[Iccrg] LT-TCP followup

[Lachlan Andrew]

Greetings Shiv,

If we use ECN to distinguish between congestion and loss, how can we
detect that "there is loss that is caused due to congestion on the
path (and ECN signals are absent)" and know to revert to TCP-SACK?

The problem is that the flow may be ECN-enabled, and there may be (a)
some ECN packets, (b) some packets lost due to corruption, and (c)
some packets lost due to congestion of a non-ECN queue.  How can we
distinguish (b) from (c)?

Thanks,
Lachlan

On 08/08/2007, Shivkumar Kalyanaraman <shivkuma at ecse.rpi.edu> wrote:
>
> If ECN is used, the likelihood of congestion related loss may be
> minimized. However, if there is congestion related loss, because either
> ECN is absent, or there are also end-systems that do not respond to ECN,
> then LT-TCP will have a robust method for safely reverting back to
> TCP-SACK behavior. When there is loss that is caused due to congestion
> on the path (and ECN signals are absent), LT-TCP will revert back to
> TCP-SACK.

> best
> -Shiv
>
> On Mon, 6 Aug 2007, Michael Welzl wrote:
>
> > in the presence of
> > packet loss (which can always be due to an overflowing queue,
> > ECN notwithstanding), the right thing to do is to assume congestion.


-- 
Lachlan Andrew  Dept of Computer Science, Caltech
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