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Re: from the academic side of the house

  • From: JP Velders
  • Date: Sun Apr 29 08:03:02 2007 
On Tue, 24 Apr 2007, Jim Shankland wrote:

> Date: Tue, 24 Apr 2007 09:24:13 -0700
> From: Jim Shankland <[email protected]>
> Subject: Re: from the academic side of the house

> (1) Do the throughput figures count only the data payload (i.e.,
> anything above the TCP layer), or all the bits from the protocol
> stack?  If the latter, it seems a little unreasonable to credit
> IPv6 with its own extra overhead -- though I'll concede that with
> jumbo datagrams, that's not all that much.

Data payload is counted as bytes transmitted and received by iperf. So 
application layer all the way.

> (2) Getting this kind of throughput seems to depend on a fast
> physical layer, plus some link-layer help (jumbo packets), plus
> careful TCP tuning to deal with the large bandwidth-delay product.

That last part has been researched for quite some time already, though 
mainly with "long" transatlantic layer 2 (Ethernet) paths mainly.

> The IP layer sits between the second and third of those three items.
> Is there something about IPv6 vs. IPv4 that specifically improves
> perfomance on this kind of test?  If so, what is it?

Not that was specificly mentioned for this test I believe...

Kind regards,
JP Velders