Re: Question about test results
On Thu, 22 Apr 2004, Dan Watts wrote:
>
> A theory I have is that one side starts transmitting and fills the
> outbound TCP/IP queue so that it takes a significant amount of time for
> the TCP/IP connection establishment for the second connection to
> complete. This would explain why the UDP test shows a very nice
> symmetrical result but the TCP/IP test does not.
>
> I've thought about modifying the code so that the transmit test delays
> for a few seconds before starting but I think I may still run into the
> same issue with ACK packets getting stuck behind so many transmitted
> packets.
Dan,
Your theories and thoughts are pretty dead on. The best way to get
around this problem is not actually found in the delay or some other way
to manipulate two connections to be nicer to each other. A more ideal
solution is to actually use ONE connection. This is a feature that many
people has asked for (gets around NAT issues, etc) but we have not
implemented at this time. Also UDP is a better way to measure raw
throughput of a pipe. The different congestion control mechanisms can
generate wide differences in values and depends to a much greater extent
on the end nodes (TCP implementation, window sizes, etc) rather than the
network itself. Though obviously customers may be more interested in what
they can expect from a HTTP, FTP, SSH aka TCP transfer.
Kevin