Abstract: Multipath inter-domain routing has better effect in routing reliability and link utilization than traditional single-path routing policy, but how to guarantee the loop-freeness is still a new question. Through analyzing the incompleteness of AS_PATH detection mechanism,this paper proved the loop-freeness condition and offerd a method based on the collaborative operation of control and data plane(LFPM).By analyzing the theoretical conclusion and simulation experiments, LFPM could guarantee the loop-freeness demand in multipath routing. Moreover, the number of available routes could be increased greatly than equal cost multipath routing method and best routing method which could provide more probability for better routing selection results.

Key words: Multipath inter-domain routing, Routing loop