Internet and analogies: Riding a bus through the submarine fibre
Updated on 07 August 2022
How does the Internet work? Well, let’s think of a traditional phone, or telegraph – imagine it as the Einstein’s cat… Or, think of data packets as letters… or envelopes. Better still: think of packets as passengers. Or cars, or buses. Or…
How many analogies can we think of to explain a certain complex phenomenon, such as the Internet? The analogy with cars and highways has been particularly popular since mid-1990s when the term ‘information superhighway’ was coined, allegedly by Al Gore. This analogy presents the Internet link as a highway, providing transport from one end to another.
The ITU Secretary General Hamadoun Touré referred to it, among others, to send a political message on Internet regulation and ownership: ‘It is not because you own the highways that you are going to own all the trucks or cars running on them, and certainly not the goods that they are transporting, or vice versa.’ Diplo has also used the analogy a number of times, including in a video on the net neutrality debate:
In a recent blog post on TeleGeography.com, the author used the analogy of the ‘Internet data as cars traveling down a multi-lane highway of existing submarine cables’. The post triggered some interesting discussions among the technical community. Among them were the fact that in order to explain the advantages of the new FASTER cable – a 11,629km-long fibre optic link connecting Japan and Taiwan to the United States – the author reached for an unusual extension to a usual analogy: ‘Staying with our traffic analogy, FASTER’s data is packed on a bus instead of a car, but the bus is traveling within the same speed limit as the car; it’s not going any faster.’
Some engineers have argued that the increased bandwidth is not about sending buses instead of cars, but rather about increasing the capacity of the highway. In other words, the size of the vehicle doesn’t matter; what matters is the number of vehicles that can enter each lane. So is it about cars, buses, or the highway?
I believe it can be both or neither. It depends on what we want to explain, and how. We can choose a data packet to be a car – but we can also chose it to be a passenger, or even a suitcase that passenger brings. A lane can be an entire cable, a single fibre strand, or each wavelength in a single strand. Either is good for certain circumstance; yet, both have flaws.
Using the same analogy, let me try to explain how fibre optic cables work. Technically, each fibre optic cable has a number of fibre optic strands; each strand works as a bunch of wavelength-channels; and through each of those channels we can simultaneously send a number of packages thanks to multiplexing (by time or phase).
To explain better such a complexity, I choose to use the analogy of a data packet as a passenger, rather than as a vehicle. Imagine, therefore, that our goal is to transfer as many passengers as possible from one end to another, having in mind that we have a huge highway (i.e. a single fibre optic strand) with a number of lanes (i.e. wavelength-channels in each strand). If we let passengers go through the lanes each on his/her own (say: rent-a-) car, they may end up queuing at some point.
To increase the efficiency, at the interchange before the highway we may decide to instantly move people from their cars onto buses; naturally, we will be able to take more people from one end to another in the same time interval (provided that both cars and buses drive at the same speeds – the speed of light). At the next interchange, then, we can ask people out of the bus and back in the (rented) cars, and have each of the passengers go his/her own way.
Does this analogy explain how fibre optic cables work? Some might find it works well; some might prefer other analogies. Would you suggest a different one?
The key is that analogies are one of the key cognitive tools that make it easier to understand complex new developments. There is no one single logic and no perfect analogy. Rather, there are good analogies, and perhaps better ones – depending on how they are interpreted by the readers. Analogies can be misleading as well, and turn into a slippery slope when used in legal and political processes, such as in resolving legal cases related to the Internet.
Kudos, therefore, to cars, buses and passengers, highways and lanes, letters and envelopes, postmen and packages, whenever they serve a purpose to explain a new development; and long-live engineers and other professionals engaged in digital policy debates, who readily engage in creative discussions on the benefits, uses, risks, and flaws of analogies.
 An excerpt from the Secretary General’s speech delivered at the ICANN meeting in Cairo in 2008. Full transcript is available here.
 Interestingly, in the subsequent net neutrality illustration, we decided to move to an analogy with postal packets.
 According to TeleGeography, the FASTER cable that should provide a 60Tbps link is under the consortium of five carriers, including China Mobile, China Telecom and Google, available here.