I believe the formula applies when the TCP window size is held constant (and maybe as large as is necessary for the bandwidth-delay product). Obviously P going to zero is a problem; there are practical limitations. But bit error rate is usually not zero over long distances.

The formula is not mine, it's not new, and there is empirical evidence to support it. Check out the links for more (and better :-) info.

Joe

owner-nanog@merit.edu wrote on 04/12/2007 04:48:09 PM:

>
> On Thu, 12 Apr 2007, Joe Loiacono wrote:
>
> > Window size is of course critical, but it turns out that MTU also impacts
> > rates (as much as 33%, see below):
> >
> >        MSS      0.7
> > Rate = ----- * -------
> >        RTT    (P)**0.5
> >
> > MSS = Maximum Segment Size
> > RTT = Round Trip Time
> > P   = packet loss
>
> So am I to understand that with 0 packetloss I get infinite rate? And TCP
> window size doesn't affect the rate?
>
> I am quite confused by this statement. Yes, under congestion larger MSS is
> better, but without congestion I don't see where it would differ apart
> from the interrupt load I mentioned earlier?
>
> --
> Mikael Abrahamsson    email: swmike@swm.pp.se