Abstract:
A method for use in diverse networks that authenticates inter-network resource requests. A router in a first network receives a request for a resource from a second network. The router sends a query to an element in the second network to determine whether the request actually originated there. If the request did originate from the second network, the request is processed according to the procedure for the requested resource. If the request did not originate from the second network, then the first network terminates the request. Thus, no network resources are consumed unnecessarily by accidental or malicious requests.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to the field of sharing resources between diverse communication networks, and, more specifically, to protecting such shared resources from accidental or deliberate depletion.  
         [0002]     In the not-too-distant past, there was only one communication network available to the public: the telephone network (herein called the “public switched telephone network” or “PSTN”). Now data communication networks, formerly available solely to government or big business, are also generally available to the public. Because the telephone and data networks were developed for different purposes and at different times, the PSTN is a “circuit switched” network and data networks are generally “packet switched” networks. Given these differences in purpose and protocol, there was initially little to no interaction between them. Thus, there was no motivation to design or develop resources that could be shared between or among the diverse networks. Over the past decade or so, however, the line of demarcation between these networks is becoming blurred to the point of disappearing.  
         [0003]     For example, data networks now carry voice calls. A popular class of service that carries voice calls in a data network is voice over Internet protocol (VoIP). Gateways that translate format and protocol are used to connect calls that span the PSTN and VoIP data network. Because of this relatively recent interaction between voice and data networks, there is a need for resources and services in the data networks that were formerly only available in the PSTN.  
         [0004]     One essential telecommunications resource that is primarily implemented in the PSTN is emergency services, the services that are popularly known in the U.S. as “9-1-1.” However, one system and method for providing 9-1-1 service in VoIP telephony has recently been implemented by Intrado, the assignee of this invention (herein referred to as the “Intrado solution”). This system and method is described in U.S. Pat. No. 6,771,742, to McCalmont et al., U.S. patent application Ser. No. 10/288,737 and U.S. patent application Ser. No. 10/402,741 by Knox, all of which are assigned to the assignee of this invention and all of which are hereby incorporated by reference in their entirety.  
         [0005]     In the above-referenced system, the user of a VoIP telephone dials 9-1-1, which is received by the VoIP controller for routing. The VoIP controller assigns an emergency services routing number (ESRN) and sends the call into the PSTN. The ESRN is a preassigned telephone number that causes the PSTN to route the 9-1-1 call to a public safety answering point (PSAP) that is proximal to the calling telephone.  
         [0006]     A problem in the current art is that the ESRN comprises a 10-digit telephone number that may be dialed at any telephone in the PSTN or the data network. For example, the ESRN can be dialed by any auto-dialer (used by solicitors, for example) that incrementally or randomly dials telephone numbers. Further, a user on the data network may accidentally or maliciously cause the same number to be dialed repeatedly, causing resource flooding and ultimately resulting in denial of service to those who really need emergency services.  
       SUMMARY OF THE INVENTION  
       [0007]     This problem is solved and a technical advance is achieved in the art by a system and method that authenticates an inter-network resource request to verify that the request for a resource on a first network is properly originating on a second network. In one embodiment, a router in the first network receives a resource request from an inter-network gateway. The router then sends a query to the network gateway to determine whether the request actually originated there. If the request did originate from the network gateway, processing continues according to the procedure for the requested resource. If the request did not originate from the network gateway, then the system terminates the request, sends it to announcements, etc., thus using fewer system resources.  
         [0008]     An example of the first network is the public switched telephone network (PSTN) and an example of the second network is a data network that supports voice over Internet protocol (VoIP) telephony. An exemplary resource that is available only on the first network is emergency services (9-1-1). When a VoIP telephone dials 9-1-1, a gateway between the two networks out-pulses an emergency services routing number (ESRN) and an emergency services query key (ESQK) or an automatic number identification (ANI) into the PSTN. In accordance with this invention, a router in the PSTN receives the ESRN and requests authentication from the gateway that apparently initiated the call. Advantageously, the gateway may be determined from the ESRN and the ESQK or ANI of the calling telephone. The gateway passes a token indicating whether it did in fact initiate the call. If the call is thus authenticated, the call is completed to emergency services. If the call cannot be authenticated, then the call is terminated or given some type of call treatment, such as sent to signals (e.g., fast busy, reorder) or announcements.  
