by the narrowband portion of the hybrid switch  420 . The switching of the communication  1050  may be performed by both the narrowband and the broadband portions after accommodation of the differing formats (e.g., by a circuit emulation board). The termination of the outgoing (e.g., ATM) side of the communication  1050  is effectuated (e.g., by an exchange termination (ET) board) at the broadband portion of the hybrid switch  420 . In  FIG. 10H , the incoming side of a communication  1060  is terminated (e.g., by a circuit emulation board for a narrowband transport format) at the broadband portion of the hybrid switch  420 . Switching of the communication  1060  may be performed entirely within the switching fabric of the broadband portion of the hybrid switch, and termination (e.g., by an exchange termination board for a broadband transport format) of the outgoing side of the communication  1060  may be accomplished by the broadband portion as well. 
     In  FIG. 10I , the incoming side of a communication  1070  is terminated (e.g., by an exchange termination board for a broadband transport format) at the broadband portion of the hybrid switch  420 . Switching of the communication  1070  may be performed entirely within the switching fabric of the broadband portion of the hybrid switch  420 , and termination (e.g., by a circuit emulation board for a narrowband transport format) of the outgoing side of the communication  1070  may be accomplished by the broadband portion as well. In  FIG. 10J , a communication  1080  is terminated at the incoming (e.g., ATM) side by the broadband portion of the hybrid switch  420  (e.g., using an exchange termination board). The switching of the communication  1080  may be performed by both the narrowband and the broadband portions after accommodation of the differing formats (e.g., by a circuit emulation board). The termination of the outgoing (e.g., TDM) side of the communication  1080  is effectuated at the narrowband portion of the hybrid switch  420 . 
     In  FIG. 10K , the hybrid switch may act as a “pure transit node” for ATM connections, such as the illustrated portion of the communication  1000 , which is denoted as a communication  1090 . Both of the incoming and the outgoing sides of the communication  1090  are terminated by the broadband portion of the hybrid switch  420  (e.g., by two exchange termination boards). Also, the communication  1090  may be switched entirely by the switching fabric (e.g., as realized by an ATM switch  630 ) of the broadband portion of the hybrid switch  420 . As also described and alluded to with reference to, for example,  FIG. 6  hereinabove, a hybrid switch  420  may establish various connection paths within to thereby enable a myriad of combinations of external ingress points and external egress points for different types of communications. The hybrid switch  420  may thus receive and forward communications  1000  in any combination of incoming and outgoing narrowband and broadband formats to accommodate, for example, the next node along the communication path, a node that is proximal to the final destination of the communication  1000 , etc. 
     Referring now to  FIG. 11 , an exemplary outgoing communication format selection for a hybrid switch in accordance with the present invention is illustrated generally at  1100 . An incoming communication  1105  is illustrated as being either broadband (e.g., ATM formatted) or narrowband (e.g., TDM formatted). The hybrid switch  420 , as described hereinabove with reference to  FIGS. 10A–10K , for example, may forward the communication  1105  as either an ATM communication or a TDM communication. (It should be understood that an outgoing TDM communication may be terminated by either the narrowband portion or the broadband portion of the hybrid switch  420 . However, this detail is not directly addressed further in the context of  FIG. 11 .) The hybrid switch  420  may forward the communication on the outgoing side according to any of various algorithms. For example, the hybrid switch may forward all incoming communications  1105  as outgoing TDM communications  1115  (e.g., if the hybrid switch  420  is the first or one of the first hybrid switches to be installed in a traditionally narrowband network) or as outgoing ATM communications  1120  (e.g., if the hybrid switch  420  is the last or one of the last hybrid switches to be installed in a formally narrowband network). Refer also to the text hereinabove describing  FIG. 3H . 
     Alternatively, the hybrid switch  420  may consult a table  1110  that provides an indication as to the viability and/or desirability of forwarding the communication  1105  in either a broadband or a narrowband format. For example, the table  1110  may indicate whether a node associated with the destination terminal  1155  or  1170  is capable of broadband transport. The table  1110  may also or in the alternative indicate whether any nodes between the hybrid switch  420  and the destination terminal  1155  and  1170  are capable of broadband transport. An exemplary embodiment for table  1110  is discussed hereinabove with reference to, for example,  FIG. 3A , Events E 8  and E 9 , and may involve the ascertainment of the bearer type (of either or both of the incoming side of the communication and the destination terminal). It should be noted that the table  1110  may be realized, instead of being part of the narrowband portion of the hybrid switch  420  but separate from the GS as illustrated, as part of the GS (e.g., the GS  615 ), as any part of the broadband portion (e.g., the ATM switch  630 ), as another part of the hybrid switch  420 , or even at an external location (e.g., an IN node), etc. 
