通过地标节点选取机制，TZ 紧凑路由算法很好地保证了路由系统的扩展性。但 TZ 紧凑路由算法并没有限制地标节点的覆盖面，也没分析覆盖面过小的地标节点是否利于信息的传递。本文研究发现覆盖面过小的地标节点不利于紧凑路由的性能，因此通过限制地标节点的覆盖面，并在地标节点选取过程中删除覆盖面过小的地标节点，改进了 TZ 紧凑路由算法；同时，系统地分析了地标节点的覆盖面与平均伸长系数、平均路由表的关系。在连续10年的 Internet AS 图上进行仿真，实验结果表明，随着地标节点最小覆盖面的增大，平均伸长系数先减小而后逐渐增加，平均路由表先减小而后保持不变；当选取一个合适的阈值时，改进的算法比原始算法有更小的平均伸长系数和平均路由表，有效提升了紧凑路由的性能。%TZ compact routing algorithm guarantees the scalability of routing system by the mechanism of selecting landmarks ,but though it does not limit the coverage of landmark or analyse whether the landmarks with small coverage are beneficial for the message transfer .It was found that the landmarks with small coverage go against the performance of compact routing ,so landmarks were deleted whose coverage was less than the threshold to keep the coverage of landmarks .Also ,its relationships with the average stretch and the average routing table size were analyzed systematically .Applying TZ compact routing algorithm to the snapshots of the AS graph spanning a 10 year period ,it was found the average stretch decreases first and then increases gradually ,the average routing table size decreases first and then keeps invariant .When choosing an approximate threshold ,the improved algorithm shows lower average stretch ,lower average routing table size and which effectively improves the performance of TZ compact routing .
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