Conservative Approach
deadlock avoidance algorithm requires:
a. Links to be statically specified.
b. Non-decreasing timestamp messages sent over a link to ensure events are executed in increasing time order.
c. Each link has a clock associated with it. Clock times is set to the timestamp of message at the head of the queue on the last received message.
d. The process looks at each link in turn and selects the message with the smallest clock time. If the selected queue is empty, the process blocks. DEADLOCKS!
e. Null messages are sent to avoid deadlocks.
A null message (Tnull) from LPA to LPB is a promise by LPA that it will
not sent a message to LPB with a timestamp smaller than Tnull.