     Alternatively, instead of relying on information in a table  1110 , the hybrid switch may query a node at or proximate to the destination node, may send a test signal/communication, etc. Regardless, if the hybrid switch  420  determines that there is a broadband node associated with the destination terminal, the hybrid switch  420  may elect to forward the incoming communication  1105  as a broadband (e.g., ATM) communication  1120 . The hybrid switch  420 ′ receives the incoming broadband communication  1120  and forwards an outgoing narrowband (e.g., TDM) communication  1160  to a local exchange node  1165  (e.g., which may correspond to, for example, an access node  322 , etc. of  FIG. 3  et seq.), which connects to the destination terminal  1170  (e.g., which may correspond to, for example, a terminal  324 , etc. of  FIGS. 3  et seq.). 
     If, on the other hand, the hybrid switch  420  determines that there is not a broadband node associated with the destination terminal, the hybrid switch  420  may elect to forward the incoming communication  1105  as a narrowband (e.g., TDM) communication  1115 . However, the hybrid switch  420  may optionally include provisions for determining that one or more (e.g., a sufficiently high enough number of intervening nodes have broadband capability, a sufficiently shorter route may be defined across intervening broadband-enabled network nodes, etc.) intervening broadband nodes may be advantageously utilized along the overall communication path. If such a determination is made, the hybrid switch  420  may elect to forward the incoming communication  1105  as a broadband (e.g., ATM) communication  1125  through a broadband-enabled network portion  1130 . Regardless, the communication is or ultimately becomes/is converted to a narrowband (e.g., TDM) communication and is submitted as narrowband communication  1135  to the narrowband node  1140 . The narrowband node  1140  forwards the incoming narrowband communication  1135  as an outgoing narrowband (e.g., TDM) communication  1145  to a local exchange  1150  (e.g., which may correspond to, for example, an access node  322 , etc. of  FIG. 3  et seq.), which connects to the destination terminal  1155  (e.g., which may correspond to, for example, a terminal  324 , etc. of  FIG. 3  et seq.). 
     Referring now to  FIG. 12 , exemplary interactions between a hybrid switch and other telecommunications technology in accordance with the present invention are illustrated generally at  1200 . The hybrid switch  420  of  1200  illustrates the traffic scenarios or communication portions  1010 – 1090  of communication  1000  (of FIGS.  10 A– 10 K). Communication  1205  (illustrated generally as a line or loop) enables a communication  1010 – 1090  according to any of the various traffic scenarios to access telecommunications technology using TDM communication and a STM switch (e.g., a GS  615 ). For example, one or more IN nodes  815  of an IN (not explicitly shown in  FIG. 12 ) may be accessed via the communication  1205 . Many telecommunications services and features may be utilized by accessing the IN. A DTMF receiver  1210 , for example, may be accessed for password and account number reception and for sending announcements from the IN. Generally, specialized resource function (SRF) and service control function (SCF) features are accessible via the IN node  815 . These and other IN features are represented generally by the other block  1215 . Access to the IN node  815  may be accomplished during the call establishment phase. Thereafter, routing of the communication  1000  may optionally be maintained through the narrowband portion of the hybrid switch  420 . Regardless, the communication  1000  may be routed through the narrowband portion (e.g., the GS  615 ) during an active call phase in order to access IN features. 
     The communication  1205  may also enable access to the operator  1220  for the communication  1000  (of  FIGS. 10A–10K ). The operator  1220  may handle the telecommunications situation and thereafter route the connection further along communication  1205  to implement one of the illustrated traffic scenarios. Alternatively (e.g., depending on how the operator  1220  handles the telecommunications situation), the operator  1220  may independently forward the connection towards, e.g., another exchange as indicated by arrow  1225 . The communication  1205  may also enable access to legal intercept (LI) equipment  1230 . It should be noted that with respect to  FIG. 12 , as well as other FIGS. described herein, certain elements may be moved, changed in number, etc. without departing from the scope of the present invention. For example, with regard to the hybrid switch  420  of  FIG. 12 , only two ET equipments may be associated with the GS (instead of the four illustrated), and the CE equipment between the GS and the ATM switch may be more closely associated with the ATM switch than the GS (e.g., as illustrated in  FIG. 11 ). 
     The hybrid nature of the hybrid switch  420 , in addition to enabling a gradual migration from a narrowband-oriented network to a broadband-oriented network, also enables seamless integration with networks of other carriers, networks of mobile systems, and networks that are international (all of which are designated generally by the external networks  1240 ). The external networks  1240  currently operate in accordance with TDM principles (or at least they are designed to interface with other networks using TDM principles), and they may continue to do so for quite some time into the future. The hybrid switch  420 , while providing the ability to transport communications on a broadband transport mechanism, also maintains the ability to utilize a narrowband transport mechanism and the ability to interface with external networks  1240  using traditional protocols. For example, communication  1205  enables outgoing connections (as represented by arrow  1235 ) and incoming connections (as represented by arrow  1245 ) between the hybrid switch  420  and the external networks  1240 . 
