AT&T: A Terminal Server Case Study

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AT&T Deploys Terminal Server Providing its Engineers With Real Time Access to Lab Data

Using Microsoft® Windows NT® Server 4.0, Terminal Server Edition, AT&T engineers can run tests in real time from anywhere in the world, using a fraction of the bandwidth previously required. As a result, AT&T has been able to reduce the cost of maintenance, respond more quickly to network problems and provide better service.

"Windows NT Server, Terminal Server Edition has made it easier for us to monitor and maintain the quality of our growing wireless network. It provides a window for us into important data. We can now-for the first time-monitor our entire network in real time from anywhere. This means that we can respond quickly to changes and maintain the optimal settings for services and call quality."

- Tim Boeve, director, Production Test Lab, AT&T Wireless Services.

In the wireless telecommunications industry, the name of the game is quality. As a leader in this very competitive industry, AT&T Wireless Services strives to ensure, first, that its services are always available to customers and second, that every mobile phone call sounds as good as a wired call. AT&T achieves its high levels of service quality through exhaustive testing, re-testing, analysis, and adjustment of its wireless network infrastructure. In the past, the staggering amounts of data that AT&T engineers collected from network components around the country/region consumed massive amounts of bandwidth to monitor remotely. As a result, engineers wishing to run tests on core service and call quality data had to perform these tests at the lab at AT&T's headquarters. This greatly limited the amount of testing that could be done and made it nearly impossible for an engineer in one region to do benchmarking comparisons against data in other regions, which would help them raise their own standards by better understanding how the best regions were performing. In short, there is a great deal of interest in the ability to both access and run analyses on call quality data from around the country/region.

Happily for AT&T, the difficulties it encountered using this data are becoming a thing of the past. In the past year, AT&T has begun using Windows NT Server, Terminal Server Edition 4.0 to provide a window into this mission-critical data. Today, engineers can run their tests in real time from anywhere in the world, using a fraction of the bandwidth previously required. As a result, AT&T has been able to reduce the cost of maintenance, respond more quickly to network problems and provide better service.

On This Page

Company Background
Ensuring Core Service Availability
Improving Call Quality

Company Background

AT&T is the largest cellular carrier in the United States. Its service area covers 40 percent of the U.S. population and it provides cellular phone service to more than 6 million users. In 1995, AT&T obtained 21 additional licenses which, when fully constructed, will increase this coverage to more than 80 percent of the U.S. population.

As AT&T's service area has grown, and as wireless phone services become more sophisticated, offering such features as voice mail and call forwarding, the job of maintaining the wireless network has become more complex. Most aspects of a phone call are controlled by a data format known as Signaling System 7 (SS7), a telecommunications industry standard. Making the call work is a matter of managing this SS7 data flow in the context of the network components being used, the services being offered, and countless other factors.

AT&T is using Terminal Server as its solution for two important functions. First, with this new means of providing access to the SS7 data residing in AT&T's production test lab, Terminal Server allows engineers to monitor and diagnose the state of the entire wireless network from anywhere in the world. Second, by giving timely access to important call quality data, Terminal Server allows districts to quickly adjust their local network components to their optimal settings, thus providing customers with the highest quality in wireless communications.

Ensuring Core Service Availability

In the wireless communications industry, the first order of business is making sure that all core services are fully functional all the time. Industry standards dictate that these services be available 99.997 percent of the time, so AT&T takes its network's health very seriously. In AT&T's production and test lab, every piece of hardware used in the real-world network is tested before being deployed into the field. Also, before AT&T adds new components or new services to the network, engineers in this test lab simulate the effect of any new additions to ensure that the network will continue to operate flawlessly. These two needs, the need to monitor the health of the network and the need to pre-test additions to the network, are both satisfied by collecting and analyzing switching and SS7 data in the lab.

In order to run tests on this data, an engineer required access to the entire 8+ megabit per second data stream, the equivalent of five T1 lines. Attempting to run tests from anywhere but the lab would have a serious impact on AT&T's wide area network (WAN) performance. As a result, first-hand real-time access to lab data was limited to only a handful of engineers. Providing such access to others across the WAN could not be done reasonably.

