Archived from www.tiaonline.org/standards/category6/faq.cfm, which is sadly no longer available.
What is the difference between enhanced category 5e cable rated for
400 MHz and category 6 cable rated for 250 MHz?
Category 5e
requirements are specified up to 100 MHz. Cables can be tested up to any
frequency that is supported by the test equipment, but such measurements are
meaningless without the context of applications and cabling standards. The
Category 6 standard sets minimum requirements up to 250 MHz for cables,
connecting hardware, patch cords, channels and permanent links, and therefore
guarantees reasonable performance that can be utilized by applications.
Why did all category 6 cable used to have a spline, and now is
offered without one?
Some Category 6 cable designs have a spline to
increase the separation between pairs and also to maintain the pair geometry.
This additional separation improves NEXT performance and allows Category 6
compliance to be achieved. With advances in technology, manufacturers have found
other ways of meeting Category 6 requirements. The bottom line is the internal
construction of the cable does not matter, so long as it meets all the
transmission and physical requirements of Category 6. The standard does not
dictate any particular method of cable construction.
Is there a limitation on the size of bundles one can have with
category 6? Can you have 200-300 and still pass category 6?
There is
no limit imposed by the standards on the maximum number of Category 6 cables in
a bundle. This is a matter for the market and the industry to determine based on
practical considerations. It should be pointed out that after six or eight
cables, the performance in any cable will not change significantly since the
cables will be too far away to add any additional external (or alien) NEXT.
If we use a Cat 5e RJ45 connector and connect it to a Cat 6 UTP
cable, will the installation be Cat5e or Cat 6?
By definition (of
the standard), it will be a Cat 5e channel. The actual performance will probably
be somewhat better, but nowhere near Cat 6 requirements. Of course, you can set
up a channel using any components and measure it using a Cat 6 (level III)
compliant tester, and if it passes, it is Cat 6 performance compliant. It would
not be standards compliant however, because the components have requirements in
and of themselves to assure interoperability with other Cat 6 components.
I am receiving a lot of questions about a multipair Cat 6, is any
specification available for this cable? Does it exist?
Multipair
cables are not specifically called out in ANSI/TIA-568-B.2-1, the Category 6
standard. See section 6.1.2 below which recognizes 4-pair cables for backbone
applications. Additionally, hybrid cables consisting of multiple 4-pair cables
in a single jacket or binder may also be used for both horizontal and backbone
applications provided that the requirements of section 6.1.3 below are met.
Since Category 6 cabling is based on a 4-pair, 4-connector, 100 meter channel,
multipair cables are implemented as hybrid cables consisting of 4-pair
sub-units.
6.1.2. Backbone cable section, ANSI/TIA-568-B.2-1 Category 6 standard. Four-pair 100. UTP and ScTP cables are recognized for use in Category 6 backbone cabling systems. The cable shall consist of 22 AWG to 24 AWG thermoplastic insulated solid conductors that are formed into four individually twisted-pairs and enclosed by a thermoplastic jacket. The cable shall meet all of the mechanical requirements of ANSI/ICEA S-80-576 applicable to four-pair inside wiring cable for plenum or general cabling within a building. In addition to the applicable requirements of ANSI/ICEA S-90-661-1994, the physical design of backbone cables shall meet the requirements of clauses 4.4.3.1 to 4.4.3.6 of ANSI/TIA/EIA -568-B.2. NOTE: Additional requirements for 100 ScTP cables are located in annex K of ANSI/TIA/EIA-568-B.2.
6.1.3 Bundled and hybrid cable, ANSI/TIA-568-B.2-1 Category 6 standard. Bundled and hybrid cables may be used for horizontal and backbone cabling provided that each cable type is recognized (see clause 6.1.1 of this standard and clause 4.4 of ANSI/TIA/EIA-568-B.1) and meets the transmission and color-code specifications for that cable type as given in ANSI/TIA/EIA-568-B.2, ANSI/TIA/EIA-568-B.3, and clause 7 of this standard. Additionally, for all frequencies from 1 MHz to 250 MHz, the total power sum NEXT loss for any disturbed pair from all pairs internal and external to that pair's jacket within the bundled or hybrid cable shall not exceed the values determined using equation (1). Calculated power sum NEXT loss limit values that exceed 65 dB shall revert to a limit of 65 dB.
