I have a number of mux DS-3s coming in - right now they drop straight into aggregation routers. What I like to do is drop them into a local DACS and comb them out to DS-1s and then re-mux them back on to internal DS-3s. This will let me move circuits around digitally inside our equipment.

You're looking for digital cross connect, for the most part. You should take a look at the Cisco line i.e. 15454 et. al. You can bring in ds3, groom on the backplane, and send out ds3. I've used the 15454 et. al. in production and for your stated purpose it's more economical than buying some big iron. You may also want to consider your physical layer architecture if you do this i.e. interconnecting vs. cross connecting so that you have test access where you need it. IIRC, the 15454 et. al. will do passive monitoring at a line level and will SNMP alert on outages down to the smallest mux' unit. Very nice for the IP NOC. -M<