a.(1) In the Schiper-Eggli-Sandoz protocol, how are the out of order messages in one communication channel handled? (the protocol assumes non-FIFO channels)

The sender of the message always sends the message first and then updates its time stamp. This ensures that the check for t !< tp2 where t is the time stamp of the last sent message to P2 is checked with the current time stamp of P2 and not the time stamp of the message that has been sent. This ensures that P2 wait for prevoius message if hasnít seent it and buffer any message with tí > t. Once it sees the previous message, then it updates its own timestamp and rechecks all the messages in the buffer. This allows the channel to be non FIFO. e.g

b.Consider Figure 5.8, explain why states LS_{11} and LS_{22} can never be recorded in a global state using the Chandy-Lamport global state recording algorithm.

Because of the requirement of the channel to be FIFO. The marker is sent after LS_{11} snapshot and the message is sent after the marker. On LS{22} the message is received before the marker. Which is not possible based on Chandy-Lamport GS recording algorithm