Making the grade in VDV testing

The challenges of network testing are growing in a multi-dimensional fashion, with installers and maintenance staff having to deal with a widening range of physical cabling types and network services. Today's commercial and residential network environments present a variety of voice, data and video (VDV) communications requirements, which can stretch the capabilities of technical staff.

In many cases, this means that both contract installers and internal IT staff need to expand beyond their traditional knowledge base to test and troubleshoot other services in which they are not as familiar. With the proliferation of multimedia networks in residential and small business situations, many end users also are looking for cost-effective and easy-to-use devices that enable them to do their own first-level testing.

In addition to handling passive cabling of various types, users need testing tools to navigate, test and maintain "active" networks. Here again, the test devices need to be simple to operate, guiding the user through easy-to-understand testing procedures, and also need to be "fail-safe" to protect both the tester and the network from incorrect connections or usage.

Current market research indicates that by the end of 2004, nearly 50 percent of all new homes were pre-wired with structured wiring solutions. The market demand for such home wiring has been growing rapidly during the past decade to support both new residential construction and retrofit requirements.

The growth in residential wiring also is being driven by the tremendous growth in wireless networking, where smart home structured wiring provides a natural complement to flexibly position broadband access points as well as distributing video, data and voice services. Interest in Voice over IP (VoIP) is fueling demand for residential structured wiring installations.

Increasingly sophisticated consumers and homeowners want to be able to move into their new homes and immediately take advantage of hassle-free services for voice, data, video, high-fidelity entertainment, integrated security systems and HVAC control capabilities. They want integrated control over everything on the home network at their fingertips, as well as being able to remotely control all functions when they are away from home.

In addition to the dramatic growth in new residential requirements for VDV testing and structured wiring, the industry is seeing a similar evolution of commercial requirements, moving from the conventional deployment of separate voice and data networks to a convergence of voice, data and video. This convergence is being driven by the need to simplify network maintenance and lower costs as well as new business-oriented applications such as integrated VoIP, security and bio-metric applications.

Current and future VDV installations may use a variety of cabling types. A single residential installation may include coaxial cable, structured cable, phone wiring and power-line carrier functions. Similarly, although commercial installations will continue to predominately use structured wiring for data traffic, a significant percentage also use coax for closed circuit security as well as various legacy phone wiring modes for delivering POTS, PBX, ISDN and others.

For installers, network maintenance staff and end-users in both residential and commercial environments, the noted trends mean a greater demand for handheld instrumentation that can handle the whole spectrum of VDV testing and troubleshooting requirements. These testers can come with a variety of features and capabilities that allow them to be tailored to specific requirements and situations.

The first level of testers is designed for simple operation, but with the ability to test a variety of VDV cabling in a passive network mode; that is before any active components such as routers are installed. These handheld test devices should provide push-button operation and easy-to-read displays that can be used and understood by relatively unsophisticated users, such as homeowners. They also provide the core set of features and the robust operation needed by more demanding users, such as cabling installers.

Key measurements that should be included with any tester are wiremap, length testing, and the ability to detect opens, shorts and splits. Wiremap can be very effective for identifying the 80 percent of wiring problems that typically can be traced back to poor terminations. Length testing is another key feature that helps in spotting common problems. For instance, length tests that show a significantly different result for only one out of the four pairs on a cabling run can quickly point to problems, such as a broken pair.

To allow for flexible testing across a variety of media types without juggling different add-on components, these testers should have built-in interfaces for multiple cables, including RJ45 (data), RJ11/12 (voice) and coaxial (video/data).

In addition, to allow for easy one-person operation, testers should include remote units that support all of the same cabling interfaces. Ideally, this type of tester should be simple to operate so that any user could pick it up, turn it on and begin testing without having to spend time in training or reading a complex manual.

Testers that provide users a single device that combines physical interfaces to support a full range of VDV connections, with flexible "instant-on" testing that can be activated via a single button push for each type of media are suggested. Selecting between any of three buttons (voice, data or video) on the face of the unit immediately puts the tester into the proper mode and sets it up for the correct continuity. Such testers support USOC voice specifications, and shielded and unshielded data cable testing to T568A/B specifications.