     Referring now to  FIG. 13 , an exemplary traffic scenario migration for a hybrid switch in accordance with the present invention is illustrated generally at  1300 . The hybrid switch  420  may be “installed” in an existing network that utilizes, at least primarily, a narrowband transport mechanism. The hybrid switch  420  may be “installed”, for example, by augmenting an existing TDM switch with ATM switching fabric. When the hybrid switch  420  is initially installed, especially if it is one of the first such switches installed, the hybrid switch may be activated or set up to operate entirely or predominantly within a first exemplary mode. Such a first exemplary mode may entail receiving a communication  1305  (e.g., as incoming TDM) and forwarding the communication  1305  (e.g., as outgoing TDM) using the switching fabric (e.g., a GS  615 ) of the existing narrowband switch. Gradually, as additional broadband-enabled nodes are “brought on-line”, the hybrid switch  420  may enter a second exemplary mode. Such a second exemplary mode may entail receiving a communication  1310  (e.g., as incoming TDM) and forwarding the communication  1310  (e.g., as outgoing ATM) using the switching fabric of the existing narrowband switch as well as the switching fabric (e.g., an ATM switch  630 ) of the broadband switch. 
     As the hybrid switch  420  of  1300  begins to receive incoming communications that use a broadband transport mechanism such as ATM, the hybrid switch  420  may enter a third exemplary mode. Such a third exemplary mode may entail receiving a communication  1315  (e.g., as incoming ATM) and forwarding the communication  1315  through the switching fabric of the broadband switch and the switching fabric of the narrowband switch to be handled by narrowband telecommunications technology and/or telecommunications technology with narrowband interface(s). For example, the communication  1315  may be forwarded from the narrowband switch as communication  1315 ′ to a voice response unit  1320  to provide voice response service to the communication  1315  that originally arrived at the hybrid switch  420  using a broadband transport mechanism. Alternatively, the communication  1315  may be forwarded from the narrowband switch as communication  1315 ″ (as indicated by the arrow so labeled) to external network(s)  1240 . If the communication  1315  is to continue within the network of the hybrid switch  420  (or otherwise forwarded as a broadband connection therefrom), the communication  1315 ′ is returned to the narrowband switching fabric (e.g., after being serviced by the voice response unit  1320  or other such existing narrowband features) and forwarded to and through the broadband switching fabric as the communication  1315 ′ (e.g., as outgoing ATM). 
     Eventually, as the network becomes wholly or primarily a broadband transport mechanism network (optionally including broadband provision of IN-type services, etc.), the hybrid switch  420  of  1300  may enter a fourth exemplary mode. Such a fourth exemplary mode may entail receiving a communication  1325  (e.g., as incoming ATM) and forwarding the communication  1325  (e.g., as outgoing ATM) using the switching fabric of the broadband portion of the hybrid switch  420 . It should be understood that the four modes illustrated and described herein with reference to  FIG. 13  are exemplary only. Modes may be added, subtracted, or substituted for the four exemplary modes depending, for example, on the percentage of the network that has been upgraded to broadband. Furthermore, the modes may be activated in a different order depending, for example, on whether or not the hybrid switch in question is a “transit-type” node. 
     Referring now to  FIG. 14 , an exemplary method in flowchart form for enabling a gradual migration from a primarily narrowband network to a primarily broadband network in accordance with the present invention is illustrated generally at  1400 . Initially, a network node (e.g., a hybrid switch  420 ) receives an incoming communication that includes an identifier corresponding to a destination terminal (e.g., a destination terminal  1155  and  1170  (of  FIG. 11 )) (step  1405 ). The incoming communication may be transported, for example, on a broadband or narrowband mechanism. The identifier that corresponds to the destination terminal is analyzed (step  1410 ). The identifier may correspond to, for example, a B-number, and the identifier may be analyzed, for example, in a narrowband portion of the network node. The analysis may include a determination as to whether or not the identifier is associated with a node having broadband capability (step  1415 ). If not, then the communication may be forwarded over a narrowband transport mechanism (step  1420 ) and ultimately to the destination terminal. 
     If, on the other hand, it is determined that the identifier is associated with a node having broadband capability (at step  1415 ), then the communication may be forwarded over a broadband transport mechanism (step  1425 ) and ultimately to the destination terminal. The identifier may be associated with a node when, for example, the node is the most proximate node (or the most proximate non-local exchange and/or non-end office node) to the destination terminal. The identifier, in addition to or in the alternative, may be associated with a node when the node is somewhere between the analyzing node and the destination terminal, but the node is sufficiently far from the analyzing node and sufficiently close to the destination terminal so as to warrant diverting (if necessary) the communication onto a broadband transport mechanism. The analysis may involve accessing a table (or other data structure) (e.g., a table  1110 ), which may be gradually updated as nodes in the network are upgraded to provide broadband transport. In an alternative embodiment, a communication may only be forwarded using a broadband transport mechanism (e.g., in step  1425 ) if a node having broadband capability is also associated with an identifier that corresponds to an originating terminal and/or if the incoming communication “arrives” over a broadband transport mechanism. In yet another alternative, the broadband capability of a node associated with the identifier that corresponds to the originating terminal may be another factor to account for when analyzing the proximity of the node associated with the identifier of the destination terminal. A hybrid switch operated in accordance with certain principles of the present invention therefore enables a gradual migration from a narrowband-oriented network to a broadband transport mechanism-oriented network. 
