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Re: from the academic side of the house

  • From: Leigh Porter
  • Date: Tue Apr 24 12:48:00 2007


Jim Shankland wrote:
[email protected] writes:

The next day, the team used a modified version of TCP to achieve an
even greater record. Using the same 30,000 km path, the network was
able to achieve a throughput of 9.08 Gbps which is equal to 272,400
Tb-m/s for both the IPv6 multi and single stream categories. In doing
so, the team surpassed the current IPv4 records, proving that IPv6
networks are able to provide the same, if not better, performance as
IPv4.

Good job. Two questions, though:


(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.

(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.
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?

Jim Shankland

Also, it's a "modified" TCP not just tuned. I wonder how modified it is? Will it talk to an un-modified TCP stack (whatever that really is) ?


--
Leigh Porter