Testing the alternatives

According to a recent survey, 10% of local area network (lan) installations require the contractor to return to the job because of network performance problems. Callbacks are costly; they waste time and damage the contractor's reputation. Most callback problems are caused by improperly terminated cables and jacks, or cable damage caused by other contractors.

The case for certification

The obvious solution to minimise the possibility of callbacks is to carry out a full certification test to the appropriate EIA/TIA or ISO/IEC standards on every link in the system. This is the basis on which manufacturers issue long-term warranties through their approved installer schemes.

The certification test procedure and report proves that the structured cabling system will support the applications running over it and will perform well under normal network load conditions provided that the system components are suitable for the job. Certification testing is essential for all large-scale commercial installations and will undoubtedly be integral to such contracts. Such procedures should be insisted upon by the end-user, and indeed by all responsible contractors, who will routinely build in the cost of full certification testing and reporting to every job.

However, there are some jobs that just do not justify the expense of full certification testing. For contractors involved in networks for small business premises or residential projects for example, the cost of a full certification tester (typically in the range £3500-6000) may be prohibitive.

Rental of test equipment is one option in such cases; and certification may be offered at extra cost. Open discussion with the end-user is key here. Many end-users on smaller projects will not have the benefit of high level IT expertise in-house or through a consultant and will be relying to some degree on the contractor for networking advice.

Qualification test equipment

Qualification testers have been developed by manufacturers to provide a simple and affordable method for verifying and qualifying the performance of installed cable in small installations.

Unlike certification testers, qualification testers do not certify installations to EIA/TIA or ISO/IEC standards and can't be used to validate a manufacturer's warranty. Instead they provide a simple pass/fail test against specific application standards such as IEEE 802.3ab for Gigabit Ethernet. That way, an installer can demonstrate to the end-user that specific applications will run across the network without problem.

Qualification testers provide comprehensive cable testing for voice, data and video applications. They test a link's ability to support applications by transmitting 10/100/1000 Mb/s Ethernet packets and measuring the link performance and errors according to the IEEE 802.3ab Gigabit Ethernet standard. This simple pass/fail test determines within seconds whether or not the installed cable can support applications such as Ethernet or Gigabit Ethernet. Most testers offer the capability to speed-test actual data transmission rates up to 1 Gb. Some testers also support bit error rate testing (BERT) for VoIP, data and video over IP applications.

On more advanced models, users can configure the tester to run for several minutes or hours at a time to stress test the link for dropped packets. This monitoring mode allows the qualification tester to be used in place of traditional monitoring tools that can cost thousands of pounds to deploy.

Some models feature an integrated time domain reflectometer (TDR) to locate faults on Category 3, 5, 5e and 6 cable as well as co-axial, telephone, security alarm and audio lines. The tester's TDR can be used to show cable length and distance to shorts, split pairs and opens. Most testers can also inform technicians what device is at the end of a cable run, such as its own remote handset, a live network device or an open link. It can then perform the correct test suite based on the links' current configuration.

The best qualification testers are designed for ease of use and flexibility and include good reporting and data storage systems.

Making the choice

Qualification testers are a cost-effective alternative for contractors working on smaller installations where certification is not required or demanded by the client. They may also be a useful addition to the toolset for end-users, who may need to check performance issues as the demands on their network change.

This new generation of tester is considerably less expensive and easier to use than instruments designed for certifying cabling installations - typically in the range £700-1100. The testers provide even the most novice technician with the ability to check the network speeds a cable can support, to test every piece of installed cabling and prove that the cabling system worked when the installation was completed.

Qualification testing also provides the contractor with a more affordable way to document that installations are defect-free and will meet user's expectations for quality and reliability. The creation of documentation helps prove the performance of every cabling run.

As so many networks are classed as mission-critical, more end-users are starting to take a serious interest in test results as a way to check, document and report to management that their constantly changing network is functioning to specification. For example, organisations making the transition from 10 Mb/s to 100 or 1000 Mb/s Ethernet are finding that higher speed transmissions are more susceptible to cable and connector-related problems, so being able to test and quantify performance to identify where any problems may be, rather than just waiting for the network to fail, is a major advantage. In the same way, qualification testing is always a good idea after moves, adds and changes, or prior to a cabling upgrade.

The cabling standards such as EN50173-1, ISO/IEC11801 and TIA/EIA-568-B define how local area networks are designed, installed and tested, and they remain the principal points of reference for all contractors working on large-scale and mission-critical commercial projects. The standards system and the full certification testing it demands is central to maintaining the quality and performance of commercial IT infrastructures and protecting the interests of contractors and their customers.

For contractors working on smaller jobs where certification is not required or demanded by the customer, qualification testing is a cheap, reliable and versatile way of proving that the cabling met agreed performance criteria when the installation was complete. It will also confirm whether an existing system has the capacity to support higher bandwidth applications.

While no qualification tester completely replaces a high-end cable certifier, the latest products provide a cost-effective solution for everyday network performance testing and troubleshooting.