     Referring now to  FIG. 15 , an exemplary tri-level nodal environment in accordance with the present invention is illustrated generally at  1500 . A call/connection control node  405  (e.g., which may correspond to, for example, PSTN/ISDN nodes  330  of the embodiment(s) of  FIGS. 3  et seq.) is illustrated connected to a modified connection control node  410 ′ (e.g., which may correspond to, for example, ATM node  340   7-1  of the embodiment(s) of  FIG. 3  et seq.) via line  1510  (e.g., which may correspond to, for example, interface  300   a  and/or interface  300   d  of the embodiment(s) of  FIG. 3  et seq.). The modified connection control node  410 ′, in the exemplary tri-level nodal environment  1500 , includes an interworking function (IWF)  1505  (e.g., which may correspond to, for example, an IWF  344   7-1  of the embodiment(s) of  FIG. 3  et seq.). The IWF  1505  may be composed of, for example, hardware, software, firmware, some combination thereof, etc. 
     The IWF  1505  may include emulation and mapping capabilities. For example, the IWF  1505  may include the ability to emulate a switch interface for the call/connection control node  405 . Advantageously, this eliminates any absolute requirement to modify the call/connection control node  405  because the call/connection control node  405  is able to act and interact as if it is functioning within a traditional telecommunications network. The IWF  1505  may also include the ability to map/translate one network address into or to another network address. The modified connection control node  410 ′ is illustrated connected to multiple connection control nodes  410  (e.g., which may correspond to, for example, ATM node  340   7-2 , ATM node  340   7-3 , etc. of the embodiment(s) of  FIG. 3  et seq.) via lines  1515  (e.g., which may correspond to, for example, interfaces  300   a  and/or interfaces  398  of the embodiment(s) of  FIGS. 3  et seq.). In the exemplary tri-level nodal environment  1500 , the call/connection control node  405  may advantageously provide/share its switching intelligence with more than one connection control node  410 . It should be understood that the various nodes may be physically co-located, physically separated, etc. 
     Referring now to  FIG. 15A , a first exemplary tri-level nodal environment alternative in accordance with the present invention is illustrated generally at  1525 . In the first exemplary tri-level nodal environment alternative  1525 , the call/connection control node  405  is in communication with the modified connection control node  410 ′ via a first line  1530  and a second line  1535 . The first line  1530  and the second line  1535  may be used for communicating signaling information and data information, respectively, between the call/connection control node  405  and the modified connection control node  410 ′, which has the IWF  1505 . Also illustrated in the first exemplary tri-level nodal environment alternative  1525  is an ATM network  215  cloud interconnecting the modified connection control node  410 ′ and the connection control nodes  410 . In other words, the modified connection control node  410 ′ need not employ direct and dedicated links to the individual connection control nodes  410 . It should be understood that the ATM network  215  may alternatively be realized as any circuit-switched network. 
     Referring now to  FIG. 15B , a second exemplary tri-level nodal environment alternative in accordance with the present invention is illustrated generally at  1550 . In the second exemplary tri-level nodal environment alternative  1550 , a “combined” tri-level nodal environment is illustrated. The modified call control node  405 ′ does not include connection control (e.g., it was designed and built without such connection control, it had its connection control removed or rendered inoperable, etc.), and no single connection control is directly associated with (or co-located with) the IWF (node)  1505 . The switching intelligence of the modified call control node  405 ′ operates in a first address space, which is designated address space A  1555 . The switching fabric of the multiple connection control nodes  410 , on the other hand, operate in a second address space, which is designated address space B  1560 . The IWF  1505  maps/translates the addresses of the address space A  1555  to the addresses of the address space B  1560  so as to enable the switching intelligence of the modified call control node  405 ′ to provide call control to the switching fabric of the multiple connection control nodes  410 . 
     It should be understood that while the address spaces A  1555  and B  1560  are illustrated only in the second exemplary tri-level nodal environment alternative  1550 , they are also applicable to the exemplary tri-level nodal environment  1500  as well as the first exemplary tri-level nodal environment alternative  1525 . It should also be understood that the different aspects illustrated in the various embodiments of  FIGS. 15 ,  15 A, and  15 B may be interchanged without departing from the present invention. For example, a circuit-switched network cloud (e.g., the ATM network  215 ) may interconnect the multiple connection control nodes  410  in any or all embodiments embraced by the present invention. 
     Referring now to  FIG. 15C , an exemplary interworking function in accordance with the present invention is illustrated at  1505 . The IWF  1505  includes an emulator  1580  and a mapper (or translator)  1585 . The emulator  1580  emulates an interface to which the call/connection control node  405  “expects” to be connected. In other words, the emulator  1580  may provide an interface that the call/connection control node  405  is already designed to utilize and/or interact with. Advantageously, this eliminates or minimizes or at least reduces the need to modify the call/connection control node  405 . It should be noted that the interface may be equivalent to a GS input/output (I/O), E1/T1 trunk lines, etc. The mapper  1585  provides a mapping (or more generally a correspondence) between addresses of a first address space and addresses of a second address space. 