Why do I need all the bandwidth of category 6? As far as I know,
there is no application today that requires 200 MHz of bandwidth.
Bandwidth precedes data rates just as highways come before traffic. Doubling the
bandwidth is like adding twice the number of lanes on a highway. The trends of
the past and the predictions for the future indicate that data rates have been
doubling every 18 months. Current applications running at 1 Gb/s are really
pushing the limits of Category 5e cabling. As streaming media applications such
as video and multi-media become commonplace, the demands for faster data rates
will increase and spawn new applications that will benefit from the higher
bandwidth offered by Category 6. This is exactly what happened in the early �90s
when the higher bandwidth of Category 5 cabling compared to Category 3 caused
most local area network (LAN) applications to choose the better media to allow
simpler, cost effective, higher speed LAN applications, such as 100BASE-TX. It
is also important to note that cabling infrastructure is generally considered a
10 year investment as opposed to two or three years for electronics. Work has
already started on 10G BASE-T, and Category 5e cabling is not being considered.
With additional throughput requirements right around the corner, it makes sense
to plan ahead. Note: Bandwidth is defined as the highest frequency up to
which positive power sum ACR (attenuation-to-crosstalk ratio) is greater than
zero.
What is the general difference between category 5e and category 6?
The general difference between Category 5e and Category 6 is in the transmission
performance and extension of the available bandwidth from 100 MHz for Category
5e to 200 MHz for Category 6. This includes better insertion loss, near end
crosstalk (NEXT), return loss and equal level far end crosstalk (ELFEXT). These
improvements provide a higher signal-to-noise ratio, allowing higher reliability
for current applications and higher data rates for future applications. The
additional performance parameters provide a sort of "forgiveness factor" for
things that happen within a cabling infrastructure over its lifetime assuring
that bandwidth remains available for applications. Please note that the
bandwidth referred to above is the bandwidth to achieve a positive signal to
noise ratio between insertion loss and power sum near end crosstalk (PSACR is
greater than 0). Cat 6 cabling performance is specified to 250 MHz, or 25
percent beyond the 0 dB PSACR frequency of 200 MHz.
Will category 6 supersede category 5e?
Yes, analyst
predictions and independent polls indicate that 80 to 90 percent of all new
installations will be cabled with Category 6. The fact that Category 6 link and
channel requirements are backward compatible to Category 5e makes it very easy
for customers to choose Category 6 and supersede Category 5e in their networks.
Applications that worked over Category 5e will work over Category 6.
What does category 6 do for my current network vs. category 5e?
Because of its improved transmission performance and superior immunity from
external noise, systems operating over Category 6 cabling will have fewer errors
vs. Category 5e for current applications. This means fewer re-transmissions of
lost or corrupted data packets under certain conditions, which translates into
higher reliability for Category 6 networks compared to Category 5e networks.
I understand that a Cat 5e connector is an RJ45. Is a Cat 6 connector
also an RJ45 and will it fit into our Cat 5e socket?
The standard
connector is defined in IEC 603-7 and FCC part 68 as an "8 position modular
interface." This is commonly referred to as an RJ-45 in the United States. The
interface is required by the standard at the telecommunications outlet, but may
be used at any connection point in the channel. The physical dimensions of the
Cat 6 connector interface are identical to Cat 3, Cat 5, and Cat 5e modular
connectors and are fully backward compatible.
When should I recommend or install category 6 vs. category 5e?
From a future proofing perspective, it is always better to install the best
cabling available. This is because it is so difficult to replace cabling inside
walls, in ducts under floors and other difficult places to access. The rationale
is that cabling will last at least 10 years and will support at least four to
five generations of equipment during that time. If future equipment running at
much higher data rates requires better cabling, it will be very expensive to
pull out Category 5e cabling at a later time to install Category 6 cabling. So
why not do it for a premium of about 20 percent over Category 5e on an installed
basis?
