Consider three processes P, Q, and R using message-passing for communications. Their behaviors are illustrated below. Let BS = blocking send, NS = nonblocking send, BR = blocking receive, and NR = nonblocking receive.

Process P:

...
send(Q, msg1)
receive(R, msg2)

Process Q:

...
send(R, msg3)
receive(P, msg4)

Process R:

...
send(P, msg5)
receive(Q, msg6)