Networking

Data centre cabling warnings

The cabling vendor has also cautioned against the use of non-standards compliant 26AWG conductor cabling. To ensure 10GBASE-T capability, Siemon recommends standards compliant category 6A or higher for data centre environments.

Siemon’s warnings come on the heels of ISO/IEC, TIA and other telecommunications standards organisations giving clear messages that the minimum grade of cabling to be deployed in the data centre is category 6A. ISO/IEC 247643 states that main distribution cabling systems supporting data centres shall be designed to provide a minimum of class EA (equivalent to TIA category 6A) channel performance. The working draft of ANSI/TIA-942-A2 explicitly states that category 6A is the recommended grade of horizontal and backbone cabling to install in new data centres.

This alert from Siemon is likely to concern a large number of data centre sites that have already adopted category 6: Industry market research firm IDC recently reported that one million 10 Gigabit Ethernet ports were shipped during the second quarter of 2010 and a proportion of these switches are highly likely to have been deployed in the data centre. As 10GBASE-T network equipment becomes increasingly available, data centre decisions makers will want to take advantage of the cost savings, convenience and flexibility provided by deploying 10 Gb/s technology over twisted-pair copper cabling. Whilst previously installed legacy category 6 systems may provide limited support of 10GBASE-T in some environments, category 6 cabling is not recommended for new data centres and smaller 26AWG cabling is not recognised by the Standards.

Moreover, legacy category 6 installations for 10GBASE-T are significantly distance limited. According to Standards, category 6 channels of less that 37 metres (121ft) in length should support the 10BASE-T application and channels between 37 metres and 55 metres (180 ft) may or may not support the application, depending upon the alien crosstalk environment and mitigation steps. However, Siemon points out that supporting 10GBASE-T over installed legacy category 6 requires alien crosstalk field tests on every channel, which can be time-consuming and not fully conclusive.

Compounding the concern for category 6 cabling, Siemon points out that there are no applications under development for this standard. Both TIA and ISO state that the cabling systems specified in their standards are intended to have a useful life in excess of 10 years. Since the category 6 and class E cabling standards were published in 2002, these systems are already beyond the halfway point of their targeted lifecycle. Furthermore, application development groups such as IEEE 802.3 or ATM are not investigating the development of new Ethernet or other data transmission solutions for deployment over category 6 cabling.

Adding to the justification for the category 6 data centre warning, Siemon concludes that, as category 6 UTP or 26AWG cables cannot support a full 100 metre 10GBASE-T channel, it limits design flexibility. The standard cannot support power-saving short reach mode (data centre mode) and these cables, having reduced diameter conductors, cannot dissipate heat as well as category 6A or higher systems. These factors add to the reasons to specify category 6A or higher grade in the data centre, says Siemon.

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