The system boundaries are set differently depending on the study.
Examples of different system boundaries:
mobile network: data transfer between base station and end-user device
data exchange between data centers
internet traffic / transmission network: data transfer between a data center and a end-user device (data center and end-user devices are excluded; differentiation between fixed-line and mobile access is important)
Often the metric kWh/GB is used to calculate the energy consumption of network transfer. However, there is no correlation between the amount of transferred data and energy consumption!
Currently, our application takes into account only the data exchanged between different geographical data centers.
For networking, it is safe to assume that the electricity used to power the internal network is close to 0, or at least negligible compared to the electricity required to power servers.
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There have not been many studies that deal specifically with estimating the electricity impact of exchanging data across data-centers. Most studies focus on estimating the impact of end-user traffic from the data center to the mobile phone; integrating the scope of the core network (what we are interested in), the local access to internet (optical fiber, copper, or 3G/4G/5G) and eventually the connection to the phone (WiFi or 4G).
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It is safe to assume hyper-scale cloud providers have a very energy efficient network between their data centers with their own optical fiber networks and submarine cable. Data exchanges between data-centers are also done with a very high bitrate (~100 GbE -> 100 Gbps), thus being the most efficient use-case. Given these assumptions, we have decided to use the smallest coefficient available to date: 0.001 kWh/Gb.
Estimates for average transmission network electricity intensity that meet these criteria show a halving of intensity every 2 years.
stephens.etal.2021.carbonimpactvideo (pg. 21)
Aslanβs rule
Analysis of estimates for the average electricity intensity of fixed-line internet transmission networks for data transfers from 2000 to 2015 concluded that electricity intensity (in kWh/GB) decreased by half approximately every two years over that time period (Aslan et al., 2018).
Fixed network energy intensity (2020) = 0.0065 kWh/GB
Mobile network energy intensityΒ (2020) = 0.1 kWh/GB
Home router energy intensity (2019) = 0.025 kWh/GB
we estimate that the yearly carbon footprint of data-use by advertising and tracking services in smartphone apps in Europe is between 5 and 14 Mt CO2-eq.
Data used by website carbon calculators
The calculation model of SustainableWebDesign.org that is used by the CO2.js library and multiple website carbon calculators not only includes the energy used by the IP network, but also the energy used by consumer devices, data centers and the production of the hardware components.
The Internet peak traffic increases. That is driving network growth, which results in emptier networks on average.
Networking hardware is far from power proportionality; It is very inefficient at low utilization.
β It can and must be improved.
Even if direct cost of traffic is minuscule, sending more traffic has an important systemic cost. Cf. Point 1.
β Don't send if you don't need to.
β Stay away from the peak!
