[openssl-users] OpenSSL Behaviour under low bandwidth

Martin Beynon mebeyn at gmail.com
Fri May 15 11:44:03 UTC 2015

Sorry Rich,

It does - as in; look like a network issue. But I fail to see how.

If I try to push 10MB/s into openssl and everything works as expected until
the available network bandwidth drops below 150 kpbs, this points at
openssl - I think.

That is right from 100Mbps down to 150 kpbs everything works as expected.
As I continue tuning down the bandwidth below 150kbps openssl starts to
stop sending data. It becomes very bursty and there are whole periods of
seconds where no data is sent from openssl even though it's 17KB TLS buffer
is full and pings, for example, can be sent and received normally.

There appears to be some relation to the size of this buffer and the
minimum achievable throughput we can get.. Unless my maths is off; 140 Kbps
would give about 17KB/s throughput.. Coincidence?

Have you tested sending large amounts of data between two s_clients across
a limited bandwidth link?
On 15 May 2015 12:20, "Salz, Rich" <rsalz at akamai.com> wrote:

>  “It does”  Does that mean you have the same behavior?  If so, it is
> possible that your simulator is, well, not great. But this doesn’t seem an
> openssl issue. Not sure where to suggest you go for help.
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