         [0009]     In accordance with another embodiment of this invention, an authentication request is sent from the router to a network component, such as a service control point, which traces the origin of the call to ensure that it is legitimate. According to another embodiment of this invention, a token is passed from a network gateway to the selective router (on, for example, a signaling network) when the network gateway outpulses an ESRN. When the selective router receives the ESRN, it checks for the token on the signaling network to authenticate the call. In this manner, randomly dialed and malicious flooding are avoided at the network resource, helping to ensure its availability for real requests for services from both networks. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     A more complete understanding of this invention may be obtained from a consideration of this specification taken in conjunction with the drawings, in which:  
         [0011]      FIG. 1  is a block diagram of exemplary networks in which embodiments of this invention operate;  
         [0012]      FIG. 2  is a call flow diagram of authenticating an inter-network request for use of a resource in accordance with an exemplary embodiment of this invention in the context of the networks of  FIG. 1 ;  
         [0013]      FIG. 3  is a call flow diagram of authenticating an inter-network request for use of a resource in accordance with another exemplary embodiment of this invention in the context of the networks of  FIG. 1 ; and  
         [0014]      FIG. 4  is a block diagram illustrating an alternate embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0015]      FIG. 1  is a block diagram of exemplary diverse networks in which embodiments of the current invention may be implemented, shown generally at  100 . This exemplary embodiment includes a data network  102 , which provides packet switched communications for digital devices. Such digital devices are represented by and include (but not limited to) personal computer  104  and voice over internet protocol (VOIP) telephone  106 . Data network  102  may be any public or private network including, but not limited to, the Internet.  
         [0016]     Data network  102  is connected via gateway  108  to the public switched telephone network (PSTN)  110 . PSTN  110  provides circuit switched communications for telephones and other devices, represented by telephone  112 . PSTN  110  includes selective router  114  and service control point  116 . Service control point  116  may comprise an automatic location identification (ANI) node, as is known in the art, or other database system. PSTN  110  also includes public safety answering point (PSAP)  118  to provide emergency or 9-1-1 service for a predefined geographic area.  
         [0017]     An interface line  120  defines the limits of each network for purposes of clarity. One skilled in the art will realize that the various components illustrated herein are not segregated into discrete networks with one definable interface. While gateway  108  is herein illustrated at interface  120  between data network  102  and PSTN  110 , it is known in the art that gateway  108  may be a part of data network  102 , PSTN  110  or both.  
         [0018]     Providing emergency service for VoIP is used herein to illustrate the features and advantages of this invention. VoIP operates in one network (data network  102 ) but uses a resource (PSAP  118 ) from a diverse network (PSTN  110 ) in order to provide such 9-1-1 service. One skilled in the art will appreciate how to apply the principals of this invention to other diverse network applications after studying this specification. Further, one skilled in the art will appreciate that the principals of this invention apply to sharing resources between diverse data networks.  
         [0019]     An exemplary embodiment of this invention is now described with reference to  FIG. 1 , which illustrates a block diagram of one network using a resource on a diverse network, and  FIG. 2 , which illustrates a call flow in the context of  FIG. 1 . The call flow steps are indicated in the following text by parentheses. The herein described system and method employs the principals of the Intrado solution for 9-1-1 VoIP. For a more detailed explanation of the Intrado solution, see the above-incorporated patents and applications.  
         [0020]     When the user of VoIP telephone  106  dials 9-1-1, the call is first handled by the user&#39;s service provider&#39;s VoIP controller  130  ( 202 ). The initial call may include the telephone number of telephone  106 , the data address of telephone  106  or both. VoIP controller  130  recognizes the special number (9-1-1) and requests instructions from a VoIP positioning center  132 , passing the telephone number, the data address, or both, of the calling telephone  106  ( 204 ).  
         [0021]     In accordance with this exemplary embodiment of this invention, VoIP positioning center  132  maintains a database of the locations of VoIP telephones and the PSAP that serves each location. VoIP positioning center  132  uses the telephone number, the data address, or both, to perform a look up in its database. If the telephone number is found in its database, VoIP positioning center  132  passes an emergency services routing number (ESRN) and an emergency services query key (ESQK) to VoIP controller  130  ( 206 ). The ESRN comprises a 10 digit number in the same format as all telephone numbers (i.e., NPA-NXX-XXXX). The ESRN causes PSTN  110  to route the call to a predetermined selective router ( 114  in this exemplary embodiment) that serves the general geographic area in which the calling telephone is located. The ESQK is the equivalent of the automatic number identification (ANI), which is used by selective router  114  to further define which PSAP  118  serves the specific area in which the calling telephone is located.  
