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Alan Bullen
Lynx Networks and Data Cabling

Aliens cause trouble in cabling

The menace has always been there but, until now, it's not been causing a problem. It's alien crosstalk and it's the effect of signals in one cable causing interference in an adjacent cable. Actually, a cable gets a sum of alien crosstalk from all of its adjacent cables.

The good news is that alien crosstalk has negligable effect in a network until you start to use 10Gigabit Ethenet (10GBase-T). The high frequencies and sensitive encoding make it susceptable but there are things we can do to mitigate the effects. The best solution is to use a Cat6a / Class Ea cabling system. Although this is not yet fully ratified, there are systems on the market that conform to the draft standard. An alternative is to use Cat6 up to distances of 35 metres (some say 55 metres) but make sure it's installed with loose looms to mitigate against alien crosstalk.

Testing for alien crosstalk in the field is time consuming and it's virtually impossible to do with 100% certainty; that would mean putting signal on to every cable and then testing each cable as a victim cable.

Luckily, the better companies in the data cabling industry are able to provide clients with cabling systems that will work at 10G so those aliens needn't bother you.

Alan Bullen
Lynx Networks plc

What's the cost of a risk assessment?

The mention of a risk assessment can make some project managers groan but it shouldn't be that way. If done properly, a risk assessment preserves health and safety and is not a bureaucratic burden. At Lynx Networks we follow the HSE's "Five Steps to Risk Assessment".

1. Identify the hazards

2. Decide who might be harmed and how.

3. Evaluate the risks and decide on precautions.

4. Record our findings and implement them.

5. Review the risk assessment and update if necessary.

To make it easier to manage our health and safety we have determined safe systems of working for each of the data cabling tasks that our installers carry out. We train our workforce and adopt the safe practices across the range of installations we carry out.

Of course, the answer to the question, "What's the cost of a risk assessment", is that it could cost you a much more, in accidents and damages, not to do it properly. If you want more information, please contact me.

"Five Steps to Risk Assessment" and example risk assessments can be found at www.hse.gov.uk/risk. For the HSE's Myth of the Month go to www.hse.gov.uk/myth.

Alan Bullen

Lynx Networks

Cabling to last a lifetime

Lifetime Cost Effectiveness
A cabling system represents the element of an voice / data network which has the longest life span and therefore requires to be designed and installed with upwards of 10 years useable life. To ensure consistent performance throughout the life of the system, the following should be considered:
• Warranty and performance guarantees from component manufacturer
• Quality components proven to meet appropriate Standards
• Manufacturers & suppliers support
• The installers have relevant qualifications and training and their installation methods fully comply with BS and EN Standards if the installation is in the UK.

Alan Bullen
Lynx Networks plc
Data Cabling Division

Read this if it's the only thing you read today; it's brilliant.

"There is hardly anything in the world that someone cannot make a little worse and sell a little cheaper, and the people who consider price alone are that person’s lawful prey. It is unwise to pay too much, but it is also unwise to pay too little. When you pay too much, you lose a little money, that is all. When you pay too little, you sometimes lose everything because the thing you bought is incapable of doing the thing you bought it to do. The common law of business balance prohibits paying a little and getting a lot .... it can’t be done. If you deal with the lowest bidder it is well to add something for the risk you run. And if you do that you will have enough to pay for something better."

John Ruskin 1819-1900

The above applies as much today as it ever did. It's particularly applicable when considering the installation of data cabling.

Cabling standards

OK, I know standards can be dull but adherence to them is crucial if your data cabling is going to support your applications.

Your cabling system should comply with British Standards. I recommend:
• BS EN 50173 series of standards for performance and components
• BS EN 50174 series of standards for design, installation, operation and maintenance
• BS 6701 for installation, operation and maintenance
• BS EN 50310 – grounding and bonding
• BS EN 50346 - testing

Alternative standards for the design and performance of cabling systems are acceptable where a specific need is identified. However care should be exercised since, whilst these standards are harmonised to a greater extent with equivalent British standards, compliance with these standards is dependent upon compliance to cross-referenced standards and this may not always be possible. Examples are:
• ISO/IEC 11801 (International)
• ANSI/TIA/EIA 568-B series of standards (USA)

Particular manufacturers may state compliance to one or more of these standards.

The standards specify a range of Classes or Categories of balanced cabling systems. Amongst these are:
• Class D (comparable with TIA Category 5e) - able to support Gigabit Ethernet (1000BASE-T).
• Class E (comparable with TIA Category 6) - able to support Gigabit Ethernet (1000BASE-T), and able to support 10Gigabit Ethernet (10GBASE-T) to a distance of at least 37m and up to 100m dependent upon the cabling type and the installation.
• Class EA (comparable with TIA Category 6A) and able to support 10 Gigabit Ethernet (10GBASE-T)
• Class F and able to support 10 Gigabit Ethernet (10GBASE-T).
• Class FA and able to support 10 Gigabit Ethernet (10GBASE-T).

Choose the specification that meets the network bandwidth needs for the foreseeable future and fits within the budget. Bear in mind that higher Class / Category cabling usually requires larger containment and pathways as the cables are a larger diameter.

