Saku Ytti wrote:
And you will be wrong. Packet arriving out of order, will be considered previous packet lost by host, and host will signal need for resend.
As I already quote the very old and fundamental paper on the E2E argument: End-To-End Arguments in System Design https://groups.csail.mit.edu/ana/Publications/PubPDFs/End-to-End%20Arguments... : 3.4 Guaranteeing FIFO Message Delivery and as is described in rfc2001, Since TCP does not know whether a duplicate ACK is caused by a lost ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ segment or just a reordering of segments, it waits for a small number ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ of duplicate ACKs to be received. It is assumed that if there is just a reordering of the segments, there will be only one or two duplicate ACKs before the reordered segment is processed, which will then generate a new ACK. If three or more duplicate ACKs are ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ received in a row, it is a strong indication that a segment has been ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ lost. ----- in networking, it is well known that "Guaranteeing FIFO Message Delivery" by the network is impossible because packets arriving out of order without packet losses is inevitable and is not uncommon. As such, slight reordering is *NOT* interpreted as previous packet loss. The allowed amount of reordering depends on TCP implementations and can be controlled by upgrading TCP. Masataka Ohta