Workloads

For the peer-to-peer experiments, we used the default Quake 2 game rules for ``death match.'' In general, this game type implements a free-for-all where each player attempts to kill as many opponents as possible. For the edge-server experiments, we simulated a ``dungeon'' type game where half of the entities in the game are computer controlled monsters and players only attack monsters (and vis versa). In both cases, players are simulated with computer controlled bots¹⁰ and respawn after being killed (that is, they are regenerated). We did not notice a quantitative difference in results dependent on the game rule set. Each experiment ran for approximately 15 minutes and, unless otherwise specified, our results examine 5 minutes during the middle of each game.

図 5: A section of the map used in our experiments.

図 6: Statistics about (a) the size of subscriptions generated by players and monsters during a game, and (b) replica lifetimes.

(a)	(b)

For both game types, we constructed a large map, shown in Figure  (in actuality, the map shown was replicated at 4 levels with stairwells connecting each level). On average 1% of the map is visible at any given point, compared to about 10% in an original map designed for a maximum of 64 players, though our map is only 4 times as large. Hence we estimate that the ``maximum'' number of players it supports is probably between 256 and 640, though there is interactivity with numbers far below that. Figure 6(a) shows a cumulative distribution of (predictive) subscription sizes generated by players and monsters during a game with 200 players and 200 monsters. Figure 6(b) shows the cumulative distribution of replica lifetimes (excluding missiles, since they usually live for less than a second), which roughly corresponds to how long an object remains in a player's area-of-interest. Most replicas live only for a few seconds, as is expected since players move rapidly from one region to another when not fighting. Note however that over 10% of replicas last longer than 10 seconds and hence it would occasionally reduce communication costs to colocate objects with mutually long-running interests.

In addition to players, monsters, and the missiles they fire at each other, there are items in the game world such as different weapons and health packs.