Now I have connected 2 hosts directly, and evaluate the each throughput.
Then all the results of UDP, TCP and XTP are the same and 94Mbps. (My
netwrok is 100Base/TX).

In this case round-trip time between 2 hosts is less than 0.1ms
because they are directly connected. But my previouse case, round-trip
time between 2 hosts are 4ms. (I use IPSEC between the security
gateways to increase delay).
I think that's the reason TCP throughput is slow. If ACK packets are
delayed, sending window cannot slide and sending packets cannot be
fully bursted.

If I changes wmem size through /proc/sys/net/ipv4/tcp_wmem, TCP's
throughput may improve, but congestion control becomes more difficult
for TCP.

That is TCP's disadvantage to XTP.

Best
Shigeo

On 4/24/08, Andi Kleen <andi@firstfloor.org> wrote:
quoted text
> "Shigeo N" <shigeonx@gmail.com> writes:
> >
> > I tested in the network where UDP throughput is 29Mbps, then TCP
> > throughput was 13Mbps, but XTP's reached to 25Mbps.
>
> One interesting question is why TCP was so much slower than UDP
> on your test. It shouldn't be on a fair test setup.
>
> Please post details. Was the network losing packets?
>
> New protocols might be interesting, but even more interesting is to
> fix any (real) problems in existing protocols.
>
> -Andi
>
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