How far should network capacity be increased?

Is the exponential growth of its traffic putting the internet at risk of a “catastrophic collapse”? Notwithstanding the limits of bandwidth capacity, technological innovation should make it possible to avoid this.

According to the annual report published by TeleGeography, the total international bandwidth capacity used by worldwide networks reached 786 Tbps in 2021, an increase of 29 %. This figure, which has been measured annually for the past four years, matches that of worldwide internet traffic growth over the same period (except for 2020 which was an atypical year due to the general lockdowns).

Global demand for bandwidth should see an upward trend over the coming years, according to TeleGeography, due to the introduction of new technologies based on artificial intelligence and virtual reality, which are very bandwidth hungry.

Is supply (bandwidth) at risk of reaching breaking point faced with the simultaneous growth of demand (internet traffic)? Is the “prophecy” put forward by British researcher Andrew Ellis, according to which the “capacity crunch” (when the explosion of data consumption exceeds the available bandwidth) was foreseeable for around 2023, about to be fulfilled?

Since then, in view of the evolution of network capacity, specialists have been more cautious and rather reassuring on the subject. As Paul Brodsky, Senior Research Manager at the TeleGeography institute stresses, “although some internet backbones are currently being decommissioned due to ageing, this should not prevent the total international transmission capacity from continuing its onward march, be this thanks to the commissioning of new submarine cable networks across the globe or to the use of new signal processing technologies”.

Optimizing cables and fibers

In order to satisfy the exponential growth of demand, the initial avenue for increasing supply consists in taking action on the internet’s long-distance data transport network, that is the multitude of submarine or terrestrial optical fiber cables, which are the true backbone of the internet. The traditional single-mode fibers currently deployed in optical transport networks, are reaching their maximum capacity, the limit of which is thought to be around 75 Tbps per fiber.

It is however possible to increase the number of cables and therefore of fibers. “Investments in this area are continually on the rise; they are approaching 2 billion euros per year”, highlights Paul Brodsky, who also stresses that, “the full capacity of the fibers already installed is not fully exploited”.

It is also possible to increase the transport capacity of a fiber. In this area, research has already made great advances. Thanks to Wavelength Division Multiplexing (WDM) technology combined with the use of optical amplifiers, each optical wavelength that carried 2.5 Gbps in 1990 now carries 100 Gbps.

New solutions being tested

Although the potential optical transmission speed may not be infinite, the limits of optical transport can still be pushed back further. Improvement of its performance can be founded on various technical solutions: “higher-order modulation”, distributed Raman amplifiers, parallelization on N fibers, space-division multiplexing, flexible optical networks, etc. By using advanced digital communications technologies, (higher-order QAM, Nyquist filtering, advanced digital signal processing, error-correcting codes, optical amplification), research can continue to improve data rates without changing the fibers currently deployed or modifying the current architecture of the transport networks.

Researchers are also working on new optical mediums based on the use of “multicore” and/or “few-mode” fibers. The former provide several independent optical channels in parallel, while the latter make it possible to have several coexisting parallel optical flows within the same fiber. These technologies are far from mature.

Beyond the fibers themselves, other avenues are being explored to improve the performances of physical transport technologies (optical fiber, radio), to reduce the amount of data needed to transmit a video or given content, or still to optimize data positioning by placing the most in-demand content closest to the consumer, thus reducing the need for long-distance transport.

The question of equipment resilience

The physical and technological limit of a network is not the only angle from which to respond to the challenge of increasing traffic, according to Leonardo Linguaglossa, a teacher-researcher at Télécom Paris in the Networks, Mobility and Services team.

“The room for improvement for quality connections depends also, and probably foremost, on the capacities and performances of the devices we are using, of which the number (29.3 billion) in 2023 will be three times that of the global population. The problem is that of resilience, in other words the capacity to provide continuity of service and resistance to failures.”

For the teacher-researcher, incidents related to the increase in usages (overheating, outages, fires) and behavioral changes due mainly to the boom in remote working, modify the nature of traffic and can perturb the system. An increase of 61 % in the number of network outages on ISP networks and 44 % on those of cloud providers was thus observed between February and March 2020, according to the Cisco ThousandEyes “Internet Performance Report COVID-19 Impact Edition”.

“The miniaturization of devices provides a continuous path for improvement. This is evident in connected TVs, which have gone from 2 Mbps in SD to 15-18 Mbps in UHD. The same is true of smartphones and smart watches”, Leonardo Linguaglossa notes, “but at some point, all these devices go through the internet service providers’ boxes, which are technically limited. This creates real bottlenecks”.

De facto, according to the “Cisco Annual Internet Report (2018–2023) White Paper”, in 2023, only 27.4 % of WLAN (Wireless Local Area Network) endpoints will be equipped with Wi-Fi 6, the latest wireless network standard.

Bandwidth capacity, usages, and devices: it is well and truly on all fronts that battle must be done in order to avoid a potential “capacity crunch”.

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