Average ‘kill lag’ over time (the time it takes between firing the last bullet and seeing the enemy drop down)

Curiously, we’re still seeing reports from players that the lag has become worse over time. We spent a lot of time looking at all the ‘ping’ and ‘kill lag’ data available to us to determine a cause, but were unable to detect anything out of the ordinary. Indeed, the average kill lag has been consistent since we started tracking it in the beginning of December 2013, as shown in the graph above. With regards to the perception of lag, however, we did discover that players find a game to be very ‘laggy’ if only one or two kills during a match have a high kill lag – even if the rest of the match runs smoothly.

This prompted us to run a little experiment. We defined a ‘laggy kill’ as a kill that takes more than 0.5 seconds to register. We then determined that, given the measured ‘ping’ across the globe, the lowest realistically attainable percentage of laggy kills during a match would be 2%. Finally, we compared this number to what we could measure.

To our surprise, we saw that the percentage was really dependent on the region: US-East showed 13% laggy kills, US-West 6%, and other regions around 4%. Moving some of our servers in the US-East region to a different data center resulted in the percentage of laggy kills on those servers decreasing by a whopping 10%. A similar move in the US-West region unfortunately didn’t yield any further improvements.

So why is this? The US has many different networks, and not all networks have ‘peering agreements’ (a direct connection between the two networks). This means that sometimes, packets have to take a detour to arrive at their destination. For some players in the US-East region, we would even see packets travel from the east coast to the west coast and back before finally arriving at our server. This obviously introduces a lot of undesired lag.

All servers in the US-East region have been moved to the new data center, so players in this region should see an improvement.

Wireless versus Wired

For players who experience even more frequent ‘laggy kills’, we’ve found that the quality of their wireless connection may be a contributing factor. In such instances, switching to a wired connection has proven to halve the percentage of laggy kills.

The reason for this is that radio interference causes data to get lost much more easily on a Wireless connection. When that data happens to be your headshot, it takes a little while before the data is considered lost and is resent. This adds a couple of tenths of a second, and when the interference lasts longer (because, for instance, your neighbors are streaming a movie on their wireless connection on the same Wi-Fi channel) this process can easily cause a kill lag of a couple of seconds.