Patent Publication Number: US-2006002403-A1

Title: Distributed IP architecture for telecommunications system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of the filing date of United States Provisional Application for Patent entitled DISTRIBUTED IP ARCHITECTURE FOR TELECOMMUNICATIONS SYSTEM, filed on Jun. 30, 2004 and assigned Ser. No. 60/584,117. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not applicable.  
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX  
      Not applicable.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to distributed IP systems and telecommunication systems and, more particularly, to a multi-functional telecommunications system with geographically dispersible components that interact over a distributed IP architecture.  
      Over the past several decades, voice mail has continued to expand and establish itself as a key element in the successful operations of most businesses. The typical voice mail system today can take on a variety of forms, including a computer card that can operate within a personal computer that is connected to a businesses telephone system, or a computer card or component that is directly integrated into the businesses telephone system, or as a service provided by a telecommunications company.  
      The common ingredient to each of the voice mail systems available today is that the components that make up the voice mail system must communicate with each other and thus, must be co-located. This can be a great disadvantage for companies that have geographically dispersed offices.  
      In today&#39;s global economy, even small business may have a need for multiple offices for serving clients, interacting with vendors, or various other reasons. The advent of the Internet, email and video conferencing helps to allow such dispersed operations appear more seamless. However, a significant problem that still exists for dispersed offices is having a common telephonic system that operates as a single, co-located system but serves the needs of the various offices. Generally, each office purchases and maintains its own telephone system without any direct interface between the telephone systems of the various offices and without any central control. This can be a costly endeavor in that duplicative hardware must be purchased and maintained at each site. In addition, the logistics of inter-office communication such as call transfers, voice mail retrieval etc. can be complex. Thus, there is a need in the art for a telecommunications system that allows seamless integration for remotely located offices.  
      In addition, even if a seamless integration of a telephone system is obtained, there still exists a need for personalization of the telephone systems in the various offices. For instance, if the offices are located in different time zones, it may be important to have the ability for each office to uniquely set up the system for handling incoming calls, switching the system to night or weekend mode, entering or deleting individuals from the system etc. Thus, there is a need in the art for a distributed telephone system that provides seamless integration, while at the same time allowing components of the system to be individually programmed and/or maintained at the remote offices.  
     SUMMARY OF THE INVENTION  
      The present invention is directed towards a distributed telecommunications system and a distributed architecture for building such a telecommunications system. The telecommunications system provides functionality that is typical of what is required in most modern small or large business settings, such as call forwarding, auto-attendant, voice mail, voice messaging, etc. The telecommunications system is made up of several components that can be located in various locations that are remote from each other. Each of the components includes an interface to an IP network such as the Internet. A single component or class of components (signaling gateway) interfaces to a switched telephone network using the signaling system seven (SS7) protocol. Each of the other components in the telecommunications system that would require such an interface to the switched telephone network simply communicates through the signaling gateway.  
      Each component in the telecommunication system communicates with the other components through the IP network. This advantageously allows the components to be geographically dispersed yet to operate as a single, seamless telecommunications system.  
      More particularly, one embodiment of the present invention includes a signaling gateway, a media server, an application server and a central message and data store. The signaling gateway includes a signaling interface to a telephone network, such as an SS7 interface and an interface to an IP network. The media server includes a circuit-switched interface to the telephone network for receiving and initiating telephone services over the telephone network. The media server also includes an interface to the IP network. The media server operates to provide communication services, such as voice mail, voice messaging, voice-based menus, etc to callers and subscribers over circuit switched connections through the telephone network.  
      The media server operates closely in conjunction with the application server and communicates with the application server over the IP network. The media server receives requests for services and then request the provision of those services through the application server. The application server provides the functionality for providing various communication servers to callers and subscribers. The central data and message store provides configuration information that is used to control the operation of the communication services provided by the application server.  
