**A square root formula for non persistent TCP flows**

**F. Baccelli, INRIA & ENS Paris, (a joint work with D.R. McDonald)**
**Abstract:**

In this paper, we derive a closed form formula for
the average rate attained by a non persistent TCP source which
alternates between idle periods and download periods
subject to a fixed packet loss probability.
We also derive closed form expressions for the mean time to transfer
a file and for the distribution of the transmission rate.
Several distributions for the file sizes and idle times
are considered including heavy tailed distributions.
The formula for the mean transmission rate is
shown to boil down to the classical
square root mean value formula for persistent flows when the
average file size tends to infinity. Using fixed point methods,
these formulae can be applied to predict
bandwidth sharing among competing HTTP flows subject to
Active Queue Management.