Confused about how the matchmaking works in Call of Duty: Black Ops II? You certainly aren’t alone—similar complaints have compelled Activision to release an article on their support page explaining the system.
The support article broaches the issue in detail, but here are a few of the steps Activision says the search filter uses to generate matches:
Filter all games that can be joined by proximity to the player. Proximity does not adhere strictly to city, state or country as seen on a map. Rather, it breaks down into four tiers of geographical region surrounding the player. The query starts in the tier closest to the player and expands from there if it cannot find enough matches. The query also ignores all full or “non-joinable” games, which could be half or more of the total available games in a playlist.
Filter by broad skill range. This step takes the proximity-filtered list and narrows it further to the set of games that fall roughly in the same broad skill range. This is very loose criteria in Public Match and is a broad-stroke filter that avoids games at the extreme ends. A player of very high skill should generally not get matched to games where the average skill of players is very low, and vice versa.
Steps 1 and 2 normally take a fraction of a second and result in a list of “top 50” available games. From here, the game tests for the best connection quality of those 50 games. Connection quality includes a measure of ping, bandwidth between you and the host, and NAT compatibility. The game attempts to join the you to the game with the best connection quality of all possible matches, starting at the top of the list.
All this happens, Activision says, within several seconds—depending on connection speeds.
They also list several variables that influences the quality of online matches:
The first is your local network connection quality which itself is determined by a number of variables. If the quality of your network doesn’t meet minimum criteria, the matchmaking won’t matter – the game cannot control variables that are general aspects of internet connectivity. For steps on improving your local connection quality, see the article on decreasing lag. Here are some factors that can decrease your quality of network service:
Low bandwidth to the internet due to ISP bandwidth limits.
High bandwidth usage by other services in your home (video/audio streaming or high-volume concurrent downloads, for example).
Your local home network has restrictive NAT settings.
You are playing the game over a WIFI connection rather than wired Ethernet.
Your ISP is throttling data throughput from your location. Some ISPs erroneously flag online games as “spam” and will throttle the speed at which data can transfer in and out of those games. If you experience consistently laggy games or games that lag during the same time periods every day and there are no other problems with your home network, check with your ISP to ensure that they aren’t throttling specific types of data.
The second variable is your region. If you live in a remote region, it will be more difficult to find hosted games that match your profile. The best option for those in extremely remote regions is to play during local peak hours in playlists with high player counts.
The third variable is time of day. Since matchmaking works to find the game with the best connection quality, it will have a much easier time finding high quality connections when there are more players online in your area. As a general rule, peak usage occurs during the late afternoon and evening hours in each time zone.
One last variable to be aware of is DLC. DLC map packs divide matchmaking pools into groups of players who have DLC and players who don’t have DLC. The more map packs that are released, the more matchmaking pools there are. Nine months after the initial launch of the game, for example, the highest single population of players is that which owns all map packs.
Hopefully this helps shed some light on any questions our Call of Duty: Black Ops II fans have about the online matchmaking. If not, uh … sorry.
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Tue Mar 10, 2015 2:54 am by 
Subject: Activision explains Call of Duty Black Ops II Matchmaking 
