# Patent

## Title
System and method for bypassing data from egress facilities

## Abstract

An open architecture platform bypasses data from the facilities of a telecommunications carrier, e.g. an incumbent local exchange carrier, by distinguishing between voice and data traffic, and handling voice and data traffic separately. An SS7 gateway receives and transmits SS7 signaling messages with the platform. When signaling for a call arrives, the SS7 gateway informs a control server on the platform. The control server manages the platform resources, including the SS7 gateway, tandem network access servers (NASs) and modem NASs. A tandem NAS receives the call over bearer channels. The control server determines whether the incoming call is voice traffic or data traffic, by the dialed number, and instructs the tandem NAS how to handle the call. Voiced traffic is transmitted to a switch for transmission from the platform. Data traffic is terminated at a modem NAS, where it is converted into a form suitable for a data network, such as a private data network or an Internet services provider (ISP). The converted data is sent by routers to the data network. The data network need not convert the data, as the function has already been provided by the platform. In lieu of a conversion, the modems can create a tunnel (a virtual private network) between a remote server and the data network.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of application Ser. No. 11/627,875, now U.S. Pat. No. 7,720,081, filed Jan. 26, 2007, which is a divisional of application Ser. No. 10/179,613, now U.S. Pat. No. 7,200,150, filed Jun. 24, 2002, which is a continuation of application Ser. No. 09/196,756, now U.S. Pat. No. 6,442,169, filed Nov. 20, 1998, which applications are incorporated herein by reference.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to telecommunications networks and, more particularly, to a system and method for the signaling, routing and other manipulation of voice and data calls within the public switched telephone network.
2. Related Art
Telecommunication networks were originally designed to connect one device, such as a telephone, to another device using switching services. Circuit-switched networks provide a dedicated, fixed amount of capacity (a “circuit”) between two devices for the entire duration of a transmission session.
Originally, a circuit was created manually, i.e., by a direct connection from a calling party to a human operator (a “ring down”) along with human cross-connection by the operator to a called party.
More recently, a circuit is set up between an originating switch and a destination switch using a process known as signaling. Signaling sets up, monitors, and releases connections in a circuit-switched system. Different signaling methods have been devised. Telephone systems formerly used in-band signaling to set up and “tear down” calls. Signals of an in-band signaling system are passed through the same channels as the information being transmitted. Early electromechanical switches used analog or multi-frequency (MF) in-band signaling. Thereafter, conventional residential telephones used in-band dual-tone multiple frequency (DTMF) signaling to connect to an end office switch. Here, the same wires (and frequencies on the wires) were used to dial a number (using pulses or tones), as are used to transmit voice information. However, in-band signaling permitted unscrupulous callers to use a device such as a whistle to mimic signaling sounds to commit fraud (e.g., to prematurely discontinue billing by an interexchange carrier (IXC), also known as long distance telephone company).
More recently, to prevent such fraud, out-of-band signaling systems were introduced that use, for example, a packet network for signaling that is separate from the circuit switched network used for carrying information. For example, integrated services digital network (ISDN) uses a separate channel, a data (D) channel, to pass signaling information out-of-band. Common Channel Interoffice Signaling (CCIS) is a network architecture for out-of-band signaling. A popular version of CCIS signaling is Signaling System 7 (SS7). SS7 is an internationally recognized system optimized for use in digital telecommunications networks.
SS7 out-of-band signaling provided additional benefits beyond fraud prevention. For example, out-of-band signaling eased quick adoption of advanced features (e.g., caller-id) by permitting modifications to the separate signaling network. In addition, the SS7 network enabled long distance “Equal Access” (i.e., 1+ dialing for access to any long distance carrier) as required under the terms of the modified final judgment (MFJ) requiring divestiture of the Regional Bell Operating Companies (RBOCs) from their parent company, AT&T.
While SS7 and other out-of-band signaling systems have advantages over in-band systems, they still have deficiencies. For example, the SS7 network is still more like X.25 rather than a broadband network. Also, SS7 is a limited protocol in that it only addresses setup, teardown, and monitoring of calls.
An SS7 network includes a variety of components. Service Switch Points (SSPs) are telephone offices which are directly connected to an SS7 network. All calls must originate in or be routed through an SSP switch. Calls are passed through connections between SSPs within the telecommunications network. A Signal Transfer Point (STP) is a component which passes signals between SSPs, other STPs, and Service Control Points (SCPs) for processing. An STP is a special application packet switch which operates to pass signaling information. Two STPs may be used together to provide redundancy.
An SCP is a special application computer which maintains information in a database required by users of the network. SCP databases may include, for example, a credit card database for verifying charge information or an “800” database for processing toll-free calls. The components in the SS7 network are connected by links. Typically, links between SSPs and STPs can be, for example, A, B, C, D, E or F links. Typically, redundant links are also used for connecting an SSP and its corresponding STPs. Customer premises equipment (CPE), such as a telephone, are connected to an SSP or an end office (EO).
To initiate a call in an SS7 telecommunications network, a calling party using a telephone connected to an originating end office (EO) switch, dials a telephone number of a called party. The telephone number is passed from the telephone to the SSP at the originating end office (referred to as the “ingress EO”) of the calling party's local exchange carrier (LEC). A LEC is commonly referred to as a local telephone company. First, the SSP will process triggers and internal route rules based on satisfaction of certain criteria. Second, the SSP will initiate further signals to another EO or access tandem (AT), for example, if necessary. The signaling information can be passed from the SSP to STPs, which route the signals for communication between the ingress EO and the terminating end office, or egress EO. The egress EO has a port designated by the telephone number of the called party. The call is set up as a direct connection between the EOs through tandem switches if no direct trunking exists or if direct trunking is full. If the call is a long distance call, i.e., between a calling party and a called party located in different local access transport areas (LATAs), then the call is connected through an inter exchange carrier (IXC) switch of any of a number of long distance companies. Such a long distance call is commonly referred to as an inter-LATA call. LECs and IXCs are collectively referred to as the public switched telephone network (PSTN).
Emergence of a competitive LEC (CLEC) was facilitated by passage of the Telecommunications Act of 1996, which authorized competition in the local phone service market. Traditional LECs or RBOCs are now also known as incumbent LECs (ILECs). Thus, CLECs compete with ILECs in providing local exchange services. A large cost associated with setting up and operating a CLEC is the equipment needed to circuit switch data and voice calls.
Since the LECs handle both voice and data communications, large amounts of information are communicated. Bandwidth concerns are always present. The PSTN still has deficiencies, particularly with regard to data communications, for such problems as network congestion and bottlenecks.
The PSTN is ill-equipped to handle the integration of data and voice communications. Today, data and voice calls are sent through the same network. Data communications are presently layered on top of voice switching.
Circuit switching is the process of setting up and keeping a circuit open between two or more users, such that the users have exclusive and full use of the circuit until the connection is released. Packet switching is like circuit switching in that it can also switch information between users. Unlike circuit switching, packet switching does not leave a circuit open on a dedicated basis. Packet switching has conventionally been a data switching technique. Packet switching separates a communication into pieces called packets. A packet can contain addressing information, such as, for example, a destination address. In packet switching, the addresses of a packet are read by a switch and the packet is then routed down a path toward a switch associated with the destination address. Different packets can take diverse paths to reach the eventual destination. Typically, in the last switching office before the packets reach the destination user, the packets can be assembled and sequenced.
A channel, also known as a circuit, is a 64 (Kbps) building block of T1 series. A circuit is derived from the digitization and coding of analog signals. Digitization involves taking 8000 samples per second (i.e., twice the highest voice frequency of 4,000 Hz) for voice traffic. When coded in 8 bit words a 64 Kbps building block is yielded. This circuit is termed a Level 0 Signal and is represented by DS-0 (Digital Signal at Level 0). Combining 24 of these channels into a serial bit stream using time division multiplexing (TDM) is performed on a frame-by-frame basis. A frame is a sample of all 24 channels (i.e., the multiplicative product of 24 and 8 bits is 192 bits) plus a synchronization bit called a framing bit, which yields a block of 193 bits. Frames are transmitted at a rate of 8,000 per second (corresponding to the sampling rate), thus creating a 1.544 Mbps (i.e., the product of 8,000 and 193 is 1.544 Mbps) transmission rate, which is the standard T1 rate. This rate is termed DS-1.
Queuing refers to the act of stacking or holding calls to be handled by a specific person, trunk or trunk group. Queuing theory deals with the study of the behavior of a system that uses queuing, such as a telephone system. Queuing is very important to the design of packet networks where speed of transmission more than offsets the delay of waiting for a transmission facility to become available.
Telephone call traffic is measured in terms of centi call seconds (CCS) (i.e., one hundred call seconds of telephone conversations). One hour of calling traffic, also known as an Erlang (named after a queuing theory engineer), is equal to 36 CCS (i.e., the product of 60 minutes per hour and 60 seconds per minute divided by 100, the theoretical limit of a trunk). An Erlang is used to forecast trunking and TDM switching matrix capacity. A “non-blocking” matrix (i.e., the same number of lines and trunks) can theoretically switch 36 CCS of traffic. Numerically, traffic on a trunk group, when measured in Erlangs, is equal to the average number of trunks in use during the hour in question. For example, if a group of trunks carries 20.25 Erlangs during an hour, a little more than 20 trunks were busy.
At times of high data traffic, the internal CCS of call traffic of the tandem and egress switches climbs, resulting in such problems as network blocking and busy signals. Data calls traditionally pass through tandem and egress switches before being switched to a Wide Area Network (WAN) access device. The tandem and egress switches have become bottlenecks.
Growth of the Internet has led to increased data communications traffic that has exacerbated the problem. Corporations that provide remote modem access to data networks provide dial-up and direct connections. One important example of such corporations are Internet Service Providers (ISPs) provide dial-up and direct connection access to Internet subscribers. Dial-up access is based on transmission using the serial line interface protocol (SLIP) or point-to-point protocol (PPP) to the ISP's network access device. An ISP's network access device can include a communications server. A communications server represents one of several devices connected to a local area network (LAN) or wide area network (WAN). A network router can be connected to the LAN. A network router can be, for example, a computer running routing software, or a dedicated routing device. The router's serial port is used to provide a high-speed communications connection from the ISP to an Internet network service provider (NSP).
Many ISPs are small, start-up companies that face challenges in obtaining the startup capital required to fund large capital expenditures required to purchase the data termination and protocol conversion equipment, including routers, communications servers, and racks filled with modems. ISPs must also expend significant sums of money to the ILEC for large numbers of access lines required to pass data calls through tandem and egress switches before being switched to WAN access devices. ISPs must pass on these costs to their subscribers.
Similarly, a business entity must also invest substantial capital to purchase communications equipment, when, for example, the entity needs to provide employees remote access to a private data network.
The attributes of modem or Internet-type data traffic are very different from those of voice traffic. First, the traffic is qualitatively different. The duration of data traffic (e.g., 20 minutes, 12 hours, or more) is typically longer than voice traffic (e.g., 3 minutes) and therefore requires different queuing theory. Ironically, a data call often does not even need access to the line all the time since an Internet call can contain “bursty traffic”, i.e., intermittent bursts of upstream and downstream traffic. Because voice and modem traffic are structurally different, the probability distribution must be adjusted accordingly. The statistical distribution for voice calls is an “exponential distribution,” i.e., most calls are 3 minutes or less in duration, and there is a rapidly decreasing number of calls lasting longer than 3 minutes. Data calls (e.g., modem, fax, internet, etc.) have a mean holding time on the order of 20 minutes, and the distribution of holding times instead of having an exponential distribution, has a “power law distribution,” meaning it is not extraordinary to encounter calls of very long duration such as, e.g., 12 hours, a day, or even longer.
Second, modem internet traffic is also quantitatively different from voice traffic. The Internet modem traffic generates much higher loads. Residential lines have been engineered expecting to generate loads of 3 or 4 CCS, and business lines, 5 or 6 CCS. If the same customer begins using the same line for Internet traffic, the load can easily double or triple.
Today, the public network is optimized for voice. However, modem traffic has overtaken voice in the local exchange. Queuing theory has not been adjusted for this occurrence, resulting in public network dysfunction. For example, growth in popularity of fixed rate, unlimited access services from ISPs has excessively burdened the PSTN circuit-switch infrastructure. Each unlimited access connection can tie up a dedicated circuit through a tandem switch and/or an egress end office (EO) switch. What is needed then is an improved system for handling data communications, which would allow data to bypass the local exchange's egress switches and the associated costs from local telephone companies.
SUMMARY OF THE INVENTION
The present invention includes a system implementation and a method implementation. The system implementation is directed to a system for bypassing the egress facilities of a telecommunications system. The system comprises a gateway, a network access server and a control server. The gateway communicates with a telecommunications carrier by receiving and transmitting signaling messages. The network access server terminates data calls for termination processing and/or for re-originating said data calls. The control server communicates with the gateway for distinguishing between voice calls and data calls received from the telecommunications carrier and for sending the data calls to the network access server.
The gateway communicates with a switch facility in the telecommunications carrier via the signaling messages. The switch can be, for example, a class 3/4 access tandem switch or a class 5 end office switch.
The gateway can be, for example, a first application program running on a host computer; and the control server can be a second application program running on the host computer or on a second host computer. The first application program and the second application program intercommunicate.
In one embodiment, the control server has a communications portion for communicating with the gateway. The communications portion of the control server and the gateway communicate, for example, via an X.25 protocol format, a transmission control program, internet protocol (TCP/IP) packet format, a user datagram protocol, internet protocol (UDP/IP) packet format. Many other formats are available as well.
In one embodiment, the control server has a communications portion for communicating with a communications portion of the network access server. The communications portion of the control server and the communications portion of the network access server communicate via a protocol such as the network access server (NAS) messaging interface (NMI) protocol (described below) and/or an IPDC protocol (provided in a publicly available document, as noted below).”
In one embodiment, the network access server extends a first network to a second network by establishing a protocol tunnel for the data calls. For example, the first network is a virtual private network and the second network is a data network. The tunnel is established using a point-to-point tunneling protocol (PPTP).
In an alternative embodiment to the latter, the network access server converts the data calls from a first digitized format into a second digitized format for delivery of the data calls to a destination data network. The network access server comprises a first device, this first device terminating the data calls on at least one modem. For example, this first device is a modem network access server bay.
In a preferred embodiment, the first digitized format can be a transmission control program, internet protocol (TCP/IP) packet format, or a user datagram protocol, internet protocol (UDP/IP) packet format, an asynchronous transfer mode (ATM) cell packet format, a point-to-point tunneling protocol (PPTP) format, a NETBIOS extended user interface (NETBEUI) protocol format, an Appletalk protocol format, a DECnet, BANYAN/VINES, an internet packet exchange (IPX) protocol format, and an internet control message protocol (ICMP) protocol format. The second format can be, for example, a serial line interface protocol (SLIP) protocol format, or a point-to-point (PPP) protocol format. However, the list of formats that can be used for the first format and the second format can be the same.
The network access server can comprise a second device for time division multiplexing the data calls onto the network access server. The second device can be a tandem network access server bay.
The system can further include a database for distinguishing between voice calls and data calls. The database includes a table comprising called party numbers and the terminating points corresponding to the called party numbers. If the control server determines that a called party number corresponds to a data modem, then the call is a data call.
In one embodiment, the system further includes a voice switch for switching the voice calls and for transmitting the voice calls from the system.
The system can be implemented as an open architecture platform that is leased by or owned by an incumbent local exchange carrier (ILEC), an interexchange carrier (IXC), a competitive local exchange carrier (CLEC), or an enhanced services provider. In one embodiment, the gateway, control server, network access server, and the voice switch are collocated. In another embodiment, the gateway, control server, network access server, and the voice switch are in different geographical regions.
The method implementation of the invention is directed to a method for bypassing data from egress facilities of a telecommunications carrier. The method includes establishing a call with the open architecture telecommunications system, determining whether the call is a voice call or a data call, and terminating the call onto a network access server for termination processing if the call is a data call.
The step of establishing a call with the telecommunications system includes receiving signaling information to set up a call coming into the open architecture telecommunications system, informing a control server that a call has arrived on the open architecture telecommunications system, and receiving the call at the open architecture telecommunications system. The step of receiving signaling information comprises receiving signaling information at a gateway. In one embodiment, signaling system 7 (SS7) signaling information is received at the gateway.
The step of determining whether the call is a voice call or a data call includes using a telephone number of a called party to determine whether the call is a voice call or a data call. The telephone number can be, for example, a number used to access at least one network device of an Internet Services Provider (ISP), at least one network device of a competitive local exchange (CLEC) carrier, or a customer premises equipment (CPE).
In one embodiment, the step of terminating the call onto a network access server for termination processing includes converting the call from a first protocol to a second protocol. The first protocol can include, for example, a transmission control program, internet protocol (TCP/IP) packet format, or a user datagram protocol, internet protocol (UDP/IP) packet format. The second protocol can be the same formats as well, though the second format is preferably different than the first protocol format.
In another embodiment, the step of terminating the call onto a network access server for termination processing includes providing a protocol tunnel from a first network to a second network. Here, it is possible to use a virtual private network protocol to extend the first network to the second network. The virtual private network protocol can be, for example, a point-to-point tunneling (PPTP) protocol. The first network can be a virtual private network, whereas the second network can be a data network.
The terminating step can further include terminating the call to a voice switch if the call is a voice call. The voice switch will switch and transmit the call.
The present invention provides a number of important features and advantages. First, the open architecture telecommunications system (or platform), employing SS7 signaling and open architecture protocol messaging, uses application logic to identify and direct incoming data calls straight to a terminal server. This permits the bypassing of a voice switch entirely. This results in significant cost savings for an entity (such as an ISP, an ILEC, or a CLEC) providing service, as compared to the conventional means of delivering data calls through the ILEC. This decrease in cost results partially from bypass of the egress ILEC end office switch for data traffic.
A further advantage for ISPs is that they are provided data in the digital form used by data networks (e.g., IP data packets), rather than the digital signals conventionally used by switched voice networks (e.g., PPP signals). Consequently, they need not perform costly modem conversion processes that would otherwise be necessary. The elimination of many telecommunications processes frees up the functions that ISPs, themselves, would have to perform to provide Internet access.
By separating voice and data traffic, and circuit-switching only the voice traffic through a traditional switch (e.g., a NORTEL DMS 500), the CLEC can use a smaller voice switch, decreasing the capital expense it must pass on to its customers (including ISPs). Thus, it becomes less expensive for the ISPs to route data traffic through a CLEC.
By differentiating between or separating the voice and data traffic on a single platform, different types of traffic can be optimally routed. Thus, for example, video traffic being transported over a modem, can be more efficiently routed over an appropriate carrier rather than through a dedicated circuit switched line.
The open architecture telecommunications system can virtually handle an infinite number of data modem traffic destined for Internet service providers (ISPs). This system is scalable by using fewer intelligent network access devices than conventionally used. The present invention obviates the need to purchase additional circuit switching hardware to support switching of data traffic.
The open architecture telecommunications system also enables the use of a modem pool at, for example, a CLEC. This is advantageous to the ISPs, or business entities owning private data networks, because it offloads complex functions from ISPs to a specialized platform (also known as a Network Service Provider (NSP)) and redistributes capital expenditures to the CLEC NSP. The CLEC NSP often has better access to investment capital than would an ISP. The CLEC NSP also benefits from economies of scale by servicing multiple ISPs with a large pool of modems.