This next level of testers includes a variety of handheld units that offer the capability to test and certify passive networks to meet relevant industry standards and/or to diagnose and troubleshoot problems within passive networks. These devices are typically intended for use by professional installers and/or network maintenance personnel who need more sophisticated testing capabilities, however they still must be designed for ease of use.

Testers are designed to test and certify network cabling in conformance with applicable international standards, such as TIA, EIA and ISO. Therefore, they must provide a specified set of test functions that meet stringent accuracy levels, such as Level III or Level IV.

Certification to stringent standards is an important requirement for structured networks to ensure the performance margins needed to run a variety of network protocols. This requires more than hooking up PC laptops running 10/100 Ethernet. The ability to transfer a few data packets is not a sufficient test to guarantee future performance under full load conditions or the possible deployment of other protocols, such as Token Ring, gigabit Ethernet or streaming video.

Such certification testing is critical for structured cabling because of the care that must be taken during installation and the susceptibility of such networks to failure or degraded performance if not correctly installed. For example, overstretching or excessive bending in the cable runs can negatively impact performance without necessarily exhibiting a hard failure. Sophisticated tests such as Time Domain Reflectrometry (TDR) enable the user to quickly measure the distance to such a fault condition and, therefore, aid in finding and fixing problems before the network is certified and activated. In addition to supporting copper-based interfaces, many of these higher end testers also offer options for checking and certifying fiber optic links.

Depending on the specific requirements, test functionality and accuracy levels needed, installers can choose between various testers in this category, which offer a range of price/performance alternatives. These include units that are designed for relatively low-cost testing, troubleshooting and moves, adds or changes; up through the Level III and Level IV certification testers with advanced features such as TDR, NEXT and PS ELFEXT.

The final category of testers that need to be considered are those designed for use in active networks where VDV services are up and running. In these situations, it's important that test instrumentation can automatically sense the presence of such services and to navigate within active network topologies.

In-house IT administrators or facilities staff who are responsible for network maintenance and updates (moves, adds and changes), need to inactively map network links within existing active networks and to quickly verify newly installed links. In addition, many installation contractors are increasingly called on to as surrogate facilities staff, especially for small to mid-sized business customers, which means these contractors need the ability to come back in for changes/troubleshooting.

Within active networks, these testers automatically connect to available network devices, identify available services, negotiate DHCP node assignments, and offer the ability to selectively ping remote devices. Upon power-up, the tester should immediately check for voltage on the line and connect to an active port on any hub, switch or NIC if available. The device should be able to identify the specific types of service on the link, such as Ethernet, Token Ring, ISDN or POTS, as well as reporting current and voltage capabilities for analog telephone lines.

If no connection is available upon power-up, the tester should have an automatic tone generator function to put a tone on the line. This makes it possible to quickly find the link with a tone tracer on the other end. The ability to have different types of tones also can be a big help in line tracing within complex networks.

A multi-function handheld for active networks can provide flexibility for a variety of tests and seamless navigation of multi-service network topologies. In many ways, such capabilities are equivalent to what could be achieved by connecting a laptop or other computing platform but with the ease-of-use and simplicity of a field-optimized handheld device.

For instance, such a tester can ping remote devices, either by automatically obtaining a dynamic IP address from an existing DHCP service or by directly entering a static IP address for the remote device. This feature can be very helpful for rapid troubleshooting by verifying connections from the user-end location. Most problem reports begin with a general complaint such as "I can't get on the network" that could actually result from a variety of root causes. By simply connecting the handheld tester in place of the end-user platform, a field technician can access the DHCP server or directly ping a predetermined remote static IP address inside or outside of the local network, thereby screening out or isolating any problems that might be associated with the end user's computing platform or NIC card.

As multi-service network environments become more prevalent within residential and commercial market segments, installers are faced with what seems like a difficult proliferation of choices and the need to quickly learn to deal with new challenges.

Technicians familiar with data-oriented structured networks, electricians looking to expand their market reach, and network maintenance and administration staff need to expand their knowledge and capabilities to handle VDV.

Fortunately, the newest generations of handheld testers are designed to accommodate the convergence of VDV services by providing easy-to-use automated capabilities. For contract installers serving multiple market segments, this choice between types of devices also makes it convenient to tailor their field testing capabilities for different teams (e.g. installers, certifiers, troubleshooters, etc.).

Dan Payerle is senior product manager, DataComm test, IDEAL Industries Inc.


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