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国际标准动态:
双绞线布线标准化稳步进行
Twisted-pair
cabling standards forge ahead
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摘要:随着6类标准的正式发布越来越近,人们不禁要问7类布线的前景是什么?
本文转载自《Cabling
Installation & Maintenance》,对 TIA 委员会 TR-42.7 铜质
布线系统工程分会主席 Masood Shariff 的专访内容。主要涉及 6 类标准的制订及之后的
TIA 标准发展情况。
After
the most recent Telecommunication s
Industry Association (TIA—Arlington, VA) TR-42 Engineering Committee
meeting, we posed the following questions to Masood Shariff. He
chairs TIA's TR-42.7 Engineering Subcommittee on Copper Cabling
Systems, which has primary responsibility for the TIA/EIA-568B.2
and TIA/EIA-568B.4 standards.
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CI&M: What technical issues must the TIA clarify or
resolve before a Category 6 standard can be ratified?
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Shariff: TIA
PN-3727 Draft 6 of the Category 6 standard is posted for review and
comment. There has been considerable progress in resolving key issues,
including interoperability, backward-compatibility, harmonization with
ISO/IEC (International Organization for Standardization/International
Electrotechnical Commission—Geneva), link and channel models, and measurement
procedures. This draft still has portions of the document marked "TBD,"
which stands for "to be determined." These TBD areas are awaiting more
test data for resolution. Areas so marked include insertion-loss deviation
(ILD), return-loss models, and balance for links and components, to
name a few. We expect these to be cleared up in the next couple of meetings
and intend to ballot the document by year-end.
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CI&M: When is the industry likely to see a completed
Category 6 standard?
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Shariff: The
plan for the Category 6 standard has been delayed because of several
other documents that the TIA TR-42.7 Engineering Subcommittee has been
dealing with as higher-priority items. Those other documents include
telecommunications systems bulletin TSB-95, TIA/EIA-568A-5, and the
new revision of the 568 standard, TIA/EIA-568B.2. With these items either
already completed or finishing soon, the focus and attention will shift
100% to the Category 6 effort. It is very likely that the Category 6
standard will be published in the second quarter of 2001.
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CI&M: The Category 6 standard will require system testing
to 250 MHz and specify positive attenuation-to-crosstalk ratio to 200
MHz. That is a robust transmission pipeline. For what current or future
applications or protocols will Category 6 be an ideal infrastructure?
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Shariff: The
challenge to generate interest in the applications side is to have a
stable Category 6 channel specification and plenty of installed base
over which the applications can run. We can now say the Category 6 channel
specifications have been stable for more than two years, and the installed
base of Category 6 cabling is growing rapidly, with products available
from a large number of vendors.
Applications committees
have taken notice, and Gigabit standards are in progress both in TIA
TR-41.5 and in the ATM Forum. During the week of May 15, the TIA TR-41.5
Engineering Subcommittee and its parent, the TR-41 Engineering Committee,
both approved the PN-4657 document. The document is now out for ballot.
The 1.2-Gbit ATM document is also close to ballot and should be sent
out before year-end. These standards will enable lower cost and lower-power
Gigabit transmission, making these applications much more affordable.
Both of these application
protocols are designed for Category 6 cabling and will not work over
Category 5 or Category 5E cabling. The Gartner Group (Stamford, CT)
research firm has predicted 90% of the cabling to be sold in 2003 will
be Category 6, so the message for applications developers is to move
to better cabling that can support higher data rates more robustly and
efficiently.
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CI&M: Does the TIA frequently correspond with the Institute
of Electrical and Electronics Engineers (IEEE—New York City)? Are the
two organizations currently in contact regarding any forthcoming standards?
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Shariff: The
TIA and IEEE have had a good long-standing relationship that goes back
to the days of Category 3, when the IEEE first developed its now-famous
10Base-T application. The 10Base-T standard was published well before
the TIA/EIA-568 standard, but still refers to the then-unpublished TIA
document for details on compliant Category 3 cabling to support 10Base-T.
Since the late 1980s, the cooperation and interest in each other continues
through Category 5, Category 5E, and even Category 6. Geoff Thompson,
chair of IEEE 802.3, and Jim Carlo, chair of IEEE 802, were both at
the most recent TIA meetings in Vienna, VA. Geoff makes it a point to
attend every other set of TIA TR-42 meetings. It is important to realize
that it was a request from the IEEE that extended the requirements of
Category 6 from 200 to 250 MHz.
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CI&M: Every so often, Category 7 gets mentioned. Is
the TIA currently pursuing a Category 7 standard?
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Shariff: Right
now, there are no proposals or plans from anybody in the industry to
work on a Category 7 standard in the TIA. Consequently, this is not
an active project or even a study project at this point.
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CI&M: Might that change as the ISO firms up its specifications
for a Category 7/Class F standard?
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Shariff: TIA
members who attend both ISO and TIA meetings are probably keeping tabs.
But since the market for Category 7 in North America is not clear and
the applications that will use Category 7 are not happening, Category
7 is not yet a viable option for North America.
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Masood Shariff is systems applications director at Avaya Communication
(formerly Bell Labs of Lucent Technologies—Basking Ridge, NJ).
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| Cabling Installation & Maintenance Editorial Mission
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Installers of premises and campuswide communications systems face constantly
evolving standards, products, and technology. Keeping pace with these
changes requires access to current information from informed peers who
are knowledgeable in fiber and copper technology relative to premises
communications. Cabling Installation & Maintenance provides peer-to-peer
perspective in its interpretation of standards and technology, its presentation
of installation techniques, and in the selection and use of products in
premises communications.
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| Publication |
Cabling Installation & Maintenance |
| Article Date: |
August, 2000 |
| Magazine Volume: |
8 |
| Issue: |
9 |