From: Ramin Alidousti <ramin@UU.NET>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] Rate limiting, DoS
Date: Thu, 07 Jun 2001 17:24:32 +0000 [thread overview]
Message-ID: <marc-lartc-99193471812123@msgid-missing> (raw)
In-Reply-To: <marc-lartc-99193419509928@msgid-missing>
On Thu, Jun 07, 2001 at 01:10:44PM -0400, Adrian Chung wrote:
> Hi everyone! Question about "rate limiting" and DoS mitigating
> features of 2.4's iptables.
>
> With iptables, it's possible to limit the acceptance of different
> types of packets to a certain level, in order to try to mitigate DoS
> attacks on the box (syn floods, ping floods, etc).
>
> I realize that most DoS attacks happen as a result of the CPU being
> unable to keep up, and not bandwidth limitations, but I'm unsure as to
> why rate limiting packets works to lessen CPU processing load.
>
> Doesn't the kernel still have to use cycles to process the packets
> before deciding to throw them out, or pass them on? And if so, is the
> cost savings in terms of CPU load just because they don't get passed
> to other system facilities which would otherwise respond and use more
> CPU cycles?
I think that DoS or dDoS are mainly affecting the kernel buffer usage.
Especially in case of the SYN flooding. The CPU cycle might also be a
problem but checking the packet as it comes in and dropping it is much
less CPU intensive as processing and routing the packet.
Ramin
>
> Or does this make any sense? :)
>
> --
> Adrian Chung (adrian at enfusion-group dot com)
> http://www.enfusion-group.com/~adrian
> GPG Fingerprint: C620 C8EA 86BA 79CC 384C E7BE A10C 353B 919D 1A17
> [rogue.enfusion-group.com] 1:10pm up 31 days, 23 min, 2 users
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prev parent reply other threads:[~2001-06-07 17:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-07 17:10 [LARTC] Rate limiting, DoS Adrian Chung
2001-06-07 17:24 ` Ramin Alidousti [this message]
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