When we have the following situation, message B3 will not get delivered at A:

• A and B
• B sends 3 multicast messages: B1 (regular), B2 (OOB) and B3 (regular)
• A receives B1, B3, B2
• A delivers B1
• B3 has to wait until B2 is received, so the thread returns
• B2 is received, but since it is OOB, after pushing the message up the stack, the thread terminates !
  ==> B3 will not get delivered until B4 is received !

The unit test case is OOBTest.testRegularAndOOBMulticasts()