Deltas contain information about map data. Periodically, in a networked game, the server compiles a set of deltas for each client. The deltas record the differences in the game world compared to the last time deltas were generated, e.g. the movement of map objects and planes, and sector light changes. On serverside, each client has a delta pool, which contains all the deltas about to be sent. A delta is not removed from the pool until the client acknowledges receiving it. Deltas are resent until acknowledged. All delta processing is done in sv_pool.c.