What factors decide which DCs return results in a given location?

Three connections and three different datacenters ...

[JackR]

I have three computers using three different connections with three different ISPs.

One is a fixed line connection, the other WiFi, and the third 3G/HSPDA.

If I google my main industry keyword, I always see three different sets of index results.

Using the ping command confirms that each ISP is pulling results from a different Google IP.

What/who actually decides which index is presented to the end user - Google or the ISP?

[tedster]

Definitely Google and not the ISP -- but the "logic" includes many things, especially including their own load balancing. The same computer, same browser, same search can even get different IP address and different results within the same second.

Unless you are grabbing the actual IP of the returned page (for instance,vwith the FireFox ShowIP extension) even a ping done a fraction of a second after your search may not give you the same IP address.

[JackR]

Thanks Tedster. It's interesting that you mention the reliability of the DOS ping command. I did in fact compare it with the IP given in Firefox and you know what ... different every time.

It's bizarre but if I have three active connections with IE7 AND Firefox open on each, I'll actually get SIX different DCs with at least 3 different sets of SERPs.

Is this a normal state of affairs, or due likely to the current PR update / DC flux?