The choice of optical fibre to use will depend on the applications to be supported and the distances over which they are to be transmitted. Guidance is given in the BS EN 50173-1 standard. This refers to optical fibre cabling based upon five main types - OM1, OM2 & OM3 (multimode) and OS1 & OM2 (singlemode) - and the channels over which the applications can be supported as:
• Class OF-300 supporting various applications to ≥ 300m over multimode optical fibre.
• Class OF-500 supporting various applications to ≥ 500m over multimode optical fibre.
• Class OF-2000 supporting various applications to ≥ 2km over multimode optical fibre.
• Class OF-5000 supporting various applications to ≥ 5km over single mode optical fibre.
• Class OF-10000 supporting various applications to ≥ 10km over single mode optical fibre.

I hope this helps.

Alan Bullen
Lynx Networks plc

Testing of Data Cabling

Here’s some excellent info to help you negotiate a good deal from your cabling installer and to make sure you get value for money.

There are three forms of testing data cabling:
Certification – Tests all parameters required by ratified standards and provides a certificate for each link or channel.
Qualification – Only tests the cabling to work for particular applications or network standards.
Verification – Tests only the most essential parameters.

Lynx Networks recommends certification testing for every link or channel. This should prove cost effective in the long term. It is condition of most manufacturers’ warranties that the cabling system is 100% certified.

For every installation where either certification or qualification testing is undertaken, complete individual test reports (or certificates where appropriate) configured in accordance with the agreed standard, should be included with the installation documentation. The format and material on which these reports are to be presented should form part of the contract. (See the Labelling, Records and Documentation section above).

Certification Testing of Data Cabling
Certification is carried out with a standards-compliant tester, such as a Fluke DTX, with the required accuracy for the Class or Category of cabling installed. You specify whether the cabling system is to be certified to BS EN50173 series of standards, ANSI/TIA/EIA 568-B series of standards or ISO/IEC 11801, although the choice of cabling system manufacturer may predetermine this.
By definition, certification testing includes qualification testing.

Qualification Testing of Data Cabling
For installations where a manufacturer warranty is not offered, qualification is a less stringent alternative to certification but it is important to note that qualification testing:
Uses less accurate test equipment to compare installed cabling performance with the requirements of specific applications.
Can only provide results for existing application standards.
Cannot provide any form of ‘future proofing’ as it deals only with existing applications.
Is limited to the ‘Channel’ test model, i.e. includes the equipment, patch and work area type cords.

Verification Testing of Data Cabling
This will eliminate common installation errors but will not guarantee that the cabling system will support the network or bandwidth requirements.
Minimum test and inspection for copper cabling
A visual inspection of the terminations
Wire-mapping test to confirm there are no open circuits, short circuits or crossed wires, including the cable screen if present. This will also confirm that telecommunication outlets and patch panels are identified and labelled correctly.
Plus, optionally:
Cable length
Test to ensure there are no split pairs.
For more information like this, go the www.lynxdatacabling.co.uk and download the free guide "Specifying an IT Cabling System".

Alan Bullen, Oct 2007.

Cat7 cabling

At Lynx Networks we installs thousands of cabling systems every year but we only get about one enquiry per year for Cat7. Although Cat7 cabling has a vastly superior performance to Cat5e of Cat6 data cabling, there are very few applications that can use its greater bandwidth. The good news for Cat7 is that is was ahead of it's time and can support the IEEE 10Gigabit Ethernet standard, unlike Cat5e or Cat6. Howver, there is little need for 10Gigagit Ethernet outside of the backbone or the data centre, and it competes with fibre in the applications.

The drawback for Cat7 is that it is much more expensive. It's also physically bigger than Cat5e or Cat6 so requires much bigger containment.

Fibre optic Industry Association - Approved Installer Scheme

The Fibre optic Industry Association (FIA) has recently re-launched its approved installer scheme. This has two main purposes: firstly to ensure that customer using an approved installer get a risk-free, high quality installation and secondly, to make it easier for the installer to provide it.

The software supplied to approved installers as part of the scheme ensures that over three hundred potential risks to a project are addressed and alleviated. The FIA now has the task of getting as many installers and integrators as possible join the scheme to give it critical mass, and recognition amongst the users and consultants. The scheme is soundly based on the demands of the BS 6701 and BS EN 50174 Standards.

As believers that standards in IT infrastructure and data cabling need to be maintained, Lynx Networks were the first company to sign up to the scheme.

Don't buy Cat6 cabling

Most cabling companies and virtually all manufacturers of cabling systems would prefer you to buy Cat6 cabling rather than Cat5e. My belief, as Managing Director of an honest cabling company, is that it's unlikely you'll need Ethernet speeds of more than 1Gigabit to the desk for the next ten years unless you running very demanding applications. Therefore, save your money and opt for a Cat5e cabling system. No adopted standard runs on Cat6 that doesn't already run on a compliant Cat5e cabling system, so why buy Cat6?

Cat6a, when the standard is ratified, will support 10Gigabit Ethernet so there will be a case for it in backbones, data centres and for bandwidth-heavy applications. Any Cat6a cabling systems currently being installed are proprietary systems that should meet the draft standard for Cat6a channels. It will be a while before the standard is ratified for permanent link and for the individual components of the cabling system i.e. patch leads, cable, sockets etc. Until then, every component in your cabling system would have to be supplied by the same manufacturer.

www.lynxnetworks.co.uk/cabling.asp