Tag: structured cabling

Is there a minimum length?

For Category 5e and 6, there is no minimum length requirement. ANSI/TIA/EIA-568-B.2-1 in Annex K does give a warning about reflected FEXT on shorter links with minimally compliant components. The obvious solution is not to purchase minimally compliant components. In the early days of Cat 6 when vendors were struggling to do better than marginally compliant, short links were an issue. Today, this is not an issue if you stay with a main stream vendor.

Within this same standard, there is also advice on distance when using a consolidation point. It advises a minimum distance of 5 m between the CP and TO. In ISO/IEC they are a little more clearer is specifying 15 m between the DP and CP. This is all for Category 6/Class E.

With regards to Category 6A, there is a minimum length requirement – kind of. In Annex J of ANSI/TIA-568-B.2-10 is describes worst case modeling using a 10 m link. The suggestion therefore is that you should not go less than 10 m. But again, that is with minimally compliant components. As with Category 6 stated above, there are now components available that will give you passing field tests below 10 m. HOWEVER, even vendors with good components may still have a minimum length requirement in their design specifications. The only way to know where you stand is to talk to the vendor AND test it to see.

If you are talking specifically about patch cords, then 0.5 m is the implied minimum length in ANSI/TIA/EIA-568-B.2-1 for a certified patch cord. That’s because the math for the limit lines really does not work below this. Infact, getting a certified patch cord of 0.5 is going to be tricky. Many vendors only offer a certified patch cord of 1.0 m or longer. I suspect that this may be the most useful information with regards to your question.

Kind regards

Adrian Young
Sr. Customer Support Engineer

Fluke Networks Technical Assistance Center
6920 Seaway Blvd, Everett, WA 98203
Toll Free 1 800 283 5853
International + 1 425 446 4519

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Kind regards

Adrian Young
Senior Technical Support Engineer
Fluke Networks Technical Assistance Center


Copper Structured Cabling

Some of the most obvious advantages copper offers is that it’s less expensive than fiber cable and much easier to terminate in the field. Because copper structured cabling is the most commonly installed cable, there is a vast selection of connecting hardware and networking devices, which are also less expensive than fiber equipment.

Unshielded twisted pair (UTP).
UTP. This is the most widely used cable. Known as balanced twisted pair, UTP consists of twisted pairs (usually four) in a PVC or plenum jacket. When installing UTP cable, make sure you use trained technicians. Field terminations, bend radius, pulling tension, and cinching can all loosen pair twists and degrade performance. Also take note of any sources of EMI. Choose UTP for electrically quiet environments.

Shielded twisted pair (STP, F/UTP, S/FTP, ScTP, S/STP).
Use shielded cable to extend distances and to minimize EMI. Sources of EMI, commonly referred to as noise, include elevator motors, fluorescent lights, generators, air conditioners, and printers, etc. In 10-GbE, shielded cable can also reduce ANEXT. Shielded cable can be less balanced than UTP cable because of the shield. The metal sheaths in
the cable need to be grounded to cancel the effect of EMI on the conductors. Shielded cable is also more expensive, less flexible, and can be more difficult to install than UTP cable. Most shielded cable is thicker than UTP, so it fills conduits quicker. Keep that in mind as you plan your cable pathways. STP. This is twisted pair cabling with a shield. There are two common shields: foil sheaths and copper braids. Foil gives a 100% shield while a copper braid
provides 85% to 95% coverage because of the holes in the braid. But, a braided shield offers better overall protection because it’s denser than foil and absorbs more EMI. A braided shield also performs better at lower frequencies. Foil, being thinner, rejects less interference, but provides better protection over a wider range of frequencies. For these reasons, combination foil and braid shields are sometimes used for the best protection. Shields can surround all
the twisted pairs and/or the individual twisted pairs.Foiled/Unshielded Twisted Pair (F/UTP). Foil is the
most basic cable shield. Cables with an overall foil shield surrounding all the pairs are called F/UTP. These may also be called FTP cables. Shielded Foiled Twisted Pair (S/FTP). This cable features individual foil-shielded pairs and an outer shield, which can be braided or foil. It offers the best protection from external noise and ANEXT. This cable
was traditionally called Screened Twisted Pair (ScTP). You may also see it listed as S/STP.