      In operation, a media server, located at a first location, may receive a request for a communications service. The request for a communications service can take on a variety of forms including, but not limited to receiving an incoming call, receiving a request for a call origination, receiving a menu selection of a voice-based menu. The media server response to the request by either invoking or calling up an application from the application server. Depending on the particular embodiment of the invention, the application server can simply provide the application to the media server to render, or can be partially or entirely rendered by the application server. In rendering the communications service, the central data and message store may be accessed to obtain particular configuration or customization information pertaining to the provision of the communications service. While the communications service is being provided, the media server may receive additional feedback from a calling party or subscriber and the application will respond correspondingly. For instance, the communications service may include a voice mail function. In this case, the application will prompt a calling party to leave a voice message. The voice message can then be received and stored in the central data and message store. Other features, capabilities and advantages of the present invention are more fully described with reference to the figures and the detailed description.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Various aspects, features and advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:  
      Brief Description of the Drawings  
       FIG. 1  is a system diagram illustrating the components and the connectivity of an exemplary next-generation communications platform of the present invention.  
       FIG. 2  is a block diagram illustrating the inter-working of a media server  130  in a next generation communications platform.  
       FIG. 3  is a block diagram illustrating the integration of the facsimile feature into the media server  130 .  
       FIG. 4  is a conceptual diagram of the employment of the SGFs 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention provides a distributed IP architecture, also described as a next-generation communications platform, for telecommunications equipment, such as a PBX, voicemail system, or the like. By utilizing the architecture of the present invention, the various functionalities of the telecommunications equipment can be divided amongst various physical components and the physical components can be geographically dispersed. Each of the components communicates with each other, as needed, through independent interfaces to an IP network. The complexities of interfacing to the telephone network are handled through a single gateway component and a simplified protocol is used for communication between the remaining components of the telecommunications equipment or to the telephone network through the gateway component.  
      Now turning to the drawings, in which like labels refer to like elements throughout the several views, various aspects and features of the present invention are described.  
       FIG. 1  is a system diagram illustrating the components and the connectivity of an exemplary next-generation communications platform of the present invention. One aspect of the present invention is a distributed IP-based architecture for telecommunications equipment that, among other things, can provide telecommunication services such as voice mail, call forwarding and other telecommunication features. In the illustrated embodiment, the next-generation communications platform  100  has a distributed IP architecture and is connected to the Public Switched Telephone Network (PSTN)  110 . The communications platform  100  is illustrated as including a signaling gateway function (SGF)  120 , one or more media servers (MS)  130 , one or more system management units (SMU)  140 , one or more application servers (AS)  150  and one or more central data and message store (CDMS)  160 . It should be understood that the distribution of functionality illustrated in the figures and described, although having novel aspects in itself, is not the only acceptable arrangement, and aspects of the present invention could be incorporated into a system that includes fewer or more components and a different arrangement of functionality among the components.  
      In general, the SGF  120  serves as the Signaling System 7 (SS7) interface to the PSTN  110  and allows one or more components or sub-systems to share the same point code (thereby reducing the need for destination point codes (DPC) and signaling links for call-control. This makes the telephonic system appear as single trunk group in the network. The media server  130  terminates IP and/or circuit switched traffic from the PSTN via a multi-interface design and is responsible for trunking and call control. The application server module  150  generates dynamic VoiceXML pages for various applications and renders the pages through the media server  130  and provides an external interface via a web application server configuration. The SMU  140  is a management portal that enables service providers to provision and maintain subscriber accounts and manage network elements from a centralized web interface. The CDMS  160  stores voice messages, subscriber records, and manages specific application functions including notification. Each of these sub-systems are described in more detail following.  
      Each of the components in the next-generation communications platform is independently scalable and independently interconnected onto an IP network. Thus, the components can be geographically distributed but still operate as a single communications platform as long as they can communicate with each other over the IP network. This is a significant advantage of the present invention that is not available in state-of-the-art communication systems.  
      Signaling Gateway Function (SGF)  
      The SGF  120  offers a consolidated signaling interface creating a single virtual SS7 signaling point for the next generation communications platform. SS7 provides the extra horsepower networks need, whether large or small. A SIGTRAN interface (IETF SS7 telephony signaling over IP) to the multi-function media server  130  as well as IP Proxy functions are supported via the SGF  120 . Consolidating SS7 into a single component (in this case the SGF  120 ) of the next-generation communications platform provides the benefits of reduced point codes, cost efficiency in the design of the other components and easier maintenance.  
