研究了數據分組在IP網絡中傳輸時RTT時延的組成，給出了RTT時延與分組長度的線性表達式。分析了傳統利用UDP測量分組RTT時延與測量分組長度的線性關系進行鏈路帶寬測量的算法，針對該測量算法不能對非對稱鏈路帶寬進行測量的缺陷，提出了一種新的非對稱鏈路帶寬測量算法Asy_pathchar。同時使UDP報文和ICMP報文作為測量報文，Asy_pathchar能夠對測量分組所經過的每一跳非對稱鏈路的帶寬進行測量，實驗結果驗證了算法的正確性。
關 鍵 詞 鏈路帶寬; 帶寬測量; 非對稱鏈路; RTT時延

Abstract By studying the construction of the RTT latency, alinear expression between the RTT latency and the packet size is presented. Then pathchar,traditional bandwidth measurement algorithm,based on the relationship between the RTT latency and the packet size, is analyzed particularly. But pathchar can not measure the asymmetric link bandwidth. To solve this problem, Asy_pathchar, a new algorithm, is put forward, which can measure each hop’s link bandwidth in both directions in an IP network using the UDP packet and ICMP packet.Finally an experiment is given to validate the new algorithm.
Key words link bandwidth; bandwidth measurement; asymmetric link; RTT latency