What makes a successful standard? And why are standards important to the industry? Here is a brief overview...
November 1, 2001
The very first set of structured cabling standards, EIA/TIA 568 and 569, were published in 1991. It was also around this time that IEEE published the 10BASE-T Ethernet standard for local area networking. This was a powerful combination of standards that came together at the right time for the industry to reap the benefits of a star cabling topology for data applications.
Before this time, each data application had its own topology and its own proprietary cabling system. These proprietary cabling systems could not be easily adapted to changes in technology or reconfigured for new applications. Consequently, these systems had both a limited use and life span. In addition, the vestiges of these cabling systems were often left cluttering up cable passageways and creating a cabling management headache.
The introduction the TIA/EIA 568-B.1 standard identifies the purpose, scope and applicability of a structured cabling standard. The following points highlight the essential building blocks:
A structured cabling system is built up from generic components and is not proprietary in nature. These components are specified for performance and for intermateabilty. TIA has a policy to ensure that any patent covering essential designs are disclosed before the publication of a standard and made available to all manufacturers under fair and non-discriminatory terms and conditions.
There are multiple products and multiple vendors that can satisfy the requirements of a standard, thus providing a choice to the end user and ways for manufacturers to differentiate their products.
The standard specifies a minimum set of performance requirements. The way that the standards process works is to encompass as broad a range of products as possible for the applications under consideration. TIA have chosen to specify different Categories of performance for a channel, for a link and for individual components.
The standard is intended to support a wide range of applications including voice, video and data for commercial building sites extending up to 3000 metres. The topology is hierarchical star with two levels of backbone cabling in a campus environment. The nodes of a star allow for flexible connectivity between the different elements comprising a cabling system.
The useful life of a cabling system is at least 10 years and many manufacturers offer extended warranties up to 25 years. Historically, networking speeds have been increasing by a factor of ten every five to seven years.
A standard is a living document that evolves to keep pace with technological advances and market needs. Over the years, the performance of copper cabling has evolved from Category 3 to Category 4, 5, 5e and currently Category 6, which is still under development. During this evolutionary period, additional transmission parameters were added and the performance was enhanced significantly. Table 1 provides a brief summary of the significant changes for the different Categories of performance.
WHAT’S THE DIFFERENCE?
What makes a particular cable or a connector different from another? You cannot tell from the outward appearance; what is on the inside makes all of the difference. A lot has changed on the inside, including the pair twists, materials, pair separators, pair symmetry and insulated conductor tolerances. The key difference is in performance.
One of the most important objectives in the development of higher performance Categories is to ensure backward compatibility and interoperability. The transmission parameters and requirements for components are specified in such a way that any higher performing component can be substituted in a lower performing channel without compromising channel performance.
People often ask why it takes so long to develop and reach agreement on a standard. One reason, is the complexity of the technical work to be done, as is currently the case for Category 6 connecting hardware. A second reason is more philosophical: A standard, like a good wine, takes time, patience and the right conditions to reach perfection.CS
Paul Kish is Director of IBDN Systems & Standards at NORDX/CDT in Pointe Claire, PQ. He is also Chair of the TR-42 engineering committee.
Disclaimer: The information presented is the author’s view and is not official TIA correspondence.
TABLE 1: Channel Performance specified at 100 MHz unless otherwise indicated
|Parameter||Category 3||Category 5||Category 5e||Category 6|
|Frequency Range||1 to 16 MHz||1 to 100 MHz||1 to 100 MHz||1 to 250 MHz|
|Insertion Loss||* 14.9 @ 16 MHz||* 24||* 24||* 21.3|
|Delay Skew (nS)||* 50||* 50||* 50||* 50|
|NEXT (dB)||* 19.3 @ 16 MHz||* 27.1||* 30.1||* 39.9|
|PSNEXT (dB)||not specified||Not specified||* 27.1||* 37.1|
|ELFEXT (dB)||not specified||Not specified||* 17.4||* 23.3|
|PSELFEXT (dB)||not specified||Not specified||* 14.4||* 20.3|
|Return Loss (dB)||not specified||Not specified||* 10||* 12|