What is Cat6a?
A Cat6a cabling system is higher performance than Cat6 (500MHz v 250MHz) and designed to support 10GBase-T over the full 100 metre, 4 connector channel. Cat6a uses 4-pair twisted cables and will typically use RJ45 connectors. It is backwards compatible with Cat6 and Cat5e. TIA Cat6a and the corresponding ISO/IEC Class EA standards were ratified in 2008.
What is 10GBase-T?
10GBase-T is the new IEEE Ethernet standard for running 10 Gigabit (10GBits/sec) over a suitable twisted pair copper cable of up to 100 meters. It is ten times faster than 1000Base-T and one hundred times faster than 100Base-T (Fast Ethernet).
Is it possible to run 10GBase-T over Cat5e/Cat6?
Cat5e – definitely not. Cat6 stands a chance for shorter lengths, but nothing is guaranteed. Although it was initially proposed that Cat6 systems should be able to run 10GBase-T up to 55 meters (subject to appropriate mitigation activity to reduce alien crosstalk, such as separating cables), in reality this limit may be closer to 37 metres. The problem is that correct operation at any length could depend on factors which will change with moves & changes etc. Some manufacturers will warranty their Cat6 product up to 37 meters or even 55 meters.
Why not use fibre for 10 Gigabit Ethernet?
Cost, cost and cost. There are several established fibre based 10 Gigabit Ethernet standards, including 10GBase-SR for multi-mode fibre and 10GBase-LR for single-mode fibre. However, fibre interfaces and cables are very expensive and so their use tends to be limited to backbone and data centre applications. Meanwhile 10GBase-T interfaces already cost less than their 10 Gigabit fibre counterparts and will continue to decrease. Not too long in the future, the main application of 10 Gigabit fibre interfaces is likely to be restricted to where lengths are greater than 100 metres.
Why install Cat6a?
At the time of writing (2011), 10GBase-T interfaces are still very new, expensive and power hungry. Most users are still choosing either Cat5e or Cat6 systems, on the basis that these systems are perfectly capable of running Ethernet up to 1000Base-T, which should prove more than adequate for the foreseeable future.
The argument for installing Cat6a now is one of future proofing. We expect to start seeing server motherboards coming fitted with 10GBase-T interfaces later in 2011. PC’s coming equipped as standard with 10GBase-T network interfaces will follow in due course. Thereafter, only installations with Cat6a cabling will be sure of being able to exploit this new bandwidth. Therefore, the logic goes, if the planned lifetime of a new cabling system is five or more years, Cat6a should be considered as an option. If the planned lifetime is ten or more years, Cat6a definitely appears to be the favoured solution, even for relatively low performance users.
Areas where Cat6a is already proving popular include Data Centres and Building Backbones, where users will wish to exploit the 10GBase-T interfaces as soon as it becomes more cost effective than the 10GBase-X fibre equivalent. Again, this is likely to be by around 2012 or even earlier.
Who makes Cat6a?
Most major cabling manufacturers offer Cat6a cabling systems. These come in various shapes and sizes (literally) with different manufactures making claims as to how effectively their system will meet the new standards. One thing to watch is that unlike Cat6, where effectively Cat6 = Class E, Cat6a is not exactly equivalent to Class EA. Class EA is a tighter specification, so it is possible that a system which meets the Cat6a standard will not meet Class EA
Is it better to install Shielded or Unshielded Cat6a?
One of the biggest Cat6a debates is the one regarding shielding. Traditionally in the UK, Cat5e and Cat6 systems have been installed as unshielded systems (UTP), on the basis that UTP works and shielded cabling is bulkier, more expensive to install and harder to maintain. However, one of the biggest technical problems when designing a Cat6a system is of meeting the strict alien crosstalk requirements necessary for a cable operating at 500MHz. Therefore many manufacturers and some consultants recommend a shielded Cat6a solution as the best way of meeting the requirements. The answer to this question will therefore depend on who answers it.
Is it difficult to install Cat6a?
Although definitely not a job for the general contractor, most specialist data cabling installers will be able to install Cat6a with only a little more difficulty than Cat6. However, the important consideration when planning a Cat6a cable system is planning for the physical size of the cable. Cat6a cable, either because of the shielding or because of the UTP spacing, can be as much as twice the size (measured by cross sectional area) of UTP Cat6 cable. Patch leads are also typically bulkier and less flexible. For high density applications, such as data centres or dealing room floors, this can create severe problems with the increased size requirement of cable trays, outlet boxes and patch frame managers. For this reason, some manufacturers have developed restricted Cat6a systems with smaller cable and patch cords, which will be guaranteed to support 10GBase-T only for lengths less than the full standard. Examples of such systems are the SYSTIMAX GigaSPEED Xpress solution and Brand-Rex 10GPlus Zone Cable, both supporting 10GBase-T on channels up to 70 meters (permanent link up to 60 metres).
How much does Cat6a cost?
The complete installation price of a Cat6a system will typically work out 20% more than the Cat6 equivalent and 50% more than the Cat5e equivalent. This differential will vary between manufacturers and installations.
What if I cannot justify the additional cost of Cat6a?
Even if it not possible to justify the cost of installing Cat6a to the desk, it would probably still make sense to install Cat6a links in the backbone. Traditionally data cabling systems are designed with horizontal copper cables (for connecting users) and vertical fibre cables (for connecting network equipment). However, if the lengths of the backbone links are less than 100 metres, 1000Base-T or 10GBase-T links offers a far more cost effective way of linking the network equipment. So for the relatively small cost of installing a few backbone Cat6a cables up front, far greater savings can then be achieved on the cost of the network equipment.