[LARTC] Ingress Shaping using IMQ

["Aron Brand" <Aron@sofaware.com>]

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Hi Guys,

Here is a question that is probably of concern to many of us.

I am under pressure to provide some solution for ingress traffic
shaping. What my customer demands is to divide the downstream (ingress)
of an ADSL lines to two classes of traffic - important traffic and non
important downloads. He has a very reasonable requirement: he wants a
guarantee of at least 1000kbps at all times for the important traffic on
the downstream. 

Using ingress policing would be the trivial solution. But no says the
customer - when the important traffic is not fully utilizing its rate, I
want it to share the excess with other classes. 
After looking around, the answer I found was to use imq, which claims to
allow traffic shaping on ingress traffic. So far so good.

And now I arrive to the question: It is possible to configure everything
in THEORY. The question is, it it really possible for me to give the
guarantee that my customer is asking for? I can think of examples why it
seems that the answer is no. For example, lets say the ingress line is
completely saturated with non-important traffic. How on earth can the
poor HTB determine whether important traffic is being drowned out - or
there is simply no important traffic?
My speculation so far - it is possible to configure these rules, and
indeed this is what IMQ was invented for, but in true life there is no
solution that works - since it is inherently impossible!

Has anyone really created and tested a working ingress traffic shaping
solution?

Aron



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