Date: Thu, 7 Jun 2001 10:25:35 +0200 (CEST) From: Luigi Rizzo <luigi@info.iet.unipi.it> To: Thierry Herbelot <thierry@herbelot.com> Cc: mi@aldan.algebra.com, question@FreeBSD.ORG, net@FreeBSD.ORG Subject: Re: using ipfw's ``pipe'' to limit icmp traffic Message-ID: <200106070825.KAA40095@info.iet.unipi.it> In-Reply-To: <3B1F0EC3.28C7A21C@herbelot.com> from Thierry Herbelot at "Jun 7, 2001 07:18:59 am"
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> > if it ever needs more than 64Kbit/s, it is an attack... > > > > This seems to work, but when I try to ping something outised the > > network, the ping time is around 10 msec. Without the above piping, it > > is around 0.5 msec. It is the bandwidth, that I'm trying to limit, not > > the minimum latency! > > the pipe facility is using the kernel clock, which has a default > frequency of 100 Hz (thus the 10ms latency). on top of this, 512 bit (64 bytes) take about 8ms to run through a 64Kbit/s pipe (transmission time) so even reducing the granularity will not change things much. cheers luigi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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