Date: Thu, 8 Jun 2000 10:35:47 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Luigi Rizzo <luigi@info.iet.unipi.it> Cc: freebsd-net@freebsd.org Subject: Re: HEADS UP- WF2Q and RED now available in -current Message-ID: <Pine.NEB.3.96L.1000608102951.33329A-100000@fledge.watson.org> In-Reply-To: <200006081348.PAA03955@info.iet.unipi.it>
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Luigi, I was perusing your ip_dummynet web page, and noticed the following: ipfw add prob 0.33 pipe 1 ip from A to B ipfw add prob 0.5 pipe 2 ip from A to B ipfw add pipe 3 ip from A to B ipfw pipe 1 config ... ipfw pipe 2 config ... ipfw pipe 3 config ... afterwards, you describe: Given the right packet, the first rule will match with probability 1/3; in the remaining 2/3 of occurrence we move to the second rule, which will match with prob 1/2 (so overall 1/2*1/3 = 1/3), and the remaining 1/3 of occurrence will move to the third rule, which has a deterministic match. We can then configure the three pipes as desired to emulate phenomena such as packet reordering etc. My impression was that, at the IP level, a pipe match resulted in packets being reinserted into the ruleset following the pipe rule. With the BRIDGE implementation, this would behave exclusively (one pipe per packet) as a pipe implies an accept, but in the non-BRIDGE implementation, it would allow multiple pipes per packet. I.e., a packet will always get hit by the last rule, will be hit by the first rule 33% of the time, and by the second 50% of the time. As a result with IP level forwarding, 16.5% of packets will hit all three pipes. Robert N M Watson robert@fledge.watson.org http://www.watson.org/~robert/ PGP key fingerprint: AF B5 5F FF A6 4A 79 37 ED 5F 55 E9 58 04 6A B1 TIS Labs at Network Associates, Safeport Network Services To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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