BRIEF DESCRIPTION OF THE FIGURES
The present invention will be described with reference to the accompanying figures, wherein:
FIG. 1 is a block diagram providing an overview of a standard telecommunications network;
FIG. 2 is a block diagram illustrating an overview of a standard telecommunications network;
FIG. 3 illustrates a signaling network in greater detail;
FIG. 4 provides an overview of the present invention in that it provides an enhanced telecommunications network;
FIG. 5 illustrates an open architecture platform in detail;
FIG. 6 illustrates an object oriented or wire line protocol format Open Architecture SS7 Gateway application and SS7 adapter communicating directly with lower level libraries;
FIG. 7 illustrates an object oriented or wire line protocol format Open Architecture Control Server application;
FIG. 8 illustrates an exemplary Network Access Server bay;
FIG. 9A is a more elaborate view of the present invention;
FIG. 9B depicts multiple collocated or geographically diverse SS7 Gateways, Control Servers, Databases and Network Access Servers;
FIGS. 10A, 10B and 10C, are flow charts illustrating how an originating caller gains access to an open architecture platform;
FIG. 11 is a flow chart describing how the open architecture platform handles an inbound call;
FIG. 12 is a block diagram illustrating a complex outbound call;
FIG. 13 is a state diagram illustrating NAS side inbound call handling on the open architecture platform of the present invention;
FIGS. 14A and 14B are flow charts illustrating a state diagram of NAS side exception handling;
FIG. 15 is a state diagram illustrating NAS side release request handling;
FIG. 16 is a state diagram illustrating NAS side release TDM connection handling;
FIGS. 17A and 17B are state diagrams illustrating NAS side continuity test handling; and
FIGS. 18A and 18B are state diagrams illustrating NAS side outbound call handling initiated by a NAS for use in callback.



In the figures, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figure in which an element first appears is indicated by the leftmost digit(s) in the reference number.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Table of Contents
I. An Example Environment
II. Definitions
III. Introduction
A. An Overview of a Telecommunications Network
B. The Signaling Network
IV. The Present Invention
A. Overview of Data Bypass
B. Detailed Description of Data Bypass

    
    
        1. The Open Architecture Platform
        2. Data Bypass Operations
        3. NAS Bay to GW Communications
        4. Control Messages
        5. A Detailed View of the Control Messages
        
            a. Startup Messages
            b. Protocol Error Messages
            c. System Configuration Messages
            d. Telco Interface Configuration Messages
            e. Gateway Configuration Messages
            f. Maintenance-Status (State) Messages
            g. Continuity Test Messages
            h. Keepalive Test Messages
            i. LAN Test Messages
            j. DTMF Function Messages
            k. Inbound Call Handling Messages
            l. Outbound Call Handling Messages
            m. Pass-through Call Handling Messages
            n. Call Clearing Messages
        
        
        6. Control Message Parameters
        7. A Detailed View of the Control Messages
        
            a. Startup Flow
            b. Module Status Notification
            c. Line Status Notification Flow
            d. Blocking of Channels Flow
            e. Unblocking of Channels Flow
            f. Inbound Call Flow (Without Loopback Continuity Testing)
            g. Inbound Call Flow (With Loopback Continuity Testing)
            h. Outbound Call Flow (Starting from the NAS)
            i. Outbound Call Flow (Starting from the GW)
            j. Outbound Call Flow (Starting from the NAS, with Continuity Testing)
            k. TDM Pass-through Call Request Flow (Inter-Switch Connection)
            l. Call Releasing Flow (from NAS)
            m. Call Releasing Flow (from GW)
            n. Complex Outbound Call Request Flow Example
            o. Continuity Test Flow
            p. Keep-alive Test Flow
            q. Reset Request Flow

V. Conclusion

        
        
    
    


I. AN EXAMPLE ENVIRONMENT
The present invention is described in terms of an example environment. The example environment uses an open architecture platform for transmission of voice and data information received from a telecommunications carrier. As used herein, a telecommunications carrier can include domestic entities such as ILECs, CLECs, IXCs and Enhanced Service Providers (ESPs), as well as global entities recognized by those skilled in the art. In addition, as used herein a telecommunications system includes domestic systems used by such entities as ILECs, CLECs, IXCs and Enhanced Service Providers (ESPs), as well as global systems recognized by those skilled in the art.
In the preferred embodiment, the open architecture platform is implemented on a SUN Workstation model 450, available from Sun Microsystems, Inc., Palo Alto, Calif. The Sun workstation is interconnected with tandem network access service (NAS) bays and modem NAS bays and provides signaling and control functions. The tandem NAS bays and modem NAS bays can be ASCEND Access Concentrators, model TNT, available from Ascend Communications, Inc., Alameda, Calif. Voice traffic is received at the tandem NAS bays and routed to a NORTEL DMS switch, model DMS 500, available from NORTEL, Richardson, Tex. for routing to a called party.
Data traffic is received at the tandem NAS bays, and is routed to a modem NAS bay for modem termination, where the data traffic is modulated from, for example, the point-to-point protocol (PPP) to an auxiliary protocol such as, for example, the internet protocol (IP) for reorigination and transmission to a data network.
In the alternative, a virtual private networking protocol, such as the point-to-point tunneling protocol (PPTP), can be used to create a “tunnel” between a remote user and a data network. A tunnel permits a network administrator to extend a virtual private network from a server (e.g., a Windows NT server) to a data network (e.g., the Internet).
Where a conversion does take place, the converted data traffic is routed, for example, over an Ethernet/WAN (e.g., an Ethernet switch) connection to an internal backbone on the network, and sent to network routers for transmission to a data network, such as for example the network of an Internet Service Provider (ISP). Network routers can include, for example, a computer, such as the SUN workstation running routing software or a dedicated routing device such as various models from CISCO of San Jose, Calif., ASCEND of Alameda, Calif., NETOPIA of Alameda, Calif., or 3COM of Santa Clara, Calif.
Although the invention is described in terms of this example environment, it is important to note that description in these terms is provided for purposes of illustration only. It is not intended that the invention be limited to this example environment or to the precise inter-operations between the above-noted devices. In fact, after reading the following description, it will become apparent to a person skilled in the relevant art how to implement the invention in alternative environments.
The invention provides two functions which those skilled in the art will recognize can be implemented in many ways. The first function is that the invention bypasses data from the egress facilities used to complete a call. This includes, for example, the network nodes or systems used to terminate a switched voice call to a called party or to terminate a data connection with a data network.
The second function is that the invention provides for termination and reorigination of the call. In one embodiment, data is converted from a first digital form (e.g., in a point-to-point (PPP) digital format) used by the ingress telecommunications services provider (telecommunications carriers including enhanced service providers) to a second form used by a destination data network (e.g., IP data packets). This function is traditionally performed by the entities controlling the destination data network (e.g., ISPs).
In another embodiment, a virtual private networking protocol (e.g., a point-to-point tunneling protocol (PPTP)), can be used to create a “tunnel” between a remote user and a data network. The call terminates at the modem and reoriginates from that destination to another point.
After having the benefit of reading this disclosure, those skilled in the art will recognize that many types of resources, whether collocated or geographically separated, may be used to perform these functions.
II. DEFINITIONS
Table 1 below defines common telecommunications terminology. These terms are used throughout the remainder of the description of the invention.








TABLE 1





Term
Definition







local exchange carrier
LECs are providers of local telecommunications


(LEC)
services.


inter-exchange carrier
IXCs are providers of US domestic long distance


(IXC)
telecommunications services. AT&T, Sprint and MCI are



example IXCs.


incumbent LEC (ILEC)
ILECs are the traditional LECs, which include the



Regional Bell Operating Companies (RBOCs).


competitive LEC (CLEC)
CLECs are telecommunications services providers



capable of providing local services that compete with



ILECS. A CLEC may or may not handle IXC



services as well.


local access and transport area
A LATA is a region in which a LEC offers services.


(LATA)
There are 161 LATAs of these local geographical



areas within the United States.


end office (EO)
An EO is a class 5 switch used to switch local calls



within a LATA. Subscribers of the LEC are



connected (“homed”) to EOs, meaning that EOs are



the last switches to which the subscribers are



connected.


central office (CO)
A CO is a facility that houses an EO homed. EOs



are often called COs.


access tandem (AT)
An AT is a class 3/4 switch used to switch calls



between EOs in a LATA. An AT provides



subscribers access to the IXCs, to provide long



distance calling services. An access tandem is a



network node. Other network nodes include, for



example, a CLEC, or other enhanced service



provider (ESP), an international gateway or



global point-of-presence (GPOP), or an



intelligent peripheral(IP).


switching hierarchy or
An office class is a functional ranking of a telephone


office classification
central office switch depending on transmission



requirements and hierarchical relationship to other



switching centers. Prior to divestiture, an office



classification was the number assigned to offices



according to their hierarchical function in the U.S.



public switched network (PSTN). The following



class numbers are used: class 1 - Regional



Center(RC), class 2 - Sectional Center (SC), class 3 -



Primary Center (PC), class 4 - Toll Center (TC) if



operators are present or else Toll Point (TP), class 5 -



End Office (EO) a local central office. Any one



center handles traffic from one to two or more



centers lower in the hierarchy. Since divestiture and



with more intelligent software in switching offices,



these designations have become less firm. The class



5 switch was the closest to the end subscriber.



Technology has distributed technology closer to the



end user, diffusing traditional definitions of network



switching hierarchies and the class of switches.


class 5 switch
A class 5 switching office is an end office (EO) or



the lowest level of local and long distance switching,



a local central office. The switch closest to the end



subscriber.


class 4 switch
A class 4 switching office was a Toll Center (TC) if



operators were present or else a Toll Point (TP); an



access tandem (AT) has class 4 functionality.


class 3 switch
A class 3 switching office was a Primary Center



(PC); an access tandem (AT) has class 3



functionality.


class 1 switch
A class 1 switching office, the Regional Center(RC),



is the highest level of local and long distance



switching, or “office of last resort” to complete a



call.


transmission control
TCP/IP is a protocol that provides communications


protocol/internet protocol
between interconnected networks. The TCP/IP


(TCP/IP)
protocol is widely used on the Internet, which is a



network comprising several large networks



connected by high-speed connections.


internet protocol (IP)
IP is part of the TCP/IP protocols. It is used to



recognize incoming messages, route outgoing



messages, and keep track of Internet node addresses



(using a number to specify a TCP/IP host on the



Internet). IP corresponds to network layer of OSI.


transmission control
TCP is an end-to-end protocol that operates at the


protocol (TCP)
transport and sessions layers of OSI, providing



delivery of data bytes between processes running in



host computers via separation and sequencing of IP



packets.


point-to-point (PPP)
PPP is a protocol permitting a computer to establish


protocol
a connection with the Internet using a modem. PPP



supports high-quality graphical front ends, like



Netscape.


point-to-point tunneling
A virtual private networking protocol, point-to-point


protocol (PPTP)
tunneling protocol (PPTP), can be used to create a



“tunnel” between a remote user and a data network.



A tunnel permits a network administrator to extend a



virtual private network (VPN) from a server (e.g., a



Windows NT server) to a data network (e.g., the



Internet).


point of presence (POP)
A POP refers to the location within a LATA where



the IXC and LEC facilities interface.


global point of presence
A GPOP refers to the location where international


(GPOP)
telecommunications facilities and domestic facilities



interface, an international gateway POP.


bearer (B) channels
Bearer (B) channels are digital channels used to



carry both digital voice and digital data information.



An ISDN bearer channel is 64,000 bits per second,



which can carry PCM-digitized voice or data.