     The mapper may map (or more generally a correspondence may be established between) address space A  1555  (of  FIG. 15B ) to the address space B  1560 . For example, one or more of the addresses A 1  . . . An of the address space A  1555  may be mapped to one or more of the addresses B 1  . . . Bn of the address space B  1560 . As a specific instance, the address A 3  may be mapped to the address B 1 . In exemplary embodiment(s), the address space A  1555  may include 10-digit B-numbers, and the address space B  1560  may include ATM identifiers such as VPIs and VCIs. Other exemplary address space realizations are also embraced by the present invention. 
     Referring now to  FIG. 16 , an exemplary tri-level nodal environment implementation in accordance with the present invention is illustrated generally at  1600 . A telecommunications node (TN)  1605  (e.g., which may correspond to, for example, a call/connection control node  405  of the embodiment(s) of  FIGS. 15  et seq.) is shown connected to media gateway functionality  1615  (e.g., which may correspond to, for example, a modified connection control node  410 ′ of the embodiment(s) of  FIGS. 15  et seq.). The TN (a.k.a. legacy switch (LS))  1605  may have a circuit switch such as a GS  615  (not explicitly shown in  FIG. 16 ). The media gateway functionality  1610  may include a media gateway (MG)  1615 , which may have a packet switch such as an ATM switch  630 , and mediation logic (ML)  1620  (e.g., which may correspond to, for example, an IWF  1505  of the embodiment(s) of  FIGS. 15  et seq.). 
     The media gateway functionality  1610  is illustrated as being connected to multiple MGs  1625  (e.g., which may correspond to, for example, the multiple connection control nodes  410  of the embodiment(s) of  FIGS. 15  et seq.). Each of the MGs  1625  may be responsible for handling one or more different types of media. The media, and nodes corresponding thereto, may include, for example, a remote subscriber switch (RSS) node  1630 A, a V5.2 interface access network (V5.2) node  1630 B, a local exchange (LE) node  1630 C, a primary rate access (PRA) node  1630 D, etc. An MG  1625  (or an MG  1615 ) may convert media provided in one type of network to the format requirements of another type of network. 
     Exemplary and/or appropriate protocols for the links between the various illustrated nodes (including the gateways) are illustrated at the exemplary tri-level nodal environment implementation  1600 . As an explanatory example, the connections between the media gateway functionality  1610  and the multiple MGs  1625  may be ATM-ET to ATM-ET PVPC pipes defined through an ATM network to carry signaling information. A PVPC is an ATM connection in which the switching is performed only on the VPI field of each cell. A PVPC is termed “permanent” because it is provisioned through a network management function and maintained (or left up) indefinitely. The signaling information between the media gateway functionality  1610  and any one or more of the MGs  1625  may be effectuated transparently over a PVPC pipe. Such a PVPC pipe is at least similar to one establishable through the switching fabric of a connection control node  410  for transparently piping signaling information to the switching intelligence of a call/connection control node  405  (as alluded to hereinabove with reference to  FIG. 3  et seq.). 
     Referring now to  FIGS. 17A and 17B , two other exemplary tri-level nodal environment implementations in accordance with the present invention are illustrated generally at  1700  and  1750 , respectively. The exemplary tri-level nodal environment implementations  1700  and  1750  include call servers  1705 . The call servers  1705  each include a TN  1605  and ML  1620 . Each call server  1705  may control one or more MGs  1625  (denoted as “MGW” in  FIGS. 17A and 17B ) via the packet-switched network cloud, such as an ATM network  215 . Each call server  1705 , being based on pre-existing TNs  1605  in certain exemplary embodiment(s), may only handle a finite number of MGs  1625 . Accordingly, a given tri-level nodal environment may need more than one call server  1705 , as indicated by the two call servers  1705  illustrated in the exemplary tri-level nodal environment implementation  1750 . 
     The bearer services for call data information are provided by the packet-switched broadband network (e.g., via encapsulation), and the telecommunications services/call control may be transported over this packet-switched (broadband) network in an un-modified format (e.g., transparently in pipes), as indicated by the dashed lines. For example, control communications to the private branch exchange (PBX) nodes  1710 A are effectuated using DSS 1 , control communications to the generic access nodes (AN)  1710 B are effectuated using V.5, and control communications to the LE nodes  1630 C are effectuated using ISUP. Likewise or similarly, the two call servers  1705  may communicate therebetween using a bearer independent call control (BICC) protocol that may be transported over the packet-switched network. It should be emphasized that TDM as used herein, including the claims, encompasses and embraces time-division multiplexed protocols in general, and it is not limited to any particular TDM protocol, including the exemplary 2M PCM link definition of  FIGS. 17A and 17B . 