      Each signaling point in the SS7 network is uniquely identified by a numeric point code. Point codes are carried in signaling messages exchanged between signaling points to identify the source and destination of each message. Each signaling point uses a routing table to select the appropriate signaling path for each message.  
      There are three kinds of signaling points in the SS7 network: SSP (Service Switching Point), STP (Signal Transfer Point) and SCP (Service Control Point). SSPs are switches that originate, terminate or tandem calls. An SSP sends signaling messages to other SSPs to setup, manage and release voice circuits required to complete a call. An SSP may also send a query message to a centralized database (an SCP) to determine how to route a call (e.g., a toll-free 1-800/888 call in North America). An SCP sends a response to the originating SSP containing the routing number(s) associated with the dialed number. An alternate routing number may be used by the SSP if the primary number is busy or the call is unanswered within a specified time. Actual call features vary from network to network and from service to service.  
      Network traffic between signaling points may be routed via a packet switch called an STP. An STP routes each incoming message to an outgoing signaling link based on routing information contained in the SS7 message. Because it acts as a network hub, an STP provides improved utilization of the SS7 network by eliminating the need for direct links between signaling points. An STP may perform global title translation, a procedure by which the destination signaling point is determined from digits present in the signaling message (e.g., the dialed  800  number, calling card number or mobile subscriber identification number).  
      An STP can also act as a “firewall” to screen SS7 messages exchanged with other networks. Because the SS7 network is critical to call processing, SCPs and STPs are usually deployed in mated pair configurations in separate physical locations to ensure network-wide service in the event of an isolated failure. Links between signaling points are also provisioned in pairs. Traffic is shared across all links in the link set. If one of the links fails, the signaling traffic is rerouted over another link in the link set. The SS7 protocol provides both error correction and retransmission capabilities to allow continued service in the event of signaling point or link failures.  
      The availability of point codes is typically limited. The consolidation of signaling links eases the pressure on these resources or eliminates the need for additional point codes altogether. Thus, the consolidated signaling interface in the SGF  120  provides immediate network simplification and cost savings. The SGF  120  presents the appearance of a single identity to the SS7 network via the single “virtual” point code of the messaging network and recognizes and processes messages in a transparent manner. The SGF  120  can potentially reduce the maximum number of point codes needed in some cases from 50 to only four.  
      From a networking perspective, the SGF  120  looks like an STP to the rest of the network giving access to the various components of the next-generation communications platform through the use of virtual point codes. In accordance with the distributed aspects of the present invention, multiple SGFs may be incorporated into the system. In this configuration, multiple paths to the various components of the next-generation communications platform are available.  
      Each SGF  120  includes virtual point codes that are used to access the various components in the communications platform. Only one destination point code is necessary for the entire communications platform. The SGFs communicate with each other to synchronize the virtual point codes for the media servers and other components integrated into the communications platform. Thus, if one SGF fails, access to the communications platform is easily provided through another SGF.  
      This is significantly different and advantageous over each of the components in the next generation communications platform looking like synchronized SS7 stacks.  
      In and exemplary embodiment, the SGF  120  server supports N+1 fail over redundancy schemes and load sharing configurations and is built on an Intel server. A minimum of two SGFs is recommended for load sharing and redundancy purposes for increased availability. As with all platform components, SNMP alarming, logging, and transaction detail records are generated. Features, advantages and benefits of the SGF include:  
      Allows multiple media servers to share signaling links and point codes providing significant cost savings; 
          Provides concentrated SS7 signaling links;     Can provide one tnmk group across multiple multi-function media servers;     SGF  120  requires less SS7 links resulting in reduced monthly connection fees; and     The SGF  120  is a key component in the ability to implement an IP distributed architecture for the communications platform.        

      Another aspect of the present invention allows each SGF in the system to be coupled to an interface block that mimics a subset of an STP interface. In implementation, each SGF in the system includes a virtual point code that is used when accessing the SGF. Since each SGF looks like an STP to the switching network, the switching network can route any communications to any SGF by simply directing it towards a different STP. Thus, if a failure occurs, the system can still reach any SGF in the system. This technique advantageously alleviates the expense associated with obtaining and maintaining Destination Point Codes (DPC) within a system. Using this invention, only one DPC is required for the entire system. Other systems that provide such an STP interface, generally require a complex synchronization process to occur between the private networks attached to the STP interfaces. However, in this invention, the synchronization process is not necessary and thus, the system is substantially less complex. Referring to  FIG. 4 , a conceptual diagram of the employment of the SGFs is illustrated. The SGF&#39;s  410  look to the switch  420  as a standard STP and thus, the switch can communicate with any SGF through any STP. In addition, the switch can access a Media Server  430  on the platform through any SGF on the platform. Only one DPC is required for this architecture whereas in prior art systems, each media server would require its own DPC.  
