Computational devices

Now that we know we can have an arbitrarily large number of computational devices as nodes in our network, it bears further scrutiny to discern what exactly a computational device is. While this may seem obvious, at least initially, we can quickly identify where it becomes unclear by way of an example.

As per our definition of a network, the device I'm using to draft this book right now might well qualify as a self-contained network. I have a keyboard, mouse, monitors, and computer, all connected by standardized channels of communication. This looks awfully network-like at a conceptual level, but intuitively, we would be inclined to say that it is a network of one, and so, not really a network at all. However, while the what of the non-network status of my computer seems obvious, the why might be less clear.

This is where we benefit from clearly explicating what constitutes a computational device for the purposes of our definition of a network. Simply being able to perform computation is insufficient for a network node. In my example, I can tell you that my mouse (a relatively high-end gaming mouse) certainly performs a number of complex calculations transforming a laser-sensor signal into directional inputs to pass to my computer. My monitors certainly have to do a fair amount of computation to transform the raw binary data of pixel color values into the rendered screens I see 60 or 120 times per second. Both of these devices are connected by way of reliable, standardized communication protocols to my machine, but I wouldn't necessarily be inclined to consider them nodes on a network. My computer, when connected to the internet, or my local home network, surely constitutes a node, but its individual peripherals? I'm inclined to say no.

So, if peripherals aren't network devices, then what essential property is it that they're missing? Open communication. While a monitor and a keyboard can communicate over a connection with a wide variety of other devices, the manner in which they can communicate is restricted to a very specific and limited range of possible signals. This highlights an important distinction to be made between distributed systems and networks. While a network is always a distributed system, a distributed system may not necessarily always constitute a network.

My computer is a distributed system; its components can function independently of one another, but they operate in a coordinated fashion to perform the responsibilities of a computer. However, my computer is very obviously not a network. It lacks device-agnosticism, as each component is explicitly configured to communicate its presence to the next node in the graph, so that it can be used to service the needs of the end user. It is also not arbitrarily scalable. I can only have, at most, three monitors connected to my machine at any given time, and only under very specific conditions of connection interfaces and organization. While being connected to a network, my computer and each of its peripherals can instead be conceptually considered a single, atomic computational device. Thus, on a network, we can specify that a computational device is something that can facilitate the requirements of the network. It accepts and communicates openly over device-agnostic channels of communication to provide or leverage computational resources on that network.