[95976] in North American Network Operators' Group
Re: Thoughts on increasing MTUs on the internet
daemon@ATHENA.MIT.EDU (Saku Ytti)
Thu Apr 12 14:23:28 2007
Date: Thu, 12 Apr 2007 21:08:05 +0300
From: Saku Ytti <saku+nanog@ytti.fi>
To: Iljitsch van Beijnum <iljitsch@muada.com>
Cc: NANOG list <nanog@merit.edu>
In-Reply-To: <4474325C-E4F4-4B29-B405-3EBC51E488C8@muada.com>
Errors-To: owner-nanog@merit.edu
On (2007-04-12 19:51 +0200), Iljitsch van Beijnum wrote:
> 8 bytes preamble
> 14 bytes ethernet II header
> 20 bytes IP header
> 20 bytes TCP header
> 12 bytes timestamp option
> 4 bytes FCS/CRC
> 12 bytes equivalent inter frame gap
>
> 90 bytes total overhead, 52 deducted from the ethernet payload, 38
> added to it.
>
> 90 / (1500 - 52 = 1448) * 100 = 6.21
>
> 90 / (9000 - 52 = 8948) * 100 = 1
>
> Also note that the real overhead is much bigger because for every two
> full size TCP packets an ACK is sent so that adds 90 bytes per 2 data
> packets, or increases the overhead to 9% / 1.5%.
Aren't you double penalizing? Should it be:
[ytti@nekrotuska ~]% echo "90 / (1500+38) * 100"|bc -l
5.85175552665799739900
Or other way to say it:
[ytti@nekrotuska ~]% echo "100-(1448/(1+7+6+6+2+1500+4+12)*100)"|bc -l
5.85175552665799740000
--
++ytti
