Asynchronized Internet Connections?

Zid asks: "I've got a cable modem, and the apartment I live in has a T1. The problem I have is that my cable goes out constantly, and the T1 is shared among the entire complex (200+ people) and it's behind a 3com NAT, so I'd like to be able to have my Linux box (which is a Masquerade box for the cable right now) to be able to automatically switch over to the T1 as a backup when cable goes out. My second question is whether it's possible to use the T1 as the uplink and cable as the downlink since the T1 can upload 4 times faster than the cable can."