      Media Server (MS)  
      The MS  130  terminates IP traffic from the SGF  120  and circuit-switched traffic from the PSTN  110 . The MS  130  is responsible for call set up and control within the platform architecture. The MS  130  processes input from the user in either voice, DTMF format or other signaling scheme (much like a web client gathers keyboard and mouse click input from a user). The MS  130  then presents the content back to the user in voice form (similar in principle to graphic and text displayed back to the user on a PC client). This client/server methodology is important in the platform architecture in that it enables rapid creation of new applications and quick utilization of content available on the World Wide Web.  
      The MS  130  processes incoming calls via requests to the AS  150  using HTTP. A load balancer preferably directs traffic arriving at the multi-function MS  130  to one of a plurality of ASs  150 . This functionality ensures that traffic is allocated evenly between active servers. The multi-function MS  130  works as the VoiceXML client on behalf of the end user in much the same manner as a client like Netscape works on behalf of an HTML user on a PC. A VoiceXML or CCXML browser residing on a multi-function media server interprets the VoiceXML documents for presentation to users.  
      VoiceXML is a standards-based scripting language for developing voice-enabled software applications. This means that developers use and leverage Web-based (HTML) development expertise in developing speech-based telephony applications.  
       FIG. 2  is a block diagram illustrating the inter-working of a media server  130  in a next generation communications platform. The media server  130  interfaces with the PSTN  110  through a mobile switch center  210  over a T1/E1 interface and/or an ISDN/PRI interface and through a class  5  switch  220  or similar switch through a T1/E1 interface. The media server  130  may also interface to an automatic speech recognition (ASR) server  230  and/or a text-to-speech server (TTS)  240 . The media server  130  may also provide voice over IP (VoIP) support based on the SIP, the H.323 or other standards through an appropriate interface  262  to an IP network  260 . In a typical embodiment, the VoIP can be supported through G.711 and G.723 voice encoding—techniques that are well known to those skilled in the art. Preferably, the media server  130  can include a built-in abstraction layer for interface with multiple speech vendors. Advantageously, this aspect of the media server  130  enables the elimination of dependency on a single ASR  230  or TTS  240  vendor.  
      In addition, in a preferable embodiment, the media server  130  is constructed of commercial-off-the-shelf (COTS) hardware and software components and is a carrier-grade server. Telephony interface and resource boards for telephony-specific applications can also be added. For instance, a facsimile card or software can be added to the media server  130  to manage facsimile termination.  
       FIG. 3  is a block diagram illustrating the integration of the facsimile feature into the media server  130 . A software based facsimile modem  310  is shown as installed within the media server  130  to provide support for the delivery and reception of facsimiles with regular fax machines  330  or IP fax machines  340 . Facsimile messages can be stored in a facsimile message store  320  under the control of the central data and message store  160  and be accessed via the application server  150 . Other preferred features of the media server  130  include built-in code and echo cancellation, maintaining call detail records (CDRs) to be used by service providers for billing purposes, and SNMP alarming, logging, and transaction detail records. The media server preferably connects to the other components in the platform through Ethernet connections.  
      Application Server (AS)  
      The modular design of the next-generation communications platform has the added advantage that it is easy to deploy enhanced services, such as voice dialing and voice navigation, unified communications solutions, multimedia messaging services, and presence &amp; availability management applications. Adding applications to the platform is accomplished via the addition of standard application servers  150  to the common platform.  
      Each application server  150  generates application documents (VoiceXML pages) in response to requests from the media server  130  via the internal Ethernet network. The application server  150  leverages a web application infrastructure to interface with back-end data stores (messages stores, user profile databases, content servers) to generate the VoiceXML based documents.  
