摘要： Elastic optical network (EON) has been a promising technology for the next generation of core transport networks, because it can support flexible spectrum assignment. Routing, modulation and spectrum assignment (RMSA) is one of the key issues in EON. In this paper, two indexes are considered during the spectrum assignment process, number of consumed resources R and distance to boundary I. Minimizing R means using the least resources to establish a connection while minimizing I implies that remainder idle resources are more lumped after a connection is established. Both of them can reduce blocking probability of network. However, optimizations of R and I are sometimes contradictory, so we propose three policies to make a tradeoff between them, which are R I I R policy sets I as the optimizing objective. as the chief one; the I policy can get the best Simulations are taken on the NSF-Net and UBN topologies, which show that the +R performance in most cases. We further compare the +R I policy with two existing well-performed algorithms, the First-Last-Fit algorithm and the Block-Assignment algorithm. Simulation results reveal that blocking probability of the +R I . The R I: policy takes R as the primary objective while the I R: I policy is far less than that of the comparative objects. I policy takes a linear combination and +R +R α I ) αR (1 + ? : :,