That is, until now. Using Windows NT Server operating system, Terminal Server Edition, AT&T has been able to provide access to engineers around the world with very little impact on the WAN. In fact, an analog dial-up session at 28.8 kilobits per second (Kbps) provides more than enough bandwidth to remotely monitor these volumes of data. What makes this possible is the way that client sessions interact with Terminal Server. When an engineer establishes a client session with a server running Terminal Server in the lab, the Terminal Server-based server does all data manipulation locally on the local area network (LAN) and passes only the display of the test results (rather than the data itself) to the end user. Terminal Server responds as if the engineer were sitting on the server's console: It only uses the bandwidth required for the engineer's keystrokes and mouse movements to be sent to the server, and for the server to send the display to the engineer's laptop. That laptop runs the Terminal Server thin client application emulating the desktop and applications running on the Terminal Server-based server. The beauty of this is that an engineer can effectively run tests on staggering amounts of data without increasing bandwidth usage. Also, many engineers can connect to the same server running Terminal Server and use it in a similar manner. Each engineer can take remote control of the server and give it instructions-and the server responds to each engineer as if that individual were the only user.

Terminal Server sessions give remote engineers all the granularity of control over tests that they would have in the lab. This is because the Terminal Server-based server uses the same applications that an engineer would use. It simply runs its tests locally and sends the results to users. Currently, 20 engineers around the country/region use Terminal Server to gain real-time access to lab data using a WAN, dial-up connection, or Web connection.

Improving Call Quality

In addition to ensuring that core services are functioning properly, AT&T devotes much attention to maintaining high call quality. Call quality means simply, how well the call worked and how it sounded. The goal for AT&T is for callers to be unaware that they are on a mobile phone. To achieve this goal, it is important that technologies hosting the wireless call are properly configured. Like the production test lab, AT&T's phone network contains many different components, and the network provides various services, such as call forwarding. The challenge to engineers in maintaining optimal call quality is in properly setting the switching parameters that handle call setup, call handoff, call completion, call delivery, and voice quality. Engineers must always maintain a balance in these settings based on the types of service offered, the physical and logical environments, and the amount and type of traffic.

In order to know what settings to configure, engineers must collect huge amounts of data. This data is gathered from around the country/region, deposited into a central database in the lab, and analyzed to determine optimal switch settings. Timely access to this data is crucial for AT&T, because regions around the country can improve the quality of calls in their area based on the information engineers receive.

In the past, many AT&T engineers used an application created using the Visual Basic® development system to query this data. This application was written on top of Microsoft® Excel, and it allowed users to generate their own queries over the WAN. However, engineers wishing to use this application had to generate client-server queries that used a lot of bandwidth because they were being run directly against the remote data. AT&T's solution to these issues was to set up a machine running Terminal Server as a window into call quality data. By placing the Visual Basic-based application on the Terminal Server, AT&T significantly reduced the amount of bandwidth needed to run queries. Terminal Server actually runs the queries, and because it is physically near the database, there is no impact on the WAN. Engineers simply connect to Terminal Server-based server and receive the results of their queries. Furthermore, because the application now resides on the Terminal Server-based server, engineers don't need to use or update the application on their own computers. They can use the application on the Terminal Server either over the WAN, dial-up connection or the Internet.

Tim Boeve, director of the Production Test Lab, says, "Because 200 users around the country/region are now using this functionality to help improve call quality, the reductions in the time it takes to make a query, the amount of bandwidth used, and the administrative overhead in maintaining the application are important benefits to us. But the key benefit is that engineers now have real-time access."


The Windows NT Terminal Server-based solution has been very successful for AT&T. Since they began using it less than a year ago, engineers throughout the company have come to rely on its ease-of-use. Also, hardware vendors are beginning to recognize the value of being able to view remotely how well their equipment works within the lab environment and to get critical interoperability data. AT&T has been receiving a few requests each day from vendors who want this information without having to travel.

As demand for the services of Terminal Server increases, AT&T is making plans to increase availability and scalability through clustering and load balancing. According to Rob Hamblet, manager of Data Networking and Windows NT Architecture in the Production Test Lab at AT&T Wireless Services, "So far, we have had fantastic software and hardware reliability. Clustering will bring us up to the level of the near-perfect Telco standards. It will also allow us to easily add additional servers if demand exceeds our initial expectations. Judging from the success of Terminal Server so far, it probably will."