Related: http://en.wikipedia.org/wiki/Two_Generals%27_Problem http://en.wikipedia.org/wiki/Two_Generals%27_Problem It might be worth reading that first to get

Related: http://en.wikipedia.org/wiki/Two_Generals%27_Problem http://en.wikipedia.org/wiki/Two_Generals%27_Problem It might be worth reading that first to get into the right frame of mind. For reference, I've had to code solutions for both of these problems for real in safety-critical situations. Interesting challenge. ADDED IN EDIT: The paper with the original solution: http://delivery.acm.org/10.1145/360000/357176/p382-lamport.pdf?key1=357176&key2=8126308921&coll=DL&dl=ACM&ip=192.168.2.38&CFID=10522886&CFTOKEN=86594853 http://delivery.acm.org/10.1145/360000/357176/p382-lamport.p... ADDED IN EDIT (2) Amazon's S3 service suffered a failure of this type: http://status.aws.amazon.com/s3-20080720.html http://status.aws.amazon.com/s3-20080720.html