The question is whether IMA exists on DS3 interfaces. I would suspect that
the cell rate may be kind of high to support even load-balancing/splitting.
Kinda like doing MLPPP on a pair of OC-12s.
However, this is generally not needed unless your VC(P) needs to run at
greater than the theoretical peak cell rate of the interface. If you have
small DSL PVCs, you can just round-robin them via static PVC provisioning,
or PNNI load-sharing of soft vcs.