One day, a communications technician went into town to grab a burger instead of eating his usual brown bag fare. On his way back to the central office (CO), he spotted a line of people extending around the corner. With mounting curiosity, he followed the queue. He found, to his surprise, that the line led to a pay phone at the local gas station. Returning to work, he reported the sighting and began his investigation. Testing revealed that the pay phone was provisioned to permit worldwide calling for the price of a local call. To make matters worse, several other switches had recently been updated with similar faulty translations. Some days later, systems personnel confirmed the downstream fallout of related billing errors. Although the problem was quickly identified and corrected, significant write-offs resulted.
The scenario on the preceeding page illustrates the potential impact of switch inaccuracies and how they can quickly become a billing nightmare. The dynamic nature of translation tables presents an ongoing challenge to their accuracy. This article outlines some risks associated with translation errors, along with methods of ensuring integrity of the switch. In addition, two products designed to automate the testing of switch accuracy are discussed.
Risks of Switch Translation Errors
The central office switch contains information necessary to rate, route and record a call properly. This translation information is stored in tables and changes frequently as new customer lines are provisioned or service is changed. The dynamic nature of the translation tables poses a challenge for network reliability groups.
Errors in switch translations frequently impact the completeness and accuracy of customer bills. For example, the switch may correctly record a call but misroute it. As a result, the call rating would be inaccurate, causing overbilling or underbilling. Likewise, the switch may provide the service but fail to create any automated message accounting (AMA) for billing purposes. For instance, the switch may not create AMA records for terminating switched access. In this case, carriers would not be charged for terminating their calls on the local network. Furthermore, customer service could be degraded by translation errors. Unintentional call blocking could occur during an NPA split, causing customers to become frustrated enough to initiate dial-around calling. In contrast, service blocking may be requested but not provided. In the case of information services providers, this could result in services being provided that cannot ultimately be billed. Each of these examples illustrates how switch translation errors can impact an organization's bottom line. To lessen these risks, telecommunications companies employ various methods to ensure the integrity of their switched services network. (See Methodology Comparison Table pg.55)
Switch Integrity Approaches Call-Through Testing
The method of placing actual test calls through the switch is widely used to determine the accuracy of the central office switching data and the resulting AMA records.
One of the advantages of this approach is being able to test certain attributes of the created AMA, including format and structure. In addition, call-through testing can detect whether the switch is generating AMA records for all billable call events. For example, tests can be designed to determine if answer supervision occurs to trigger the creation of AMA. Furthermore, test calls can be placed to a terminating test line to verify the creation of terminating switched access AMA.
While there is no substitute for generating AMA by placing actual test calls, it is difficult to achieve complete switch coverage because of the associated costs and resources required. Establishing and maintaining a network of dedicated test lines also presents challenges. The setup of the lines must be verified for correct provisioning that meets testing objectives. Once established, dedicated test lines may not remain intact, and they need to be rechecked periodically. Cost considerations include items such as the initial investment in dialer hardware at each central office where testing occurs, test line maintenance costs and any long distance charges for test calls.
Product Overview: PAT
One of the most comprehensive call-through testing products on the market today is the PAT system (Proactive AMA Testing), offered by The Board Room Inc. Glenn E. Ross, Director of PAT System Development, succinctly describes the system as follows: "It makes calls, logs the results and compares it against the AMA." The core functionality of the PAT system is discussed below. (See figure 1.)
A key feature of the software is the automated process of building test call scripts. Once the user defines the calling patterns and other criteria to be tested, the scripts are automatically built from a user-defined table of all available terminating test numbers. This feature automates the tasks of dial clerks and communications technicians who would otherwise have to place the calls manually, log the results, and manually compare computer printouts of AMA results against expected results. "We have taken a tediously manual, error prone process and automated it, replacing the old 'stare and compare' routine," explained Ross.
Test call scripts are then automatically uploaded to call generation hardware located at the CO. The hardware places the test calls and logs the results (i.e., tone encountered, time of call). The results are then downloaded into a database that contains the details of actual test calls placed. While on site at GTE, Robbie McCarty, senior administrator, Switch Certification, shared his thoughts on the use of this product. "One of the product's strengths is the ability to do the testing any time you need to without having to utilize field resources to perform mundane and tedious tasks. Field resources can now be utilized to work on higher priority issues directly affecting the customers, such as ensuring dial tone, adding new services and optimizing the infrastructure."
After the calls are placed, the AMA data is captured and imported into the compare process. Before the match occurs, the AMA is checked for proper format, structure and required number of fields. Then the AMA is matched to the logged result of each call from the dialer. Finally, the actual call records are compared to the expected results based on user-defined fields. All test call results are stored in a database along with the corresponding AMA record.
