Anyone familiar with first-person shooters knows the cold and unfair reality of global networking. But what if there is a deeper lesson within these split second interactions?
“The introduction of lag compensation allows for each player to run on his or her own clock with no apparent latency. In this respect, it is important to understand that certain paradoxes or inconsistencies can occur.” - Yahn Bernier, Valve Software, Latency Compensating Methods in Client/Server In-game Protocol Design and Optimization
A networked computer is known in general as a client. A client connects to a central server. Modern servers accept connections from clients of all type: your browser is a client, your apps are clients, your workstation is a client.
Gaming, with its deep requirement for fluidity and fairness, is a prime example of the client/server relationship. Games are fast and competitive and so a server must be extra diligent. A server must build a seamless consensus so that each client can experience a shared state, a shared reality, in near real time. It does this thousands of times every second, across nations, with little room for error.
In games, players move in nondeterministic patterns. When players are observed by the server each one acts as an input source that exhibits differing, unpredictable behaviour patterns. The server must then decide how events will unfold based on chaotic micro-inputs, activated on each keystroke or mouse movement. To do so, it applies two methods: interpolation and extrapolation.
Extrapolation is best understood through the framework of ballistics. An object going to a certain location at a certain speed will, in all likelihood, arrive at a given location. Extrapolation is effective, for bullets anyway. But on the Internet and in games, a server can never be quite sure where an object is heading.
If a server were to extrapolate a state given only where it thinks everything is going, it would be in disarray because of latency. It does not know for certain “the speed” or “the current location” and so it cannot generate the “destination”. To make it even more awkward, the client’s, the player’s, latency is never guaranteed even if their input is, and so a server can never extrapolate a stable course with so many unknowns.
Latency is represented in milliseconds (ms). It shows up as a well known number: a ping! A ping! such as 100ms means it took 100 milliseconds for data to make a round-trip between a client and a server. That seems fast! But it is not, not when you consider the hyper-acute requirements of precision gaming and the limitations of the speed of light at which the information travels. Even 100ms is far too slow to extrapolate cohesion. And the nature of latency is that it can be any number, at any time, up to seconds in extreme cases with no warning.
If extrapolation were to be the only method used to build consensus, latency would make things appear to be warping from place to place! And that wouldn’t do as that would break the illusion of an organized and cohesive virtual reality. It would not make for an enjoyable game. Therefore extrapolation is not enough, it is but one computational axis of a required many. And so we look towards interpolation.
Interpolation is where algorithmic predictability meets introspection. It places people into the past, confirming their most recent, valid position, and it waits. Or rather it makes the client wait.
The server renders a notion of truth and sends an update containing it to each client every second. After delivery, it will pause for a fraction of that second and interpolate. During that time it will look at what occurred between the last reported position of each client and the position just prior to that. It will then use the “extra padding” of the second to place each client somewhere with it in the past, aligning them all within the flow of their shared existence.
After the second has passed, the clients will then receive their rendering, their instruction, and each will know that it can continue on its path over the next fraction of a second. All of the data received from each client, its orientation, timing and movement, are then evaluated in reverse, thousands of time per second, to ensure a fluid and graceful experience. It is a dizzying feat of split-second, predictive engineering.
And yet all of this relies on the integrity of the connection. It assumes that each packet will arrive on-time and in optimal condition. We expect this knowing how far it must have travelled and how fraught with peril the wires running through the Earth and over the ocean must be at any given moment. And that’s not to mention the packets in the air, traveling through even flesh and bone to arrive intact at your computer.
Alas, network packets get lost from time to time. Yet each bit is vital in conjuring a believable reality, the slightest glitch and we feel it through our fingertips.
“If one of the update packets fails to arrive, then there are two choices: We can start extrapolating the player position as noted above (with the large potential errors noted) or we can simply have the player rest at the position in the last update until a new update arrives…”
Extrapolation alone is risky. The server is never quite sure what a latent client will do, but together with interpolation, it is more resilient. Yet even together, there is still ample opportunity for oddities.
In the event of missing data such as if the client has a poor connection, interpolation will ask a client to wait. It will hang the client, a player, in the ether until it receives a new update from which the server can then render it a new picture and produce it a clear path. But if the connection never resolves into a healthy state, that player may stay lost in limbo, or even disconnected.
I marvel at the sophistication of netcode. Like many of humanities profound inventions, it makes me wonder whether we are reducing greater realities down into machine terms. As above, so below, consolidating the experience of life into simpler terms on our way to a deeper understanding of our collective consciousness.
I am like a client and so are you. Which is to say, we connect to a central server and need to generate a cohesive, consensus reality in real time. We sit next to other clients each of whom go about their own business. And the server sits… somewhere, everywhere, waiting for updates. How many updates, and what we update, varies and we each have a differing ping!
The Grand Operational Determining server interpolates, it extrapolates, and it conjures all possible outcomes through an intelligence that we can never comprehend, that no code no matter how elegant can ever replicate. For it works much deeper than algorithm.
Should you lower your ping enough through meditation or disconnect through death, the boundaries of your client disappear and the server need no longer strategize where it will put you. The distinction becomes meaningless. For just like in the material world, the client is, and always has been, an extension of the server, yet it forgot.
It forgot because it knew its self as separate. Even as the shared laws of electric light governed the speed at which it could send its messages and even as both of them were born of the same source code, it went on acting as an “other”, a mere module of a server and all of its greatness. It simply forgot. But they are the same.
Clients feel separate because they each send signals to the server and they each want to have the deepest impact on its rendered reality. The Grand Operational Determining server, the infinite processor humming at the core of existence, needs to thread all of this data into one coherent tapestry, into a conherent Universe, and it does so without complaint and it never ceases and it makes no errors. It is perfect.
Yet many clients become lost in the ether, waiting for a server to tell them what to do. I was there once, hanging alone, waiting and wondering for someone or something to tell me what to do. To know this disconnection is to know anger and depression, to know fear. But fear not.
Your network layer can be optimized and your ping can be improved. Return your attention to the moment, breathe and meditate. The server is with you, here and now. The world you feel blossoms from its centre with your awareness at its core. Live with it, surrender to it and the server need never guess at where to put you.
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