     With reference now to  FIGS. 18A and 18B , two exemplary call setups in an exemplary tri-level nodal environment implementation in accordance with the present invention are illustrated generally at  1800  and  1850 , respectively. In the exemplary call setup  1800 , a TN  1605  determines that a communication path between points A and B are needed for a call. The TN  1605  therefore instructs the ML  1620  to establish a path between the points A and B. The instruction may include direction(s) for establishing such a path in a TDM network. The ML  1620 , applying the points A and B and/or the direction(s) to a mapping data structure for example, determines how to establish a communication path between points A and B. The ML  1620  then instructs/requires that such a communication path be established (e.g., added) in the broadband network of which the MG  1625  is a part. In the exemplary call setup  1800 , an intra MG call setup case is illustrated, so the single MG  1625  that is illustrated is capable of establishing the communication path. 
     In the exemplary call setup  1850 , on the other hand, a multi-MG (but intra domain) call setup case is illustrated, so more than a single MG  1625  is required to establish the communication path. Specifically, after the ML  1620  receives the instruction (and possibly the direction(s)) from the TN  1605 , the ML  1620  determines that the communication path needs to extend between at least two MGs  1625 . Namely, the MGs  1625  that include the points A and B need to be interconnected, optionally with no intervening MG(s)  1625 . In the exemplary call setup  1850 , the ML  1620  then instructs/requires that such an interconnection for the communication path be established (e.g., added) in the broadband network between the MG  1625 AC′ and the MG  1625 D′B, as indicated by the dashed line. The MGs  1625 AC′ and  1625 D′B also complete the communication path between point A and point B by establishing interconnections between points A and C′ and points D′ and B, respectively. By determining a communication path and/or instituting a routing of a communication path between point A and point B through a packet-switched (broadband) network, the ML  1620  effectively maps from one address space to another address space. 
     Referring now to  FIG. 19 , exemplary communication path configuring in an exemplary tri-level nodal network in accordance with the present invention is illustrated generally at  1900 . The entities responsible for configuring various communication paths in the exemplary tri-level nodal network  1900  are indicated by the type of line (e.g., solid, dashed, thick, thin, etc.) illustrating/representing the particular communication path. The signaling link parts represented by the solid thick lines (also labeled “(A)”) are configured by TN  1605  commands. The signaling link parts represented by the solid thin lines (also labeled “(B)”) are configured by ATM management system commands. The leased line parts represented by the dashed thick lines are configured by TN  1605  commands. The leased line parts represented by the dashed thin lines (also labeled “(C)” and “(D)”) are configured by ATM management system commands. The parts labeled “(A)” and “(C)” pertain to intra-domain segments while the parts labeled “(B)” and “(D)” pertain to inter-domain segments. It should be noted that segments within the ATM network are configured by the ATM management system commands while segments extending beyond the ATM network are configured by TN  1605  commands in the exemplary communication path configuring of the exemplary tri-level nodal network  1900 . 
     Referring now to  FIGS. 20A and 20B , exemplary mapping embodiments in an exemplary tri-level nodal environment implementation in accordance with the present invention are illustrated generally at  2000  and  2050 , respectively. The exemplary mapping as illustrated at  2000  includes a man machine line (MML) handler  2005  and an ATM management system  2010  that enable the general management of the illustrated tri-level nodal environment implementation. Specifically, the MML handler  2005  enables the configuring of the TN  1605  portion, and the ATM management system  2010  enables the configuring of the ML  1620  and MG  1625  portions. Switch device management (SDM) parts  2015 TN and  2015 ML enable communication between the TN  1605  and the ML  1620 , along with the transport handler (TRH)  2020 . In exemplary embodiment(s), a switch device (SD) may correspond to a logical device that terminates a 31 channel logical E1 line. A context handler  2025  controls the connections and connection topology of the domain. 
     In exemplary embodiment(s), an H.248 protocol may be employed for communication over the ATM network. A mapping part portion  2030  stores the topology of one or more MGs  1625  as well as a protocol mapping of the SDM part(s) (e.g., of the circuit-switched address space) to the H.248 (e.g., of the packet-switched address space). The exemplary mapping as illustrated at  2050  includes indications of an add port instruction  2055  and an add port response instruction  2060  exchanged between the TN  1605  and the ML  1620 . These instructions, which may originate at the MML terminal  2005 , configure the mapping providing by the H.248 table  2065  and the SD table  2075 . The H.248 table  2065  and the SD table  2075  together provide a mapping between H.248 addresses (e.g., termination addresses: “MG/Subrack/Slot/Port” (H.248 addresses)) and SD addresses (e.g., and “SD 1 ” address). 
     It should be noted that the H.248 addresses may have an unrestricted and/or unstructured format that differs from and may be more flexible than the “MG/Subrack/Slot/Port” as illustrated in  FIG. 20B . In fact, an operator may be empowered to select such names. The MG  1625  includes an H.248 object table  2080 , which may be configured at least in part by the ATM management system  2010 , for establishing communication paths through the MG  1625 . The tri-level approach described hereinabove in various embodiments enables pre-existing narrowband technology to be used with broadband technology. Moreover, the tri-level approach multiplies the ability to reuse a pre-existing narrowband switch by enabling a single narrowband switch to provide switching intelligence to multiple broadband switches. 
