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

Bicsi

BICSI is an association that support the IT infrastructure industry with information and education for individuals and companies, and it does a good job.

If an end-user sees that a provider has BICSI accreditations then it's a good sign. However, there's a massive difference between membership and accreditation. It irritates me that for £160 a year a company can use the BICSI logo on its stationery and advertisments and fool many people into thinking that it's some sort of endorsement of quality; it is not.

Now, a BICSI qualification is another matter. It takes a lot of hard studying to gain one and maintain it, particularly the RCDD (Registered Communications Distribution Designer). To be a BICSI Platinum Prestige Contractor is even harder. The company has to have several qualified staff and pay a higher annual fee.

So, if you're impresses by the Bicsi Corporate Member logo why don't you simply buy yourself one for just £160 a year.

Alan Bullen
Lynx Networks

IP Telephony saves data cabling costs

As you may know, at Lynx Networks we provide IP telephony as part of our portfolio of IT infrastructure. A significant benefit of IP telephony is that only one network outlet is required per desk; the phone is connected to the outlet and the user's PC plugs into the phone.

Because voice traffic is time sensitive, the phone handset assigns each voice packet a priority flag. I liken this with putting a blue light on top of a police car to it isn't delayed by ordinary traffic. At the communications cabinet, the phone / PC is patched to a single switch port. The switch and other devices in the network see the priority flag and pass the voice traffic before ordinary data.

Alan Bullen

Lynx Networks

Superfast cabling installation with pre-build assemblies

For data cabling that has to be installed over a very short period, an excellent solution is to use pre-build cable assemblies.

HellermannTytons RapidNet, a pre-tested, pre-terminated complete network cabling system, is an example of this.

The solution only works for sites where cables are to be installed in raised-floor voids of with overhead ladder raceways, and costs may be higher. However, it can be very economical solution when time it tight and quality must be guaranteed.

Alan Bullen
Lynx Networks

WARNING - Watch out for aluminium "Cat5e" or "Cat6" cable

If you're offered some cheap (so called) Cat5e or Cat6 data cable be warned that it could have aluminium as opposed to copper conductors. Even though it may say Cat5e or Cat6 on the jacket, it won't be. It's not possible to produce a Cat5 or Cat6 compliant cable without copper.

The conductors will probably be coated with copper to try and fool you.

Always buy a well known brand of cable from a reputable supplier.

Alan Bullen
Lynx Networks for data cabling and IT infrastructure

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.