Do many ISP's cache A records with TTL of 0 ?

[Mark van Kerkwyk]

Hi,
         I was looking for some information on whether many ISP's out there
ran name server caches which are very unfriendly to A records/zones with a
TTL of 0 (or very low anyway) for global server load balancing purposes.

I was told that a while back AOL used to cache all records for a number of
days, irrespective of whether it had a TTL of 0 or anything (eg over 1
day).

Does anyone know of any ISP's perform this practice and in turn screw up
any global server load balancing which utilises a TTL of 0, if so, where
might one find a list of who does this ?

I can only assume that this practice can't be too widely used , as there
are so many DDNS service offerings out there ? The one I use runs a TTL of
15.

Thanks

Mark