Huihu Long Lu Cheng Yongguo Zeng Li Wu Active Diagnosis of High-Level Faults in Distributed Internet Services. 72-81 2008 APNOMS http://dx.doi.org/10.1007/978-3-540-88623-5_8 conf/apnoms/2008 db/conf/apnoms/apnoms2008.html#LongCZW08