vendors have already released Category 6 compliant cables
and related products. But is the standard stable as yet?
by A Sitaramaiah
guess the honest answer to the title of this article is, "We're
working on it." Most manufacturers promote CAT 6 "compliant
products" like cables, jacks, patch cords, and test equipment
in the market place. IT professionals might remember that
there was a similar entry of the Category 5 and Category 5e
"compliant products" in the past. The so called
"Category 6 compliant products" started to enter
the market place in early 1998 and the list of products and
suppliers continued to grow. However, number of questions
remain unanswered. What is the real storyis Category
6 here or not? If not, where do we stand, why is it taking
so long, and when will it be finished?
The standardization process actually began in late 1997 when
ISO (International Standards Organization) proposed the objective
of a cabling system called Class E/Category 6. The basic objective
was to provide the same level of performance as Category 5
and twice the positive ACR (Attenuation Crosstalk Ratio).
Since the positive ACR of Category 5 is 100 MHz, Category
6 was designed to provide 200 MHz.
Surprisingly, the basic objective for Category 6 cabling system
performance formed in late 1997, has remained relatively unchanged
till date. The most significant change occurred in 1998 when
the IEEE (Institute of Electrical and Electronics Engineers)
asked the TIA (Telecommunications Industry Associationan
organization which sets telecommunications standards worldwide)
and ISO groups to extend the testing to 250 MHz. They were
asked to do so although the performance requirements at 200
MHz remained unchanged. So why is development on Category
6 still held up? The reason for the hold-up is largely due
to interoperability between manufacturers.
Unfortunately, getting from Category 5 to Category 6 has been
extremely challenging. Not only does the behavior of the components
become more complex as frequencies get higher, our knowledge
of what needs to be tested has changed as network protocols
become more sophisticated. Category 5 specifications were
based on two-pair applications like 10/100BaseT and Token
Gigabit Ethernet has completely changed the way we view cabling
system performance. 1000BaseT is unique because it uses all
four pairs of the cable. And each pair transmits and receives
at the same time. To accommodate multi-pair, bi-directional
applications like 1000BaseT, additional parameters have been
specified for Category 6 and Category 5e cables. The parameters
are skew, FEXT (Far End Crosstalk), PSNEXT (Power Sum NEXT),
and return loss (see box for explanations).
It seems that, more the cabling system technology evolves,
more there is to learn. It has been determined that secondary
signal reflections (those headed away from the transmitter)
are a significant, additional source of noise not accounted
for in other parameter measurements. The effect of these reflections
shows up as differences between the actual insertion loss
(attenuation) of a link or channel and the insertion loss
as determined from adding the component losses. This ILD (Insertion
Loss Deviation) is taken into consideration in the Category
Another 'new' performance parameter involved in the Category
6 standard is balance. Balance refers to the ability of the
cabling system to cancel out ambient (common mode) noise picked
up from the environment. The requirements for balance are
still under discussion and are represented by placeholders
in the draft standard.
So, where does the industry stand in the Category 6 development
process? What will you get if you install a Category 6 system
today? Well, the good news is that the system (channel and
link) performance requirements for Category 6 has been stable
throughout the development process and there are no indications
that these system specifications will change. But the main
issue of interoperability between manufacturers has yet to
The biggest challenge faced by Category 6 product designers
and the standard committee is the connecting hardware and
patch cords. The performance of the jack is highly dependent
on the plug connected to it. The jacks must be optimized to
a certain range of plug performance. The definition of this
range is still under discussion. Part of the problem is that
the range is so narrow that it is difficult to measure consistently,
from lab to lab. And until this issue is resolved there will
be little interoperability between Category 6 products. The
problem also affects manufacturers of field test equipment.
Until all Category 6 jacks are tuned to a standard plug, test
equipment will have to be provided with multiple test leads,
each suitable for a particular jack.
Now that TIA has approved TIA/EIA-568-B.1 and is wrapping
up TIA/EIA-568-B.2, the committee will be able to dedicate
much needed time to Category 6. The TIA sent out the latest
draft of the Category 6 standard for the internal committee
ballot in December 2000. They have reviewed the comments in
February 2001 and plan to send it out for an industry ballot.
However, do not expect the standard to be finalized for several
months at best. In the meantime, you should be fine as long
as you stick with your system manufacturer of choice and are
willing to accept system (channel and link) performance. Interoperability
and support for the LAN systems like 1000BaseT, is not the
issue. It is the ability to mix-and-match cable and connectivity
products, specifically jacks and patch cords.
Interference from an adjacent channel.
A change of timing or phases in a transmission signal.
(Near End Cross Talk): A measurement of crosstalk between
two wire pairs. It is the difference in signal strength between
the interfering pair and the interfered pair. The higher the
number, the less the crosstalk.
(Far End Crosstalk): A measurement of crosstalk between
two wire pairs taken at the far end of the line.
(Power Sum NEXT): In a four-pair cable, it is the algebraic
sum of the NEXT of the three pairs as they affect one pair
and return loss.
The writer is Senior Manager, Systems Engineering
& Marketing, Tyco Electronics Corporation India (P) Ltd.