What is the shortest link that the standard will allow?
There is no short length limit. The standard is intended to work for all lengths
up to 100 meters. There is a guideline in ANSI/TIA/EIA-568-B.1 that says the
consolidation point should be located at least 15 meters away from the
telecommunications room to reduce the effect of connectors in close proximity.
This recommendation is based upon worst-case performance calculations for short
links with four mated connections in the channel.
What is a �tuned� system between cable and hardware? Is this really
needed if product meets the standard?
The word "tuned" has been used
by several manufacturers to describe products that deliver headroom to the
Category 6 standard. This is outside the scope of the Category 6 standard. The
component requirements of the standard have been carefully designed and analyzed
to assure channel compliance and electrical/mechanical interoperability.
What is impedance matching between cable and hardware? Is this really
needed if product meets the standard?
The impedance matching
requirements of the standard are addressed by having return loss requirements
for cables, connectors and patch cords.
Is there a use for category 6 in the residential market?
Yes, Category 6 will be very effective in the residential market to support
higher Internet access speeds while facilitating the more stringent Class B EMC
requirements (see also the entire FCC Rules and Regulations, Title 47, Part 15).
The better balance of Category 6 will make it easier to meet the residential EMC
requirements compared to Category 5e cabling. Also, the growth of streaming
media applications to the home will increase the need for higher data rates
which are supported more easily and efficiently by Category 6 cabling.
Why wouldn�t I skip category 6 and go straight to optical fiber?
You can certainly do that, but you will find that a fiber system is still very
expensive. Ultimately, economics drive customer decisions, and today optical
fiber together with optical transceivers is about twice as expensive as an
equivalent system built using Category 6 and associated copper electronics.
Installation of copper cabling is more craft-friendly and can be accomplished
with simple tools and techniques. Additionally, copper cabling supports the data
terminal equipment (DTE) power standard developed by IEEE (802.3af).
PCs ship with copper network interfaces included, in fact, recent announcements
indicate that the major PC vendors are shipping 10/100/1000 with all new
systems. Moving to fiber would mean buying a fiber-based network card to replace
equipment already included in the PC.
We have a Category 6 installation in a campus dormitory environment
and recently discovered that several horizontal runs exceed 295 feet.
The application is 10/100 access from the dormitory room to the Internet. For
those locations beyond the 295 feet, we found the only workable solution is for
the PCs to run 10Mbps 1/2 duplex.
What is meant by the term "electrically balanced"?
A
simple open wire circuit consisting of two wires is considered to be a uniform,
balanced transmission line. A uniform transmission line is one that has
substantially identical electrical properties throughout its length, while a
balanced transmission line is one whose two conductors are electrically alike
and symmetrical with respect to ground and other nearby conductors.
* "Electrically balanced" relates to the physical geometry and the dielectric properties of a twisted pair of conductors. If two insulated conductors are physically identical to one another in diameter, concentricity, dielectric material and are uniformly twisted with equal length of conductor, then the pair is electrically balanced with respect to its surroundings. The degree of electrical balance depends on the design and manufacturing process. Category 6 cable requires a greater degree of precision in the manufacturing process. Likewise, a Category 6 connector requires a more balanced circuit design. For balanced transmission, an equal voltage of opposite polarity is applied on each conductor of a pair. The electromagnetic fields created by one conductor cancel out the electromagnetic fields created by its "balanced" companion conductor, leading to very little radiation from the balanced twisted pair transmission line. The same concept applies to external noise that is induced on each conductor of a twisted pair. A noise signal from an external source, such as radiation from a radio transmitter antenna generates an equal voltage of the same polarity, or "common mode voltage," on each conductor of a pair. The difference in voltage between conductors of a pair from this radiated signal, the "differential voltage," is effectively zero. Since the desired signal on the pair is the differential signal, the interference does not affect balanced transmission. The degree of electrical balance is determined by measuring the "differential voltage" and comparing it to the "common mode voltage" expressed in decibels (dB). This measurement is called longitudinal conversion loss "LCL" in the Category 6 standard. * The ABCs of the Telephone, Vol. 7
I was under the impression that Cat 6 could run 1000 Mbps out to 295
feet. That being the case, why can't we run 100 Mbps beyond 295 feet if the Cat
6 specifications provide for better performance? Is there a distance matrix for
Cat?
