Linux Traffic Shaping

Michael Torrie torriem at
Wed Mar 20 17:12:30 MDT 2013

On 03/20/2013 01:35 AM, Dan Egli wrote:
> Admittedly 3 mbits isn't much for scp (I was thinking of only the actual
> interactive ssh, not it's derivatives), 

Interactive SSH only takes as much bandwidth as you can type anyway.
Other things that come over ssh like X11 forwarding, or scp, they can
take everything you give them.

> so I could move it up to the #2
> priority that gives 9mbits. Maybe even 9.5 mbits. But I've seen the
> slowdowns when I have a file downloading (via scp or http or ftp or other
> doesn't matter) and I try to view a web page with a few graphics, or I try
> to download my mail. It works, no arguments. But the slowdown is apparent.
> What I'd like to accomplish is that the low bandwidth items (like imap &
> smtp) always get a bit of room, even if it's only 256kbits, then normal
> operational things that would create heavy bandwidth (http, scp, etc...)
> would get the lion's share, and what's left over goes to whatever other
> bandwidth gobbler there is, be it a online game (maybe an MMORPG or
> something) or downloading the latest movie, or transferring other large
> files, be it on Bittorrent, or a file sharing network like gnutella2 or
> kazaa or others. And the problem with telling the program itself to
> throttle is that it will ALWAYS throttle. The other point was that in
> instances where nothing else is happening (I'm typing something up locally,
> or I'm not even at the computer, or whatever) the major bandwidth gobblers
> like file sharing and Bittorrent can have free reign to saturate the link.*
> Hopefully that explains it better. If there's a better way to handle the
> situation than traffic shaping then please enlighten me. The only one that
> came to mind was shaping, but I will easily bow to superior wisdom if it is
> presented to me.

I see what you are saying.

I don't know of anyone throttling or setting QoS on their home networks
in this matter, so I have little wisdom, even inferior wisdom to offer.

I regularly saturate my link and during such times only interactive ssh
sessions are really impacted.  Sure latency is added to things like
making IMAP connections, but in practice I just don't notice it.  And
normally when my bandwidth is saturated, the normal TCP/IP congestion
algorithms seem to work well enough and all my downloads get a share.

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