Re: UDP Connection tuning questions regarding the -b and -l options
Kevin Gibbs wrote:
> Actually you are quoting my post ever so slightly out of context.
Apologies for this, I was just pleased to find something that seemed to
confirm what I saw.
> It is
> true that there is no _programatical_ way to before hand compute the
> amount of headers, i.e. Iperf will never be able to do it. However a
> user (or more likely network admin) can "easily" compute this
> information before hand. The caveat being if you are sending data over the
> Internet in general then you will not be able to calculate it. If you know
> exactly the path that every packet will take and what those network types
> are then you can calculate the header size. For instance if I have 2 GigE
> (or 10 or 100 Mb/s ethernet link) cards connected over a crossover cable
> then I know that the headers (and footers) are ethernet, IP, UDP. Even if
> I threw in a ethernet switch I would still get the same headers. However
> if I connected two machines directly through a ATM link I would get a
> different set of headers. Since Iperf can not detect these link types or
> any along a multi-hop path it can not provide the functionality you are
> looking for. You should be able to provide it yourself given you know your
> setup.
This is what I thought, but my testing doesn't seem to prove the theory
that I can calculate -b for a known network configuration. So either my
logic/understanding is wrong or the server/network set-up cannot deliver
the calculated throughput. I need to do some more work on this and will
probably ask further questions if that is OK?
Jim Mozley