Date: Sat, 3 Mar 2007 02:56:18 -0800 From: Luigi Rizzo <rizzo@icir.org> To: John Mok <jmok@attglobal.net> Cc: freebsd-ipfw@freebsd.org Subject: Re: Dummynet cascade of pipes Message-ID: <20070303025618.B76051@xorpc.icir.org> In-Reply-To: <45E8D473.5090808@attglobal.net>; from jmok@attglobal.net on Sat, Mar 03, 2007 at 09:50:43AM %2B0800 References: <45E8D473.5090808@attglobal.net>
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On Sat, Mar 03, 2007 at 09:50:43AM +0800, John Mok wrote: > Hi, > > I am new to Dummynet. I would like to setup a FreeBSD QoS box to replace > the one using Linux IMQ. However, I have the following questions :- > > 1. Is it possible to cascade pipes, such that the bandwidth management > could be easier by hierarchical control rather than flat-out? For instance, no. hierarchical bandwidth management means inheritance and this leads to inefficient algorithms. WFQ does a decent job in most cases where you would want inheritance, it's just a slightly different way of modeling things. > pipe 100 is the total bandwidth 2Mbps of the serial link to Internet > pipe 110 cascade pipe 100 with a weight 8Kbps and ceiling 16 Kbps > pipe 120 cascade pipe 100 with a weight 32Kbps and ceiling 256 Kbps > pipe 130 cascade pipe 100 with a weight 384Kbps and ceiling 2Mbps > pipe 140 cascade pipe 100 with a weight 224Kbps and ceiling 2Mbps > > Pipe 130 and pipe 140 are allowed to consume the total bandwidth if > there is no other traffic, but would only get its share 224 / (8 + 32 + > 384 + 224) when all pipes are fully loaded. > > 2. Is there any FIFO queue rather WFQ? If there are 3 queues defined top > sahre the bandwidth of pipe 110, how to make the traffic to go in FIFO > manner? all queues are FIFO, individually (meaning that packets are served in FIFO order within each queue). There is no FIFO servicing of queues, but i am unclear when one would need this -- it seems _almost_ equivalent to serving individual packets in FIFO order, except with a bit of uncontrolled reordering (uncontrolled means that you cannot make estimates on when a packet will be served, hence cannot compute guarantees etc., which is the whole point of having WFQ or bandwidth management) If you can find a convincing motivation for adding this feature, it can be done - it is not hard or inefficient, just don't see how it could help. cheers luigi > Thanks a lot. > > John Mok > > _______________________________________________ > freebsd-ipfw@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-ipfw > To unsubscribe, send any mail to "freebsd-ipfw-unsubscribe@freebsd.org"
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