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Date:	Tue, 9 Sep 2008 14:31:19 +0800
From:	"Eugene Teo" <eugeneteo@...nel.sg>
To:	"Stephen Hemminger" <stephen.hemminger@...tta.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Internet-Draft on Port Randomisation

On Tue, Sep 9, 2008 at 12:58 PM, Stephen Hemminger
<stephen.hemminger@...tta.com> wrote:
> Eugene Teo wrote:
>>
>> Has anyone read this Internet-Draft?
>>
>> http://www.gont.com.ar/drafts/port-randomization/draft-ietf-tsvwg-port-randomization-02.txt
>>
>> In this memo, there are descriptions of four different ephemeral port
>> randomisation algorithms (see page 17).
>>
>> Algo #1 and #2 are simple port randomisation algorithms. Algo #3 is
>> what we have in Linux. The memo suggested algorithm #4, double-hash
>> randomisation algorithm, which is an improvement to algo #3 (see page
>> 15).
>>
>> Does anyone have any thought about the improved algorithm? Is this
>> worth implementing,
>
> No the added lock overhead of a global next free port array is not worth it.
> Think of big web server under
> DoS pressure. The existing port search can run in parallel, Algo #4 was
> suggested by people
> who don't work on a real SMP OS.

Thanks Stephen.

Eugene
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