DCN April 2016 - Page 18

cabling Category 6A cabling is well suited to support a variety of architectures for switch-to-server connections, including switches placed in ToR, MoR and EoR configurations. compatibility with the reach to support a much broader range of architectures than direct attach twinaxial connections. Another future option for edge connections is the upcoming IEEE 802.3 standard currently under development that will define 25Gb/s operation over up to 100m of multimode optical fibre cabling and up to 5m over two pairs (ie. one ‘lane’) of twinaxial cable. This standard is expected to support switch-to-server connections at the edge with SFP28 direct attach cable assemblies, and may be ideal for migration to higher speeds among those that are already familiar with using SFP+ or other cable assemblies in ToR configurations. Considering the backbone While copper cabling’s position is stable at the data centre edge, backbone switch-to-switch data centre deployments for networking and storage area networks (SANs) are better served by multimode optical fibre. The distances in these environments typically extend beyond the range supported by copper and transmission speeds here are evolving from 10 to 40 and 100Gb/s for Ethernet based networks and from 8 18 to 16 and 32Gb/s for Fibre Channel based SANs. But again there are cabling considerations. Both 40Gb/s (40GBase-SR4) and 100Gb/s (100GBase-SR4) transmission is based on eight multimode optical fibres – four transmitting and four receiving at 10Gb/s or 25Gb/s each. These applications use 12-fibre MPO/MTP interfaces with 12- or 24-fibre trunk cables. With MPOs/MTPs being a 12-fibre connector but only requiring eight for transmission, 33 per cent of the optical fibre goes unused. An ideal way for data centre managers to ensure 100 per cent utilisation of optical fibre in both 40 and 100Gb/s applications is to use conversion cords or modules that transition two 12-fibre or one 24-fibre trunk from backbone cabling to three 8-fibre MTPs for connecting to 40 and 100 Gb/s equipment. Staying within optical insertion, loss budgets is another consideration and is essential for ensuring proper transmission of data signals between switches, b