      The overall web application infrastructure separates the core service logic (i.e., providing the business logic) from the presentation details (VoiceXML, CCXML, SALT, XHTML, WML) to provide a more extensible application architecture. The application server  150  utilizes Java 2 Enterprise Edition (J2EE) environment and Java Server Pages (JSP) to create the dynamic VoiceXML pages for the multi-function media server. Combining these technologies enables rapid incorporation of Speech Application Language Tags (SALT) to provide interoperability (multimodal) between applications like WAP, HTML, XHTML and voice—allowing the end user to simultaneously input data via voice command and receive presentation via WAP or HTML.  
      To create an environment for easy application development, the application server  150  preferably supports Template+JSPs. Applications are implemented in JSPs using an API for access to messaging functions. These JSPs are readily modifiable making changes in application behavior and creation of new applications very easy.  
      The cooperation of the media server  130  and the application server  150  allows for customization of certain features to be offered to particular subscribers. For instance, if a company has one office on the west coast and another office on the east coast, the operation of the telephone system, particularly the media server  130  and the application server  150  for each office may be quite different. For instance, the voice mail system and auto attendant may go to night-time mode in the east coast office at 6:00 PM Easter Time and at the west coast office at 6:00PM Pacific Time. In addition, the menu structure and prompts provided by the various offices may be substantially different. For instance, a dial by name directory would include different employees. With the present invention, separate media servers can be located at the two offices and the media servers  130  can render different communication services. The different communication services could be rendered from different application servers  150 , co-located with the media servers  130 , or through a common application server that can serve a communications services application based on the location or an ID of the media server  130 .  
      In addition, remotely located media servers  130  can provide common functionality to the various subscribers and callers as well as provide a seamless integration of the telephone system from the perspective of both the subscribers and users. A company may want to present a voicemail and auto attendant interface that seamlessly serves all locations of the company. The present invention can be utilized to provide such functionality. The application server  150  can render a tiered dial by name or menu selection function that first allows callers to select an office and then, an application server  150  and/or media server  130  invokes a particular function to provide dial by name services for that particular office. Alternatively, the application server  150  may maintain access to a single CDMS  160  or multiple CDMSs  160  that include all of the subscriber information for all offices of the company. The application server  150  can then provide a single level menu structure for a company wide dial by name directory.  
      Common Database and Message Store (CDMS)  
      The next-generation communications platform uses the CDMS  160  to store voice/audio messages, subscriber records, and to manage certain application functions such as notification schedules. The CDMS  160  is preferably designed with fully redundant components and utilizes reflective memory and Redundant Array of Independent Disks (RAID) technology for fault tolerance, immediate fail over and recovery. This ensures five  9 &#39;s availability for associated hardware and software components. Essential disk drive and RAID controller components are preferably “hot swappable” eliminating the need to power down the system for replacements. With the CDMS  160 , performance is optimized for the unique characteristics of voice messaging, eliminating the performance degrading, unnecessary e-mail-centric database functionality that comes with the searching and sorting of e-mail stores.  
      The CDMS  160  can utilize standard of the shelf e-mail storage systems. The message store is abstracted through the use of Java middleware that allows the selection of the message store to be transparent to the application, enabling each message type to be stored in the most efficient store possible.  
      System Management Unit (SMU)  
      The SMU  140  provides a centralized point for service providers to manage all network elements, providing remote access, maintenance, and backup functionality. The SMU  140  provides a single interface for provisioning, alarming, reports, and subscriber migration. The SMU  140  integrates and customizes systems with new elements and applications, and provides operational support and network management functions for carriers experiencing swiftly growing networks and exploding traffic volumes. Core features of the SMU component include:  
      Element Auto-Discovery—when service providers add new network elements, the SMU automatically recognizes them and includes the new elements in the graphical network map.  
      Graphical Network Map—a network/cluster map and map editor provides a snapshot of the entire network or cluster and facilitates quick problem identification and resolution.  
      Time Synchronization—a central time source ensures all network components maintain a uniform time reference across the entire messaging network—important for any distributed architecture.  
      Centralized network logging—logging for the entire messaging network is centralized on the SMU  140 .  