         [0022]     Alternatively, a VoIP telephone, such as  104 , may have information regarding its position stored in its memory system. When queried, VoIP positioning center  132  sends a message to VoIP telephone  104  requesting its position. VoIP telephone  104  sends its position to VoIP positioning center  132 , which then uses the received position to determine the ESRN and ESQK.  
         [0023]     VoIP controller  130  routes the call into PSTN  110  via gateway  108  using the ESRN as the dialed number and the ESQK as the dialing number (i.e., ANI or caller ID) ( 208 ). The ESRN directs call processing to route the call through PSTN  110  to selective router  140  that is proximal to the calling telephone  106 . Selective router  140  queries a database, herein illustrated as service control point  142 , to determine which PSAP handles calls from the area of the calling telephone ( 210 ). “Service control point” is used herein to mean a network component that performs a function. In the exemplary embodiments of this invention, service control point may also be called an “ALI database” and have the same functionality as an ALI database as known in the art. Further, service control point  142  is illustrated herein as comprising the routing database for purposes of clarity, one skilled in the art will appreciate that the routing database for selective router  114  may be, for example, a dedicated system or may be an entity on a separate signaling network (e.g., an SS 7  network), data network or the switch itself.  
         [0024]     Continuing with this exemplary embodiment of this invention, service control point  142  requests authentication from VoIP position server  132  ( 212 ). Service control point  142  forwards the ESQK and the ESRN it received to determine if VoIP position server  132  assigned these numbers to an emergency call.  
         [0025]     In the above-described scenario, VoIP position server  132  did assign the ESRN and ESQK numbers for a 9-1-1 call from VoIP telephone  106 . Therefore, VoIP position server  132  sends a validation or positive response to service control point  142  ( 214 ). Such positive response may include a token. Advantageously, VoIP position server  132  may additionally deliver the telephone number of VoIP telephone  106  (for call back or other purposes). Service control point  142  also sends an identification of the PSAP (in this example, PSAP  118 ) that serves the location of calling telephone  106 . The call is connected to PSAP  118  ( 220 ).  
         [0026]     If, on the other hand, the ESRN, ESQK or both were not issued by VoIP position server  132 , service control point  142  may cause the call to terminate, send the call to announcement or signals and take other action as appropriate. Alternatively, service control point  142  may send a denial of service signal back to selective router  114  or some other point in PSTN  110  to take appropriate action.  
         [0027]     The above-described 9-1-1 call scenario illustrates an authenticated resource request between diverse networks. Because the ESRN is a dialable 10 digit number, any telephone in either PSTN (such as telephone  112 ) or in data network  102  (such as VoIP devices  104  and  106 ) can dial it at any time, either accidentally (a misdial or an automatic dialer) or maliciously. Furthermore, a computer device such as PC  104  can dial an ESRN repeatedly in just a few seconds, which quickly ties up all connections to PSAP  118  and causes a denial of service to real emergency calls from both networks. Furthermore, a PC in PSTN  104  with a network card (e.g., a T 1  card) may flood the PSAP  118  by repeatedly dialing an ESRN.  
         [0028]     Thus, calls from PSTN  110  (e.g., from telephone  112 ) to the ESRN can be rejected and delivered to terminal call treatment (e.g., fast busy signal, reorder signal, announcement, etc.). Further, gateway  108  can verify that the call is from a legitimate source on the network and not one source attempting to flood the resource without legitimate reasons.  
         [0029]     Alternatively, VoIP controller  130  may block calls to predetermined numbers. Thus, no calls to one or more ESRN&#39;s may be blocked at VoIP controller  130 , thus stopping the call before it reaches PSTN  110 . Further, SCP  116 , selective router  114  or both may be programmed to recognize when a string of calls arrives from the same ANI and stop processing the call at that point.  
         [0030]     Turning now to  FIG. 1  and  FIG. 3 , a further exemplary embodiment and method of this invention is described. As in the above-described embodiment, the user of VoIP telephone  106  dials 9-1-1, which call is routed to VoIP controller  130 , along with the telephone number, the data address, or both, of the VoIP telephone  106  ( 302 ). VoIP controller  130  queries VoIP position system  132  with the telephone number, data address, or both ( 304 ) as described above. VoIP position system  132  responds with an ESRN and an ESQK ( 306 ). Additionally, and in accordance with this exemplary embodiment, VoIP position system  132  produces a token and delivers it to the VoIP controller  130  ( 308 ). Alternatively, VoIP controller  130  may generate a token when it receives an ESRN and ESQK.  
