Updates using idle bandwidth

[Bruno Wolff III]

On Tue, Mar 11, 2008 at 18:07:02 -0700,
  Andrew Farris <lordmorgul at gmail.com> wrote:
> 
> Isn't this exactly what QOS is intended to do, provided the connections are 
> made with priorities assigned?

If you are talking about the qos flags in IP packets, the answer is no.
There aren't that many states and generally you can only describe broad
things about packets (such as I want low latency or I want high throughput)
not detailed bandwidth allocations. Also I tried a few experiments with
testing qos bits and found that they seemed to be getting stripped (I expected
them to be ignored, but that at least they would be preserved) in transit.
I didn't do enough experiments to see where this was happening or to get a
good idea of how common this was.

There are tools for doing this under Linux. You want to use the iproute2
suite to do most of the work and you might need netfilter to do some marking
to allow you to be able to classify packets. You need to know the capacity of
your link. There are also limitations on the effectiveness of shaping on
the wrong side of the link (for incoming traffic). The LARTC Howto is
a good starting point for learning about this, though it is a bit dated.