[pfSense Support] Strange TCP connection behavior 2.0 RC2 (+3)
andreas at naund.org
Tue Jun 28 15:23:46 UTC 2011
On Tue, Jun 28, 2011 at 10:52:55AM +0200, Eugen Leitl wrote:
> ----- Forwarded message from William Salt <williamejsalt at googlemail.com> -----
> From: William Salt <williamejsalt at googlemail.com>
> Date: Tue, 28 Jun 2011 08:03:25 +0100
> To: support at pfsense.com
> Subject: [pfSense Support] Strange TCP connection behavior 2.0 RC2 (+3)
> Reply-To: support at pfsense.com
> Each TCP connection starts very slowly, and will max out at around 190mbps,
> taking nearly 2 minutes to climb to this speed before *plateauing*.
> We have to initiate many (5+) connections to saturate the link with tcp
> connections with iperf.
> ----- End forwarded message -----
You pretty much solved your own puzzle right there: the throughput on a
single TCP connection will max out at the value determined by the bandwidth
delay product (excluding other strange conditions, such as deep buffers).
Here is a calculator online:
[who has to explain this about once a week to customers who think
that they bought a GigE connection but then can't "ftp" a file from
coast to coast at 1Gbps throughput. Use multiple TCP streams!]
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