Internet service provider
An ISP is a company that provides Internet access to


(ISP)
subscribers.


integrated services digital
ISDN is a network that provides a standard for


network (ISDN)
communications (voice, data and signaling), end-to-



end digital transmission circuits, out-of-band



signaling, and a features significant amount of



bandwidth.


local area network (LAN)
A LAN is a communications network providing



connections between computers and peripheral



devices (e.g., printers and modems) over a relatively



short distance (e.g., within a building) under



standardized control.


private branch exchange
A PBX is a private switch located on the premises of


(PBX)
a user. The user is typically a private company



which desires to provide switching locally.


customer premises
CPE refers to devices residing on the premises of a


equipment (CPE)
customer and used to connect to a telephone



network, including ordinary telephones, key



telephone systems, PBXs, video conferencing



devices and modems.


wide area network (WAN)
A WAN is a data network that extends a LAN over



the circuits of a telecommunications carrier. The



carrier is typically a common carrier. A bridging



switch or a router is used to connect the LAN to the



WAN.


public switched telephone
The PSTN is the worldwide switched voice network.


network (PSTN)


packetized voice or voice
One example of packetized voice is voice over


over a backbone
internet protocol (VOIP). Voice over packet refers



to the carrying of telephony or voice traffic over a



data network, e.g. voice over frame, voice over



ATM, voice over Internet Protocol (IP), over virtual



private networks (VPNs), voice over a backbone, etc.


digitized data (or digital
Digitized data refers to analog data that has been


data)
sampled into a binary representation (i.e., comprising



sequences of 0's and 1's). Digitized data is less



susceptible to noise and attenuation distortions



because it is more easily regenerated to reconstruct



the original signal.


number planning area
NPA is an area code. NXX is an exchange,


(NPA); NXX
identifying the EO homed to the subscriber. (The



homed EO is typically called a central office (CO).)


digital access and cross-
A DACS is a device providing digital routing and


connect system (DACS)
switching functions for T1 lines, as well as DS0



portions of lines, for a multiple of T1 ports.


modified final judgment
Modified final judgment (MFJ) was the decision


(MFJ)
requiring divestiture of the Regional Bell Operating



Companies (RBOCs) from their parent company,



AT&T.


equal access
1 + dialing as used in US domestic calling for access



to any long distance carrier as required under the



terms of the modified final judgment (MFJ)



requiring divestiture of the Regional Bell Operating



Companies (RBOCs) from their parent company,



AT&T.


regional Bell operating
RBOCs are the Bell operating companies providing


companies (RBOCs)
LEC services after being divested from AT&T.


inter machine trunk (IMT)
An IMT is a circuit between two commonly-



connected switches.


network node
A network node is a generic term for the resources in



a telecommunications network, including switches,



DACS, regenerators, etc. Network nodes essentially



include all non-circuit (transport) devices. Other



network nodes can include, for example, equipment



of a CLEC, or other enhanced service provider



(ESP), a point-of-presence (POP), an international



gateway or global point-of-presence (GPOP).


intelligent peripheral
An intelligent peripheral is a network system (e.g. a



general purpose computer running application logic)



in the Advanced Intelligent Network Release 1



(AIN) architecture. It contains a resource control



execution environment (RCEE) functional group that



enables flexible information interactions between a



user and a network. An intelligent peripheral



provides resource management of devices such as



voice response units, voice announcers, and dual



tone multiple frequency (DTMF) sensors for caller-



activated services. The intelligent peripheral is



accessed by the service control point (SCP) when



services demand its interaction. Intelligent



peripherals provide an intelligent network with the



functionality to allow customers to define their



network needs themselves, without the use of



telephone company personnel. An intelligent



peripheral can provide a routing decision that it can



terminate, but perhaps cannot regenerate.


telecommunications carrier
A LEC, a CLEC, an IXC, an Enhanced Service



Provider (ESP), an intelligent peripheral (IP), an



international/global point-of-presence (GPOP), i.e.,



any provider of telecommunications services.


calling party
The calling party is the caller placing a call over any



kind of network from the origination end.


called party
The called party is the caller receiving a call sent



over a network at the destination or termination end.


ingress
Ingress refers to the connection from a calling party



or origination.


egress
Egress refers to the connection from a called party or



termination at the destination end of a network, to



the serving wire center (SWC).


ingress EO
The ingress EO is the node or serving wire center



(SVC) with a direct connection to the calling party,



the origination point. The calling party is “homed”



to the ingress EO.


egress EO
The egress EO is the node or destination EO with a



direct connection to the called party, the termination



point. The called party is “homed” to the egress EO.


signaling system 7 (SS7)
SS7 is a type of common channel interoffice



signaling (CCIS) used widely throughout the world.



The SS7 network provides the signaling functions of



indicating the arrival of calls, transmitting routing



and destination signals, and monitoring line and



circuit status.


centum call seconds (CCS)
Telephone call traffic is measured in terms of centum



call seconds (CCS) (i.e., one hundred call seconds of



telephone conversations). 1/36 of an Erlang.


Erlang
An Erlang (named after a queuing theory engineer)



is one hour of calling traffic, i.e. it is equal to 36



CCS (i.e., the product of 60 minutes per hour and 60



seconds per minute divided by 100). An Erlang is



used to forecast trunking and TDM switching matrix



capacity. A “non-blocking” matrix (i.e., the same



number of lines and trunks) can theoretically switch



36 CCS of traffic. Numerically, traffic on a trunk



group, when measured in Erlangs, is equal to the



average number of trunks in use during the hour in



question. Thus, if a group of trunks carries 20.25



Erlangs during an hour, a little more than 20 trunks



were busy.


Enhanced Service Provider
A network services provider.


(ESP)


trunk
A trunk connects an access tandem (AT) to an end



office (EO).


inter machine trunk (IMT)
An inter-machine trunk (IMT) is a circuit between



two commonly-connected switches.


Private Line with a dial
A private line is a direct channel specifically


tone
dedicated to a customer's use between two



specificed points. A private line with a dial tone



can connect a PBX or an ISP's access concentrator



to an end office (e.g. a channelized T1 or PRI). A



private line can also be known as a leased line.


plain old telephone system
The plain old telephone system (POTS) line provides


(POTS)
basic service supplying standard single line



telephones, telephone lines and access to the public



switched telephone network (PSTN). All POTS



lines work on loop start signaling. One “starts”



(seizes) a phone line or trunk by giving a supervisory



signal (e.g. taking the phone off hook). Loop start



signaling involves seizing a line by bridging through



a resistance the tip and ring (both wires) of a



telephone line.


integrated service digital
An ISDN Basic Rate Interface (BRI) line provides 2


network (ISDN) basic rate
bearer B channels and 1 data D line (known as


interface (BRI) line
“2B + D” over one or two pairs) to a subscriber.


ISDN primary rate interface
An ISDN Primary Rate Interface (PRI) line provides


(PRI)
the ISDN equivalent of a T1 circuit. The PRI



delivered to a customer's premises can provide



23B + D (in North America) or 30B + D (in Europe)



channels running at 1.544 megabits per second and



2.048 megabits per second, respectively.


Pipe or dedicated
A pipe or dedicated communications facility


communications facility
connects an ISP to the internet.









III. INTRODUCTION
A. An Overview of a Telecommunications Network
FIG. 1 is a block diagram providing an overview of a standard telecommunications network 100 providing local exchange carrier (LEC) services within a local access and transport area (LATA). Telecommunications network 100 provides a switched voice connection from a calling party 102 to a called party 110, as well as a data connection from calling party 102 to, for example, an Internet service provider (ISP) 112. Calling party 102 and called party 110 can be ordinary telephone equipment, key telephone systems, private branch exchanges (PBXs), or applications running on a host computer. ISP 112 can in the alternative be, for example, a private data network. For example, calling party 102 can be an employee working on a notebook computer at a remote location who is accessing his employer's private data network through, for example, a dial-up modem connection.
FIG. 1 also includes end offices (EOs) 104 and 108. EO 104 is called an ingress EO because it provides a connection from calling party 102 to public switched telephone network (PSTN) facilities. EO 108 is called an egress EO because it provides a connection from the PSTN facilities to a called party 110. In addition to ingress EO 104 and egress EO 108, the PSTN facilities associated with telecommunications network 100 include an access tandem (AT) 106 that provides access to one or more inter-exchange carriers (IXCs) for long distance traffic. Alternatively, it would be apparent to a person having ordinary skill in the art that AT 106 could also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral.
EO 104 and AT 106 are part of a switching hierarchy. EO 104 is known as a class 5 office and AT 106 is a class 3/4 office switch. Prior to the divestiture of the RBOCs from AT&T, an office classification was the number assigned to offices according to their hierarchical function in the U.S. public switched network (PSTN). An office class is a functional ranking of a telephone central office switch depending on transmission requirements and hierarchical relationship to other switching centers. A class 1 office was known as a Regional Center (RC), the highest level office, or the “office of last resort” to complete a call. A class 2 office was known as a Sectional Center (SC). A class 3 office was known as a Primary Center (PC). A class 4 office was known as either a Toll Center (TC) if operators were present, or otherwise as a Toll Point (TP). A class 5 office was an End Office (EO), i.e., a local central office, the lowest level for local and long distance switching, and was the closest to the end subscriber. Any one center handles traffic from one or more centers lower in the hierarchy. Since divestiture and with more intelligent software in switching offices, these designations have become less firm. Technology has distributed functionality closer to the end user, diffusing traditional definitions of network hierarchies and the class of switches.
Network 100 includes an Internet service provider (ISP) 112. The Internet is a well-known, worldwide network comprising several large networks connected together by data links. These links include, for example, Integrated Digital Services Network (ISDN), T1, T3, FDDI and SONET links. Alternatively, an internet can be a private network interconnecting a plurality of LANs and WANs, such as, for example, an intranet. ISP 112 provides Internet services for subscribers such as calling party 102.
To establish a connection with ISP 112, calling party 102 can use a host computer connected to a modem (modulator/demodulator). The modem will modulate data from the host computer into a form (traditionally an analog form) for transmission to the LEC facilities. Typically, the LEC facilities convert the incoming analog signal into a digital form. In one embodiment, the data is converted into the point-to-point protocol (PPP) format. (PPP is a well-known protocol that permits a computer to establish a connection with the Internet using a standard modem. It supports high-quality, graphical user-interfaces, such as Netscape.) As those skilled in the art will recognize, other formats are available, including a transmission control program, internet protocol (TCP/IP) packet format, a user datagram protocol, internet protocol (UDP/IP) packet format, an asynchronous transfer mode (ATM) cell packet format, a serial line interface protocol (SLIP) protocol format, a point-to-point (PPP) protocol format, a point-to-point tunneling protocol (PPTP) format, a NETBIOS extended user interface (NETBEUI) protocol format, an Appletalk protocol format, a DECnet, BANYAN/VINES, an internet packet exchange (IPX) protocol format, and an internet control message protocol (ICMP) protocol format.
Note that FIG. 1 and other figures described herein include lines which may refer to communications lines or which may refer to logical connections between network nodes, or systems, which are physically implemented by telecommunications carrier devices. These carrier devices include circuits and network nodes between the circuits including, for example, digital access and cross-connect system (DACS), regenerators, tandems, copper wires, and fiber optic cable. It would be apparent to persons of ordinary skill that alternative communications lines can be used to connect one or more telecommunications systems devices. Also, a telecommunications carrier as defined here, can include, for example, a LEC, a CLEC, an IXC, an Enhanced Service Provider (ESP), a global or international services provider such as a global point-of-presence (GPOP), and an intelligent peripheral.
EO 104 and AT 106 are connected by trunk 116. A trunk connects an AT to an EO. Trunk 116 can be called an inter machine trunk (IMT).
AT 106 and EO 108 are connected by a trunk 118 which can be an IMT. EO 108 and ISP 112 can be connected by a private line 120 with a dial tone. Private line 120 with a dial tone can be connected to a modem bay or access converter equipment at ISP 112. Private line 120 can also connect a PBX (not shown) to EO 108, for example. Examples of a private line are a channelized T1 or PRI. ISP 112 can also attach to the Internet by means of a pipe or dedicated communications facility. A pipe can be a dedicated communications facility. Private line 120 can handle data modem traffic to and from ISP 112.
Trunks 116 and 118 can handle switched voice traffic and data traffic. For example, trunks 116-118 can include digital signals DS1-DS4 transmitted over T1-T4 carriers. Table 2 provides typical carriers, along with their respective digital signals, number of channels, and bandwidth capacities.











TABLE 2









Bandwidth in



Digital
Number of
Designation 
Megabits per



signal
channels
of carrier
second (Mbps)




















DS0
1
None
0.064



DS1
24
T1
1.544



DS2
96
T2
6.312



DS3
672
T3
44.736



DS4
4032
T4
274.176









Alternatively, trunks 116 and 118 can include optical carriers (OCs), such as OC-1, OC-3, etc. Table 3 provides typical optical carriers, along with their respective synchronous transport signals (STSs), ITU designations, and bandwidth capacities.










TABLE 3







International




Electrical signal,
Telecommunications




or synchronous
Union
Bandwidth in


Optical carrier
transport signal
(ITU)
Megabits per


(OC) signal
(STS)
terminology
second (Mbps)


















OC-1 
STS-1 

51.84


OC-3 
STS-3 
STM-1
155.52


OC-9 
STS-9 
STM-3
466.56


OC-12
STS-12
STM-4
622.08


OC-18
STS-18
STM-6
933.12


OC-24
STS-24
STM-8
1244.16


OC-36
STS-36
 STM-12
1866.24


OC-48
STS-48
 STM-16
2488.32









As noted, private line 120 is a connection that can carry data modem traffic. A private line is a direct channel specifically dedicated to a customer's use between two specified points. A private line can also be known as a leased line. In one embodiment, private line 120 is an ISDN/primary rate interface (ISDN PRI) connection. An ISDN PRI connection includes a single signal channel (called a data or D channel) on a T1, with the remaining 23 channels being used as bearer or B channels. (Bearer channels are digital channels that bear voice and data information.) If multiple ISDN PRI lines are used, the signaling for all of the lines can be carried over a single D channel, freeing up the remaining lines to carry only bearer channels.
Network 100 also includes a CCIS network for call setup and call tear down. Specifically, FIG. 1 includes a Signaling System 7 (SS7) network 114. This SS7 network is described more fully below with reference to FIG. 3 below.
FIG. 2 is a block diagram illustrating an overview of a standard telecommunications network 200, providing both LEC and IXC carrier services between subscribers located in different LATAs. Telecommunications network 200 is similar to telecommunications network 100, except that calling party 102 and a called party 224 are located in different LATAs. In other words, calling party 102 is homed to ingress EO 104 in a first LATA, whereas called party 224 is homed to an egress EO 222 in a second LATA. Calls between subscribers in different LATAs are long distance calls that are typically routed to IXCs. Sample IXCs in the United States include AT&T, MCI and Sprint.
AT 106 provides connection to points of presence (POPs) 202, 204 and 206. IXCs 214, 216 and 218 provide connection between POPs 202, 204 and 206 (in the first LATA) and POPs 208, 210 and 212 (in the second LATA). POPs 208, 210 and 212, in turn, are connected to AT 220, which provides connection to egress EO 222. Called party 224 receives calls from EO 222, which is its homed EO. Alternatively, it would be apparent to a person having ordinary skill in the art that an AT 106 can also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral.
In addition to providing a voice connection from calling party 102 to called party 224, the PSTN provides calling party 102 a data connection to an ISP 226. ISP 226 is similar to ISP 112.
B. The Signaling Network
FIG. 3 illustrates SS7 network 114 in greater detail. SS7 network 114 is a separate network used to handle the set up, tear down, and supervision of calls between calling party 102 called party 110 (or ISP 226). SS7 network 114 includes service switching points (SSPs) 316, 318, 320 and 322, signal transfer points (STPs) 302, 304, 306, 308, 310 and 312, and service control point (SCP) 314.
In the SS7 network, the SSPs are the portions of the backbone switches providing SS7 functions. The SSPs can be, for example, a combination of a voice switch and an SS7 switch, or a computer connected to a voice switch. The SSPs communicate with the switches using primitives, and create packets for transmission over the SS7 network.
EOs 104, 222 and ATs 106, 220 can be respectively represented in SS7 network 114 as SSPs 316, 318, 320 and 322. Accordingly, the connections between EOs 104, 222 and ATs 106, 220 (presented as dashed lines) can be represented by connections 334, 336, 320 and 322. The types of these links are described below.
The STPs act as routers in the SS7 network, typically being provided as adjuncts to in-place switches. The STPs route messages from originating SSPs to destination SSPs. Architecturally, STPs can and are typically provided in “mated pairs” to provide redundancy in the event of congestion or failure and to share resources (i.e., load sharing is done automatically). As illustrated in FIG. 3, STPs can be arranged in hierarchical levels, to provide hierarchical routing of signaling messages. For example, mated STPs 302, 304 and mated STPs 306, 308 are at a first hierarchical level, while mated STPs 310, 312 are at a second hierarchical level.
SCPs provide database functions. SCPs can be used to provide advanced features in an SS7 network, including routing of special service numbers (e.g., 800 and 900 numbers), storing information regarding subscriber services, providing calling card validation and fraud protection, and offering advanced intelligent network (AIN) services. SCP 314 is connected to mated STPs 310 and 312.
In the SS7 network, there are unique links between the different network elements. Table 4 provides definitions for common SS7 links.
Referring to FIG. 3, mated STP pairs are connected by C links. For example, STPs 302, 304, mated STPs 306, 308, and mated STPs 310, 312 are connected by C links (not labeled). SSPs 316, 318 and SSPs 320, 322 are connected by F links 342 and 344.
Mated STPs 302, 304 and mated STPs 306, 308, which are at the same hierarchical level, are connected by B links 350, 352, 366 and 372. Mated STPs 302, 304 and mated STPs 310, 312, which are at different hierarchical levels, are connected by D links 346, 348, 354 and 356. Similarly, mated STPs 306, 308 and mated STPs 310, 312, which are at different hierarchical levels, are connected by D links 358, 360, 368 and 370.
SSPs 316, 318 and mated STPs 302, 304 are connected by A links 334 and 336. SSPs 320, 322 and mated STPs 306, 308 are connected by A links 338 and 340.
SSPs 316, 318 can also be connected to mated STPs 310, 312 by E links (not shown). Finally, mated STPs 310, 312 are connected to SCP 314 by A links 330 and 332.
For a more elaborate description of SS7 network topology, the reader is referred to Russell, Travis, Signaling System #7, McGraw-Hill, New York, N.Y. 10020, ISBN 0-07-054991-5, which is incorporated herein by reference in its entirety.








