Subject: Re: [PATCH] Honour window_size_initial from _libssh2_channel_read

Re: [PATCH] Honour window_size_initial from _libssh2_channel_read

From: Salvador Fandiņo <>
Date: Thu, 17 Oct 2013 01:30:47 +0200

On 10/16/2013 11:14 PM, Daniel Stenberg wrote:
> On Wed, 16 Oct 2013, Salvador Fandino wrote:
>> See the commit message for the details.
> This is the first one in your series that I'm not totally convinced is
> correct. When we do SFTP over big pipes with really large RTT, I fear
> that having a "mere" 256KB in maximum window is a potential problem to
> users.

256000 is also too low for my taste.

But in any case, the correct way to solve that is not to hard-code some
arbitrary size but to use a better value for

OpenSSH uses 2MB for its window size, that would probably be a good
field-tested default.

> Have you done any performance tests with and without this patch?

As stated on the patch, just over a LAN with out any noticeable speed
degradation. I would try to write some script to simulate different
network conditions and measure the transfer speed for a few window sizes.
Received on 2013-10-17