Date: Mon, 10 Dec 2007 15:48:36 -0500 From: Stephen Clark <Stephen.Clark@seclark.us> To: Luigi Rizzo <rizzo@icir.org> Cc: rihad <rihad@mail.ru>, freebsd-net@freebsd.org Subject: Re: Pipe queues Message-ID: <475DA624.4010104@seclark.us> In-Reply-To: <20071210120353.B40679@xorpc.icir.org> References: <475D6FD7.2000500@mail.ru> <DCFF3417-FC01-4F2C-ACA5-03CC0881DE59@mac.com> <20071210120353.B40679@xorpc.icir.org>
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Luigi Rizzo wrote: >On Mon, Dec 10, 2007 at 11:22:33AM -0800, Chuck Swiger wrote: > > >>On Dec 10, 2007, at 8:56 AM, rihad wrote: >> >> >>>Hi, >>> >>>I'm having a hard time to understand what pipe queues are with >>>respect to bandwidth limitation. ipfw(8) and dummynet(4) manuals >>>didn't help me much. >>> >>> >>Pipes and queues are two different things; a pipe simulates a network >>link, and a queue is used to hold packets which are backlogged because >>they are arriving faster than the outbound link (ie, a pipe) can >>transmit them. >> >> >> >>>How does dummynet's traffic shaping function? >>> >>> >>It uses a variant of weighted fair queuing. >> >> > >actually the shaping uses a leaky bucket algorithm. >The weighted fair queuing is the queue management scheme used >when you have multiple queues attached to the same pipe > >cheers >luigi >_______________________________________________ >freebsd-net@freebsd.org mailing list >http://lists.freebsd.org/mailman/listinfo/freebsd-net >To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > > > Pipes are used to limit bandwidth. Queues are used to assign priority to different classes of traffic. As an example suppose you wanted to limit bandwidth for a specific ip to 2mbs. You set up a pipe to do this and use ipfw to put traffic from this ip into the 2 mbs pipe. If you then wanted to prioritize ftp traffic at higher than priority than all other traffic for this same user you would create 2 queues to feed the 2mbs pipe. You would send the ftp traffic into the higher priority queue and all other traffic for this user into the other queue. hth, Steve -- "They that give up essential liberty to obtain temporary safety, deserve neither liberty nor safety." (Ben Franklin) "The course of history shows that as a government grows, liberty decreases." (Thomas Jefferson)
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