[e2e] Why do we need TCP flow control (rwnd)?

Ted Faber faber at ISI.EDU
Tue Jul 1 13:53:44 PDT 2008

On Tue, Jul 01, 2008 at 08:05:12PM +0200, Michael Scharf wrote:
> On Tue, 01 Jul 2008 at 09:22:06, Ted Faber wrote:
> > But for all the folks who think there's some engineering reason to
> > substitute ECN for receiver window: using ECN this way is foolish.
> Agreed, ECN is no reasonable solution for flow control.
> But what would be the role of rwnd if we indeed had one of these
> router-assisted congestion control schemes that aim at providing more
> precise feedback than ECN? Or e. g. re-ECN?

It would continue to provide flow control.

The receiver window is a simple (to understand and implement) and
inexpensive (16-bits of header and an if in the code) mechanism that
provides a useful end-to-end coordination between transports.  Why
combine it with a related but separate feature?  The savings is minimal
and the benefits unclear.

Ted Faber
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