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FIBRE OPTIC CABLING
Building a Big Data backbone
By Keith Stewart , Product Marketing Manager , Networks Centre
www . networkcentre . com
Getting hyped up by the demand for cloud scale data centres that shows little sign of slowing down
Global data centre IP traffic is predicted to grow from 4.4 to 15.3 Zetabytes per year during the period 2015 to 2020 , at 27 % CAGR . In particular , trends towards hyperscale data centres i . e . large facilities with a single massively scalable compute architecture , are expected to grow to represent 53 % of all DC traffic by 2020 , up from 34 % in 2016 . There are estimated to be around 300 of these hyperscale facilities worldwide of which 45 % of are located in the US with just 5 % in the UK , which equates to 15 facilities .
Faster & flatter Most larger data centres have been 3-tier switch fabric architectures up until recently , but this is shifting to a flatter 2-tier architecture , e . g . Spine / Leaf , which typically reduces points of failure , power , latency and deployment time . It enables workloads to be shared across hundreds or even thousands of virtual machines . This creates substantially more ‘ east-west ’ server to server traffic and it ’ s this that is accounting for a significant proportion of machine to machine ( M2M ) traffic – 44 % CAGR 2015-2020 ( Cisco - Global Cloud Index 2016 ). In this architecture each server port should be capable of connecting to any other sever port at full bandwidth capacity i . e . non-blocking . This is helping to drive data centre connections to move from 10G / 40G to 25G / 100G and the cost / benefit in terms of $/ Gb improves with higher speeds . Due to the physical size and architecture of hyperscale data centres , 100G Spine connections are desirable and started being deployed in 2016 .
Optical shift Several technologies are facilitating this data centre evolution but optical technology is perhaps the most crucial . Developments in optics for both short wave ( SR ) and long range ( LR ), has meant that the choices facing a data centre operator planning for future expansion is growing increasingly complex . Previously , the decision on whether to deploy lower cost , lower bandwidth SR optics and multimode fibre , i . e . OM3 and subsequently OM4 , was relatively straightforward with single-mode / LR optics being restricted to mainly core & aggregation switches .
With the flatter Spine / leave architectures in larger cloud scale data centres , single mode is becoming more dominant with an eye to the next step in evolution , which will be 100G / 400G or 200G / 400G , where standards are being developed for a short reach ( 500m ) over single-mode e . g . IEEE P802.3cd ( 100GBASE-DR ). That ’ s to say 100Gbit / s transmission over one wavelength ( 2 fibres ) and IEEE P802.3bs ( 200GBASE-DR4 / 400GBASE-DR4 ) using four pairs of single mode fibres . These will use PAM-4 encoding to modulate the signal and double the data in the same amount of time on a serial channel compared to NRZ ( Non return to zero ) encoding .
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