Detecting and measuring asymmetric links in an IP network

摘要

The rapid growth of Internet traffic has made it important to pinpoint network bottlenecks. Measuring link bandwidths can help identifying such bottlenecks. Existing bandwidth measurement tools such as Pathchar, Bing and Bprobe assume symmetric links. But as ADSL lines, cable modems, satellite links, and 56K modems gain popularity, it becomes necessary to consider asymmetric links. We present an algorithm that can measure each hop's link bandwidth in both directions in an IP network. Hence it is trivial to detect link asymmetry. We performed several experiments to validate our algorithm. We also discuss factors that can adversely affect the precision and/or correctness of bandwidth measurement, and suggest some possible solutions.