TABLE 4





SS7 link



terminology
Definitions







Access (A) 
A links connect SSPs to STPs, or SCPs to STPs,


links
providing network access and database access 



through the STPs.


Bridge (B) 
B links connect mated STPs to other mated STPs.


links



Cross (C) 
C links connect the STPs in a mated pair to one 



another.


links
During normal conditions, only network 



management messages are sent over C links


Diagonal (D) 
D links connect the mated STPs at a primary 


links
hierarchical level to mated STPs at a 



secondary hierarchical level.


Extended (E) 
E links connect SSPs to remote mated STPs, 


links
and are used in the event that the A links to 



home mated STPs are congested.


Fully associated 
F links provide direct connections between 


(F) links
local SSPs (bypassing STPs) in the event 



there is much traffic between SSPs, or if a 



direct connection to an STP is not available. F 



links are used only for call setup and call teardown.









IV. THE PRESENT INVENTION
A. Overview of Data Bypass
FIG. 4 includes an overview of an enhanced telecommunications network 400 according to the present invention. This invention relates to the convergence of two types of networks, i.e., voice and data networks. Telecommunications network 400 provides a bypass connection from the ingress EO 104 (a class 5 switch) or from AT 106 (a class 3/4 switch) to the called party 110 and ISP 112. Alternatively, it would be apparent to a person having ordinary skill in the art that an AT 106 can also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral. The connection is called a bypass connection because it bypasses the connections from the egress EO 108 to called party 110 and ISP 112. In other words, for example, the facilities of the incumbent LEC (ILEC) terminating the call of originating caller 102 are bypassed.
Telecommunications network 400 includes open architecture platform 402. Telecommunications network 400 also includes trunks 404 and 406, connection 408, and trunk 410, which, for example, respectively connect open architecture platform 402 to EO 104, to AT 106 (i.e., any telecommunications carrier), to ISP 112 (i.e., or a business entity's private data network), and to called party 110. In a preferred embodiment, trunks 404 and 406 can handle both data and voice traffic. However, trunks 404 and 406 must be capable of handling at least data traffic. In a preferred embodiment, connection 408 and trunk 410 can handle data or voice traffic. However, connection 408 must be capable of handling at least data traffic (i.e. including any type of digitized data). It should also be apparent to a person having ordinary skill, that connection 408, for example, is a logical connection that can contain various network devices.
As noted, open architecture platform 402 can receive both voice and data traffic. This traffic can be received from any network node of a telecommunications carrier. A telecommunications carrier can include, for example, a LEC, a CLEC, an IXC, and an Enhanced Service Provider (ESP). In a preferred embodiment, this traffic is received from a network node which is, for example, a class 5 switch, such as EO 104, or from a class 3/4 switch, such as AT 106. Alternatively, the network system can also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral. Accordingly, open architecture platform 402 integrates both voice and data traffic on a single platform.
Data traffic refers, for example, to a data connection between a calling party 102 (using a modem) and a server 412 in ISP 112. A data connection is established between calling party 102 and EO 104, then over a trunk 404 to open architecture platform 402, then over a connection 408 to ISP 112, and then over a connection 414 to server 412. Alternatively, the connection can be established from calling party 102 to EO 104, then to AT 106, then over trunk 406 to open architecture platform 402, then over connection 408 to ISP 112, and then over connection 414 to server 412.
Voice traffic refers, for example, to a switched voice connection between calling party 102 and called party 110. It is important to note that this is on a point-to-point dedicated path, i.e., that bandwidth is allocated whether it is used or not. A switched voice connection is established between calling party 102 and EO 104, then over trunk 404 to open architecture platform 402, then over trunk 410 to called party 110. Alternatively, the connection can be established from calling party 102 to EO 104 and then to AT 106, then over trunk 406 to open architecture platform 402, then over trunk 410 to called party 110. In another embodiment, AT 106 can also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral.
Open architecture platform 402, and communications links 404, 406, 408 and 410 comprise the resources of an ILEC or a competitive LEC (CLEC). A CLEC may or may not provide inter-LATA calls, which are traditionally handled by IXCs.
B. Detailed Description of Data Bypass
1. The Open Architecture Platform
FIG. 5 illustrates open architecture platform 402 in detail. Open architecture platform 402 includes an open architecture switch 502 and a voice switch 506. Open architecture platform 402 receives data and voice traffic from the PSTN (over communications links 404 and 406) and separates data traffic from voice traffic. Data traffic is handled by open architecture switch 502, while voice traffic is handled by voice switch 506.
Voice calls switched by voice switch 506 are sent out from the open architecture platform 402. For example, an outbound voice call is sent from voice switch 506 over communications link 410 to called party 110.
On the other hand, outbound data calls are passed onto a modem NAS bay (which can be a resource on open architecture switch 502) for modem termination. For example, a data signal (e.g., in the PPP protocol) can be converted to protocol used by data networks (e.g., into internet protocol (IP) data packets), for transmission over routers to a data network, such as an ISP. Specifically, an outbound data call will be sent to modem NAS bay 514, then to routers (not shown), and then sent to ISP 112 over communications link 408. As another example, a virtual private networking protocol can be used to create a “tunnel” between the remote user and a data network. For example, calling party 102, using a server that supports a tunnel protocol (e.g., PPTP) will have an extended virtual private network connection with a data network, such as ISP 112.
As noted, open architecture platform 402 comprises open architecture switch 502 and voice switch 506. Open architecture switch 502 includes gateway (GW) 508, tandem network access server (NAS) bay 504, and modem NAS bay 514.
GW 508 comprises SS7 gateway (SS7 GW) 512, control server 510, and database 516 communicating with control server 510. GW 508 can include multiple SS7 GWs 512 and multiple control servers 510 (each having one or more databases 516). Database 516 can be internal to GW 508 or alternatively, external to GW 508.
It is important to note that the open architecture platform is defined by the function of the resources comprising it, and how these resources are interrelated. Accordingly, there is no reason that GW 508, tandem NAS bay 504, and modem NAS bay 514 would be required to be collocated, or limited to a particular geographical area, see FIG. 9B, below. Further, the architecture is infinitely scalable over geographic boundaries. As long as any resources match the functions and interoperabilities defined herein, then such resources comprise open architecture platform 402. The same holds true for the subcomponents comprising any platform resources, e.g., the subcomponents of GW 508 (defined below).
Gateway 508 has two functions: interfacing with the CCIS signaling network (e.g., the SS7 signaling network 114) and interfacing with a plurality of control servers to control a plurality of NAS bays. SS7 GW 512 provides the first function of providing an interface to the SS7 signaling network 114. The SS7 signaling information is conveyed to control server 510.
Control server 510 provides the second function of controlling one or more NAS bays which comprise resources of open architecture switch 502. Specifically, control server 510 communicates with tandem NAS bay 504 and modem NAS bay 514. This communication is performed via a protocol understood by the open architecture platform 402 resources, referred to herein as an open architecture protocol.
The open architecture protocol is represented by dotted lines 518 and 520. In one embodiment, the open architecture protocol is the network access server (NAS) messaging interface (NMI) protocol, created by XCom Technologies Inc. This protocol is defined by a series of control messages, which are defined below in table form. Another protocol is called the Internet Protocol Device Control (IPDC), recently released by a Technical Advisory Council (TAC) and Level 3 Communications, Inc. The IPDC specification, which is incorporated herein by reference in its entirety, is available in its current draft on the Level 3 Communications web site http://www.Level3.com. It will be apparent to those skilled in the art that any comparable protocol will suffice, so long as the protocol permits the resources of the open architecture platform 402 to communicate with one another.
In one embodiment, as depicted in FIG. 9B, below, one or more of SS7 GW 512, control server 510, database 516, and NAS are geographically diverse devices (or applications running on devices). For example, these devices can be connected by communications links using Ethernet, frame relay, asynchronous transfer mode (ATM), or any other conceivable protocols. In another embodiment, one or more of SS7 GW 512, control server 510, database 516, and NAS 902 are collocated devices (or applications running on devices), see FIG. 9B.
In a preferred embodiment, SS7 GW 512 and control server 510 are applications running on one or more collocated host computers. Alternatively, the applications can be run on one or more geographically diverse computers. For example, the host computers can be one or more redundantly interconnected SUN workstations, model 450, for example, available from Sun Microsystems. FIGS. 6 and 7 below are representations used to illustrate the intercommunications between SS7 GW 512 and control server 510 in the preferred embodiment.
FIG. 6 symbolically illustrates an example SS7 GW 512 application (as implemented using computer programs). The SS7 GW 512 application, labeled open architecture platform (OAP) SS7 GW application 600, provides communications between SS7 network 114 and open architecture switch 502. The SS7 signaling information is translated into, for example, an object-oriented, or wire line protocol format form for cross-platform compatibility, ease of transport, and parsing.
As illustrated in FIG. 6, OAP SS7 adapter 602 communicates directly with the lower level libraries, such as TCP/UDP 604 and IP 606, provided by manufacturers of SS7 interface cards and by manufacturers of host computers used in particular applications. OAP SS7 comservice 608 of OAP comservice 610 queues messages between OAP SS7 adapter 602 and the remainder of OAP SS7 GW application 600. It is important to note that any number of protocols recognized by those skilled in the art can be used. For example, instead of TCP/IP or UDP/IP, the X.25 protocol can be used instead.
OAP task master 620 maintains a pool of threads that are assigned to one or more OAP task slaves 622. OAP SS7 GW application 600 is cued by an OAP metronome 624 to read tasks from OAP scheduler 626. OAP task slave 622 is an abstract base class from which is derived a number of unique slaves that may initiate SS7 signals in response to messaging from SS7 network 114.
Messages from SS7 network 114 are received through SS7 adapter 602 and passed to OAP comservice 610 and OAP task master 620. OAP task master 620 schedules tasks to respond to each of the messages. Each message is then passed to OAP comservice 610 again to be transferred to an appropriate control server 510.
Messages may also be stored in OAP historian 628. If appropriate, the tasks from OAP scheduler 626 are performed and appropriate messages are passed back to SS7 network 114 through OAP adapter 602.
The processing of messages from control servers 510 operates in a similar manner. The messages come through OAP comservice 610 and are passed to OAP task master 620. OAP task master 620 then determines appropriate tasks, if any, and transfers the messages on to the adapter to be sent on SS7 network 114.
An example control server 510 application (as implemented using computer programs) is illustrated symbolically in FIG. 7. FIG. 7 illustrates the OAP control server application 700, which is a call processing coordinator.
OAP control server application 700 receives SS7 signals in object or wire line protocol form from SS7 GW 512. Based upon the signals, it handles resource allocation, signaling responses and translation services.
OAP comservice 708 is similar to OAP comservice 610 (in SS7 GW 512) because it operates to receive and send messages between itself and SS7 GW application 600. OAP task master 710 determines and schedules tasks to be performed by OAP control server application 700. OAP task slave 712 is an abstract base class from which are derived unique classes for each message.
OAP translator 714 object or wire line protocol format maps telephone numbers onto OAP database 716. OAP database 716 contains the destination of the call, any class functions associated with the call, the type of routing algorithm that should be used, and a status associated with the telephone number. OAP router service 718 is an object or wire line protocol which transports requests for routing paths, including both delivery and receipt of responses.
OAP state 720 is a collection of data on the state of each circuit identifier code (CIC) which exists between a given SS7 GW 512 originating point code (OPC) and a destination point code (DPC). This data includes the current status of the trunk and information on recent messaging. The roles of the CIC, the OPC and the DPC with respect to SS7 network 114 are discussed in greater detail below.
OAP NAS comservice 706 is a communications object or wire line protocol format that is responsible for receipt and delivery of messages from NAS bays 504 and 514. When a message is received from SS7 GW 512, it is handed to OAP task master 710. OAP task master 710 instantiates OAP task slave 712 object or wire line protocol format suitable for the particular type of message. If a call transaction is initiated, OAP task slave 712 requests information concerning the called subscriber from OAP translator 714, and a route to reach the subscriber from OAP router service 718. OAP state 720 is updated to indicate that a call is in progress from the CIC associated with the message. Finally, NAS comservice 706 signals NAS bays 504, 514 to instantiate the route for the call.
When a NAS bay responds with a control message, OAP NAS comservice 706 converts the message into an object or wire line protocol format and passes the object or wire line protocol format to OAP task master 710. OAP task master 710 instantiates a suitable OAP task slave 712. By checking OAP state 720, task slave 720 correlates the message with an earlier received message from OAP SS7 GW application 600, and formulates a response message to be delivered to OAP SS7 GW application 600 through OAP comservice 708.
Maintenance and Monitoring interface (MMI) 722 is a graphical user interface that communicates with either SS7 gateway application 600 or control server application 700 to update the starting configuration or the running state, and to monitor and modify various runtime factors. Such factors may include in-progress calls, circuit supervisory information, circuit deployment and maintenance, and similar activities. OAP router service 718 runs as a query daemon, providing a variety of routing strategies for the distribution of incoming and outgoing calls across the large, redundant network.
FIG. 8 illustrates an exemplary NAS bay 802. NAS bay 802 is a generic view of either tandem NAS bay 504 or modem NAS bay 514. NAS bay 802 includes modules 804, 806, 808, and 810. Each of these modules is a slot card used to implement one or more interfaces with network lines. A line is a set of channels (e.g., a line on a T1 carrier). A channel is a time-slot on a line. Accordingly, each connection established with a NAS bay 802 can be uniquely identified by a module/line/channel identifier. Table 5 provides definitions for NAS bay terms.









TABLE 5






NAS bay terminology
Definitions








network access server
A NAS bay is a facility that houses



(NAS) bay
modules. Lines (having channels) are




connected to the modules. Each




connection into the bay can be uniquely




identified by a module/line/channel




identifier.



module
Modules are slot cards that receive




communication lines, and perform




functions on the channels of the lines.




Modules can be used to perform time




modulation and demodulation, to name




a few functions.



line
A line is a set of channels (e.g., a line on




a T1 carrier) interconnected with




modules.



channel
A channel is a time-slot on a line.









