研究了數(shù)據(jù)分組在IP網(wǎng)絡(luò)中傳輸時(shí)RTT時(shí)延的組成，給出了RTT時(shí)延與分組長(zhǎng)度的線性表達(dá)式。分析了傳統(tǒng)利用UDP測(cè)量分組RTT時(shí)延與測(cè)量分組長(zhǎng)度的線性關(guān)系進(jìn)行鏈路帶寬測(cè)量的算法，針對(duì)該測(cè)量算法不能對(duì)非對(duì)稱鏈路帶寬進(jìn)行測(cè)量的缺陷，提出了一種新的非對(duì)稱鏈路帶寬測(cè)量算法Asy_pathchar。同時(shí)使UDP報(bào)文和ICMP報(bào)文作為測(cè)量報(bào)文，Asy_pathchar能夠?qū)y(cè)量分組所經(jīng)過(guò)的每一跳非對(duì)稱鏈路的帶寬進(jìn)行測(cè)量，實(shí)驗(yàn)結(jié)果驗(yàn)證了算法的正確性。
關(guān) 鍵 詞 鏈路帶寬; 帶寬測(cè)量; 非對(duì)稱鏈路; RTT時(shí)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