Re: Lossy cogent p2p experiences?

[Masataka Ohta <mohta () necom830 hpcl titech ac jp>]

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%20in%20System%20Design.pdf
:     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