Referring back to FIG. 5, tandem NAS bay 504 receives data and voice traffic from the PSTN (i.e., from the EO 104 over connection 404 or from AT 106 over connection 406). Call traffic can also originate from, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral. Tandem NAS bay 504 also cross-connects an incoming data call to modem NAS bay 514 through a matrix using time division multiplexing (TDM). This function, of providing pass-through of data, is referred to herein as data bypass.
Modem NAS bay 514 terminates a data call to one of its modems and the modems allow for the device to convert the inbound data call from one protocol to another. In lieu of modem NAS bay 514, any art-recognized devices providing the functions of modulation and demodulation can be used. Examples include a software implementation (an application running on a computer), a modem using a digital signal processor (DSP), or a data service unit/channel service unit (DSU/CSU). In one embodiment, modem NAS bay 514 can provide the modulation/demodulation function, of converting the signal from a first data format used by the telecommunications services provider that provides access to the open architecture platform 402 (e.g., in PPP format) to a second format (e.g., IP data packets) used by a destination data network such as ISP 112. As those skilled in the art will recognize, the particular second format need not be limited to IP data packets, depending primarily on the destination data network. As those skilled in the art will recognize, other protocol formats include a transmission control program, internet protocol (TCP/IP) packet format, a user datagram protocol, internet protocol (UDP/IP) packet format, routing table protocol (RTP) (e.g., Banyan VINES) format, an asynchronous transfer mode (ATM) cell packet format, a serial line interface protocol (SLIP) protocol format, a point-to-point (PPP) protocol format, a point to point tunneling protocol (PPTP) format, a NETBIOS extended user interface (NETBEUI) protocol format, an Appletalk protocol format, a DECNet format, and an internet packet exchange (IPX) protocol format.
In the alternative, a virtual private networking protocol can be used to create a “tunnel” between a remote user (e.g., calling party 102 using a server that supports tunneling) and the destination data network (e.g., ISP 112). One example of a virtual private networking protocol is PPTP.
An exemplary modem NAS bay 514 is an ASCEND access concentrator, model TNT, available from Ascend Communications, Inc., which is analogous to a NAS bay 802 with modems functioning on modules 804, 806, 808, and 810. Those skilled in the art will recognize that the modem function described above is conventionally performed by the destination data networks (e.g., ISP 112), not by an ILEC or a CLEC. In this sense, the present invention simplifies the functions of the destination data network providers, such as ISPs.
It must be noted that it is not necessary to implement the present invention by way of conventional NAS devices. Any network elements providing the dual functions of data bypass (i.e., as provided by tandem NAS bay 504) and conversion of data by means of modem termination into a format usable by a data network (i.e., as provided by modem NAS bay 514) will suffice. Those skilled in the art will recognize that a number of network devices can be combined to provide these functions.
As those skilled in the art will recognize, transmission control protocol (TCP) and internet protocol (IP) (collectively called TCP/IP) form a packet switching protocol comprised of the TCP and IP protocols, which are layers of protocols that act together. IP is a protocol that functions at the network layer of the Open Systems Interconnect (OSI) data network architecture model, and as noted, provides packetizing of data into units also called datagrams, containing address information. TCP is a protocol that functions at the session and transport layers of the OSI data model, providing the separation, transmission, retransmitting, and sequencing of data packets. TCP establishes a connection between two systems intending to exchange data, performing messaging control functions. IP is said to “ride on top of” TCP, i.e., IP is a simpler protocol than TCP in that IP only addresses and sends. TCP breaks a message down into IP packets and uses CHECKSUM error checking logic to guaranty delivery of the message from the first system to the second.
It is important to note that this invention deals with the convergence of voice and data networks. The reader should appreciate that voice networks and data networks were formerly two separate networks. The office classification switching hierarchy discussed above is a voice network architecture and has no correlation to the OSI model which is a data networking architecture.
It is also important to note that open architecture switch 502 can include one or more of gateways 508, one or more tandem network access server (NAS) bays 504 and one or more modem NAS bays 514. Therefore, the number of these elements is not important, so long as their respective functions are met.
FIG. 9A is a more elaborate view of the open architecture platform of the invention. The open architecture platform shown in FIG. 9A is the same as open architecture platform 402 (shown in FIG. 5), except for the additional resources described below.
In FIG. 9A, NAS bay 902 provides both the tandem functions of tandem NAS bay 504 and the modem functions of modem NAS bay 514. In other words, NAS bay 902 will provide the data bypass function of tandem NAS bay 504, as well as the modem termination function of modem NAS bay 514. Voice traffic is transmitted over trunks 930 or 932 to voice switch 506. Voice switch 506 can transmit the voice traffic, for example, over private line 934 to PBX 912.
If the call comprises data traffic, NAS bay 902 will use modems to convert the incoming data call into a form suitable for a destination data network (e.g., PPP data packets) for transmission to other data nodes over open architecture platform 402. For example, the resulting data packets are transmitted over an Ethernet/WAN connection 903 (using an Ethernet/WAN protocol), in conjunction with TCP/IP. It would be apparent to one of skill in the art that alternative network architecture could be used, such as, for example, FDDI, SONET, ATM, etc.
Connection 903 terminates in internal backbone 936. Internal backbone 936 can be any type of data link. Routers 904, 906 route the IP data packets from internal backbone 936 to ISPs 938, 940. Exemplary network routers include network routers from various companies such as, CISCO, 3COM, NETOPIA, and NORTEL, or a host computer running routing software. Specifically, the data packets are transmitted from router 904 to router 908 in ISP 938, and from router 906 to router 910 in ISP 940. Thus, the customers of ISPs 938, 940 can dial into communication servers at the ISP location, which can dedicated routers 908, 910. Thus, ISPs 938, 940 can route data traffic to routers on open architecture platform 402.
In one embodiment, ISP 948 can use a network service provider (NSP) to provide a modem pool for use by the customers of ISP 948. A CLEC implementing open architecture platform 402 can comprise an NSP. Modems in NAS bay 902 can be used by subscribers of ISPs 938, 940 and 948 for interconnectivity, and traffic can also be routed to other network nodes via the routers. Modem pooling at the NSP level reduces capital expenditures by ISPs 938, 940, 948.
The invention enables network access point (NAP) switching which involves exchanging data traffic on the architecture. A NAP switches the call based on routing instructions it receives. Online services can be performed so-called “on the box.”
NAS bay 942 can be the same type of device as NAS bay 902, in that it provides both the tandem functions of tandem NAS bay 504, and the modem functions of modem NAS bay 514. NAS bay 942 is used to represent other connections that can be established with open architecture platform 402.
Calling party 914 is another party that can establish a data connection using a modem connected to a host computer. However, calling party 914, via its host computer, has the additional feature of providing voice over IP (VoIP) service over communications link 944.
PBX 916 is a centralized switch providing its collocated customers both switching and access to NAS bay 942. This access is provided over T1/ISDN PRI private line 946.
It is possible to access open architecture platform 402 using any type of digital subscriber line (DSL) connection. Calling party 924 and computer 922 access NAS bay 942 over a high bit rate DSL (HDSL), known as a single pair HDSL (SDSL) 920. HDSL can place a two-way T1 on a normal unshielded, bridged (but not loaded) twisted pair copper wire loop. In an embodiment of SDSL, an existing single pair copper wire on the local loop is used to transmit full duplex data at up to 768 Kbps. Transmission at 1.54 Mbps is achieved by using two SDSL lines, i.e., two pairs of wires.
SDSL 920 permits simultaneous voice and data transmission through a DSL device 918 (e.g., a splitter), which can be collocated with calling party 924 and computer 922. Alternatively, access can be obtained without a splitter device. In addition, calling party 924 and computer 922 can access NAS bay 942 over ISDN DSL (IDSL) link 926. In an embodiment of IDSL, an existing local loop, i.e., a single pair of copper wires, is used to transmit full duplex data at 128 Kbps. Alternatively, calling party 924 and computer 922 can access NAS bay 942 over xDSL 928. In an embodiment of xDSL, an existing local loop, i.e., a single pair of copper wires, is used to transmit digital subscriber line communications.
In one embodiment of the invention, a CLEC implementing open architecture platform 402 can accept data traffic from other CLECs or ILECs, providing data bypass for the egress leg of data calls. In such an embodiment, the implementing CLEC can charge back the other CLECs or ILECs an “unbundled element” for providing this service to the egress facilities involved (i.e., the egress EOs belonging to the ILECs or used by the other CLECs'). It is important to note that reciprocal compensation does not exist everywhere and other arrangements do exist. While this is the predominant arrangement, this is not necessarily the only arrangement. This approach, of having an NSP/CLEC charge back an ILEC or other CLEC for offloading of data traffic, can save the offloaded CLEC or ILEC significant capital expenditures related to the switching of data traffic.
Voice traffic is transmitted over trunks 930 or 932 to voice switch 506. Voice switch 506 can transmit the voice traffic, for example, over private line 934 to PBX 912.
2. Data Bypass Operations
FIGS. 10A-10B depict flow charts illustrating how an originating caller gains access to open architecture platform 402. FIGS. 10A-10B are described with reference to FIGS. 1, 4, 5 and 9.
FIG. 10A depicts a method 1000 for receiving an inbound call which bypasses the facilities of an egress switch according to the present invention. Alternatively, other call flows are possible, including a call requiring a modem calling back for security reasons, using outbound calling from open architecture platform 402.
In step 1002 of FIG. 10A, the technique receives signaling information to set up data calls and voice calls from a calling party to a called party. In step 1004, the technique converts the signaling information into an open architecture protocol format. In step 1006, data calls and voice calls are received at open architecture switch 502. In step 1008, the technique distinguishes between data calls and voice calls. In step 1010, the technique controls NASs, i.e., NAS bays 504 and 514, using the open architecture protocol. In step 1012, the method terminates data calls to modems in a modem NAS bay, e.g., in modem NAS 514, for conversion to a packetized data format for transmission to network nodes. Alternatively, in step 1012, a tunnel is established between the user and the destination data network. In step 1014, the method transmits voice calls to a voice switch for transmission to the called party.
FIGS. 10B and 10C depict more detailed description of the technique outlined in FIG. 10A. Specifically, these figures depict an inbound call flow into open architecture platform 402. An inbound call is where an incoming call (into the open architecture platform) is connected to a called party (for a voice connection) or an ISP (for a data connection).
Referring to FIG. 10B, in step 1018 an originating caller 102 (shown in FIG. 1) gains access to LEC facilities. This is performed according to known methods as described with respect to FIG. 1. As one example, originating caller 102, using a telephone, can go off-hook to place a switched voice call to the LEC facilities. As another example, calling party 102 can use a host computer, in concert with a modem, to establish a data connection with the LEC facilities (i.e., the modem of calling party 102 takes the line off-hook). As those skilled in the art will recognize, any of the access methods described with respect to FIG. 9A, in addition to other known methods, can be used to access the LEC facilities.
In step 1020, signaling information for the call is received by the homed EO, the originating EO, indicating that calling party 102 is attempting to make a call. As noted, the homed EO, often referred to as a central office CO, is the EO having a direct connection with the originating caller. (This is true for voice calls and for data calls.) In FIG. 1, the homed EO is ingress EO 104. Conventionally, for this leg of the call, i.e., between the telephone or modem of calling party 102 and EO 104, the LEC uses in-band signaling implemented with pulse or tone dialing. The homed EO then sends back a dial tone to calling party 102.
In step 1022, the originating caller, calling party 102, hears a dial tone and dials a telephone number to access the open architecture platform 402. The dialed number, for example, in the currently used domestic US 10-digit standard NPA-NXX-XXXX format (i.e., Europe, for example, has a different 32 digit standard), can be the telephone number of called party 110, or a number used to access an ISP which can be virtually mapped to a table of terminating points.
In step 1024, the LEC facilities perform a table lookup and then transmit the call to a facility (e.g., a class 4 AT switch or a class 5 EO switch) that is connected to open architecture platform 402. First, EO 104 will look up the dialed number in translation tables (external to the EO) which will indicate which switch of the LEC facility is to receive the call. Next, EO 104 will transmit appropriate signaling information to transmit the call along a path to that facility.
It should be noted that if the regulatory environment were to change as to permit CLECs or other interconnecting parties to access originating office triggers from ILECs, then it would be possible to route the call traffic differently.
It should be noted that this step is optional, because it is possible that EO 104 (the homed EO) provides a direct connection with open architecture platform 402. It is also possible that calling party 102 will have a connection to a network node or system (e.g. an intelligent peripheral, a GPOP, etc.) that is not an EO or AT switch, which will provide a direct connection to open architecture platform 402. It is also possible that the homed EO will provide a connection to another type of network device (i.e., not an EO or an AT) that will, in turn, provide a direct connection to open architecture platform 402.
The leg of the call described in step 1024 can be connected using in-band signaling or out-of-band signaling. (The same is true for the legs of the call following this leg.) In one embodiment, SS7 signaling is used to terminate the call to the facility providing access to the open architecture platform 402. Referring to FIG. 4 or FIG. 9A, AT 106 and EO 104 are, for example, facilities providing access to open architecture platform 402. Alternatively, these facilities could include, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral.
With SS7 signaling, the ISDN User Part (ISUP) protocol can be used. ISUP features numerous messages that are transmitted within the SS7 network, which are used to establish call set up and call teardown. In the present case, an initial address message (IAM) is sent to AT 106 or EO 104. Of course, AT 106 can also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral. The IAM can include such information as the calling party number (i.e., the telephone number of calling party 102, although the IAM doesn't necessarily contain calling party, especially in local environment), the called party number (i.e., the telephone number dialed by calling party 102), the origination point code (OPC), the destination point code (DPC), and the circuit identification code (CIC). (The OPC, DPC and CIC were discussed above with respect to FIG. 7). The OPC identifies the switch from which the call is to be transmitted on the present leg of the call, which in this case is homed EO 104. The DPC identifies the switch to which the present leg of the call is to be routed. Taking the example of a call that is connected to open architecture platform 402 by AT 106, the SS7 signaling will transmit the call from EO 104 to AT 106. The CIC identifies the bearer channel over which the call is coming in to AT 106 from EO 104. Each AT 106 looks at the called number and then does its own routing, by reviewing the contents of the IAM and determining the next switch to send the call to, by setting the next DPC in order to continue routing the call.
It should be noted that ISUP messages are transmitted from signaling point to signaling point in the SS7 network in the above-noted manner, until the signaling is completed to a destination switch, node or trunk (i.e., at a called party). For example, it is possible that once the call is sent to homed EO 104, it is sent to intermediate switches (i.e., other EOs and ATs) before it arrives at AT 106. In this case, each switch along the path of the call will create an IAM with information reflecting the next leg of the call. For each leg, the OPC and DPC are modified, and the receiving switch looks for the call in the bearer channel specified by the CIC which is included in the IAM.
In step 1026, the LEC facilities perform a table lookup and then transmit the call to open architecture switch 502. AT 106 creates an IAM. This IAM can include the calling party's number (if available), the called party's number, the point code of AT 106 as the OPC, the point code of the open architecture switch 502 as the DPC, and the CIC representing the bearer channel over link 406 containing the call. The IAM is sent to the SS7 GW 512, presenting the call on a bearer channel represented by another CIC over link 406 to tandem NAS bay 504 (a bearer channel interface).
In step 1028, SS7 GW 512 receives signaling information in the IAM message from SS7 network 114, and delivers the information to control server 510. SS7 GW 512 has multiple physical A-link interfaces into the SS7 network (i.e. preferably one which supports international as well as US Domestic SS7 signaling) over which signaling data is received. In a preferred embodiment, SS7 GW 512 functionality is implemented as an application executing on a SUN Microsystems workstation model 450, for example, available from Sun Microsystems, Inc. using an SS7 adapter from, for example, DGM&S model Omni 5.0 SignalWare, available from DGM&S Telecom, Mount Laurel, N.J. In this preferred embodiment, SS7 GW 512 and control server 510 are applications in communication with one another, running on one or more such interconnected host computers. As noted, FIGS. 6 and 7 illustrate one example embodiment.
Referring to FIGS. 6 and 7, these applications are symbolically represented as OAP SS7 GW application 600 and OAP control server application 700. The communications between SS7 GW 512 and control server 510, which together comprise GW 508, were specifically described with respect to these figures. SS7 GW 512 parses the IAM message, providing the OPC, DPC, calling party number and called party number, inter alia, to control server 510.
SS7 GW 512 also functions as a protocol state machine for each ISUP SS7 circuit. In this respect, SS7 GW 512 holds a protocol state machine for each call that is in process. If SS7 GW 512 does not get a response from control server 510 within a certain timeout period, then it sends a default response out to the SS7 network, which is in the present case a release (REL) message. The REL message indicates to homed EO 104 (i.e., via its SSP portion) that the call is to be released because a timeout occurred. SS7 GW 512 does not necessarily perform the routing itself, but rather communicates with the control server 510 which controls the routing functions.
Referring to FIG. 10C, in step 1030, the control server must determine whether the call is a data call or a voice call to take appropriate actions. Control server 510 looks up the called party number in internal or external database 516 to determine whether the call is a data call or a voice call. Based on the type of call, control server 510 indicates to control facilities (associated with tandem NAS bay 504) how to route the traffic.
Control server 510 communicates with the control facilities in tandem NAS bay 504 via the open architecture protocol. The control messages comprising the protocol are defined in Table 6 generically and in Tables 7-20 in detail. The flows of the control messages, between GW 508 (primarily referring to control server 512 in GW 508) and tandem NAS bay 504 (primarily referring to control facilities in tandem NAS bay 504) are provided in Tables 22-38. For an even more detailed view of these flows, the reader is referred to FIG. 11, which illustrates the control facilities of tandem NAS bay 504 (including protocol control 1102, call control 1106 and resource management 1104) and GW 508, as well as FIGS. 13-18B, which provide detailed views of the selected flows.
If control server 510 determines the call is a data call, in step 1032, it sends a message to the control facilities of tandem NAS bay 504 indicating this condition. The tandem NAS bay sends back an acknowledgment. Table 27 illustrates an example message flow for this step.
In step 1034, a data call over a given bearer channel (e.g., a DS0 channel) is time division multiplexed by tandem NAS bay 504 for termination at particular modems. The data call arriving over a given bearer channel on connection 406 (from AT 106) is assigned to a module on modem NAS bay 514. In other words, the incoming bearer channel is assigned to a given bay/module/line/channel (BMLC) going into modem NAS bay 514 to a terminating point. Table 32 illustrates an example message flow for this step.
In step 1036, a modem performs the conversion (i.e., a modem in modem NAS bay 514 converts the call from one form into a form suitable for a destination data network.) For example, the call can be converted from one type of data signal (e.g., a PPP data signal) into another form of data, such as packets (e.g., IP data packets) for routing to another point such as an ISP. As noted, alternatively, a tunnel can be established between the originating caller and the destination data network. Here, a virtual private network, to which the originating caller 102 is connected, is extended to the data network.
Step 1038 is the acceptance of the data call by the platform. As illustrated in Table 26, a message is sent from the control facilities of tandem NAS bay 504 to control server 510, indicating the inbound call is accepted by open architecture platform 402. Control server 510 then indicates an accepted data connection to SS7 GW 512, which in turn sends an address complete (ACM) message out over SS7 network 114. When homed EO 104 is made aware of this condition, it plays a ringing signal for calling party 102, or more specifically, to the modem used by calling party 102. This indicates a connection is about to be established with a modem.
In step 1040, the call is connected between a modem on modem NAS bay 514 and the modem of calling party 102. As illustrated in Table 27, a message is sent from the control facilities of tandem NAS bay 504 to control server 510, indicating that the inbound call is connected. Control server 510 then indicates a connection indication to SS7 GW 512, which in turn sends an answer (ANM) message over SS7 network 114. The modem of called party 102 then negotiates with a modem of modem NAS bay 514. Here, the name and password of the calling party are verified by the modem of modem NAS bay 514 via a radius server. The radius server authenticates the call, and assigns an IP address from the modem NAS bay 514, using the dialed number. The call is routed between calling party 102 and another point, such as, an ISP as described with respect to FIG. 9A.
If in step 1030 it is determined that the call is a voice call, the call is transmitted to a voice switch in step 1042. In this case, control server 510 will communicate to tandem NAS bay 504 to transmit the call to voice switch 506. Voice switch 506 will, in turn, use SS7 signaling (via SS7 signaling network 114) to place the call to a called party 110. Voice traffic is handled in a conventional manner. In a preferred embodiment, a NORTEL DMS switch, model DMS 500, available from NORTEL, Richardson, Tex., is used for switching of voice traffic.
In step 1044, call teardown occurs. For voice traffic effected between calling party 102 and called party 110, teardown occurs using SS7 signaling in a known manner.
For teardown of a data call, in a typical scenario, calling party 102 initiates the procedure by disconnecting the modem connection. Homed EO 104 sends a release (REL) message, which is transmitted over the SS7 signaling network 114 to SS7 GW 512. SS7 GW 512 informs control server 510 of the condition. As illustrated in Table 34, control server 510 sends a message to the control facilities of tandem NAS bay 504 to release the call, which sends back an acknowledgment once the call is released.
It should be noted that the functions of SS7 GW 512, control server 510 and the NAS bays can all be contained in one collocated system. Many advantages can be achieved, however, by placing this functionality in several devices which can be collocated or placed in geographically diverse locations. For example, FIG. 9B depicts SS7 GWs 512a, 512b, and 512c, connected by multiple links (e.g., A-F links) to SS7 network 114. SS7 GWs 512a-512c and CSs 510a, 510b, and 510c, databases 516a, and 516b, NASs 902a, 902b, 902c, and 902d, and internal backbone 936, can be collocated or geographically diverse. In a preferred embodiment, for high availability, multiple redundant connections can connect redundant platform resources. It should also be noted that the above-noted steps need not be performed in sequential order. Those skilled in the art will recognize this fact.
It would be apparent to a person having skill in the art that the above is only one implementation of the technology and that multiple implementations are possible. The reader is referred to the following tables and FIGS. 11-18B for a more detailed perspective.
3. NAS Bay to GW Communications
FIG. 11 is a block diagram illustrating the functional components of NAS bay 902, and how these components communicate with GW 508. In this more detailed view, NAS bay 902 includes protocol control application 1102, call control application 1106 and resource management application 1104. Protocol control application 1102 communicates with call control application 1106 by transmission of primitives. Protocol control application 1102 communicates with resource management application 1104 by the execution of procedure calls. GW 508 communicates with NAS bay 902 by the transmission of control messages. These control messages, implemented using the open architecture platform protocol, are described in detail in the sections below.
FIG. 12 illustrates a diagram used to show how complex outbound calls are handled. In these calls, a plurality of NAS bays are involved. Table 35 provides a description that is to be used in concert with FIG. 12.
FIGS. 13-18 provide a series of detailed flow charts (i.e., state diagrams) describing the communications flows between the subcomponents of NAS bay 902 (including protocol control application 1102, call control application 1106 and resource management application 1104) and GW 508. The state diagrams represent the state of protocol control application 1102 through several processes. The flow charts are exemplary and not exhaustive.
FIG. 13 depicts an inbound call handling (NAS Side) 1300 state diagram detailing the states of protocol control 1102 during receipt of an inbound call. Steps 1302 through 1356 outline in detail the state flow of protocol control 1102 during the call.
FIGS. 14A and 14B depict NAS side exception handling 1400 state diagrams detailing the states of protocol control 1102 during exception handling. Steps 1402 through 1424 outline in detail the state flow of protocol control 1102 during exception handling.
FIG. 15 depicts a NAS side release request handling 1500 state diagram detailing the states of protocol control 1102 during the process of a release request. Steps 1502 through 1526 outline in detail the state flow of protocol control 1102 during the release request.
FIG. 16 depicts a NAS Side TDM connection handling 1600 state diagram detailing the states of protocol control 1102 during the receipt of a TDM call. Steps 1602 through 1630 outline in detail the state flow of protocol control 1102 during the TDM call.
FIGS. 17A and 17B depict a NAS side continuity test handling 1700 state diagram detailing the states of protocol control 1102 during initiation of a continuity test. Steps 1702 through 1766 outline in detail the state flow of protocol control 1102 during the test.
FIGS. 18A and 18B depict a NAS side outbound call handling (initiated by NAS) 1800 state diagram detailing the states of protocol control 1102 during initiation of an outbound call. Steps 1802 through 1872 outline in detail the state flow of protocol control 1102 during the call. An outbound call is a call initiated from the open architecture platform, for security reasons. In response to a call from a calling party, the platform initiates a call to the calling party, and performs password validation for the call.
4. Control Messages
Table 6 below provides a listing of the names and corresponding codes for control messages transmitted between GW 508 and NAS bay 902. Also included are the source of each message and the description for each message. For example, the NSUP message is transmitted from NAS bay 902 to GW 508, informing GW 508 that NAS bay 902 is coming up.










