for every message enterting A is there a communication done to machine B that donot accept any messages for this particaular Unique Id and then machine Ba also does the same for Machine A.
No there is no communication, there doesn't have to be as only 1 message with a unique id can ever exist in the cluster at any one time. Unless your application is floored of course and re uses ID's.
p.s. can you use the correct forum for posts please? (user forum)