Advertisment

Understanding the Options

author-image
VoicenData Bureau
New Update

IT and facilities managers may not be fully aware of the

cabling systems performance journey from Plain Old Telephone Systems (POTS) cable to

currently available high performance copper and optical fiber systems. It is also

difficult to stay current on all the attempts to classify performance by

"levels", "categories", "classes", "bandwidths",

or "approved applications" by either manufacturers or standards committees.

Advertisment

https://img-cdn.thepublive.com/filters:format(webp)/vnd/media/post_attachments/da11870a58aa4b2338b428f92c1875462c38c6202a7d06d258c5b04315924223.gif (13781 bytes) align="right" border="0" hspace="4" vspace="4">Whether you are

an end user, consulting engineer, contractor, distributor, or manufacturer, it is critical

to consider the dynamics between application (network protocols), cabling system

performance, and cabling system life expectancy. As it would be an error to specify a

cabling system that does not satisfy the current and future performance requirements

essential to accommodate a corporate or institutional information systems strategy, it

would likewise be an error to over-specify a cabling system for an application due to a

misunderstanding of the requirements or issues surrounding the alternatives.

In an effort to alleviate any misunderstandings concerning

cabling system transmission performance classifications, this box describes the history of

the industry’s efforts to define twisted pair cabling system alternatives, provides

an account of current industry designations and expectations for twisted pair cabling

systems. Although there are many differences between the various specifications written

around premises cabling systems, this will focus on the issues related to performance.

EIA/TIA-568



In July 1991, the TR41.8.1 working group of the Electronic Industries
Association/Telecommunications Industry Association published ANSI/EIA/TIA-568,

"Commercial Building Telecommunications Wiring Standard", to formally define the

mechanical and electrical requirements for the cable and components that made up premises

cabling systems. This standard included specifications for 100 Ohm UTP (unshielded twisted

pair), 150 Ohm STP (shielded twisted pair), 50 ohm coax and 62.5/125 optical fiber.

Twisted pair cable and connecting hardware were specified electrically as components from

1 to 16 MHz. Although a cable levels program had been proposed to the industry, time did

not permit its inclusion in the standard.

Advertisment



Figure

2
Next Attenuation ACR
Advertisment
Frequency 11801 TSB 67 11801 TSB 67 11801 TSB 67 Class D CAT 5 CAT 5 Class D CAT 5 CAT 5 Class D CAT 5 CAT 5 (MHz) Link Channel Link Channel Link Channel Link Channel Link
Advertisment
1 54 60 60 2.5 2.5 2.1 57.5 57.9 4 45 50.6 51.8 4.8 4.5 4 40 46.1 47.8 8 45.6 47.1 6.3 5.7 39.3 41.4
Advertisment
10 39 44 45.5 7.5 7 6.3 35 37.0 39.2 16 36 40.6 42.3 9.4 9.2 8.2 30 31.4 34.1



Advertisment
20 35 39
Advertisment
40.7 10.5 10.3 9.2 28 28.7 31.5 25 37.4 39.1 11.4 10.3 26.0 28.8 31.25 32 35.7 37.6 13.1 12.8 11.5 23 22.9 26.1 62.5 27 30.6 32.7 18.4 18.5 16.7 13 12.1 16.0 100 24 27.1 29.3 23.2 24 21.6 4 3.1 7.7 Shaded areas represent no

listed specifications by the designated standard. Although ACR is not specified by

ANSI/TIA/EIA-568-A or TIA TSB-67, the derived values based on NEXT and attenuation are

provided for comparison.

TSB 36:

However, shortly afterward in November 1991,

TIA TR41.8.1 published Technical Systems Bulletin 36 (TSB 36), "Additional Cable

Specifications for Unshielded Twisted Pair Cables", which further defined UTP cable

performance by "categories". TSB 36 included definitions for cable Categories 1

through 5 and mechanical and electrical specifications for Categories 3, 4, and 5. TSB 36

also replaced the 150 Ohm STP Level 5 cable with 100 Ohm Category 5 cable, which had

extended performance requirements for near end crosstalk (NEXT) and attenuation up to 100

MHz.

TSB 40:

In order to provide a similar definition of

UTP connecting hardware and, more precisely, to specify connecting hardware to match the

performance of the cable categories, TIA TR41.8.1 published Technical Systems Bulletin 40

(TSB 40), "Additional Transmission Specifications for Unshielded Twisted Pair

Connecting Hardware". TSB 40 classified connecting hardware by Categories 3, 4 and 5

and listed NEXT and attenuation specifications up to 100 MHz. Recognizing that

installation practices could affect cable performance, TSB 40 also included

recommendations for specific handling procedures, such as pair untwist and jacket removal

when terminating Category 4 & 5 cable.



