It was the Simpsons who first broke the story: Major League Baseball was spying on Barts thoughts with a special satellite that he shot down, only to have Mark McGwire come and hush the whole thing up. But subscribers to Major League Baseballs MLB.TV service may be surprised to hear what the big leagues are learning about them, or at least trying to learn: their physical location.
MLB.TV is a series of subscription services that allow users to view almost any Major League Baseball game live, broadcast over the Internet using Windows Media or Real streaming video technology. Viewers see one of the teams home broadcasts with that teams announcers. Afterwards, games are available in an archive and in a condensed format that has only the action in the game. (Im a subscriber and its generally a very cool service that I would recommend, especially if you live out of the TV coverage area for your team.)
Because TV networks buy the rights to these broadcasts in their viewing areas, MLB.TV enforces local blackout rules. In other words, if you live in the New York area you may not be able to watch a Mets game on MLB.TV because Channel 11 (WPIX) may be broadcasting it. MLB.TVs blackout rules provide specific lists of ZIP codes for each team in which computer users will be blacked out.
Wait a minute! How do they know what ZIP code your computer is in? Have they installed a secret homing beacon in the computer? Have they scanned your files for your home address? Are they reading your brain waves, as they did to Bart?
Perhaps the location they use is just based on the one on your credit card or some other records you produce? No, MLB.TV customer service insists its based on the IP address of the computer you are using. Since there is no "ZIP Code" field in the IP packet format, I was curious about what technique they are using to determine physical location based on network address.