[altq:1774] Re: ALTQ vs Dummynet

[Nicolas Christin <nicolas@cs.Virginia.EDU>]

On Thu, 13 Feb 2003, raysiu wrote:

>     I am a new developer on FreeBSD and i want to develop a traffic
> management on my system. As i know Dummynet and ALTQ can also do
> the same things (limit bandwidth), so where can i have the resource
> or document to discuss the difference between ALTQ and Dunmmynet
> (Performance, characteristics....etc) as i have no ideas on this
> problems......Thank You very much!!!!!

As far as I know, there is no such "altq vs. dummynet" document.
Basically, you would have to compare the manual pages to get an idea.
However, you have asked the right mailing-list, since both Kenjiro and
Luigi are subscribed here.

My take on this: dummynet is mostly a packet filter - dummynet can
provide a few queueing disciplines (wfq) but altq is much better in that
respect, there are more/fancier queuing disciplines available.

Conversely, dummynet is better (in the sense more flexible) at
filtering packets (see recent discussions on this list). Dummynet also
provides for emulating propagation delays, altq does not at the moment.

As for performance specifics, it basically depends on what you're
looking for: a FIFO queue with no filter in altq will certainly have
less overhead than a JoBS queue with 24 classes and proportional and
absolute guarantees... There is no comparison/benchmarking document that
I'm aware of, but I think it would be pretty pointless. You basically
have to test both under the conditions you want to work under in
general, and use that as your benchmark, I think.

What I had set up as a research testbed was basically a combination of
the two: dummynet would filter packets and emulate propagation delays,
passing packets to an altq router supporting a fancy queuing discipline.

There are my two cents, please someone correct me if I misspoke.
-- 
Nicolas