Design/facilities
Category 6 cabling could fail data centres for 10GBASE-T
In light of recent industry standards recommendations, global infrastructure experts Siemon warn that Category 6 cabling - still being specified and installed in new data centre projects - is highly likely to fail to deliver 10Gb/s. Graeme Stoker, marketing manager for Siemon, explains the risk.
There are two urgent warnings that we must issue: The first is that category 6 may well fail to deliver 10 Gb/s in the data centre and secondly, to beware of non-Standards compliant 26AWG conductor cabling. To ensure 10GBASE-T capability in data centre environments, we recommend that you specify and deploy standards compliant category 6A or higher grade cabling. This cautionary advice is now the view of the telecommunications standards organisations that develop the standards to address cabling system design and installation in the data centre: ISO/IEC, TIA and other standards bodies are giving clear messages that the minimum grade of cabling to be deployed in the data centre should be 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.
Migrating to 10GBASE-T As 10GBASE-T network equipment becomes increasingly available, data
centre decision makers will want to take advantage of the cost savings, convenience, reliability and flexibility provided by deploying 10 Gb/s technology over twisted-pair copper cabling. This should be straightforward for those with the infrastructure to support it, but much more difficult for those with cabling unsuitable for this technology (or impossible without re- cabling). And whilst cabling represents a minor portion of the infrastructure budget, replacing it is disruptive.
Attempting to hybrid the cabling is also thwarted, as pathway separation guidance confirms: Standards state that category 6A cabling running 10Gb/s should not be placed unbundled, in adjacent bundles or in the same bundle as category 6 transmitting 10GBASE-T signals. Laying a portion of new category 6A cabling alongside any legacy category 6 is clearly not feasible.
Whilst previously installed legacy category 6 systems may provide limited support of 10GBASE-T in some previously installed legacy environments, category 6 cabling is not recommended for new data centres and smaller 26AWG cabling is not recognised by the Standards.
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Moreover, legacy category 6 installations for 10GBASE-T are significantly distance limited. According to the Standards, category 6 channels of less that 37 meters (121 feet) in length should support the 10BASE-T application and channels between 37 meters and 55 meters (180 feet) may or may not support the application, depending upon the alien crosstalk environment and mitigation steps. However, 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.
It must be made clear that there is no 10GBASE-T application support assurance over short runs of category 6, because alien crosstalk is highly dependent on cable density.
The only way to ensure compliance to guidelines such as ISO/IEC TR 24750 and TSB-155-A is to perform complicated alien crosstalk field tests on every channel. In the majority of data centre installations, alien crosstalk mitigation will likely be required. The recognised mitigation methods cannot be easily implemented due to existing pathway fill
February/March 2011
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