Abstract:
In a large switching system, a complete record of a call through a network can be collected by having each switch that processes the call, record pertinent data and return the collected data to a particular switch where the collected data is stored. A complete call history simplifies network maintenance and permits precise identification of calling and called parties on a call-by-call basis.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to communication networks. In particular, this invention relates to a method for collecting data associated with called numbers and calling numbers. 
     BACKGROUND OF THE INVENTION 
     Telecommunication switching networks are well-known. These networks are comprised of large, computer-controlled switching systems routing telephone calls that might carry voice and/or data. Most of these switching systems include a limited ability to trap certain kinds of data for a telephone call. Call traps are software features of switching systems whereby subscribers calling to or from a certain predetermined number, i.e. the trapped number, are identified. Prior-art call traps within a single switching system identify all of the subscriber phones that dial a particular number and the incoming trunks on which the calls arrive at the switching system or all of the numbers dialed from a specified number. 
     In many instances it is desirable to be able to completely document calls through a network, including the time that a call began; when it was answered; when it was terminated; the trunk(s) it was routed on; and which party terminated the call. It is currently only possible to collect all of the foregoing data if the number being called and party calling the particular number are coupled to the same physical switch. In modern telecommunications networks a call might be routed through several switches between a calling party and the party being called. In a large network of numerous switches, a call placed to a telephone that is terminated at another switch cannot be completely documented unless each switch in the path over which the call is routed is programmed to search for and trap the particular called number. Thereafter, reconstructing or documenting the exact route through the network which the call was routed cannot be readily determined simply because of the several different switches a call traverses through a network. 
     For many reasons, knowing the exact route of a call through a network can be valuable. Knowing the exact route of a call might help diagnose problematic circuitry causing customer complaints or to identify the source of annoying calls. For example, law enforcement agencies needing to pin point an annoyance call origin might be able to do so, regardless of where a call originated from. 
     A method and an apparatus by which calls can be trapped through a network, based upon either the called number or the calling number, would be an improvement over the prior art. 
     SUMMARY OF THE INVENTION 
     Calls through a switching network can be fully documented if the switches are commonly controlled and operatively coupled together such that the switches are able to respond to externally supplied triggers and to exchange data between them. Trapping a called number or a calling number requires that each switch of a network be programmed or configured to trap a particular number. This is established via an input message into each switch, individually, or by broadcasting the request from a single source. A network management computer is normally connected to each switch and has the capability to send a common message (e.g. a trap message) to all switches. Inasmuch as a call to be trapped might originate from outside the network and might therefore enter a network at virtually any switch thereof, each switch of the network is sent a message to trap a particular call, either on a called number basis, a calling number basis, or some other data. 
     The switch at which the call originates and every switch that handles the call thereafter, must be capable of, and be programmed to identify and initiate a call trap based on some predetermined criteria. Secondly, when an incoming call to be trapped occurs, the switch at which the call originates begins collecting predetermined data and processes the call as it normally would by routing the call to a subsequent switch in the network. Finally, the originating switch that received the call being trapped, signals the subsequent switch that the call is the subject of a complete data trap and also identifies where the data should be sent. This could be in the form of a destination point code (“DPC”) known in the art as a location in a SS7 network. The subsequent switch must be capable of receiving and responding to a call trap instruction and thereafter collect pertinent data on the call being trapped as the originating switch did. Switches routing a trapped call through the switching network each collect data on the call. The data that is collected might include: the trunk on which the call came to a switch; the time of the calls arrival at the switch; the trunk on which the call was routed out of the switch; the identity of the switch the call was routed to and the time at which the call was routed out of a switch; the time when a call was answered and when a call was terminated. 
     As a call is routed by each switch in the network, it returns collected data back to the switch that routed the call to it. Alternatively, switching systems collecting trap data on a call can send collected data to one or more predetermined switches designated to collect call trap data. Other embodiments would include collecting call trap data at a dedicated, call trap data collection computer or other appropriate processor, which is not necessarily a switching system. 
     As a call is routed through a network of switches, each switch that passes the call to another switch signals the subsequent switch that the call is to be trapped. Each switch that handles the call identifies the location to send the data, which could be the original switch that received the call. In one embodiment of the invention, data from each switch in the network that handles the call is returned through each switch that previously handled the call such that all of the call data is eventually collected for subsequent processing at the originating switch. The originating switch will continue to receive data from the switches that process the call through the network from the time it is established until the call is terminated. Eventually a complete history of the call for the network is assembled at one location. 
     The call data that can be collected about the call can include: the originating phone number; the dialed number; the time the call was answered; the identity of the party that terminated call; which trunks routed the call through the network; the time that the call entered the network, i.e. the first off-hook to the network; and the time that the call was terminated, i.e. the first on-hook to the network. 
