From owner-freebsd-net Wed Jul 21 23:33:14 1999 Delivered-To: freebsd-net@freebsd.org Received: from labinfo.iet.unipi.it (labinfo.iet.unipi.it [131.114.9.5]) by hub.freebsd.org (Postfix) with SMTP id 1E66414F43 for ; Wed, 21 Jul 1999 23:33:09 -0700 (PDT) (envelope-from luigi@labinfo.iet.unipi.it) Received: from localhost (luigi@localhost) by labinfo.iet.unipi.it (8.6.5/8.6.5) id GAA25741; Thu, 22 Jul 1999 06:07:13 +0200 From: Luigi Rizzo Message-Id: <199907220407.GAA25741@labinfo.iet.unipi.it> Subject: ipfw/dummynet enhancement... To: net@freebsd.org Date: Thu, 22 Jul 1999 06:07:13 +0200 (MET DST) X-Mailer: ELM [version 2.4 PL23] Content-Type: text Content-Length: 1568 Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Hi, over time several people who use dummynet for testing asked me to add a way to simulate packet reordering. After some thinking triggered by the requests, i believe i have a decent solution: add a "match probability" to ipfw rules such that one can write things like this ipfw add ... pipe 1 ip from A to B prob P1 ipfw add ... pipe 2 ip from A to B prob P2 ipfw add ... pipe 3 ip from A to B prob P3 ipfw add ... pipe 4 ip from A to B and packets go to pipe 1 with prob. P1, pipe 2 w/ prob (1-P1)P2, pipe 3 w/ (1-P1)(1-P2)P3 ... and so on. This seems to be reasonably good to simulate multiple paths (main source of reordering) without introducing dependencies amoung queues/rules thayt would make the system more intrusive. Comments/objections to implement this (the overhead on a normal syztem is zero if "options DUMMYNET" is not used, one additional check for 0 in the normal case of deterministic rules, and one random number generation in case of probabilistic rules). I cannot think immediately of an use for probabilistic ipfw rules except for testing purposes... cheers luigi -----------------------------------+------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy) http://www.iet.unipi.it/~luigi/ngc99/ ==== First International Workshop on Networked Group Communication ==== -----------------------------------+------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message