Date: Tue, 11 Dec 2007 20:36:53 +1100 From: Peter Jeremy <peterjeremy@optushome.com.au> To: rihad <rihad@mail.ru> Cc: freebsd-net@freebsd.org Subject: Re: Pipe queues Message-ID: <20071211093653.GN11310@server.vk2pj.dyndns.org> In-Reply-To: <475E4AC4.4030903@mail.ru> References: <475D6FD7.2000500@mail.ru> <DCFF3417-FC01-4F2C-ACA5-03CC0881DE59@mac.com> <20071210120353.B40679@xorpc.icir.org> <475DA624.4010104@seclark.us> <475E1E4D.4090409@mail.ru> <20071211074353.GI11310@server.vk2pj.dyndns.org> <475E4AC4.4030903@mail.ru>
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--jx/LfW4V5TfZLeq7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Dec 11, 2007 at 12:31:00PM +0400, rihad wrote: >Peter Jeremy wrote: >> On Tue, Dec 11, 2007 at 09:21:17AM +0400, rihad wrote: >>> And if I _only_ want to shape IP traffic to given speed, without=20 >>> prioritizing anything, do I still need queues? This was the whole point. >> No you don't. I'm using pipes without queues extensively to simulate >> WANs without bothering with any prioritisation. > >Great! One fine point remains, though: ># ipfw pipe 1 config bw 128Kbit/s >will use a queue of 50 slots by default. What good are they for, if I=20 >didn't ask for queuing in the first place? 'queue' is used in two distinct ways within the ipfw/dummynet code: 1) There's a "queue" object created with 'ipfw queue NNN config ...' This is used to support WF2Q+ to allow a fixed bandwidth to be unevenly shared between different traffic types. 2) There is a "queue" option on the "pipe" object that defines a FIFO associated with the pipe. I had assumed you were talking about the former (and my response was related to this) but given your latest posting, and having re-read the thread, I suspect I may have been wrong. Whilst I don't use queue objects, I do use the queue option on my pipes. In your example, you have a pipe that can handle 128kbps (16kBps). If you write a 1600byte packet to it, then the packet will reappear 100msec later. Any further packets written to that pipe during that time will be dropped if they can't be placed on a queue. The practical throughput depends on the number of queue slots available and the number of writers. I suggest you do some reading on queueing theory for the gory details. --=20 Peter Jeremy Please excuse any delays as the result of my ISP's inability to implement an MTA that is either RFC2821-compliant or matches their claimed behaviour. --jx/LfW4V5TfZLeq7 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQFHXlo1/opHv/APuIcRAuHaAKC6fbLIe31XswBa3FjsCc0M3zbYrQCeKpOC Ie2kjpZbwCWhSSxBZ0ATmT8= =5sCA -----END PGP SIGNATURE----- --jx/LfW4V5TfZLeq7--
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