Techniques for defragmenting at least one time division multiplexed link in a communication system, wherein provisioned circuits corresponding to traffic demands are assigned to particular time slots of the link. An optimum layout of free space for the link is computed, subject to an interface rate constraint that may be specified as a minimum cross-connect rate and a maximum cross-connect rate. Particular free slots from the optimum layout of free space are selected, and a hitless migration sequence is determined for migrating one or more of the circuits to one or more of the selected free slots. The time slot assignments of one or more of the circuits are adjusted in accordance with the determined migration, sequence in order to defragment the link.