     Trapped calls through the network might be identified to network switches by a multi-digit number or other label or tag associated with a call that uniquely identifies a trapped call. A call serial number, label, or tag that identifies trapped calls could be distributed throughout a switching network using the SS7 signaling network, well-known to those skilled in the art. This information could be included in the SS7 call set up message. Trapped calls might also be identified, in part, merely by specifying the trunks over which they are routed and routing such data over the SS7 network as well. This would then be rebuilt at the collection site by linking the trunks together. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a simplified block diagram of a telecommunications network through which a trapped call is to be routed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a simplified block diagram of a telecommunications switching network  100 . A telephone subscriber  102  is coupled to a telephone end office  104 . The end office  104  provides so-called local switching to the telephone subscriber  102  in that other subscribers whose phones  106  are coupled to the end office  104  can communicate with each other through switching equipment located within the end office  104 . In practice, end office  104  provides telecommunications service to subscribers in a geographical region proximate to end office  104 . When a telephone subscriber  102  wishes to place a call to another subscriber  108  not coupled to end office  104  but coupled to a different end office  110 , the call must be routed through a network of switches. 
     In FIG. 1, several switching systems  112 ,  114 ,  116 ,  118  and  120 , are operatively coupled together through a network of communication links or trunks  122 ,  124 ,  126 ,  128 ,  130 , and  132 . If a subscriber  102  coupled to end office  104  wishes to place a call to another subscriber  108 , who is coupled to a different end office  110 , the call is routed through one or more switches that comprise a network of switching systems  112 ,  114 ,  116 ,  118 , and  120  simply because no direct connection exists between end office  104  and  110 . Those skilled in the art will recognize that the end offices  104  and  110  might be only a few miles apart but could also be thousands of miles apart, depending upon how the call is routed. 
     As set forth above, there may be many reasons it is desirable to track the precise path of a call between a first subscriber  102  and a second subscriber  108  through the network  100 . As one example, subscriber  102  might experience poor transmission quality when calling subscriber  108 . Responding to such a complaint by the service provider typically requires the diagnosis of all of the switching hardware and media that might handle calls between the first subscriber  102  and the second subscriber  108 . In a large switching network there might be thousands of circuits and trunks over which a call between subscriber  102  and  108  might be routed. Inasmuch as the call between subscriber  102  and  108  might take several different paths through the network  100 , for maintenance reasons alone, it is desirable to be able to track the exact path a call takes through network  100 . In addition, annoyance calls to or from a subscriber are frequently of concern to law-enforcement and subscribers. Presently, calls routed through a network such as the network shown in FIG. 1, cannot readily be traced because of the speed with which the call progresses through the network and because no capability of informing switches that a call is to be traced presently exists. 
     If the switches  112 ,  114 ,  116 ,  118  and  120  comprising the network  100  are commonly owned and operatively linked together, the switches can be cooperatively programmed to collect data on incoming calls to each switching system and to return collected data to the switching system that previously routed the call. By appropriately programming the switches to trap data on a particular call, the switching systems can all collect pertinent data under program control. 
     For instance, switching system  112  can be programmed to collect data to a particular number, such as the number of subscriber  108 . Alternatively, switching system  112  might be programmed to collect pertinent call data when it detects an incoming call from a particular subscriber, such as subscriber  102 . Data that the switches  112 ,  114 ,  116 ,  118  and  120  can collect may include for example: the time when the call was initiated; the identity of the number of the party placing the call; the number being called; the identify of the trunk on which the call came into a switch and the trunk on which a call leaves a switch; the time in which the call was routed from a switch in the network to another network; the time the call was terminated and the source of the termination request. Those skilled in the art will appreciate that other types of data might also be collected as well. 
     Each of the switches ( 104 ,  110 ,  112 ,  114 ,  116 ,  118 , and  120 ) are coupled to a signaling network  123  well-known as the SS7 signaling network. The SS7 network is a means by which call information is routed to switches throughout the switching network  100  such that the aforementioned switches receive pertinent call processing information on call routing and set-up and on other call parameters over the SS7 network. The SS7 network can be used to carry call trap information throughout the network  100  by virtue of the fact that all of the switches of the network are linked via SS7 signaling. 
     Inasmuch as calls to be trapped might not originate within the network but might originate from a foreign switch or network and might therefore enter the network through any switch thereof, the invention taught herein will provide optimum results if each and every switch of the network through which a call will be trapped is programmed with the call trap criteria. A message is broadcast via the SS7 network  123  to each switch of the network to trap calls matching certain criteria. Any switch then receiving a call matching the call trap criteria can be trapped through the network. At present, calls are trapped primarily on the basis of the dialed number or the dialing number. 
     When a call trap is triggered, the originating switch ( 112 ,  114 ,  116 ,  118  or  120 ) processes the call and sends a message to the next switch via the SS7 network to which the call is routed. The call trap message from the originating switch notifies the subsequent switch that receives the call that the incoming call is to be trapped, i.e. all pertinent call data is to be collected by the switch. As the call is routed from one switch to another, each of the secondary switches that route the call thereafter receive a trap call message from the previous switch included in the SS7 call set-up message and in response thereto, each switch collects pertinent call data. Eventually the call is routed to its destination. Data collected by the switches that handled the call is returned to the originating switch  112 , over well-known SS7 signaling links operatively linking the switches together, not shown. Returned data is compiled at the originating switch  112  for subsequent processing. 
     An alternate embodiment of the invention would include call trap data collection sites that are intermediate switches that routed the call, i.e. not necessarily the originating switch, or the terminating switch. Other call trap data collection sites would collect pertinent data from switches that routed the call. Other alternate embodiments include call trap data collection at other network switches as well, including switches that don&#39;t even handle the call being trapped. One or more network switches might be specifically designated by a network operator to collect call trap data from all other network switches, even if such a data collection switch did not process the call. 
     Another embodiment of the invention would include one or more stand-alone computers or other processors operatively coupled to the switching network that collect call trap data. Still other embodiments would include call trap data collection computers that collect particular types of data pertinent to a call trap. A call trap data collection computer or several such computers distributed throughout a network could be used to assemble data collected from switches that routed a call through a network and output an appropriately-formatted report. 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
             