Solid vs. stranded conductors.
Copper cable conductors can be solid or stranded, whether the cable is shielded or unshielded. Solid-conductor. This cable is designed for both backbone and horizontal cable runs. Use it for runs between equipment rooms or from the telecommunications room to the wallplate. Solid cable shouldn’t be bent, flexed, or twisted. Its attenuation is lower than that of stranded-conductor cable. Stranded-conductor. This cable is used primarily as a patch cable between the outlet and desktop and between patching equipment. Stranded-conductor cable is more flexible than solid-core cable. However, attenuation is higher, so the total length of a stranded cable in your channel should be kept to
10 meters or less to reduce signal degradation.

PVC vs. plenum.
PVC cable features an outer polyvinyl chloride jacket that gives off toxic fumes when it burns. It’s most commonly used between the wallplate and workstation. It can be used for horizontal and vertical runs, but only if the building features a contained ventilation system. Plenum cable has a special coating, such as Teflon® FEP, which doesn’t emit toxic fumes when it burns. A plenum is a space within the building designed for the movement of environmental air. In most office buildings, the space above the ceiling is used for the HVAC air return. If cable goes through that space, it must be “plenum-rated.” LS0H (Low Smoke, Zero Halogen) is a type of plenum cable with a thermoplastic compound that reduces the amount of toxic and corrosive gases emitted during combustion.

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Copper Cabling Review

Those of you who have been following my blog know that I love to write about what I classify as the soft sciences. By that I mean protocols, call flows, software, security, and other technologies that are for the most part, hardware and infrastructure independent. Does it make much difference if I run a SIP stack on a PC, virtual server, or smart phone? Not really. SIP acts like SIP no matter what platform is sending or receiving it.

So, it may come as a surprise that today I am writing about something that has little to do with source code or security certificates. I want to espouse on Ethernet cables.

Honestly, I didn’t give cabling a lot of thought until last week when I was speaking at an Avaya Users’ Group meeting in Tampa, Florida. After the president discussed old and new business, he opened the floor to the members to ask questions of their fellow Avaya users.

The questions were good. I took notes on several and chimed in where I felt I had something to add. However, the one that I found most interesting was this, “We are in the process of redoing our building’s LAN cables and I was wondering if people are installing Cat-5 or Cat-6.”

The answers varied quite a bit. Some folks already made the switch, a few decided not to, and some fell into the not-sure-what-we-will-do category.

For those of you who don’t have a plan (and I will assume that many of you are in that camp), allow me to spend some time introducing you to the Cat-5, Cat-5e, Cat-6, and Cat-6a Ethernet cables.

But first, this handy-dandy comparison table.


Length (meters) 10 Mb/s 100 Mb/s 1 Gb/s 10 Gb/s Power Over Ethernet Frequency in Mhz
Cat-5 100  Yes  Yes  Yes 100
Cat-5e 100  Yes  Yes  Yes  Yes 100
Cat-6 100 (55m for 10Gb/s)  Yes  Yes  Yes  Yes  Yes 250
Cat-6a 100  Yes  Yes  Yes  Yes  Yes 500


The Differences

As the class of cable goes up, so does the speed and frequency of the wire. The biggest difference between Cat-5/5e and Cat-6/6a is the speed. Cat-5/5e tops out at 1 Gb/s and Cat-6/6a allows speeds up to 10 Gb/s.

The difference between Cat-6 and Cat-6a is that Cat-6 is only guaranteed for a distance of 55 meters at 10 Gb/s. Cat-6a can run at that same speed for up to 100 meters.

