bandwidth aggregation

["Gary Smithe" <deb.guy@gmail.com>]

Hi folks,
    Hopefully this question makes some sense.  I work at a small ISP,
where we have 3 T1 lines coming in (from 3 different providers).  We
have split different customers and services out on these 3 address
spaces.

We'd like to aggregate bandwidth in such a way that all public
addresses still work, but that bandwidth is somewhat evenly
distributed.  This aggregation would hopefully have the side-effect of
preventing outages for any of our customers if any 1 of the upstream
links fails.

I'd prefer a GNU/Linux solution, but it doesn't have to be that way.
Heck, we'd even pay for mysterious, closed, "black box" product, if it
got the job done.

Hopefully I've phrased this right and someone knows what I mean.  Even
better, hopefully someone has a solution :-).

I did try searching the ISP mailing list, and google wasn't a big help
in finding a solution for this scenario.

Thanks for your time.

GS