               
               
             
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
             
               
                   
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
               
             
          
           
               
                      Operation Class = Call trap 
               
             
          
           
               
                 Ext 
                 Type of Operation = Notification 
               
               
                 Ext 
                  Encoding Scheme = Mixed 
               
             
          
           
               
                     Switch Sequence Number 
                 Trap options 
               
               
                   
               
             
          
         
       
     
     Table 1 is an example of how an SS7 “generic operations” parameter could be encoded in an “initial address message” by an originating switch to signal to a subsequent switch that call trap data is to be collected on a particular call. 
     Table 1 is comprised of words of eight, (8)-bit data fields. Each data field in each table entry can represent different information as shown. Ordinarily, all fields are sent using a typical default byte value of zero when no data is present in a field. 
     The data of a call trap message is sent serially in a SS7 message over the SS7 network, shown in FIG.  1 . Software at the data collection site, a switch or dedicated computer for instance, interprets the data and copies it to a file. By use of an appropriate report generator program, printed results can be prepared from the data file 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
             
               
               
             
               
               
             
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
             
               
                   
                 8 
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
               
             
          
           
               
                      -Operation class = call trap- 
               
             
          
           
               
                 Ext 
                 Type of operation = Notification 
               
               
                 Ext 
                  Encoding scheme = mixed 
               
             
          
           
               
                     switch sequence number 
                 trap options 
               
             
          
           
               
                 Switch Identifier (Binary) 
               
               
                 Switch Identifier, continued 
               
               
                 -Incoming trunk identifier (binary)- 
               
               
                 Incoming trunk identifier (continued) 
               
               
                 -Outgoing trunk identifier (binary)- 
               
               
                 Outgoing trunk identifier (continued) 
               
               
                 -additional data specified by trap options- 
               
               
                 Additional data specified by trap options 
               
               
                 Additional data specified by trap options 
               
               
                 Additional data specified by trap options 
               
               
                 Additional data specified by trap options 
               
               
                   
               
             
          
         
       
     
     Table 2 is an example of how an SS7 “generic operations” parameter could be encoded in an “address complete message” or “call progress message” by a subsequent switch to pass the call trap data back to the originating switch. 
     In the preferred embodiment and in the alternate embodiments set forth above, trapped calls might be identified to switches and/or processors of the network by assigning to trapped calls, a trapped call identifier that identifies to the network switches, a call to be trapped by the switches. A trapped call identifier, such as a serial number, or numeric messages or other indicia of a trapped call, could be distributed throughout a switching network to the switching systems and other processors via an SS7 signaling link or other data link, such as an Ethernet network for example. 
     Inasmuch as each switching system is collecting data and returning the data collected to the originating switch, or other call trap data collection site, a complete history on the call can be collected, compiled, and analyzed. The collected data makes it possible to pinpoint noisy or problematic switching equipment, but also makes it possible to know the precise origin or destination of calls to or from a number that progresses or is routed through a large complex switching network. It also identifies who terminated the call. The collection of such data might also enhance the ability of law-enforcement agencies to track communications through such large networks. 
     The embodiment shown in FIG. 1 shows a series of Lucent Technologies, Inc. No. 4 ESS™ switching systems. The Lucent No. 5 ESS™, Norte™ DMS 100 and 250 or Erickson™ switching systems might also be part of the network shown in FIG.  1 . 
     Those skilled in the art will recognize that other switching systems capable of trapping call data might function in the embodiment disclosed above. Well-known SS7 signaling format information is exchanged between the switches  112 ,  114 ,  116 ,  118 ,  120 ,  104  and  110  shown in figure 100 although other out-of-band signaling protocols would work as well. 
     The data collected might include but would not be limited to: the originating number; the called number; the time that the call was originated; the time it was answered, the time that the call was terminated; the identity of the party that terminated the call; the time that a call entered a network of commonly owned switches and the time that the call left the network; the identity of the trunks  122 ,  124 ,  126 ,  128 ,  130 ,  132  that the call was routed over.