TABLE 6





Name
Code
Source
Description







NSUP
0x0081
NAS
Notify NAS coming up


ASUP
0x0082
GW
Acknowledgment to NSUP


NSDN
0x0083
NAS
Notify NAS is about to reboot


RST1
0x0085
GW
Request system reset - Drop all channels


ARST1
0x0086
NAS
Reset in progress - awaiting Reboot 





command


RST2
0x0087
GW
Request system reset (Reboot command)


ARST2
0x0088
NAS
Reboot acknowledgment


MRJ
0x00FF
GW or
Message reject




NAS



RSI
0x0091
GW
Request system information


NSI
0x0092
NAS
Response to RSI


RBN
0x0093
GW
Request bay number


NBN
0x0094
NAS
Response to RBN


SBN
0x0095
GW
Set bay number


ABN
0x0096
NAS
Acknowledgment to SBN


RMI
0x0097
GW
Request module information


NMI
0x0098
NAS
Notify module information


RLI
0x0099
GW
Request line information


NLI
0x009A
NAS
Notify line information


RCI
0x009B
GW
Request channel information


NCI
0x009C
NAS
Notify channel information


SLI
0x009D
GW
Set line information


ASLI
0x009E
NAS
Acknowledgment to SLI


RGWI
0x00A1
GW
Request Gateway information


NGWI
0x00A2
NAS
Notify Gateway information


SGWI
0x00A3
GW
Set Gateway information


ASGWI
0x00A4
NAS
Acknowledgment to SGWI


RGWS
0x00A5
GW
Request Gateway status


NGWS
0x00A6
NAS
Notify Gateway status


RMS
0x0041
GW
Request module status


RLS
0x0043
GW
Request line status


RCS
0x0045
GW
Request channel status


NMS
0x0042
NAS
Notify module status


NLS
0x0044
NAS
Notify line status


NCS
0x0046
NAS
Notify channel status


SMS
0x0051
GW
Set a module to a given state


SLS
0x0053
GW
Set a line to a given state


SCS
0x0055
GW
Set a group of channels to a given state


NSCS
0x0056
NAS
Response to SCS


PCT
0x0061
GW
Prepare channel for continuity test


APCT
0x0062
NAS
Response to PCT


SCT
0x0063
GW
Start continuity test procedure with far 





end as loopback (Generate tone and 





check for received tone)


ASCT
0x0064
NAS
Continuity test result


RTE
0x007D
GW or
Request test echo




NAS



ARTE
0x007E
NAS or
Response to RTE




GW



RTP
0x007B
GW
Request test ping to given IP address


ATP
0x007C
NAS
Response to RTP


LTN
0x0071
GW
Listen for DTMF tones


ALTN
0x0072
NAS
Response to listen for DTMF tones


STN
0x0073
GW
Send DTMF tones


ASTN
0x0074
NAS
Completion result of STN command


RCSI
0x0001
GW
Request inbound call setup


ACSI
0x0002
NAS
Accept inbound call setup


CONI
0x0003
NAS
Connect inbound call (answer)


RCSO
0x0005
NAS or
Request outbound call setup




GW



ACSO
0x0006
GW or
Accept outbound call setup




NAS



CONO
0x0007
GW or
Outbound call connected




NAS



RCST
0x0009
GW
Request pass-through call setup (TDM 





connection between two channels)


ACST
0x000A
NAS
Accept pass-through call


RCR
0x0011
GW or
Release channel request




NAS



ACR
0x0012
NAS or
Release channel complete




GW









5. A Detailed View of the Control Messages
The following section provides a more detailed view of the control messages transmitted between GW 508 and NAS bay 902.
a. Startup Messages
Table 7 below provides the Startup messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 7







Startup (registration and de-registration)










Parameter



Message
Tag
Parameter Description





NSUP - Notify NAS
0x01
Protocol version implemented 


coming up

(initially, set to 0).



0x02
System ID



0x03
System type



0x04
Maximum number of modules 




(cards) on the system (whether 




present or not).



0x05
Bay number.


ASUP - 
0x02
System ID


Acknowledgement to




NSUP




NSDN - Notify NAS
0x02
System ID


coming down (about to




reboot)




RST1 - Request system
0x02
System ID


reset - Drop all channels




ARST1 - Reset in
0x02
System ID


progress - awaiting




Reboot command




RST2 - Request system
0x02
System ID


reset (Reboot command)




ARST2 - Reboot
0x02
System ID


acknowledgment





0x06
Result code:










0x00
Request accepted. NAS 




will reboot now.



0x01
Request denied. NAS 




will not reboot.









b. Protocol Error Messages
Table 8 below provides the Protocol error messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 8







Protocol error handling












Parameter




Message
Tag
Parameter Description






MRJ - Message reject
0xFE
ISDN cause code





This message is generated by the NAS or GW when a message is received with an error, such as an invalid message code, etc. The ISDN cause code indicates the main reason why the message was rejected.






c. System Configuration Messages
Table 9 below provides the System configuration messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 9







System configuration










Parameter



Message
Tag
Parameter Description





RSI - Request system




information




NSI - Notify system
0x01
Protocol version implemented


information

(initially, set to 0).


(response to RSI)
0x02
System ID



0x03
System type



0x04
Maximum number of modules




(cards) on the system




(whether present or not).



0x05
Bay number









This message is sent as a response to



a RSI request.









RBN - Request bay




number




NBN - Response to
0x05
Bay number








RBN
This message is sent as a response to



a RBN request.









SBN - Set bay number
0x05
Bay number


ASBN - 
0x05
Bay number








Acknowledgment to
This message is sent as a response to


SBN
a SBN request.









d. Telco Interface Configuration Messages
Table 10 below provides the Telco interface configuration messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 10







Telco interface configuration










Parameter



Message
Tag
Parameter Description





RMI - Request module
0x07
Module number


information




NMI - Notify module
0x07
Module number


information (response 
0x0A
Module type:









to RMI)
0x00
not present



0x01
Unknown



0x03
router card



0x04
8-line channelized T1



0x06
48-modem card



0x07
HDLC card



0x08
Ethernet card



0x09
Serial WAN card



0x0A
HSSI card



0x0B
10-line unchannelized T1



0x0D
T3



0x0E
48-modem 56K card



0x10
SDSL



0x11
ADSL CAP



0x12
ADSL DMT



0x13
standalone modem controller



0x14
32-line IDSL











Many other values are reserved.



0x0B
Capabilities/features: logical OR of 




any of the following flags:










0x01
Capable of continuity testing



0x02
Network interface module










0x08
Number of lines (or items, depending 




on card type).



0x09
External name (i.e., “8t1-card”, etc.) 




In ASCII format.


RLI - Request line
0x07
Module number


information
0x0D
Line number


NLI - Notify line
0x07
Module number


information (response 
0x0D
Line number


to RLI)
0x0E
Number of channels



0x0F
External name in ASCII format



0x10
Line coding:










0x00
Unknown



0x01
AMI D4 AMI



0x02
B8ZS ESF-B8ZS










0x11
Framing:










0x00
Unknown



0x01
D4



0x02
ESF










0x12
Signaling type:










0x00
Unknown



0x01
In-band



0x02
ISDN PRI



0x03
NFAS



0x04
SS7 gateway










0x13
In-band signaling details:










0x00
Unknown



0x01
Wink start



0x02
Idle start



0x03
wink-wink with 200 msec 




wink



0x04
wink-wink with 400 msec 




wink



0x05
loop start CPE



0x06
ground start CPE










0x41
T1 front-end type:










0x00
Unknown



0x01
CSU (T1 long haul)



0x02
DSX-1 (T1 short haul)










0x42
T1 CSU build-out:










0x00
  0 db



0x01
 7.5 db



0x02
  15 db



0x03
22.5 db










0x43
T1 DSX-1 line length:










0x00
 1-133 ft



0x01
134-266 ft



0x02
267-399 ft



0x03
400-533 ft



0x04
534-655 ft









RCI - Request Channel
0x07
Module number


information
0x0D
Line number



0x15
Channel number


NCI - Notify channel
0x07
Module number


information (response 
0x0D
Line number


to RCI)
0x15
Channel number



0x16
Channel status



0x17
Bearer Capability of the Channel 




(BCC) or type of the active call, 




when a call is present.



