[c-nsp] General performance based routing question?

[Scott Granados]

Hi, I have a general question and Google isn't steering me right.;)
    While BGP contains next hop information and other various knobs for traffic engineering there is no performance metric included.  Take the following example, say router A is connected to ISP1 and ISP2 via two equal bandwidth and cost links.  Suppose that ISP2 takes the bulk of the traffic but has congestion issues in the local pop.  BGP will select ISP2 based on AS-Path etc but has know knowledge that this is not the "best" path because congestion is degrading performance.  Are there any tools or techniques that could track performance and optimize the routing process either by adjusting local pref or some variable in the router to adjust traffic flow?  I've heard of some boxes that do this but but at the time the general feeling was that these were rubbish and simply thrashed around /16's for no real reason.  What are people doing to factor in traffic performance instead of making purely distance based calculations?

Thanks
Scott