     Referring now to  FIG. 21 , an exemplary tri-level nodal environment with exemplary functionality in accordance with the present invention is illustrated generally at  2100 . The exemplary tri-level nodal environment  2100  may include a telephony server (TS)  2105  (e.g., which may correspond to, for example, the call server/telephony server  1705  of the embodiment(s) of  FIGS. 17A and 17B  et seq.). The TS  2105  may include a legacy switch (LS)  2110  (e.g., which may correspond to, for example, the TN  1605  of the embodiment(s) of  FIG. 16  et seq.) and mediation logic (ML)  2115  (e.g., which may correspond to, for example, the ML  1620  of the embodiment(s) of  FIG. 16  et seq.). The TS  2105  may also include a media gateway (MG)  2120  (e.g., which may correspond to, for example, the MG  1615  of the embodiment(s) of  FIG. 16  et seq.). It should be noted that the ML  2115  and the LS  2110  may be jointly referred to as a media gateway controller (MGC). 
     The MG  2120  of the TS  2105  may be connected to a broadband network (BN)  2125  (e.g., which may correspond to, for example, the ATM network  215  of the embodiment(s) of  FIG. 4  et seq.). The BN  2125  provides a medium for the MG  2120  of the TS  2105  to be in communication with the other illustrated MGs  2120  (e.g., which may correspond to, for example, the MGs  1625  of the embodiment(s) of  FIG. 16  et seq.). It should be understood that the architecture illustrated in the exemplary tri-level nodal environment  2100  may be modified, rearranged, etc., especially in accordance with the other illustrated and described embodiments and teachings from  FIGS. 15–15C , as well as those of  FIGS. 16–20B . For example, a TS  2105  may omit a co-located MG  2120  without departing from the spirit and scope of the present invention. 
     Exemplary functionality is also illustrated in the exemplary tri-level nodal environment  2100 . For example, the LS  2110  may include routing analysis in address space-A functionality  2130  (e.g., which may correspond to, for example, B-number analysis, etc. as described hereinabove with reference to the embodiment(s) of  FIGS. 3–3I  et seq.). The LS  2110  may also include narrowband telephony services functionality  2135  (e.g., which may correspond to, for example, those services provided internally by the LS  2110  as well as those services provided externally via the LS  2110  as described hereinabove with reference to the embodiment(s) of  FIGS. 3–3I  et seq., including those described by the text related to  FIG. 12 ). Another exemplary functionality illustrated in the exemplary tri-level nodal environment  2100  is mapping from address space-A to address space-B functionality  2140  of the ML  2115 . The mapping from address space-A to address space-B functionality  2140  (e.g., which may correspond to, for example, the mapper  1585  of the embodiment(s) of  FIGS. 15–15C  et seq., the mapping part portion  2030  of the embodiment(s) of  FIG. 20A , the tables  2065  and  2075  of the embodiment(s) of  FIG. 20B , etc.) enables a conversion from, for example, a narrowband network (e.g., for which the LS  2110  may have originally been designed) to a broadband network (e.g., such as the BN  2125  in which the MGs  2120  may be operating). 
       FIG. 22  illustrates an exemplary load distribution embodiment in a tri-level nodal environment illustrated generally at  2200 . The tri-level nodal environment  2200  shown in  FIG. 22  is a portion of the tri-level nodal environment  2100  illustrated in  FIG. 21 . For example, in  FIG. 22 , only the media gateway controller (MGC)  2210  that includes the legacy switch (LS)  2110  and mediation logic (ML)  2115  is shown. However, it should be understood that the tri-level nodal environment  2200  of  FIG. 22  can be extended to include the telephony server (TS) shown in  FIG. 21 . 
     Each call within the tri-level nodal environment  2200  is handled by a call processor  2230  within the ML  2115 . The call processor  2230  implements a Gateway Control Protocol (GCP)  2240  that encodes and decodes messages according to the H.248 standard. The call processor  2230  further includes a transport handling function (TRF)  2245  for establishing and monitoring transport links  2260  between the call processor  2230  and the MGs  2120  and for sending and receiving of messages. 
     At least one call processor  2230  serves as an Operation and Maintenance (OM) call processor (not shown) that is responsible for maintaining the status of all of the transport links  2260  and call processors  2230 . Each call processor  2230  is either a primary call processor or a stand-by call processor. A set of one primary call processor and one stand-by call processor is referred to as a node pair  2250 . The primary call processor is referred to as a call handler (CH)  2220 . 
     Within the ATM network, each transport link  2260  is a physical Signaling ATM Adaption Layer (SAAL) transport link that carries H.248 messages between the ML  2115  and the MGs  2120 . The H.248 signaling protocol limits the number of active physical SAAL transport links  2260  to one per MG  2120 . Therefore, each MG  2120  has only one physical SAAL transport link  2260  to the ML  2115 . Each SAAL transport link  2260  terminates at one CH  2220  within the ML  2115 . Therefore, there is only one CH  2220  within the ML  2115  that has a SAAL transport link  2260  to a particular MG  2120 . 
