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

Ted Faber faber at ISI.EDU
Mon Jun 30 09:07:11 PDT 2008

On Mon, Jun 30, 2008 at 04:42:18PM +0200, Detlef Bosau wrote:
> As I said: What makes "ICN" (implicit congestion notificatin, i.e. by 
> missing ACK) preferable over "ECN" is: Loss cannot get lost.

Outside of some bugs in say, tunneling ECN packets, if the ECN is lost,
the packet is lost.  The missing packet transmits the congestion signal
perfectly accurately (as you point out).

Bugs where a router or endpoint deletes an ECN mark are of the same
order of acknowleging a lost packet (losing a loss).

Losing an ECN marked packet sends the exact same congestion signal as
delivering it.  That aspect of the system is remarkably robust.

Ted Faber
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