0x18
Calling Party number



0x19
Dialed Phone number



0x1A
Timestamp of the last channel status




transition


SLI - Set line
0x07
Module number


information
0x0D
Line number



0x0F
External name in ASCII format



0x10
Line coding:










0x01
AMI



0x02
B8ZS










0x11
Framing:










0x01
D4



0x02
ESF










0x12
Signaling type:










0x01
In-band



0x02
ISDN PRI



0x03
NFAS



0x04
SS7 gateway










0x13
In-band signaling details:










0x01
Wink start



0x02
Idle start



0x03
wink-wink with 200 msec 




wink



0x04
wink-wink with 400 msec 




wink



0x05
loop start CPE



0x06
ground start CPE










0x41
T1 front-end type:










0x01
CSU (T1 long haul)



0x02
DSX-1 (T1 short haul)










0x42
T1 CSU build-out:










0x00
  0 db



0x01
 7.5 db



0x02
  15 db



0x03
22.5 db










0x43
T1 DSX-1 line length:










0x00
 1-133 ft



0x01
134-266 ft



0x02
267-399 ft



0x03
400-533 ft



0x04
534-655 ft









ASLI - New line
0x07
Module number


information ACK
0x0D
Line number







This message is sent as a response to a SLI request.









e. Gateway Configuration Messages
Table 11 below provides the Gateway configuration messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 11







Gateway configuration










Parameter



Message
Tag
Parameter Description





RGWI - Request




Gateway




information




NGWI - Notify
0x1B
IP Address for Primary gateway


Gateway
0x1C
TCP port for Primary gateway


information
0x1D
IP Address for Secondary gateway



0x1E
TCP port for Secondary gateway







This message is sent as a response to a RGWI request, or


when the local NAS configuration is changed by other means.









SGWI - Set
0x02
Serial Number of Remote Unit


Gateway
0x1B
New IP Address of Primary gateway


information
0x1C
TCP port for Primary gateway



0x1D
New IP Address of Secondary gateway



0x1E
TCP port for Secondary gateway


ASGWI -




Acknowledge




to SGWI









This message is sent as a response to a SGWI request.









RGWS - Request
0x02
Serial Number of Remote Unit


Gateway status




NGWS - Notify
0x02
Serial Number of Remote Unit


Gateway status
0x1B
New IP Address of Primary Host



0x1C
TCP port for Primary



0x1D
New IP Address of Secondary Host



0x1E
TCP port for Secondary



0x1F
Gateway in use (Primary/Secondary)







This message is sent as a response to a RGWS request.









f. Maintenance-Status (State) Messages
Table 12 below provides the Maintenance-Status (State) messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 12





Maintenance - Status (State)


















Parameter



Message
Tag
Parameter Description





RMS - Request module
0x07
Module number


status









This message will force an immediate NMS.









RLS - Request line
0x07
Module number


status
0x0D
Line number







This message will force an immediate NLS.









RCS - Request channel
0x07
Module number


status
0x0D
Line number



0x15
Channel number







This message will force an immediate NCS.









NMS - Notify module
0x07
Module number


status
0x0A
Module type (see NMI above)



0x0C
Module status



0x20
Number of lines (for network




interface modules only)



0x21
Line status: one entry per line (for




network interface modules only)







This message should be issued by the NAS any time that the module


status changes or if a RMS command was received.









NLS - Notify line status
0x07
Module number



0x0D
Line number



0x14
Line status



0x22
Number of channels



0x23
Channel status: one entry per




channel







This message should be issued by the NAS any time that the line


status changes or if a RLS command was received.









NCS - Notify channel
0x07
Module number


status
0x0D
Line number



0x15
Channel number



0x16
Channel status







This message should be issued by the NAS if an RCS command was


received.









SMS - Set a module to
0x07
Module number


a given status
0x24
Requested state:










0x00
out of




service



0x01
initialize




(bring




up)







As the Module changes status, the NAS will notify the GW with NMS


messages. The correlator in those NMS messages will not be the same


as the correlator in the SMS message.









SLS - Set a line to a
0x07
Module number


given status
0x0D
Line number



0x25
Requested state:










0x00
Disable



0x01
Enable



0x02
Start




loopback



0x03
Terminate




loopback







As the line changes status, the NAS will notify the GW with NLS


messages. The correlator in those NLS messages will not be the same as


the correlator in the SLS message.









SCS - Set a group of
0x07
Module number


channels to a given
0x0D
Line number


status
0x28
Start Channel number



0x29
End Channel number



0x26
Action:










0x00
Reset to




idle



0x01
Reset to




out of




service



0x02
Start




loopback



0x03
Terminate




loopback



0x04
Block



0x05
Unblock










0x27
Option:










0x00
Do not




perform




the




indicated




action if




any of




the




channels




is not in




the valid




initial




state.



0x01
Perform




the




indicated




action on




channels




which




are on




the valid




initial




state.




Other




channels




are not




affected.












Action
Valid initial state
Final state





Reset to idle
maintenance,
idle



blocked, loopback,




idle, in use,




connected



Reset to out of service
maintenance,
out of service



blocked, loopback,




idle, in use,




connected



Start loopback
idle
loopback


End loopback
loopback
idle


Block
idle
blocked


Unblock
blocked
idle


NSCS - Response to
0x07
Module number


SCS
0x0D
Line number



0x28
Start Channel number



0x29
End Channel number



0x2A
Response code:










0x00
action




successfully




performed




in all




channels



0x01
at least




one




channel




failed










0x22
Number of channels



0x23
Channel status: one entry




per channel









g. Continuity Test Messages
Table 13 below provides the Continuity test messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 13







Continuity test










Parameter



Message
Tag
Parameter Description





PCT - Prepare channel for
0x07
Module number


continuity test
0x0D
Line number



0x15
Channel number


APCT - Response to PCT
0x07
Module number


request
0x0D
Line number



0x15
Channel number



0x2B
Result:










0x00
Resources reserved 




successfully



0x01
Resource not 




available









SCT - Start continuity test
0x07
Module number


procedure with far end as
0x0D
Line number


loopback
0x15
Channel number



0x2C
Timeout in milliseconds. 




Default is 2 seconds.







The SCT command must be received less than 3 seconds after 


the APCT was sent. The continuity test performed by the NAS is 


as follows:










1.
Start tone detection



2.
Generate a check tone



3.
Start timer



4.
When tone is detected (minimum of 60 ms):










4.1.
Stop timer.



4.2.
Stop generator




4.2.1. TEST SUCCESSFUL










5.
If timer expires:










5.1.
Stop generator



5.2.
TEST FAILED







After continuity testing, a channel is always left in the idle state.









result
0x07
Module number



0x0D
Line Number



0x15
Channel Number



0x2D
Result:










0x00
Test completed 




successfully



0x01
Test failed





1ASCT - Continuity test






h. Keepalive Test Messages
Table 14 below provides the Keepalive test messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 14







Keepalive test










Parameter



Message
Tag
Parameter Description





RTE - Request test echo
0x2E
Random characters


ARTE - Response to
0x2E
Same random characters from RTE


RTE









i. LAN Test Messages
Table 15 below provides the LAN test messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 15







LAN test










Parameter



Message
Tag
Parameter Description





RTP - Request a test
0x02
System ID


ping
0x2F
IP Address to Ping



0x30
Number of pings to send


ATP - Response to RTP
0x02
System ID



0x2F
IP Address to Ping



0x30
Number of successful pings









j. DTMF Function Messages
Table 16 below provides the DTMF function messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 16







DTMF functions












Parameter




Message
Tag
Parameter Description






LTN - Listen for 
0x07
Module number



DTMF tones
0x0D
Line number




0x15
Channel number




0x31
Time to wait for a tone 





(since either last tone 





heard or start of command) - 





in milliseconds




0x32
Maximum number of tones 





to recognize




0x34
Tone to cancel the wait







If resources are available, the NAS starts listening for DTMF tones on the 


given channel. The procedure is as follows:








1.
Starts timer.


2.
When a tone is recognized:










2.1.
Restart timer.



2.2.
If the recognized tone is the ‘tone to cancel’, 




the operation is concluded and a




response is generated (cancel tone received).



2.3.
Add the tone to the response string. If the 




number of tones on the string exceeds the




maximum allowed, the operation is 




concluded and a response is generated 




(max tones received).



2.4.
When the tone is removed, restart the 




timer and continue from step 2.



2.5.
If the timer expires, the operation is 




concluded and a response is generated 




(tone too long).








3.
If the timer expires, the operation is concluded and a response is 



generated (timeout).











ALTN - Response 
0x07
Module number



to LTN
0x0D
Line number




0x15
Channel number




0x35
Completion status:










0x00
Timeout



0x01
No resources available 




for this operation



0x02
Operation was interrupted



0x03
Cancel tone received



0x04
Maximum tones received



0x05
Tone too long












0x32
Number of tones received




0x33
String of tones received (ASCII





characters ‘0’-‘9’, ‘*’, ‘#’)



STN - Send DTMF 
0x07
Module number



tones
0x0D
Line number




0x15
Channel number




0x32
Number of tones to send




0x33
String of Tones to send (ASCII





characters ‘0’-‘9’, ‘*’, ‘#’,





‘d’ - contiguous dialtone,





‘b’ - contiguous user busy,





‘n’ - contiguous network busy,





‘s’ - short pause,





‘r’ - contiguous ringback)



ASTN - Completion
0x07
Module number



result of STN 
0x0D
Line number



command
0x15
Channel number




0x36
Completion status:










0x00
Operation succeeded



0x01
Operation failed



0x02
Operation was interrupted









k. Inbound Call Handling Messages
Table 17 below provides the Inbound call handling messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 17







Inbound call handling










Parameter
Parameter


Message
Tag
Description





RCSI - Request inbound
0x07
Module number


call setup
0x0D
Line number



0x15
Channel number



0x17
Bearer Capability 




of the Channel 




(BCC)




required for the 




call.



0x19
Called Phone 




number



0x18
Calling Party 




number







This message is a notification from the GW to the NAS that 


an inbound call is pending. The NAS should respond


with an ACSI message indicating if it accepts or


with an ACR if it rejects the call.


The valid channel states for this command are idle or 


loopback. If the lchannel is in loopback state, loopback 


mode is ended and the call proceeds.











ACSI - Accept 
0x07
Module 





number



inbound
0x0D
Line number



call setup
0x15
Channel 





number







This message is a notification from the NAS to the GW that an 


inbound call has been accepted. Appropriate resources have 


been reserved at the NAS for this call.











CONI - Connect
0x07
Module 





number



inbound call 
0x0D
Line number



(answer)
0x15
Channel 





number




0x40
Call identifier 





assigned by 





the NAS







This message is an indication from the NAS to the GW to 


answer an inbound call.









l. Outbound Call Handling Messages
Table 18 below provides the Outbound call handling messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 18







Outbound call handling










Parameter



Message
Tag
Parameter Description





RCSO - Request
0x07
Module number


outbound call setup
0x0D
Line number



0x15
Channel number



0x17
Bearer Capability of the 




Channel (BCC)




required for the call.



0x19
Called Phone number1



0x18
Calling Party number1



0x37
Destination module2



0x38
Destination line2



0x39
Destination channel2



0x40
Call identifier assigned by 




the NAS3







If the call is initiated by the NAS, the Module, Line and Channel 


numbers are set to 0, because it is up to the GW to assign an 


appropriate channel for the outgoing call.


If the call is initiated by the GW, the Module, Line and Channel 


numbers indicate the channel that should be connected to the 


outbound call. The NAS will place a call in one of its regular 


trunks (such as an ISDN PRI line).


The GW or the NAS will respond with a ACSO (if the call was 


accepted) or with a RCR (if the call was rejected).


When the outbound call is established, it will be connected to 


the channel specified by the tags 0x07/0x0D/0x15.









ACSO - Accept
0x07
Module number


outbound call setup
0x0D
Line number



0x15
Channel number







If the call was initiated by the NAS, this is a notification from the 


GW that an outbound call was accepted and it is pending. The 


Gateway should send an RCR message if it wants to reject a call.


If the call was initiated by the GW, this is a notification from the 


NAS that an outbound call was accepted and it is pending. The 


NAS would have sent an RCR message if it wanted to reject a call.









CONO - Outbound call
0x07
Module number


connected
0x0D
Line number



0x15
Channel number



0x40
Call identifier assigned 




by the NAS.4







This message is a notification from the GW to the NAS that an 


outbound call has been connected.





1Optional - can be omitted. When RCSO is initiated by the Gateway, either this tag or complete address of the TDM destination channel must be present for the NAS to establish a call.


2Optional. Meaningful only for outbound calls initiated by the Gateway. If the address of a TDM destination channel is present, the specified channel will be used to setup the outbound part of the call.


3Present only when RCSO is originated by the NAS.


4Present only if this call was initiated by the Gateway.






m. Pass-through Call Handling Messages
Table 19 below provides the Pass-through call handling messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 19







Pass-through call handling










Parameter



Message
Tag
Parameter Description





RCST - Request pass-
0x07
From Module number


through call setup (TDM
0x0D
From Line number


connection between two
0x15
From Channel number


channels)
0x17
Bearer Capability of the 




Channel (BCC)




required for the call.



0x37
To Module number



0x38
To Line number



0x39
To Channel number







This message is a request from the GW to the NAS to link two 


channels. The NAS should respond with an ACST if it accepts 


the connection or with a RCR if it rejects the connection.


The indicated channels are interconnected at the time slot level. 


The NAS will not perform any rate adaptation. It is the Gateway's 


responsibility to specify compatible channels









ACST - Accept pass-
0x07
From Module number


through call
0x0D
From Line number



0x15
From Channel number



0x37
To Module number



0x38
To Line number



0x39
To Channel number







This message is a notification from the NAS to the GW that a 


TDM connection has been accepted and connected. The two 


indicated channels are now connected.









n. Call Clearing Messages
Table 20 below provides the Call clearing messages, the parameter tags and the parameter descriptions (associated with these messages).







TABLE 20







Call clearing










Parameter



Message
Tag
Parameter Description





RCR - Release channel
0x07
Module number


request
0x0D
Line number



0x15
Channel number



0xFE
ISDN cause code







In the case of a pass-through call (TDM connection), the channel


identified should be the ‘from’ side.









ACR - Release channel
0x07
Module number


completed
0x0D
Line number



0x15
Channel number



0xFE
ISDN cause code









6. Control Message Parameters
Table 21 below provides a listing of the control message parameters, and the control messages which use these message parameters. More specifically, Table 21 provides the tags associated with the parameters, the size (in bytes) of the parameters, the type of the parameters (e.g., ASCII), the parameter descriptions, and the control messages which use the parameters.











TABLE 21






Size





Tag
(bytes)
Type
Parameter description
Usage



















0x00
0

End marker
All messages.