     Referring now to  FIG. 23 , instead of assigning all calls routed through a selected MG ( 2120  shown in  FIG. 22 ) to the CH  2220  with the SAAL transport link ( 2260  shown in  FIG. 22 ) to that selected MG, the LS  2110  can include a load distribution function (LDF)  2310  that assigns CH&#39;s  2220  on a load basis. The LDF  2310  distributes the load amongst the CH&#39;s  2220  to prevent overloading or under-use of any of the CH&#39;s  2220 . A CH  2220  is assigned for a call by the LDF  2310  sending an Establish Path message  2320  from the LS  2110  to the particular CH  2220  in the ML  2115  using the Point Association (PA) of the CH  2220 . Upon receipt and assignment by the particular CH  2220 , the ML  2115  sends an Establish Path Response message  2325  to the LDF  2310  in the LS  2110 . Thereafter, the PA is used to route message to the assigned CH  2220 . 
     In one embodiment, the LDF  2310  assigns the CH&#39;s  2220  on a round-robin basis, in which the CH&#39;s  2220  are assigned in order from the first CH  2220  to the last CH  2220  and back to the first CH  2220 . However, it should be understood that any type of load sharing method can be used to assign the CH&#39;s  2220 . For example, the LDF  2310  may maintain load information on each of the CH&#39;s  2220 , and select a particular CH  2220  based on the load information. 
       FIG. 24  illustrates an exemplary message encoding and transmission embodiment in the tri-level nodal environment. After a CH  2220   a  has been assigned for the call, all messages  2410  transmitted from the LS  2110  to the selected MG  2120  for the call are routed to the assigned CH  2220   a  within the ML  2115 . The assigned CH  2220   a  uses the GCP to encode the message  2410  (e.g., convert the message from an internal (Erlang) format into a format specified by the H.248 standards for transmission across the BN  2125  to the selected MG  2120 . As mentioned above in connection with  FIG. 22 , within the ATM network, only one CH  2220  has a physical SAAL transport link  2260  to the selected MG  2120 . Therefore, if the assigned CH  2220   a  does not have the SAAL transport link  2260  to the selected MG  2120 , the assigned CH  2220   a  passes the encoded message  2415  to the linked CH  2220   b  for transmission to the selected MG  2120  over the SAAL transport link  2260 . 
       FIG. 25  illustrates an exemplary message decoding and transmission embodiment in the tri-level nodal environment. All messages  2510  sent from the selected MG  2120  to the LS  2110  are received at the linked CH  2220   b  within the ML  2115  that has the physical SAAL link  2260  to the selected MG  2120 . The linked CH  2220   b  decodes the message  2510  for transmission to the LS  2110 . However, if the linked CH  2220   b  is not the assigned CH  2220   a  for the call, the linked CH  2220   b  passes the decoded message  2515  to the assigned CH  2220   a  for transmission to the LS  2110 . Therefore, although load sharing for messages  2410  (shown in  FIG. 24 ) sent from the LS  2110  to the ML  2115  is achieved by assigning CH&#39;s  2220  on round robin and CH load basis, load sharing for messages  2510  sent from the MG  2120  to the LS  2110  is not possible due to the H.248 signaling protocol requirement of a single active SAAL transport link  2260  to the MG  2120 . 
       FIGS. 26A and 26B  illustrate an exemplary method in flowchart form for transmitting messages between nodes within a tri-level nodal environment in accordance with the present invention. When the LS has assigned a certain CH for a particular new call (step  2600 ), the LS sends an Establish Path message for the call to the assigned CH in the ML using the PA of the assigned CH (step  2605 ). In response, the CH sends an Establish Path Response message back to the LS (step  2610 ). Thereafter, when the LS sends a message to the selected MG for the call (step  2615 ), the message includes the PA of the assigned CH, so that the ML can forward the message to the assigned CH (step  2620 ). The assigned CH encodes the message (step  2625 ) into the format suitable for transmission across the BN to the selected MG. 
     If the assigned CH does not have the SAAL transport link to the selected MG (step  2630 ), the assigned CH passes the encoded message to the linked CH that has the SAAL transport link to the selected MG (step  2635 ) for transmission of the encoded message to the selected MG (step  2640 ). However, if the assigned CH does have the SAAL transport link to the selected MG (step  2630 ), the assigned CH transmits the encoded message directly to the selected MG via the SAAL transport (step  2640 ). 
     Referring now to  FIG. 26B , when the selected MG sends a message to the LS for the call (step  2650 ), the message is received at the linked CH having the SAAL transport link to the selected MG (step  2655 ). The linked CH decodes the message (step  2660 ) into a format suitable for transmission to the LS. If the linked CH is the assigned CH (step  2665 ), the linked CH transmits the decoded message directly to the LS (step  2675 ). However, if the linked CH is not the assigned CH (step  2665 ), the linked CH passes the decoded message to the assigned CH (step  2670 ) for transmission to the LS (step  2675 ). 
     Although embodiments of the methods, systems, and arrangements of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the present invention is not limited to the embodiment(s) disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit and scope of the present invention as set forth and defined by the following claims.