      The SMU  140  uses a dual processor computer and allows remote dial-in for access to the SMU  140  server as well as all other servers in the system via Telnet. Backup of system configurations and other critical data can also accomplished via the SMU.  
      Advantageously, the next-generation communications platform as described, allows for the quick and cost-effective deployment of a variety of applications, all from a single architectural source. Utilization of an open-source, Java-based Applications Creation environment makes this high degree of flexibility possible. Utilizing the communications platform, operators can create compelling bundles of best-in-class messaging and communications services ranging from basic call answering to forward looking applications like multimedia messaging and presence enabled solutions. To further facilitate the user experience, the next generation communications platform may also provide a web interface for subscribers to add and modify their preferences and features on a “self-serve” basis. This capability increases usage by consumers, improves customer loyalty, and also reduces service provider operating costs through fewer routine service calls.  
      Another advantage of the communications platform is the ability to include and incorporate a variety of applications. Whether the application is native on the platform or sourced from a third party vendor, the applications allow the communications platform to be customized for various customer needs and product differentiation. Some of the applications that can be easily incorporated into the communications platform include the following.  
      Voice Mail—Provides subscribers with a variety of features designed around the exchange of voice messages content.  
      Missed Call Notification—An extension of Caller ID and heavily demanded by wireless operators. Missed Call Notification picks up where Caller ID leaves off. Unlike Caller ID service, which only provides an incoming call number if the wireless phone is on and in the network coverage area, Missed Call Notification provides a continuous, network-based service providing subscribers with the added peace of mind that they will never miss an important call. Now when a subscriber is unable to receive calls, their Missed Call Notification service will capture and store the incoming call information until they become available. At that time, an SMS message containing a list of all missed calls is sent to the subscriber, allowing them to return calls at their convenience.  
      Multimedia Messaging—MMS allows subscribers to personalize their communications with up-to-the-minute multimedia content such as photos and music to create messaging that breaks the boundaries of traditional communication. With features like Message Composer, Photo Album and Greeting Cards, subscribers can send and receive dynamic multimedia content on their MMS-capable mobile phones, PDAs and PCs. Subscribers can also send multimedia content to non-MMS subscribers via the Internet, driving traffic to an operator&#39;s website thereby increasing subscriber usage.  
      Unified Communications—A complete package of services customized to your subscribers&#39; needs, including voice, fax and e-mail messaging, a single mailbox for all message types, an integrated address book, and special on-line management and personalization tools.  
      Multi-Party Personal Conference Service—Gives subscribers the ability to initiate instant conferences with friends/family.  
      Voice-Enabled Messaging Services—Powerful voice-controlled telephony services. Subscribers have access to an array of services through their own personal contact number and an easy-to-use voice interface that features natural language recognition and optional text-to-speech capability. Features common to a Voice Enabled Messaging Suite include navigation of voice mail via spoken commands, voice dialing and a voice controlled address book, delivered on an IP-based architecture compliant with industry standards such as VoiceXML and SALT.  
      Voice MMS—Enables subscribers to have greater access and control over their communication channels by allowing newly deposited voice mail messages to be delivered to an MMS-capable handset or e-mail box in the form of an audio clip. Subscribers can also share voice messages via e-mail and to forward voice messages to destinations outside of their voice mail system.  
      Another aspect of the present invention is a transaction vehicle for the delivery of control and data. Utilizing the same SGF  120  components as previously described, a transactional vehicle centered around the Transaction Capabilities Application Part (TCAP) component of the SS7 protocol is provided. More specifically, short messaging service can be provided within the distributed architecture of the next-generation communications platform utilizing the TCAP component of the SS7 protocol. A sender of a short message establishes communication with a media server  130  over the IP network. The sender gets the media server  130  to request the SGF  120  to send an SS7 TCAP message for the delivery of the short message. This technique brings the single point access node as described above for the STP Interface for SGF for call processing into transactional processing.  
      Another aspect of the present invention is the utilization of a portable application protocol interface (API). This aspect of the invention is directed towards an API that can be stacked in any device and provide a transactional capability. Advantageously, this invention allows a device to avoid the expense of implementing a full SS7 protocol stack. In the telephonic system, this is especially beneficial because the various components of the system are geographically distributed and thus cannot share the same SS7 stack.