Figure

3
Addendum Parameter Cat 5 E-Cat 5 (See glossary for

definition)
Power Sum NEXT Y Power Sum ELFEXT Y Y Return Loss Y Y Insertion Loss Deviation (TBD) Y Balance Y

ANSI/TIA/EIA-568-A



In October 1995, TSB 36, TSB 40 and TSB 40A were incorporated into ANSI/TIA/EIA-568
Revision A along with worst case electrical performance characteristics (Annex E

(informative)) for a UTP "channel" (see Figure 1). The channel at this time was

defined as everything from the NIC card to the LAN concentrator or hub. The components in

this channel definition included:

  • a telecommunications outlet/connector
  • a transition point
  • balanced UTP cable of 90 m (295 ft) length
  • horizontal cross-connect consisting of two connecting blocks

    or patch panels
  • a total of 10 m (33 ft) of equipment and patch cords
  • The equipment plugs were excluded since field test

    equipment couldn’t separate them from the jacks on the equipment. This was the first

    time that a published standard provided electrical performance parameters for something

    more inclusive than cabling system components. Annex E specified NEXT and attenuation

    performance for a channel constructed of Category 3, 4 or 5 components over a frequency

    range of 1 to 100 MHz. This work acknowledged the importance of cabling system performance

    and the fact that component specification alone did not assure that result.

    ISO/IEC 11801



    Also in 1995 the International Organization for Standardization (ISO) and the
    International Electro-technical Commission (IEC) published the International Standard

    ISO/IEC 11801, "Generic Cabling for Customer Premises". Like TIA/EIA-568-A,

    ISO/IEC 11801 defined the channel as all the horizontal cabling including the patch cords

    but less the equipment plugs. ISO also added a second definition called a link. The link

    was everything from the equipment panel to the workstation outlet and was considered to be

    what the contractor would leave in the wall. The link included patch cables (between two

    halves of the cross connect) but not equipment cables.

    The link model was used to determine minimum performance

    (Figure 2). Four link performance classifications were also established (Class A, B, C and

    D). Class D has the highest performance and is specified up to 100 MHz. Another difference

    between ISO/IEC 11801 and TIA/EIA-568A was the inclusion of 120 ohm UTP and 100/120 ohm

    FTP .

    Although not the first to be published, the International

    Standard ISO/IEC 11801 provides a basis for global consistency and is now strongly

    considered during the modification of all regional or national standards, including the

    American National Standard ANSI/TIA/EIA-568-A, European Standard CENELEC EN 50173,

    Canadian Standard CSA T 529, and Australian/New Zealand Standard AS/NZS 3080:1996.

    TSB 67



    Directly following TIA/EIA-568-A in 1995 was Technical Systems Bulletin 67,
    "Transmission Performance Specifications for Field Testing of UTP Cabling

    Systems". The purpose of TSB 67 was to more clearly define performance requirements

    for premises cabling systems and how they should be measured in the field. This TSB

    included separate definitions for the "Channel" and the "Basic Link"

    (Figure 1) and specified different performance levels for each (Figure 2). The numbers

    specified for basic link were more strict to allow for the addition of patch cables at a

    later time and still maintain the channel performance requirements. TSB 67 also specified

    the measuring accuracy of hand held testers in order to control the variation in results.

    Industry Stability



    At this time there appeared to be stability in the cabling system industry. Standards were
    now established that specified performance requirements for components and completely

    installed systems, providing guidelines to:

    • manufacturers of cable and connecting hardware
    • cabling system manufacturers who provide warranties on

      components or systems
    • manufacturers of hand-held field testers
    • contractors who install and verify complete cabling systems
    • Stability, however, is relative. As this brief summary of

      the premises cabling systems business has already shown, performance requirements are

      constantly changing. This first series of standards were written for cabling systems that

      supported network protocols like 10BASE-T, 4 or 16 Mbps token ring, 100 Mbps FDDI, 100

      Mbps Fast Ethernet and even 155 Mbps ATM. It would seem that these applications,

      especially the latter, would be sufficient for most any application. Right? Guess again,

      because it’s not unusual:

      • to change out workstations or PCs every one or two years.
      • to be three performance revisions behind on your PC six

        months after you purchased the fastest on the market.
      • to have 90 % of your memory resources used up on your PC or

        workstation.
      • to have creative engineers or designers staring at their

        screens waiting for networks to respond when printing or saving files.
      • to be desirous of new hardware and applications that allow

        you to be more efficient at your work.
      • for software companies to come up with new applications that

        make you desirous.
      • for hardware companies to continue to come up with machines

        that are "best in class".
      • that even though standards have been written, end users

        don’t understand cabling system performance issues.
      • and it’s not unusual for businesses, health care

        facilities, education providers, financial institutions or governments to want to install

        the highest performance cabling infrastructure they can afford in order to accommodate the

        things that are not unusual.
      • Based on the facts that hardware continues to get faster,

        application software continues to use more memory and require more bandwidth and end users

        continue to buy faster equipment, we know that network bandwidth requirements will

        continue to increase. It would also be reasonable to presume that requirements for cabling

        system performance will also change.