         [0031]     VoIP controller  130  uses the ESRN to route the call through gateway  108  to selective router  114 , passing the ESRN and the ESQK ( 310 ). At this point, VoIP controller  130  may pass the token to selective router  114 , either over the same connection as the ESRN and the ESQK (known in the art as “in band”) or over a separate signaling network (“out of band”) ( 312 ). Alternatively, selective router  114  may request a token from either the VoIP controller  130  or VoIP position system ( 314 ) to which either may respond with the token ( 316 ).  
         [0032]     Once the token is received, selective router  114  requests routing information from service control point  116  ( 318 ). The identification of the destination PSAP (i.e., ESN or PSAP ID) is returned ( 320 ) and the call is connected ( 324 ). If selective router  114  does not receive the token then it can assume that the call is not authentic and can take appropriate action (disconnect, announcement, signals, etc.).  
         [0033]     Turning now to  FIG. 4 , an alternative embodiment of this invention illustrating two diverse data networks is shown, generally at  400 . In  FIG. 4 , data networks  400  comprise a first Internet protocol network  402  and a second Internet protocol network  404 . First and second data networks are separated by boundary  406 , which is, of course, for convenience of illustration. Internet protocol network  402  and Internet protocol network  404  are connected at boundary  406  by a gateway  408 . Gateway  408  performs any protocol or other conversion as is known in the art. Gateway  408  is optional (in the case where no conversion is needed between the two networks), is known in the art and is therefore not further discussed.  
         [0034]     In the illustration of  FIG. 4 , Internet protocol network  402  supports a plurality of VoIP telephones, represented by telephone set  410  and PC  412 . Further, Internet protocol network  402  supports a public safety answering point (PSAP)  414 . PSAP  414  is connected to Internet protocol network  402  via a PSAP controller  416 . PSAP  414  may communicate using VoIP protocol, in which case PSAP controller  416  comprises a router. PSAP  414  may also be a conventional circuit-switched system, in which case PSAP controller  416  provides conversion from VoIP to circuit switch communication, signaling conversion, etc. PSAP controller  416  is also illustrated as connected to service control point  420  (which may be an ALI database). As described above in connection with  FIG. 1 , service control point  420  may be a separate system, part of PSAP controller  416  or some other node in data network I. Internet protocol network  402  also includes a VoIP controller  422 , which is connected to VoIP positioning center  424 .  
         [0035]     Internet protocol network  404  in data network II supports a plurality of VoIP telephone sets, represented by telephone set  426  and PC  428 . VoIP is supported in Internet protocol network  404  by VoIP controller  430 . VoIP controller  430  is connected to VoIP positioning center  424 .  
         [0036]     In the exemplary embodiment of  FIG. 4 , a 9-1-1 call is made at telephone  426 , for example. The call initiation is routed through Internet protocol network  404  to VoIP controller  430 . VoIP controller  430  recognizes the special nature of the call, queries VoIP positioning center  424  for the location of VoIP telephone  426  and assigns an ESRN and ESQK accordingly. The call initiation is then routed back through Internet protocol network  404 , through gateway  408  (if required) and into Internet protocol network  402 . VoIP controller  422  receives the call initiation and routes the call initiation according to the ESRN and ESQK, which causes the call to be routed to PSAP controller  416 .  
         [0037]     PSAP controller  416  causes a call to be set up between one of the positions at PSAP  414  and queries service control point (ALI)  420  for information regarding the call. Service control point  420  uses the ESRN and ESQK to query VoIP positioning center  424  to obtain information related to telephone  426 . Service control point  420  delivers the received information to PSAP  414  via PSAP controller  416 .  
         [0038]     It is to be understood that the above-described embodiment is merely illustrative of the present invention and that many variations of the above-described embodiment can be devised by one skilled in the art without departing from the scope of the invention. For example, a third network may be used for communication among the components of PSTN  110 , such as an SS 7  network. Any of the network control points or service control points in either or both networks can communicate over the communications network to request verification from gateway  108 , VoIP controller  130 , VoIP position system  132  or any combination thereof. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.