Total cost of ownership is increasingly important in the purchasing decision for structured cabling systems, but what must be considered?
There are several factors that must be considered when determining the category or class of cabling to use in a network infrastructure. This is true for both copper and fibre.
Factors include:
- expected installed lifetime;
- applications that will run on the cabling;
- the timeframe during which standards, applications and electronics manufacturers will support the cabling;
- cost of active electronics;
- warranty length and components covered; price as it relates to performance;
- time the end-user will occupy a facility.
There is an intricate balance between forward movement in technology and addressing the needs of legacy systems. The final cabling choices for the pending 10GBase-T standard is installed legacy Category 6 with a supported distance up to 55 m; augmented Category 6 (UTP or F/UTP) and Category 7/class F, with the latter two supporting up to 100 m.
It is important to note that Category 5e is not considered suitable for 10G operations. In order to support future 10GBase-T applications, which is likely to occur over the next ten years, Category 5e systems will be replaced. You will pay fees for removal of abandoned cable (now required by fire codes and legislation in many countries) and to allow some reuse of pathway and spaces.
Cost factors
Part of the selection process should include the cost of the cabling itself as well as other factors that contribute to the overall cost over its entire lifetime.
A costly factor in these calculations is labour, which will vary depending on geographic location. In many locations, labour will be the single most costly factor over the life cycle of a cabling system. The comparison table (over) is based on ‘normal' installations and does not account for overtime or tracing of cables if the labelling and documentation on the system was not adequately maintained. These would increase the overall total cost of ownership.
The analysis shown in the bar chart, over, compares the total cost of ownership for a 24 channel cabling system ranging from Category 5e through Category 7/class F. Initial costs include the components, installation and testing. The figures are based on average installation costs for a low smoke zero halogen (lsoh) system.
The total cost of ownership includes the cabling and components at the original installation and the costs for remediation of each cabling plant to go from today's 10/100 applications to 1G through 10G. This result is divided by the years of useful life to give annualised costs. Category 7/Class F systems have a longer life cycle as this will support 10G and 40G, which is expected to be the next speed increase for copper.
The effects of life cycles
Remediation costs include downtime and lost productivity costs due to testing or recabling. Downtime costs are based on national average wages and average lost revenues from published figures.
While there is a small differential in the component costs at the original installation, adding labour to test for additional performance parameters or remove non-compliant channels increases the total cost of ownership for the lesser performing systems over their useful life.
Note the Category 6 and 5e systems also have a shorter useful life so their annualised costs are higher than systems that support faster applications over time.
From the time that 5e is installed to run Gigabit (including retesting for the new power sum parameters and remediation of channels that fail), adding the labour to remove the system for 10G, we can see that the overall total cost of ownership (total cost of installation + additional labour costs/useful life = annualised costs) is the most expensive system.
The 5e system shown in the bar chart is depicted in annualised form to the point at which it is removed. When a new system is installed, a new total cost of ownership will apply, so for the costs shown with 5e at 10G speeds, we have no cabling system for our network.
Total cost of ownership is increasingly important in the purchasing decision for structured cabling systems, but what must be considered? Carrie Higbie explains.
For the Category 6 system, the installation costs, plus testing to determine channel length and to replace channels over 55 m are all added for a total cost of ownership. Again, we divide the total cost of ownership by the useful life for the annualised cost.
Additional labour will be needed for mitigation to support 55 m, but varies by site and is not included. Examples of this include allocating more space for new patch panels and increasing the number of core drills to accommodate lower fill limits. The lower fill limits are necessary to mitigate alien crosstalk (AXT). No change is necessary for 10G 6, 10G 6A F/UTP or Category 7 TERA to support 10 Gigabit.
To shield or not to shield?
The greatest disturber in 10G systems is AXT. In order to decrease this cable-to-cable noise you must mitigate it or move to a shielded system where AXT is not a concern. Table 1 does not include mitigation costs for existing plants, only the testing and replacement for channels over 55 m. Mitigation techniques include shortening lengths, moving to shielded patch cords, unbundling cables, providing port separation at outlets and panels etc.
There is also a new augmented Category 6 UTP cable that has an overall allowable diameter of 9 mm. This increased diameter mitigates AXT by providing separation of conductors from one cable to the next. Compare the 9 mm diameter to Category 6 cable (6·35 mm) and Category 6A F/UTP (6·73 mm). In instances where the larger cable is installed, conduit and cable tray fill ratios must also be increased. For 1000 channels at 100 m, the additional costs for an augmented Category 6 system including pathways are shown in table 1.
As you can see, moving to a shielded system with a smaller diameter can save nearly £1 million per 1000 channels. This figure includes the cost for adding the ground connector to the screened system.
Pathway costs are significant and should be included in any cost calculations. Figures are based on average retail pricing for conduit, cable tray, installation and channel costs.
At the point where a larger diameter cable is considered, Category 7/Class F is nearly the same cost, but with an increased life cycle due to its ability to support speeds beyond 10G, it proves to be a better investment.
While some countries such as Germany and France have held fast to shielded systems, others such as the UK have traditionally embraced UTP systems outside of factory environments. There are some benefits to shielded systems, in particular through increased capacity due to the reduction of disturbing noise such as AXT. Category 7/Class F systems are under a change to become Category 7A/Class FA systems capable of carrying 1 GHz as opposed to 10G Category 6 systems rated for 500 MHz.
10G 6A F/UTP is an untwisted pair cable with an overall shield. It provides the second highest level of immunity to noise and has an increased data capacity. This means that shielded systems will carry 10G signals and are likely to support an additional speed increase when those products are introduced.
Points to remember
For anyone responsible for selecting the right cabling infrastructure and planning to occupy the premises for at least five years, the analysis shows that higher performing cabling systems capable of 10G transmissions or greater are the most economical solutions to provide a solid return on investment. One should consider not only the initial costs, but ensuing follow-on costs as well.
Remember, cabling should represent only 5-7% of the overall investment. It should outlive most network components and is the most difficult and potentially costly component to replace. Shielded systems are regaining popularity, and with pathway and space considerations these prove to be the most cost-effective system for 10G and beyond.
Carrie Higbie is the Siemon global network applications market manager.
Source
Electrical and Mechanical Contractor
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