Data network infrastructures are changing completely. This is, in no small part, due to increased device processing power, uptake of smartphones, laptops and tablets, virtualized servers, I/O-intensive applications, cloud computing and wireless technology advances.
As 10GBase-T availability continues to grow, more data centers are planning migrations to 10GbE. Its broad deployment is expected to make data center infrastructure more transparent. It should also make managing server connectivity easier while delivering vastly increased bandwidth.
In just a few years 10G will be the most widespread Ethernet protocol. Transmitting at 10Gbps, however, involves the use of a sensitive, high-frequency, coding method.
In the higher frequency spectrum in which 10G operates (500MHz), sensitivity to interference is significantly higher, and the sampling rates are many times higher than for 1000Base-T. This means higher levels of self-radiation in the relevant 250 to 500 MHz bandwidth, meaning more crosstalk. Susceptibility to interference increases by a factor of 100, due to small differences in potential between input signals from one bit level to the next. These are caused by the rise in cable attenuation at high frequencies, and by increased coding.
Crosstalk – A close-up
In every multicore bundle each cable pair picks up interference from other pairs.
In the higher frequency range – where 10G operates – sensitivity to noise is larger. At that level the noise from the directly neighboring cable pair can influence the signal as well as the noise from the other cables.
In order for 10GBase-T to work correctly it is crucial to control and suppress interference from outside individual cables.
Alien crosstalk – or ANEXT – is the term used to describe this interference. In this case, ANEXT refers to crosstalk as a result of operating multiple 10GBase-T terminals in adjacent cabling systems, when energy is coupled between pairs with the same lay length in adjacent cables.
With regular Ethernet, the resulting interference could slow down the network. But over a 10G network interference can shut everything down in an instant, which then requires a restart. When looking at all the parameters that can affect 10GBase-T performance ANEXT is the most significant. Conventional unshielded twisted pair (UTP) systems offer little protection against this type of interference. The only way to reduce alien cross-talk in a traditional UTP system is to increase the physical distance between the cable pairs concerned. In the past, this could be achieved through various measures, all of which were designed to prevent the pairs in the cable from being too close together. The most frequent method was to use specific shapes to increase sheath thickness. There are, however, serious disadvantages to this in terms of cable handling. Larger cable diameter means less efficient use of cable ducts. The cables are stiffer and less flexible and there is a greater fire load due to the increased use of plastic.
A cable shield offers additional mechanical stability as well as reliable protection against unwanted signals and the resulting crosstalk. Shielded cabling, by design, automatically curbs ANEXT if it is installed correctly and is of a sufficiently high quality.
In many respects, shielded cables are an ideal solution for 10GBase-T. However, the shielding for this type of cable must be handled carefully and consistently. Because many markets have not traditionally used shielded cables, installers in these markets have little experience in the correct way to handle shielding. Unshielded copper cabling is easier to install, and therefore less expensive. This is an important part of the reason for its widespread global adoption.
The unshielded solution
It is hardly surprising that the question ‘shielded or unshielded?’ will inevitably come up when investment decisions for local data networks or structured office cabling are made. But that does not mean that a total transition from copper to shielded cabling is inevitable? If installed correctly, both shielded and unshielded technologies offer sufficient reserves for applications up to and including 10GbE. You can reach your goals with unshielded cabling, providing you make sure the conditions are right and you take care to select the right quality.
As explained above, use of traditional unshielded cabling means distances between individual components need to be increased as much as possible. However, the latest generation of unshielded cables can, in fact, offer ANEXT reserves that were previously only possible with shielding. Choosing the best possible quality of unshielded cable is vital. If opting for 10GbE-compatible class EA cabling, the user has to find the best solution, in technological terms, to ensure the LAN will continue to work reliably in the long term. After all, your investment should keep operating for at least 15 years and longer without error. Once a network has been installed or upgraded, it should outlive several consecutive generations of active equipment. If, after installation, you find out your choice of cabling does not offer the performance you had hoped for when switching from 1 to 10GbE, it is generally much too late to take corrective measures.
So which cabling is the best choice to fulfil the demands of 10G?
A safe bet would be to choose cabling specified in accordance with class EA as stipulated by ISO/IEC 11801 coupled with connection technology in accordance with Cat. 6A as stipulated by IEC 60603-7-41/-51. Compared with Telephone Industry Association requirements, this standard has stricter regulations regarding transmission parameters. Therefore, it is better equipped to cope with the challenges that the future will bring.
Other criteria should also be considered during evaluation.
Comprehensive quality control, process security, simple handling, extensive guarantees and low overall costs are a few of the most important selection points.
Users can save a considerable amount of money in the long term, with relatively low-cost additional investment, by selecting quality cabling solutions. In large projects, physical infrastructure only accounts for 7% of the entire IT investment. Only half of this is spent on the actual products; the other half covers the cost of the installation work.
Although top products may cost between 10 and 20% more than average products, when seen in relation to the entire investment, the increase in cost is a mere 0.5%. There are a number of additional benefits: low failure rates mean less costly network interruptions and fault tracking, the user can achieve the best performance in data transmission and users can work faster and more efficiently. Systems maintenance, move, add and change can be taken care of more quickly with an easy-to-use system, saving money on IT personnel.
These top-grade products support future applications, so the network can remain in use for much longer and depreciation costs are reduced significantly.
The service life of a LAN is 15 to 20 years – 0.38 % annual depreciation for cabling of the original IT investment is reasonable when top-quality cabling has been used. If you had to replace the cabling after seven years because it no longer supported new applications, the depreciation requirements would increase to more than 1%.
Quality and care
10GbaseT does not require shielded cabling by default but it does require high-quality cabling and careful installation. Unshielded cabling can deal with the higher transmission rates, higher frequencies and the increased sensitivity to disturbances that come with 10GbaseT. Fortunately, the problem of interference sensibility can be controlled by implementing resolute cabling measures.
It really does, however, mean zero tolerance with regard to individual components and installation errors. Only the most absolute precision during rollout can prevent electromagnetic interference and ensure good signal quality. With 10G, this depends on preventing or reducing crosstalk.
Unshielded cabling, which is less costly and easier to handle, can definitely provide the required quality of performance for 10G networks. It is vital, however, to take the utmost care in implementation and to use top quality products to counter the effects of alien crosstalk, to which 10G is far more sensitive.
Selecting high quality products also brings a range of additional benefits and helps future-proof investment.