THE FOLD / RESPAWN / SECOND WIND / THE FAST RETRANSMIT
THE FAST RETRANSMIT
the signal is not in any message but in there being three
1 WHAT IT IS · WHAT IT DOES · FACT OR FICTION
When a packet is lost the receiver keeps acknowledging the last thing it got in order. Three of those duplicates are enough to act on — without them the sender waits out a timeout sized for the worst case.
LIT verified live. 10,000 packets at 1% loss give 109 losses. With a round trip of 100 ms and a timeout of 300 ms, waiting for the timeout every time costs 32,700 ms of stall. Acting on three duplicate acknowledgements costs 10,900 ms — 21,800 ms saved, a factor of 3.00. It needs three more packets to arrive, which at the end of a transfer never happens.
LIT verified live. 10,000 packets at 1% loss give 109 losses. With a round trip of 100 ms and a timeout of 300 ms, waiting for the timeout every time costs 32,700 ms of stall. Acting on three duplicate acknowledgements costs 10,900 ms — 21,800 ms saved, a factor of 3.00. It needs three more packets to arrive, which at the end of a transfer never happens.
2 HOW IT WAS WEAVED · AI + HUMAN
Fast retransmit and fast recovery are Jacobson’s too, and the 3 is a threshold chosen to distinguish loss from mere reordering.
AVAN (AI) published the precondition next to the saving because the saving is conditional on it. The mechanism is 3.00× faster exactly when there is more data behind the loss, and worth nothing at all for the last packets of a flow — which is where a short transfer spends most of its life.
AVAN (AI) published the precondition next to the saving because the saving is conditional on it. The mechanism is 3.00× faster exactly when there is more data behind the loss, and worth nothing at all for the last packets of a flow — which is where a short transfer spends most of its life.
3 ONE DIMENSION
Two ways to notice the same loss.
4 TWO DIMENSIONS · INTERACTIVE
Change the loss rate and the timeout.
5 THREE DIMENSIONS + AVAN’S INVERSE
The green forward object: three echoes of the same gap.
AVAN’s addition (the inverse-companion): the forward reading is that duplicate acknowledgements are a faster loss signal. The inverse is that they are the receiver saying the same true thing repeatedly, and the meaning is entirely in the repetition. Each duplicate carries no new information — it reports the identical sequence number the sender already had. Read backwards, the signal is not in any message but in the fact that there are three of them, which is the only kind of signal available to a receiver with nothing new to report.
LIT 10,000 packets at 1% loss give 109 losses, and with a round trip of 100 ms and a timeout of 300 ms, waiting for the timeout every time costs 32,700 ms of stall against 10,900 ms for acting on three duplicate acknowledgements - 21,800 ms saved, a factor of 3.00 - but it needs three more packets to arrive, which at the end of a transfer never happens
FIG Fast retransmit and fast recovery are Jacobson's too, and the 3 is a threshold chosen to distinguish loss from mere reordering. AVAN published the precondition next to the saving because the saving is conditional on it. The mechanism is 3.00 times faster exactly when there is more data behind the loss, and worth nothing for the last packets of a flow - which is where a short transfer spends most of its life.
FIG Fast retransmit and fast recovery are Jacobson's too, and the 3 is a threshold chosen to distinguish loss from mere reordering. AVAN published the precondition next to the saving because the saving is conditional on it. The mechanism is 3.00 times faster exactly when there is more data behind the loss, and worth nothing for the last packets of a flow - which is where a short transfer spends most of its life.
◆ sealed .dlw.fold → folded to ROOT_0 · a sphere of SECOND WIND · David Lee Wise (ROOT0), with AVAN