100 Mbps will have the same constraints as 1000 Mbps or even
worse due to the quality of the electronics. The 2 volt nominal signal for both
drops away due to signal strength past 295 feet in the link, which then allows
for a further 33 feet for patching and cross connecting. 10BaseT uses a 5-volt
nominal signal that can support further distances more frequently, but it still
comes down to the quality of the transceivers. For example, just because port 1
in a switch can support a 110% of the recommended length for a particular
protocol doesn't mean that port 2 will. You can have great noise reduction, but
if your signal strength isn't sufficient any extended length support is lost.
The problem network administrators face is that they don't know which ports have
the best signal strength to support longer than standard runs. Cycling back to
10BaseT half duplex is the safest bet for such circumstances, but then not only
slows the speed, but introduces localized collisions and in many cases CRC/FCS
errors.
The use of a repeater/hub/switch can be implemented to support extended runs at the end of the link. This will then allow for further extension, but add an additional hop and latency. As extended runs are typically the exception rather than the rule, this solution will ensure full speed is supported, but will limit the amount of network management on the drops extended, without SNMP at the repeater.
It is also important to check the full length of the cable run to be sure
that there is not interference being introduced such as a cable sitting on top
of a fluorescent light or having sheaths cut. Consult the manufacturer for
specific warranty provisions that may be applicable.
Are the connectors for category 5e and category 6 different? Why are
they more expensive?
Although Category 6 and Category 5e connectors
may look alike, Category 6 connectors have much better transmission performance.
For example, at 100 MHz, NEXT of a Category 5e connector is 43 decibels (dB),
while NEXT of a Category 6 connector is 54 dB. This means that a Category 6
connector couples about 1/12 of the power that a Category 5e connector couples
from one pair to another pair. Conversely, one can say that a Category 6
connector is 12 times less "noisy" compared to a Category 5e connector. This
vast improvement in performance was achieved with new technology, new processes,
better materials and significant R&D resources, leading to higher costs for
manufacturers.
How can I determine the installation requirements for Cat 6 such as
termination, minimum radius around corners, proximity to electrical devices
(ballasts, wiring, etc.)?
The requirements for installation of
Category 6 are essentially the same as the requirements for Category 5e.
Installation practices are in the TIA-568-B.1 and TIA-569-A documents.
Which standard addresses the combination of electrical cable and Cat
6 regarding performance or sensitivity?
I'm an ICT Consultant for a
university and in process of designing the infrastructure for them. They are
using Cat 6 cable as horizontal cabling and fiber optic as backbone. We are
facing a problem with M & E consultant on the trunking design. They are
proposing the use of a 4-way service box which contains cables for electrical
and Cat 6. We cannot find in the standard about the combination of electrical
cable and Cat 6 cabling either of performance or sensitivity.
TIA/EIA-569 "Commercial Building Standard for Telecommunications Pathways
and Spaces" includes all necessary provisions for service boxes and enclosures.
There are no special considerations associated with Cat 6 cabling.
What will happen if I mix and match different manufacturers'
hardware?
If the components are Category 6 compliant, then you will
be assured of Category 6 performance. Consult the manufacturer for specific
warranty provisions that may be applicable.
Will contractors be able to make their own patch cords?
Category 6 patch cords are precision products, just like the cables and the
connectors. They are best manufactured and tested in a controlled environment to
ensure consistent, reliable performance. This will ensure interoperability and
backward compatibility. All this supports patch cords as a factory-assembled
product rather than a field-assembled product.
Do you have to use the manufacturer�s patch cords to get category 6
performance?