        Cabling systems did begin to change. Terms like

        "enhanced", "headroom", "margin", "high-end Cat

        5", "Cat 5+", "Level 6" "Level 7", "Category

        6", "Category 7" and phrases like "characterized to 350 MHz",

        "able to transmit 622 Mbps to the workstation" and "able to transmit 1000

        Mbps to the workstation" began to accompany premises cabling systems that were

        designed with various amounts of added performance margin. To better explain these current

        terms and phrases we need to look specifically at where they came from and what they were

        describing.

        E DIN-44312-5



        Due to the anticipation of increasing network bandwidth requirements, and the uncertainty
        that a Category 5 system would have high enough transmission and emissions performance for

        an emerging 622 Mbps ATM application to operate properly, a need developed to generate a

        specification to ensure that high speed data could run over copper cable systems. A

        subcommittee of the Deutsches Instutut fur Normung (DIN), the German standards body,

        generated it’s own standard for a 600 MHz cabling system. This draft specifies a

        shielded cable which a handful of mostly European manufacturers are currently producing.

        The only cable design that has met this standard is referred to as PiMF or Pairs in Metal

        Foil which describes a 4-pair cable where each pair is enveloped in foil and then an

        overall shield surrounds the 4-pair unit. The standard follows the requirements in EN

        50173 but adds a link with performance specified up to 600 MHz, which in theory would

        enable such a cabling system to support 622 Mbps ATM on two pairs using simple NRZ

        encoding.

        Additional Requirements for Category 5 and

        Enhancements




        In North America efforts are also occurring to put some boundaries around the numerous
        "enhanced" Category 5 cables that are being marketed as "enhanced

        performance" or "Cat 5+". One attempt to set boundaries comes from a

        distributor of premises cabling components. They have published a document based on a

        purchasing specification that requires their suppliers to qualify their high performance

        unshielded twisted-pair cable by a series of "levels". Three levels of

        performance are defined:

        • Level 5 – Similar to Category 5 with the additional

          specifications of 10 dB pair-to-pair ACR at 100 MHz and 10 dB power sum ACR at 80 MHz.
        • Level 6 – A new level that specifies cable with 10 dB

          pair-to-pair ACR at 155 MHz & 10 dB power sum ACR at 100 MHz.
        • Level 7 – Another new level that specifies a cable with

          10 dB pair-to-pair ACR at 200 MHz and 10 dB power sum ACR at 160 MHz.
        • The biggest concern with the effort just described is that

          it only specifies cable performance. Applications run over a system of cable and

          connecting hardware, hence the term cabling system. To cover this important issue the

          ANSI/TIA/EIA UTP System Task Group is in the process of generating two addenda to

          ANSI/TIA/EIA-568-A. One is titled, "Additional Transmission Performance

          Specifications for 100W 4 -Pair Category 5 Cabling" and the second one is entitled,

          "Additional Transmission Performance Specifications for 100W 4 -Pair Enhanced

          Category 5 Cabling" These are summarized in figure 3

          Category 6/Class E and Category 7/Class F



          Additionally, the ISO/IEC Joint Technical Committee 1/SC 25 Working Group 3 (ISO/IEC JTC
          1/SC 25/WG3) decided at the conclusion of the September 1997 meeting in Munich, Germany to

          proceed with new cabling categories and classes that will provide significant improvement

          over Category 5 and Class D. WG 3 will undertake simultaneous development of two new

          balanced cabling categories and classes. Category 6/Class E will specify cabling system

          channel performance to 200 MHz and Category 7/Class F will specify cabling system channel

          performance to 600 MHz. Category 6/Class E also specifies that the modular jack interface

          shall be maintained for all user interfaces at the TO (telecommunications outlet). The

          Category 7/Class F interface connector at the TO will be capable of 4-pair termination and

          performance. This interface connector will be internationally standardized. At this time

          the modular jack interface is the default connector.

          Extracts from a publication of AMP

          Advertisment