June 25, 2009
Today's DNS Spotlight: Eircom
Ever wonder exactly where some infected computer is, when you find it is hitting your inbounds with repetitive requests to send mail to nonexistent accounts, as in where in the world, down to ICBM coordinates? Yeah, me, too. Unfortunately, despite the best efforts of groups like the the Prefix Whois Project, who provide eerily precise longitude and latitude for any given IP, geolocation is still an infant science. Usually, the best that can be done is to provide the ICBM coordinates of the company providing the service, which while satisfying to an owner of fantasy desktop nuclear weapons, isn't quite as satisfying as taking out the actual infected computer while leaving all else around it standing. Oh, well. Maybe someday.
On the other hand, some networks do make an effort to name their systems so that they could be found by, say, firefighters. Take, for example, this wifi node in a McDonald's in Dublin, Ireland:
Now, I've never been to Lower O'Connell Street, nor Dublin, nor Ireland for that matter (though my sainted Grandmother Betty was swept away as a war bride during the second World War, from her ancient homeland in Fintona, County Tyrone). And the pwhois coordinates for this IP are a good seven minutes drive on the south side of the Liffey from Lower O'Connell Street. But still. One imagines a well-launched predator trained on the wifi node, or maybe the more imaginative can picture a Terminator preparing to tap a customer replete with laptop and large fries, and a more satisfying ending (perhaps involving a Taser).
What's sad, as anyone who's been reading will instantly recognize, is that the "dynamic" keyword is a far cry from the Most Significant Token, and is not itself actually tokenizable by the weak, dot-delimited (and limited) MTAs we're blessed with, so in order to recognize this is a dynamically assigned IP you must use a regular expression. You may be able to use a substring based on "wlan-ce1", but still there's this business of a complete street address and business name to contend with. Do we need to keep track of the wifi node at Govinda's, the vegetarian place around the corner, too?
I don't know if Govinda's is an Eircom customer, but the Citywest Hotel is:
Now, we could, I suppose, just use "cust.eircom.net", but that is less than satifying (and they also use "customer.eircom.net", or used to). And it highlights another problem - just because an ISP or telco assigns an IP statically to a customer doesn't mean that customer can't then go on to re-allocate it dynamically to Big Mac eating, laptop-wielding, customers of theirs.
(A brief scan of the PTRs in 18.104.22.168/24 informs us of the depressing reality: there are several McDonald's on O'Connell Street alone... In fact, the lower /25 of that block seems dedicated to the McDonald's restaurants of Ireland.) On the other hand, they all seem to have wireless, so, make of that what you will.
So where does that leave us? We know the IP is dynamic; we can use a regular expression to capture many similar instances, provided that Eircom sticks with its naming convention for building out wireless LANs; we can even get within a few miles of the actual location if we wanted to launch an imaginary missile. But it would be so much easier if Eircom just used "dyn.eircom.net", or even "dyn-wlan.cust.eircom.net"; they already know it's going to be handed out dynamically via wifi. Why not just say it and group all similar IPs under the same top-level token?
Posted by schampeo at June 25, 2009 10:54 AM
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