[e2e] Retransmission Timouts revisited

Detlef Bosau detlef.bosau at web.de
Thu Aug 25 13:23:08 PDT 2005

Detlef Bosau wrote:
> Some problems are:

I missed one important problem: The forecast capacity.

Particularly, the congavoid paper recommends to choose the gain in the
mean estimator according to noise etc.

Edge clearly points out that the gain should be chosen that way, that
the forecast error is minimzied.

The problem is that RTO is applied to a packet which has not yet been
Consider an estimated rtt of 5 seconds, then we forecast a networks path
properties for a duration of 5 seconds.

At the moment, we have a "one size fits all" gain in TCP, which
practically ignores, that actual RTTs span a range of 
up to eight orders of magnitude.

When I read the "cost to cost" latencies posted by several authors here,
I was highly interested. Unfortunately, I don´t live in the US,
I´m an ordinary private Internet user in Germany, connected with a DSL
Admittedly, RTT up to one or two _seconds_ two servers in the US are
extremely rate, but they _exist_.

And when 3rd generation mobile networks reach the public, we will face
much larger round trip times.

This leads to a settling time problem as well. This is particularly a
problem for short termed flows.

Just to say that.

Detlef Bosau
Galileistrasse 30
70565 Stuttgart
Mail: detlef.bosau at web.de
Web: http://www.detlef-bosau.de
Mobile: +49 172 681 9937

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