Disclosed is a two tier packet labeling technique for use in connection with network traceback in a network having multiple autonomous systems, with routers and other network resources within each autonomous system. Tier 1 labels are assigned at the autonomous system level, and tier 2 labels are assigned at the router level. In order to reduce the number of labels that are required, a technique called logical partitioned coloring may be used, in which certain autonomous systems and border routers may be logically partitioned into a plurality of mesh connected nodes, and the labels are assigned to these mesh-connected nodes. During network operation the network routers store either tier 1 or tier 2 labels in data packets. The determination of whether to store a label in any particular packet, and the determination of which label to store, may be determined probabilistically by the network router.