Tracking Users By IP Address

[Alan Kennedy]

[Fuzzyman <fuzzyman at gmail.com>]
>>Assuming that each visitor will have a unique IP address is probably
>>not 100% accurate but will have a reasonably low margin of error !! 

[Paul Rubin]
> Nah, you can't rely on that at all.  For example, all N zillion AOL
> users come through only a few hundred different IP addresses.  And
> SOMETIMES you get those proxy headers other people have mentioned, but
> not all that often.

That's probably the biggest problem, but I would also add the following 
other problems which will further widen the error margin:-

1. Modem and DSL users most often get dynamically allocated addresses, 
which means that two entirely different users can get the same address 
within seconds of each other: one disconnects, the other reconnects to 
the same endpoint. If they both visit your web site, and you're tracking 
only IPs, then you'll think they're both the same user. If your content 
raises a lot of interest in a specific phone-dial-code area, for 
example, this could seriously skew your data.

2. With corporate networks, local IP addresses (i.e. the ones you see in 
X-FORWARDED-FOR headers, etc) tend to be handed out by DHCP-style 
dynamic allocation. Which means that the head-of-IT's address this week 
could be the receptionist's address next week.

regards,

-- 
alan kennedy
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email alan:              http://xhaus.com/contact/alan