Call of Duty Matchmaking: How You Get Games

I’ve spent a large part of my professional career in the networking, data centers, and cloud technology sector over the last 25 years, and so when I saw that the Call of Duty Matchmaking Intel team released a white paper about connectivity and ping as it relates to forming lobbies, I got pretty excited.

Over my time in the tech industry, I’ve read hundreds of white papers and written dozens myself, and from my experience, this release by Activision is actually pretty solid.

The hard part about something like this is that you’re targeting an audience of “users” that have varying degrees of technical acumen (from people who struggle to connect their console to the internet to people like me) but who likely have strong opinions on matchmaking.

This white paper is good in that it explains some pretty complicated topics around distributions and network connectivity, in a way that simplifies things while still making the points they need to make.

Will it please everyone? No.

Some people have made up their minds already so facts and information don’t matter, but if you’re just interested in understanding the process, this paper is pretty good.

The first paper in the series focuses on the importance of connection, specifically Ping, in creating the best multiplayer experiences for players.

The Quest for the Best Multiplayer Experience

White Paper

According to the team, their primary goal is to create the best multiplayer experiences for players. To achieve this, they have identified several key factors that influence matchmaking:

  • Connection
  • Time to match
  • Playlist diversity
  • Recent maps/modes
  • Skill/performance
  • Input device
  • Platform
  • Voice chat

Ping: The King of Connection

White paper2

The white paper emphasizes that Ping is the most critical factor in ensuring a smooth in-game experience. High ping can lead to several issues, especially in fast-paced, first-person action games like Call of Duty:

  • Frustrating lag
  • Delayed reactions
  • Overall poor performance

The matchmaking system prioritizes minimizing network latency to keep ping as low as possible, even if it means slightly longer wait times.

This is where there is some nuance because in the online first-person shooter world, players talk about “Ping is King” meaning the lower the ping, the better, which makes sense.

But the Call of Duty team introduce this concept of “Delta Ping”.

Because there are so many criteria that go into making a match and COD has so many data centers in some regions, the matchmaking algorithm looks for the lowest ping that meets the totality of the criteria the best – the “delta ping”.

They use a great example of a person in Europe who has available data centers that are 16ms, 18ms, and 22ms away from them – the experience between those three are more or less the same when you factor in everything, so if the server that’s 22ms away meets the criteria the best for making a match with this user, then that’s an acceptable “delta ping”.

Balancing Act: Ping vs. Wait Time

While ping is the top priority, the matchmaking process also aims to find good matches quickly. The white paper discusses how several factors can impact matchmaking tuning:

  • Player population
  • Game design
  • Internet ecosystem

The Call of Duty team uses key performance indicators (KPIs) to measure the success of their matchmaking system from both a technical and player perspective. On average, the matchmaking system aims for a wait time of around 30 seconds, allowing for ping optimization without keeping players waiting too long.

Again, there’s some nuance here that is explained but likely gets missed.

When the matchmaking team talks about forming lobbies, they don’t mean from the time you touch the button to find a game to the point you’re starting the match – they talk about the time it takes to establish the search criteria (very quick), find available seeds for a match, and then collect all of the users into a lobby to hand off to the servers to establish the game.

What the matchmaking team is trying to do is find the “acceptable” balance between a good experience and how long you have to wait to get into a game.

They have a bunch of heatmap charts that show off a sample of geographies and modes from a point in time that do a good job of explaining this. They also step through a few examples to show how densely populated regions versus sparsely populated regions with fewer servers and remote geographies differ, but yet still deliver good results.

The Science of Server Selection

The white paper delves into how the matchmaking system identifies the best data centers for players. In the past, methods like IP-based geolocation combined with physical distance were used to determine expected ping values. Today, the system employs more advanced techniques to ensure players are connected to servers that will provide the best gaming experience.

There are a few things to remember that are very important:

  • Servers are a finite resource
  • The closest server to you even with the lowest ping might not be the best server for you
  • Different data centers have varying levels of hardware capability
  • The internet is a diverse and almost organic beast where traffic changes dynamically

So in densely populated areas with high player counts and multiple data centers like Europe or North America, picking which server pod you end up using is more complicated than just saying, “send me to the closest server”.

It’s worth pointing out that technically, this is normal behavior for internet-distributed applications that are latency sensitive – for example, real-time transactional systems employ the same service resolution heuristics. The closest servers are not always the best servers to deliver the most consistent and high-quality performance.

The Activision team does a pretty good job explaining this, but it’s a complex topic where the simple answer is not always the right one.

Transparency: The Key to Trust

The Call of Duty team’s effort to be transparent about their matchmaking process is noteworthy.

Without a doubt in the Call of Duty community, the matchmaking system has been a massive point of chafing over the last few years.

The rise of “Engagement Based Matchmaking” (EBMM) and the more widely discussed “Skill Based Matchmaking” (SBMM) are generally hated in the COD community.

The idea behind SBMM is that lobbies are formed to ensure that players in the lobby are of a similar skill level so that better players don’t just stomp people who aren’t as good. The feeling in COD is that SBMM is “cranked up” really high so every lobby feels like you’re playing in the Call of Duty League on the main stage at Champs.

That’s the downside to SBMM, when everyone is as good as you, or thereabouts, then unless you are trying your hardest, you’re going to get dumpstered.

The problem is that if you have “light” SBMM, the better players are going to dumpster the worse players no matter how hard they try, which isn’t fun.

How do we know it’s not fun? Because the good players aren’t FORCED to try hard in their SBMM-matched lobbies, but they don’t like getting dumpstered either. Everyone likes to win and do well.

The other aspect of this is that Call of Duty has really moved to more EBMM where they will put you in very hard lobbies for several games and then suddenly gift you a weaker lobby so that you feel good and keep playing.

EBMM is almost like psychologically abusing your players to keep them playing the game – engagement time is a key metric for live service game companies, particularly ones with microtransactions because the more time you spend playing, the more full the lobbies are, and the more likely you are to spend money on skins and blueprints.

The Future of Call of Duty Matchmaking

Read the Call of Duty Matchmaking Series: Ping for yourself.

This disdain among the player base has really negatively impacted the sentiment online around Call of Duty and eventually, that will start impacting sales.

It was inevitable that Activision had to be more open about the topic, so this series of whitepapers is a good first step and some of the experiments they are running will hopefully help them refine it.

The release of this white paper shows that the Call of Duty Matchmaking Intel team is at least aware of the problem and are endeavouring to communicate their view which for years has been entirely shrouded in mystery.

These first steps by the Call of Duty matchmaking team towards more transparency is commendable and it should be seen as a positive – more understanding of the systems and the intentions, even if people disagree, is a good thing.

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Sean Kaye
I've been playing video games since the early 1980's on a Commodore Vic 20 and then eventually a C64. I graduated up through the Amiga and into PC Gaming in the early 1990s. I've owned almost every console platform imaginable ranging from the Atari 2600, Intellivision, and Sega Genesis through to multiple Xbox, Playstation, and Nintendo systems along the way. I'm a fan of Call of Duty, Football Manager, and just about any kind of management/tycoon kind of game you can think of. My hobby extends out to the tech side of things - I like playing with PC gear and streaming tech in my spare time.

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