Date: Wed, 24 Jan 2007 18:10:21 +1100 From: Peter Jeremy <peterjeremy@optushome.com.au> To: "Andresen, Jason R." <jandrese@mitre.org> Cc: freebsd-stable@freebsd.org Subject: Re: Dummynet and simulating random delay Message-ID: <20070124071021.GG874@turion.vk2pj.dyndns.org> In-Reply-To: <53B52415C756A84E8A169F0E3673A3290E8BA4@IMCSRV6.MITRE.ORG> References: <53B52415C756A84E8A169F0E3673A3290E8BA4@IMCSRV6.MITRE.ORG>
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--wRRV7LY7NUeQGEoC Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, 2007-Jan-23 14:22:54 -0500, Andresen, Jason R. wrote: >I have a project that requires me to simulate a link with varying but >well defined delay. The link is guarenteed to deliver packets in >order, so I wish to maintain that behavior with Dummynet. I don't think dummynet can do this in its current form. Based on a quick look at the source, the packet delivery time is set to the current time plus the current delay when the packet arrives (see sys/netinet/ip_dummynet.c:move_pkt(). This means that changing the delay will not affect existing queued packets. Changing dummynet to allow variable delays whilst maintaining packet order is not immediately trivial. The only option I can see would be to change the dummynet curr_time (net.inet.ip.dummynet.curr_time) to increment at variable rate instead of one count per tick. You would probably need to do some fiddling to provide anything better than very coarse delay variation. --=20 Peter Jeremy --wRRV7LY7NUeQGEoC Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD) iD8DBQFFtwZd/opHv/APuIcRAuRZAJkBcKMagvb62xrj0wAKKSwgFJQj3ACbB8aQ v9HNayCZ+N3XKXpVhCG0f6I= =fkgJ -----END PGP SIGNATURE----- --wRRV7LY7NUeQGEoC--
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