4.3.3 Out of Order Arrivals
nThe
RFC does not specify what to do with out of order packets. TCP will only
acknowledge ordered transmissions,
but the question is: should it keep out of order packets in its buffer or just discard them? The easiest implementation is to
discard and wait for all
packets to arrive in order.
nAn
ACK is sent in response to an out of order packet, it contains the “expected”
sequence number.