You can accomplish some of this with policy routing, and your "peon ubuntu" already has the software to do it.

https://www.google.com/search?q=linux+policy+routing

This is usually best if you know the traffic that your working with.  If the connections are different speeds you could push your services to 
one connection, and your general usage to the other.  Or similar with some traffic that's higher priority being pushed to the more stable 
connection.

If you need more than that, you'll probably need a BGP setup.

On 10/31/14 12:56, gregrwm wrote:
> when two gateways are available, i want to monitor response times and use
> whichever is responding better.  this raises several questions.  this is
> presumably the sort of thing heavyweight routers do all the time?  but my
> peon ubuntu probably needs either special software or clever
> configuration?  an established connection is confined to its established
> route, or not necessarily?  for worthwhile pointers i would be very
> grateful, tia.
>
>
>
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