Those who have had to manually create test scripts, place and log the calls and compare the results will certainly appreciate the ease of use and the level of automation provided by the PAT system.
Call Simulation Testing
Call simulation is a methodology that simulates the switch routing, charging and recording logic of a phone call through the translation tables of a CO switch. This technique permits off-line testing by imitating the logic of the switch and applying it to a captured image of the translation tables. Since simulated calls are not placed on the network, large volumes of calls are tested rapidly and inexpensively, without burdening the switch or CO facilities. Simulated dialing allows for almost immediate availability of results. Another key factor is coverage. Under this approach, 100 percent of the switch translations are validated. Not only does simulated testing identify problems with working or active codes (i.e., NPA, NXX or line class codes), but it also identifies potential issues for codes that may be vacant or inactive. Another advantage is that simulation testing can be used proactively, before a switch goes "live." Call simulation software can also be useful as a training tool for switch translators.
Due to the fact that call simulation does not occur on the network, this type of testing would not detect any network outages external to the CO. Further, it assumes that the CO hardware is operating properly. In addition, since AMA is not generated, it cannot be verified for proper formatting or structure.
Product Overview: SimCall
One of the only call simulation products available is Pacific Bell's SimCall, which is marketed by Advanced Technologies and Services, Inc. SimCall validates the integrity of switch translations by means of a user-friendly GUI web-interface. In the words of Peter Mueller, SimCall product manager, "SimCall takes the guesswork out of verifying that the switch is programmed in accordance with a set of sound operational rules." SimCall functionality is described below. (See figure 2.)
First, an image of the switch is obtained by executing a software capture script on the CO switch. The capture script runs on the switch as a low priority without impact to the switch operation. The procedure is comparable to running a switch backup. The switch image is then imported into the simulation process. During a site visit to US West, Nevin Bruce, manager, Network Reliability Operations Center, stated "One of the major benefits of using SimCall is that the translations are tested outside of the switch, with no impact to the switch or our network."
Before the simulation testing occurs, the user defines specific testing parameters using a menu-driven interface. In addition, a database of expected results is built using a combination of existing customer data stores and commonly used industry data. After these components are in place, the simulation process is run. One of the key advantages of call simulation testing is that the results are available almost immediately.
Simulation results are available in the form of error reporting for all user-defined tests. According to Debby Martin, technical director, Customer Billing Services, Pacific Bell, "In the hundreds of switches already tested, SimCall has never failed to uncover service and revenue-affecting errors." Once the errors are flagged, drill-down capability is available through an on-line web interface. This interface allows the user to view all errors, then to filter down easily to a subset of errors. Further, because simulation occurs off-line, users have the ability to execute ad hoc test runs in which pro forma corrections are made to the translations, and then the simulation is re-executed. The new test results can be reviewed before actual changes are made to the switch.
Combine and Conquer
A careful review of these methodologies reveals that each is an integral part of a comprehensive revenue assurance strategy. These products, when used together, leverage the strengths of each methodology to maximize switch integrity while minimizing associated costs. This available technology enables scarce human resources to focus on the real job of solving problems and adding value to the organization. In conclusion, tomorrow's successful telecommunications companies will need to shrewdly deploy both human and technical resources to ensure the integrity of their switched services network, and in doing so, safeguard revenues and secure customer loyalty.
Deborah Charkowicz, CPA, CISA, CIA, is an independent consultant specializing in automated revenue assurance solutions for the telecommunications industry. She may be reached via e-mail at charkowicz@aol.com.
Methodology Comparison TableDescription Call Through Testing Call Simulation Testing Methodology MethodologyMethod of Operation Actual test calls are placed on the network. Simulated test results are gener- AMA records are generated by the switch and ated using switch translation captured for comparison. table image. No AMA is generated.Translation Tables Translation tables are black box "live" Translation tables are a captured "image"Switch Testing Capabilities All switches Specific switch typesInterexchange Carrier Testing Can identify specific carrier Can identify specific carrierTesting Setup and Maintenance Provisioning and maintenance of dedicated Requires setup and capture test lines of switch imageDetection of Network Network disruptions detected since the actual Network disruptions not detectedDamage or Disruptions test call would not complete since calls are simulated off lineSpeed of Test Call Placement 10,000 to 40,000 per day 50,000 to 100,000 per secondAvailability of Test Results Call Through Results: Call Simulation Results: available immediately available immediately AMA Compare Results: AMA Simulation Results: available within hours available immediatelyCost of Test Calls Includes any related long distance None charges incurredEquipment Required PC, dialer hardware PC or mid-range server, tape drive for switch image
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