The Category 6 standard has specifications for patch
cords and connectors that are intended to assure interoperable Category 6
performance. If manufacturers can demonstrate that each component meets the
requirements in the standard, minimum Category 6 performance will be achieved.
However, manufacturers may also design their products to perform better than the
minimum Category 6 requirements, and in these cases compatible patch cords and
connectors may lead to performance above the minimum Category 6 requirements.
Are there any issues with a scenario of Category 6 horizontal run,
but a user with a Category 5 office patch cable?
The main issue with
using Category 5 patch cords with Category 6 horizontal cabling is transmission
performance and Category designation by TIA standards. TIA-568-B standards
series require that all components of a link or channel be Category 6 for a
horizontal run to be classified as Category 6. Testing installed cabling is
additional and optional in TIA and if used there are additional requirements for
links and channels for Category 5e and Category 6. The horizontal run containing
Category 6 cable and Category 5 patch cords will be designated by the lowest
Category component, i.e., Category 5.
Transmission performance of Category 6 is significantly improved over Category 5, especially in the areas of NEXT, ELFEXT and Return Loss. Hence using poor patch cords could easily degrade the performance of the horizontal run, especially since these cords are so close to the equipment where cross-talk coupling is very strong. So depending on the application, this may potentially translate into increased frame errors, or CRC errors.
Can Cat 5e patch cords be used with a Cat 6 horizontal
infrastructure, specifically for 10/100 Mbps Ethernet applications? I imagine
lower Cat 5 characteristics would be the expected performance.
Cat
5e patch cords can be used with a Cat 6 horizontal cabling infrastructure. This
is one of the advantages of Cat 6 in that it is backward compatible. However,
the resultant channel will be rated Cat 5e, because a channel is rated according
to the lowest performing component that is included in the channel
(TIA-568-B.1).
Can you tell me where I can find a list of test facilities that can
certify that a Cat 6 cable tester complies to TIA-568?
Testing
facilities such as UL and Intertek/ETL SEMKO provide assessment services for
various products. Typically the tester manufacturer participates in a program
with one or more of these facilities. These services are much wider in scope
than simply verifying the accuracy and calibration of a particular testing
device. For more information on calibration services you should refer to the
technical documentation accompanying your tester.
When Category 6 systems are being installed, do the standards
encourage both channel and permanent testing? I have heard that channel testing
has been taken out of the Cat 6 standard. Is this true?
No, Cat 6
channel testing is still in the standard. There is nothing to preclude you from
doing this in the standards. There may be issues relating to the installation,
bend radius of the cable, etc., but these can be overcome with the correct
design of back box, etc.
Why do field tester manufacturers offer many different link adapters
if everyone meets the standard?
This was an interim solution while
the standard was still being developed and the interoperability requirements
were not yet established. It is likely that soon one or more adapters will work
for testing of cabling from all vendors.
Would you get passing test results if you used a link adapter not
recommended by a manufacturer?
You should expect to get passing
results if both the link adapter interface and the mating jack that is part of
the link are both compliant to Category 6 requirements. Consult the manufacturer
for specific warranty provisions that may be applicable.
I just installed a Category 6 system and tried to certify the channel
with "field tester A" and it failed. Then my other technician brought our "field
tester B" to the site and the channel passed. Why am I getting such different
results between testers?
This is a difficult question to answer from
a general standpoint. There may be a calibration problem or adapter problem with
field tester A for example. It may be also instructive to look at the detailed
results for the test. It may be that the channel configuration is just barely
passing with tester B and just barely failing with tester A. All test equipment
has a finite level of accuracy and repeatability. These levels are stated in the
tester documentation. Also with Cat 6 cabling, the magnitude of many parameters
being measured is much lower than that of Cat 5e. The measurement frequency
range is also much wider. So while it may appear that two testers have greatly
different results (in dB), the total difference may be less than the Level III
accuracy requirements. To cover this issue in detail is beyond the scope of this
document and requires a working understanding of measurement scales (dB vs
mV/V).