[e2e] Open the floodgate

[Sam Manthorpe]

On Sun, 25 Apr 2004, Cannara wrote:

> Sam,
>
> Apparently there's great bias against Source Quench because it requires a
> packet be successfully sent in the reverse direction, but that's not such an
> unreasonable thing anyway, given the congestion complained about is opposing.
> TCP already provides that via a Window=0 statement back to the sender (which
> is like what ECN can trigger).

I believe there's no algorithm defined on what it should actually do :-)

>
> The reason 99% of congestion is handled by TCP's naive shutdown is, of course,
> because it's so nonlinear, like Chicken Little.  If all flows experiencing
> even the slightest loss go back to Slow Start, of course 'disaster' has been
> averted.  This odd concept of a "control system" is like an automotive cruise
> control that jams on the brakes when speed goes over the set point.

Au contraire.  Most of the time (~ 90%) loss is dealt with by fast-retransmit,
which doesn't jam on the brakes, but eases off on the gas.  The brakes
only get jammed on when you hit timeout, which is far less common.  Then
the "self clocking" mechanism does a pretty good job of keeping loss low
(check your netstat -s).  Seems like a fairly effective control system.

Cheers,
-- Sam