from the academic side of the house

Tue Apr 24 16:46:07 UTC 2007

Jim Shankland wrote:
> bmanning at karoshi.com 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