If a state requester requests state and BARRIER drops all messages at the state requester, then a view V dispatched by the coordinator during the state transfer will never be installed at the state requester:

• The current view is V1={A,B}
• B requests the state from A
• A gets a JOIN from C
• A mcasts the new view V2={A,B,C}, seqno=6
• A sends back a unicast state response to B including the state and a digest with A:6 (including V2)
• B receives the unicast state response and installs the state and digest
  • B's digest for A is 6
• B receives V2 (A:6), but drops it as message 6 is already in its digest for A !
  --> B will never install V2 !

This applies to all state transfer protocols which use BARRIER (STATE_TRANSFER, STATE, STATE_SOCK).