Managing Higher Fibre Counts in the Data Centre

Authored by: Gary Newbold, Vice President, Enterprise, Asia Pacific

The volume of digital traffic pouring into the data centre continues to climb; with APAC data centre spending estimated to hit $32bn by 2023 and expected to grow at a rapid rate. Meanwhile, a new generation of applications driven by advancements like 5G, AI and machine-to-machine communications is driving latency requirements into the single millisecond range. These and other trends are converging in the data centre’s infrastructure, forcing network managers to rethink how they can stay a step ahead of the changes.
In recent years, networking trends have increasingly focused on—especially at the hyperscale level — increasing the amount of fibre. Today, fibre cables are deployed with as many as 20 times more fibre strands — in the range of 1,728-, 3,456- or 6,912 fibres per cable. The massive amount of fibre creates two big challenges for the data centre. The first is, how to deploy it in the fastest, most efficient way and once the foundational fibre infrastructure is installed, the second challenge becomes managing it at the switches and server racks.
Rollable ribbon fibre cabling
The progression of fibre and optical design has been a continual response to the need for faster, bigger data. As those needs intensify, the ways in which fibre is designed and packaged within the cable have evolved, allowing data centres to increase the number of fibres without necessarily increasing the cabling footprint. Rollable ribbon fibre cabling is one of the more recent links in this chain of innovation.
In the rollable ribbon fibre cable, the fibres are attached intermittently to form a loose web. This configuration makes the ribbon more flexible, allowing manufacturers to load as many as 3,456 fibres into one two-inch duct, twice the density of conventionally packed fibres. This construction reduces the bend radius making these cables easier to work with inside the tighter confines of the data centre. Inside the cable, the intermittently bonded fibres take on the physical characteristics of loose fibres which easily flex and bend making it easier to manage in tight spaces. 
New chipsets are further complicating the challenge
In today’s hyper-converged fabric networks, it is extremely rare that all servers in a row will need to run at their max line rate at the same time. The difference between the server’s upstream bandwidth required and the downstream capacity that’s been provisioned is known as the oversubscription, or contention ratio. In some areas of the network, such as the inter-switch link (ISL), the oversubscription ratio can be as high as 7:1 or 10:1. A higher ratio is chosen to reduce switch costs, but the chance of network congestion increases with these designs.
Oversubscription becomes more important when building large server networks. As switch to switch bandwidth capacity increases, switch connections decrease. This requires multiple layers of leaf-spine networks to be combined to reach the number of server connections required. Each switch layer adds cost, power and latency however switching technology has been focused on this issue, driving a rapid evolution in merchant silicon switching Application Specific Integrated Circuit (ASICs). 
The evolving role of the cable provider
In this dynamic and more complex environment, the role of the cabling supplier is taking on new importance. While fibre cabling may once have been seen as more of a commodity product instead of an engineered solution, that is no longer the case. 
Data centre owners and operators are increasingly relying on their cabling partners for their expertise in fibre termination, transceiver performance, splicing and testing equipment, and more. As a result, this increased role requires the cabling partner to develop closer working relationships with those involved in the infrastructure ecosystem as well as the standards bodies.
All comes down to balance
As fibre counts grow, the amount of available space in the data centre will continue to shrink. Look for other components, namely servers and cabinets to deliver more in a smaller footprint as well. Space would not be the only variable to be maximized. Combining new fibre configurations like rollable ribbon fibre cables with reduced cable sizes and advanced modulation techniques, network managers and their cabling partners have lots of tools at their disposal.  If the rate of technology acceleration is any indication of what lies ahead, data centres, especially at the hyperscale cloud level, better strap in. As bandwidth demands and service offerings increase, and latency becomes more critical to the end-user, more fibre will be pushed deeper into the network.  
The goal is to achieve balance by delivering the right number of fibres to the right equipment, while enabling good maintenance and manageability and supporting future growth.

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