Exploiting omissive faults in synchronous approximate agreement
Azadmanesh, M.H.; Kieckhafer, R.M.
Computers, IEEE Transactions on
Volume 49, Issue 10, Oct 2000 Page(s):1031 - 1042
Digital Object Identifier 10.1109/12.888039
Summary:In a fault-tolerant distributed system, it is often necessary for
nonfaulty processes to agree on the value of a shared data item. The
criterion of Approximate Agreement does not require processes to achieve
exact agreement on a value; rather, they need only agree to within a
predefined numerical tolerance. Approximate Agreement can be achieved
through convergent voting algorithms. Previous research has studied
convergent voting algorithms under mixed-mode or hybrid fault models,
such as the Thambidurai and Park Hybrid fault model, comprised of three
fault modes: asymmetric, symmetric, and benign. This paper makes three
major contributions to the state of the art in fault-tolerant convergent
voting. (1) We partition both the asymmetric and symmetric fault modes
into disjoint omissive and transmissive submodes. The resulting
five-mode hybrid fault model is a superset of previous hybrid fault
models. (2) We present a new family of voting algorithms, called
Omission Mean Subsequence Reduced (OMSR), which implicitly recognize and
exploit omissive behavior in malicious faults while still maintaining
full Byzantine fault tolerance; (3) We show that OMSR voting algorithms
are more fault-tolerant than previous voting algorithms if any of the
currently active faults is omissive
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