0x01
1
UINT
Protocol version
NSUP


0x02
1 to 24
ASCII
System ID/Serial Number
NUSP, ASUP, NSDN,






RST1, ARST1, RST2,






ARST2, NSI, SGWI,






RGWS, NGWS


0x03
9
ASCII
System type
NSUP, NSI


0x04
2
UINT
Max. number of modules
NSUP, NSI





(slot cards) supported



0x05
8

Bay number
NSUP, NSI, NBN


0x06
1

Reboot acknowledgment
ARST2


0x07
2
UINT
Module number
RMI, NMI, RLI, NLI, RCI,






NCI, SLI, ASLI, RMS, RLS,






RCS, NMS, NLS, NCS,






SMS, SLS, SCS, NSCS,






PCT, APCT, SCT, ASCT,






LTN, ALTN, STN, ASTN,






RCSI, ACSI, CONI, RCSO,






ACSO, CONO, RCST,






ACST, RCR, ACR


0x08
2
UINT
Number of lines on this
NMI, NMS





module



0x09
16
ASCII
Module name
NMI


0x0A
1

Module type
NMI


0x0B
1

Module capabilities
NMI


0x0C
1
Module
Module status
NMS




Status




0x0D
2
UINT
Line number
RLI, NLI, RCI, NCI, SLI,






ASLI, RLS, RCS, NLS,






NCS, SLS, SCS, NSCS,






PCT, APCT, SCT, ASCT,






LTN, ALTN, STN, ASTN,






RCSI, ACSI, CONI, RCSO,






ACSO, CONO, RCST,






ACST, RCR, ACR


0x0E
2
UINT
Number of channels on
NLI, NLS





this line



0x0F
16
ASCII
Line name
NLI, SLI


0x10
1

Line coding
NLI, SLI


0x11
1

Line framing
NLI, SLI


0x12
1

Line signaling details
NLI, SLI


0x13
1

Line in-band signaling
NLI, SLI





details



0x14
1
Line
Line status
NLS




Status




0x15
2
UINT
Channel number
RCI, NCI, RCS, NCS, SCS,






NSCS, PCT, APCT, SCT,






ASCT, LTN, ALTN, STN,






ASTN, RCSI, ACSI, CONI,






RCSO, ACSO, CONO,






RCST, ACST, RCR, ACR


0x16
1
Channel
Channel status
NCS




Status




0x17
1

Bearer capability
NCI, RCSI, RCSO, RCST


0x18
24
ASCII
Calling party number
NCI, RCSI, RCSO


0x19
24
ASCII
Dialed number
NCI, RCSI, RCSO


0x1A
4
TIME
Channel status change
NCI





timestamp



0x1B
4
Ipaddr
Primary Gateway IP
NGWI, SGWI, NGWS


0x1C
2
UINT
Primary Gateway TCP
NGWI, SGWI, NGWS





port



0x1D
4
Ipaddr
Secondary Gateway IP
NGWI, SGWI, NGWS


0x1E
2
UINT
Secondary Gateway TCP
NGWI, SGWI, NGWS





port



0x1F
1

Gateway selector
NGWS


0x20
2
UINT
Number of lines in the
NMS





Line status array



0x21
Variable
Line
Line status array
NMS




Status




0x22
2
UINT
Number of channels in the
NLS





Channel status array



0x23
Variable
Channel
Channel status array
NLS




Status




0x24
1

Requested module state
SMS


0x25
1

Requested line state
SLS


0x26
1

Requested channel status
SCS


0x27
1

Set channel status option
SCS


0x28
2
UINT
Channel number first (for
SCS, NSCS





grouping)



0x29
2
UINT
Channel number last (for
SCS, NSCS





grouping)



0x2A
1

“Set channel status” result
NSCS


0x2B
1

“Prepare for continuity
APCT





check” result



0x2C
2
UINT
Continuity timeout
SCT


0x2D
1

Continuity test result
ASCT


0x2E
0 to 16

Test echo
RTE, ARTE


0x2F
4
Ipaddr
Test ping address
RTP, ATP


0x30
2
UINT
Test ping: Number of
RTP, ATP





packets



0x31
2
UINT
DTMF listen time
LTN


0x32
1
UINT
DTMF number of tones
LTN, ALTN, STN


0x33
Variable
ASCII
DTMF string (‘0’-‘9’, ‘A’-‘D’,
ALTN, STN





‘*’, ‘#’)



0x34
1
BYTE
DTMF tone to cancel the
LTN





waiting



0x35
1

DTMF listen completion
ALTN





status



0x36
1

DTMF send completion
STN





status



0x37
2
UINT
TDM destination Module
RCST, ACST, RCSO (gw)


0x38
2
UINT
TDM destination Line
RCST, ACST, RCSO (gw)


0x39
2
UINT
TDM destination channel
RCST, ACST, RCSO (gw)


0x40
2
UINT
Call identifier (RAS's
CONI, CONO, RCSO (nas)





Route ID)



0x41
1
BYTE
T1 front-end type
SLI, NLI


0x42
1
BYTE
T1 CSU build-out
SLI, NLI


0x43
1
BYTE
T1 DSX line length
SLI, NLI


0xFE
1
UINT
ISDN cause code
RCR, ACR, others









7. A Detailed View of the Control Messages
The following section provides a detailed view of the flow of control messages between GW 508 and NAS bay 902. Included are the source (either GW 508 or NAS bay 902) and relevant comments describing the message flow.
a. Startup Flow
Table 22 below provides the Startup flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 22





Step
Gateway
NAS
Comments







1

NSUP
NAS coming up. The message contains





server information, including number of





modules in the system.


2
ASUP









b. Module Status Notification
Table 23 below provides the Module status notification flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 23





Step
Gateway
NAS
Comments







1

NMS
Notify module status.


2


If the module is in the UP state:


3
RMI

Request module information


4

NMI
Notify module information (including number





of lines in this module).









c. Line Status Notification Flow
Table 24 below provides the Line status notification flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 24





Step
Gateway
NAS
Comments







1

NLS
Notify line status.


2


If the line is in the UP state:


3
RLI

Request line information


4

NLI
Notify line information (including number of





channels).









Note: Channels will remain in the our-of-service state until the line becomes available. At that time, the channels will be set to the idle state. The Gateway must then explicitly disable or block channels that should not be in the idle state.
d. Blocking of Channels Flow
Table 25 below provides the Blocking of channels flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 25





Step
Gateway
NAS
Comments







1
SCS

Set a group of channels to be blocked state.


2

RSCS
Message indicates if the operation was





successful or if it failed.









e. Unblocking of Channels Flow
Table 26 below provides the Unblocking of channels flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 26





Step
Gateway
NAS
Comments







1
SCS

Set a group of channels to be unblocked





state.


2

RSCS
Message indicates if the operation was





successful or if it failed.









f. Inbound Call Flow (without Loopback Continuity Testing)
Table 27 below provides the Inbound call flow (without loopback continuity testing), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 27





Step
Gateway
NAS
Comments







1
RCSI

Setup for inbound call on given module/line/





channel


2

ACSI
Accept inbound call. At this time, the NAS





may start any Radius lookup, etc.


3

CONI
Connect (answer) inbound call.









g. Inbound Call Flow (with Loopback Continuity Testing)
Table 28 below provides the Inbound call flow (without loopback continuity testing), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 28





Step
Gateway
NAS
Comments


















1
SCS

Set a channel to the loopback state.


2

RSCS
Message indicates if the operation was





successful or if it failed.








3
If the gateway determines that the test was successful:










3.1
RCSI

Setup for inbound call on given module/line/





channel.


3.2

ACSI
Accept/Reject inbound call. At this time, the





NAS may start any Radius lookup, etc.


3.3

CONI
Connect (answer) inbound call.








4
If the gateway determines that the test was not successful:










4.1
SCS

Release a channel from the loopback state





(back to idle state)


4.2

RSCS
Message indicates if the operation was





successful or if it failed.









h. Outbound Call Flow (Starting from the NAS)
Table 29 below provides the Outbound call flow (starting from the NAS), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 29





Step
Gateway
NAS
Comments







1

RCSO
Request outbound call. Note that the NAS





doesn't know yet what module/line/channel





will be used for the call and so, they are set





to 0.


2
ACSO

Accept/Reject outbound call on module/line/





channel. This message is used by the





Gateway to notify the NAS which





module/line/channel will be used





for the call. If the NAS can't process





the call on that channel, it should





issue a Release command.


3
CONO

Outbound call answered by called party.









i. Outbound Call Flow (Starting from the GW)
Table 30 below provides the Outbound call flow (starting from the GW), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 30





Step
Gateway
NAS
Comments







1
RCSO

Request outbound call. The Gateway





indicates the channel that should be





connected to the outbound call.


2

ACSO
Accept/Reject outbound call on module/line/





channel. The NAS will place the call using





one of the interfaces (such as an ISDN





PRI line).


3

CONO
Outbound call answered by called party. The





pass-through connection is established.









j. Outbound Call Flow (Starting from the NAS, with Continuity Testing)
Table 31 below provides the Outbound call flow (starting from the NAS, with continuity testing), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 31





Step
Gateway
NAS
Comments


















1

RCSO
Request outbound call. Note that the NAS





doesn't know yet what module/line/channel





will be used for the call and so, they are set





to 0.








2
The Gateway requests a continuity test:










2.1
RPCT

Prepare for Continuity test


2.2

APCT
Accept continuity test


2.3
SCT

Start continuity test. If the NAS doesn't





receive this command within 3 seconds of





sending an APCT, the continuity test will be





canceled and all reserved resources





will be released.


2.4

ASCT
Continuity test result.


3
ACSO

Accept outbound call on module/line/





channel. This message is used by the





Gateway to notify the NAS which module,





line and channel will be used for the call.





If the NAS can't process the call on that





channel, it should issue a Release





command.


4
CONO

Outbound call answered by called party.









k. TDM Pass-through Call Request Flow (Inter-Switch Connection)
Table 32 below provides the TDM pass-through call request flow (inter-switch connection), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 32





Step
Gateway
NAS
Comments







1
RCST

Gateway requests a given pair of module/





line/channel to be interconnected for





inter-trunk switching.


2

ACST
Accept/Reject inter-trunk switch connection.









l. Call Releasing Flow (from NAS)
Table 33 below provides the Call releasing flow (from NAS), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 33





Step
Gateway
NAS
Comments







1

RCR
NAS needs to release a call (for example, it





received an LCP TRMREQ).


2
ACR

When Gateway completes the release, it





notifies the NAS.









m. Call Releasing Flow (from GW)
Table 34 below provides the call releasing flow (from GW), including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 34





Step
Gateway
NAS
Comments







1
RCR

Gateway requests to release a call (for example,





the remote end hung up).


2

ACR
When the NAS completes the release, it





notifies the Gateway.









n. Complex Outbound Call Request Flow Example
Table 35 below provides an Complex outbound call request flow example, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments. The reader is referred to FIG. 12 for an illustration and state flow diagrams 18A and 18B.











TABLE 35





Step
From
To
Message
Comments




















NAS#1
GW
RCSO
NAS#1 requests an outbound call. 






Gateway determines that the best 






route to destination is through a 






PRI line on NAS#3. To get there,






it will use NAS#2 as a switch point. 






The Gateway selects channel 1/2/3 






on NAS#1 for this call.



GW
NAS#2
RCST
Gateway asks NAS#2 to establish 






a TDM connection between 






channel 2/3/3 and channel 4/5/6.



NAS#2
GW
ACST
NAS#2 accepts and connects the 






connection.



GW
NAS#3
RCSO
Gateway asks NAS#3 to place a 






call to the destination and 






connect it to the channel 6/7/6.



NAS#3
GW
ACSO
NAS#3 accepts the outbound 






connection and starts setting up 






the outbound call on PRI #1.



GW
NAS#1
ACSO
Gateway tells NAS#1 that the 






call is proceeding.



NAS#3
GW
CONO
NAS#3 reports the outbound 






call has been connected.



GW
NAS#1
CONO
The call has been connected.









o. Continuity Test Flow
Table 36 below provides the Continuity test flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 36





Step
Gateway
NAS
Comments







1
RPCT

Prepare for continuity test.


2

APCT
Accept continuity test.


3
SCT

Start continuity test. If the NAS doesn't





receive this command within 3 seconds of





sending an APCT, the continuity test will





be canceled and all reserved resources





will be released.


4

ASCT
Continuity test result.









p. Keep-Alive Test Flow
Table 37 below provides the Keep-alive test flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 37





Step
Gateway
NAS
Comments







1

RTE
Response test echo is sent.


2
ARTE

A response to test echo is sent.









q. Reset Request Flow
Table 38 below provides the Reset request flow, including the step, the control message source (either GW 508 or NAS bay 902) and relevant comments.










TABLE 38





Step
Gateway
NAS
Comments







1
RST1

First step.


2

ARST1



3
RST2

Second step. If the NAS doesn't receive





this command within 5 seconds of sending





an ARST1, it will not reboot.


4

ARST2
The NAS starts the reboot procedure.


5

NSDN
NAS is now rebooting.









V. CONCLUSION
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

## Claims

1. A method for bypassing public switched telephone network (PSTN) carrier network facilities, comprising:
providing an open architecture platform independent of the Regional Bell Operating Company (RBOC) switching hierarchy comprising at least a network access node, a plurality of tandem access nodes, and a network communicatively connecting the network access node to the plurality of tandem access nodes, wherein the at least one network access node comprises a modem communicatively connected to an Internet Service provider by an Internet Protocol (IP) network;
communicatively connecting each of a plurality of PSTN tandem switches and a plurality of third party voice switches to at least one of the plurality of tandem access nodes, wherein at least a first PSTN tandem switch of the plurality of PSTN tandem switches is communicatively connected to subscribers via an end office switch; and
switching traffic between the plurality of PSTN tandem switches, the at least on network access node and the plurality of third party voice switches using the plurality of tandem access nodes, the switching act comprising:
(i) receiving signaling information associated with a telecommunications call made by a first subscriber of the plurality of subscribers, wherein the signaling information comprises an identifier;
(ii) analyzing the identifier to determine whether to send the telecommunications call to the at least one network access node or to one of the plurality of voice switches; and
(iii) terminating the telecommunications call at the modem when the analyzing step (ii) determines that the identifier indicates that the telecommunications call is a data call; and
(iv) establishing a session between the modem and a modem of the first subscriber.

2. A method as recited in claim 1, comprising:
by the modem, converting media traffic associated with the telecommunications call from time division multiplexed (TDM) format to packet format for transmission over the IP network.

3. A method as recited in claim 1, wherein the at least one network access node comprises a plurality of modems communicatively connected to at least one Internet Service provider by an Internet Protocol network, wherein when the analyzing step (ii) determines to send the telecommunications call to the at least one network access node, the switching step further comprises:
(iii) selecting one of the plurality of modems based on the identifier and; and
(iv) establishing a session between the selected modem and a modem of the first subscriber.

4. A method as recited in claim 3, wherein the selecting step (iii) comprises:
choosing the selected modem based on geographic location of the modem of the first subscriber.

5. A method as recited in claim 4, wherein the geographic location corresponds to the number planning area (NPA) of the identifier.

6. A method as recited in claim 3, wherein the selecting step (iii) comprises:
choosing the selected modem based on identity of the at least one Internet Service Provider.

7. A method as recited in claim 3, comprising:
by the selected modem, converting media traffic associated with the telecommunications call from time division multiplexed format to packet format for transmission over the IP network.

8. A system for transmitting traffic between telecommunications networks, wherein at least a first telecommunications network comprises a first public switched telephone network (PSTN) switching facility through which subscribers of the first telecommunications network access telecommunications services, the network comprising:
a network access node communicatively connected to a second telecommunications network;
a plurality of tandem access nodes comprising a first tandem access node communicatively connected to the first PSTN switching facility;
a network communicatively connecting the at least one network access node and the plurality of tandem access nodes; and
a gateway comprising software configured to analyze signaling information associated with telecommunications calls received from subscribers of the first telecommunication network and select between transmitting the telecommunications calls from the first tandem access node to the network access node or to a voice switch based at least in part on an identifier contained in the signaling information, wherein the gateway further comprises a signaling interface communicatively connected to an SS7 signaling network, wherein the signaling information comprises SS7 data comprising a dialed telephone number.

9. A system as recited in claim 8, wherein the network access node comprises at least one modem communicatively connected to an Internet Service provider by an Internet Protocol network.

10. A system as recited in claim 9, wherein the plurality of tandem access nodes further comprises a second tandem access node communicatively connected to a private branch exchange.

11. A system as recited in claim 10, wherein the second tandem access node is communicatively connected to a voice over Internet Protocol (VoIP) network.

12. A system as recited in claim 8, wherein the gateway comprises the first tandem access node.

13. A system as recited in claim 12, wherein the first tandem access node comprises the software.

14. A system as recited in claim 8, wherein the first PSTN switching facility comprises an access tandem switch.

15. A system as recited in claim 8, wherein the first PSTN switching facility comprises an end office switch.

16. A system as recited in claim 8, wherein the voice switch provides TDM connectivity to a called party associated with an identifier.

17. A system as recited in claim 8, wherein the identifier is a dialed telephone number.