Date: Thu, 22 Jul 1999 06:07:13 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: net@freebsd.org Subject: ipfw/dummynet enhancement... Message-ID: <199907220407.GAA25741@labinfo.iet.unipi.it>
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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
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