Physically, Cat-5/5e and Cat-6/6a differ in a number of ways. First, there are more twists per centimeter of wire in Cat-6/6a. Cat-5 and Cat-5e typically uses 1.5 to 2 twists per centimeter and Cat-6 and Cat-6a uses 2+ twists per centimeter. Twisting reduces interference between internal and external wires.

Second, Cat-6/6a use a thicker outside sheath than Cat-5/5e. This sheath protects against near end and alien crosstalk. Crosstalk is more likely as the frequency (Mhz) increases. Cat-6 and Cat-6a support higher frequency ranges so they have the thickest sheaths.

Lastly, a nylon spline (a longitudinal separator in the wiring) can also be used to reduce crosstalk. Cat-5e always has a spline, Cat-5 sometimes has a spline, and depending upon the manufacturer, Cat-6/6a may also have a spline. Since Cat-5e requires a spline and Cat-5 does not, Cat-5 has a thicker outside sheath than Cat-5e.

Cost-wise, Cat-6 and Cat-6a are about 10 to 20 percent more expensive than Cat-5/5e. So, cost is not a big issue considering the fact that you can obtain speeds ten times faster when you go to Cat-6/6a.

It’s important to know that Cat-6 and Cat-6a are backwards compatible and can be used with older Cat-5, Cat-5e, and even Cat-3 equipment.

Should You or Shouldn’t You?

If it were me, every new installation would use Cat-6a wiring. Running cable through a building is an expensive proposition and since most cable will stay in place for up to 10 years, I would future-proof my company by adding the fastest option available whether I was ready to rollout 10 Gb/s or not.  Running cable twice in a short amount of time would be very foolish

However, I would not pull out perfectly good Cat-5e cable if I wasn’t ready to move to a higher speed. Wait until you need it before spending the money. Besides, by that time, there may be something even better that you can run.

Mischief Managed

This is an important topic that may not jump out at you as you look at upgrading your network switches and routers. However, as you saw, cable choice can make the difference between lightening fast and yesterday’s speeds.

Notice that I didn’t mention Cat-7 cables. For some folks, Cat-6a is ancient history. However, that wasn’t the original question and I need to leave myself something for a future blog article. Stay tuned.

first article from andrew

Low Smoke Zero Halogen Cable (LSZH)

What are Halogens?
When grouped together, the elements fluorine, chlorine, bromine, iodine and astatine make up a chemical family known as the Halogens. You may not have been aware of it, but halogens have many uses, and most of us come into contact with them on a daily basis. Just think about it: the fluoride in your toothpaste, the chlorine in your pool, the iodine in your medicine cabinet…they’re all halogens!


Halogens as Flame Retardants
Pool maintenance, first aid and dental hygiene aside, halogens are also widely used as flame retardants in a variety of plastics, including the PVC (polyvinyl chloride) that makes up many cable jackets and electronics-related products. Unfortunately, when it comes to the health of both humans and the environment, halogen-based flame retardants can be a double-edged sword.
Ironically, while these halogen compounds keep plastics from catching fire and spreading flames, they can also release hazardous gases if the plastic actually ignites. Carcinogenic substances like Polychlorinated Biphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), Nitro Polycyclic Aromatic Hydrocarbons and dioxins are all by-products produced when halogenated plastics burn. These gaseous compounds pose a double threat…not only are they dangerous in vapor form, but they can also condense into caustic acids (such as hydrochloric acid) when they come into contact with water.


Low Smoke Zero Halogen Materials: a Safer Alternative
It’s all in the name… “Low Smoke Zero Halogen” sums everything up: these materials (such as polypropylene) contain absolutely no halogens, but still have excellent flame resistance and produce very little smoke when burned.
LSZH cabling is the safest choice for plenum use and any other applications in which smoke is likely to both build up and come into contact with people, since no harmful toxins are actually released.

LSZH Structured Cabling