The "center" (there can actually be multiple centers if there are bottlenecks...) is the general area of the network that is most tightly connected with the highest number of other nodes. Think of it like The 6 Degrees of Kevin Bacon. There is actually a whole new area of math and networking theory that has grown around this. In the Kevin Bacon game, there are certain actors that have been in a LOT of movies (those nodes have a lot of connections to other nodes). This makes them very close (from a network distance standpoint) to Kevin Bacon and thus are centers of activity (hubs) for the game. But there are other people that may have only ever had one role in some really obscure movie. This person has very few connections and thus is on an edge. The more hops that it takes to get from any one node to a major hub is in general (there could be bottlenecks between hubs) the distance that needs to be surmounted in order to obtain updates.


There are known de-facto hub nodes running that you can try and get your node to connect to or close to. The next best thing (actually the best thing for the strength of the network) is to make sure that your (and the pool's) bitcoind node isn't behind a firewall and can connect to as many other nodes as possible. The more connections you have, the more likely that one of those connections will be close to a hub.