Thoughts on increasing MTUs on the internet

Thu Apr 12 17:03:25 UTC 2007

I did a rough, top-of-the-head, with ~60 bytes header (ETH, IP, TCP)  
into 1500 and 4470 (a mistake, on my part, not to use 9216).

I still think the cost outweighs the gain, though there are some  
reasonable arguments for the increase.

Gian Anthony Constantine

On Apr 12, 2007, at 12:07 PM, Saku Ytti wrote:

>
> On (2007-04-12 16:28 +0200), Iljitsch van Beijnum wrote:
>>
>> On 12-apr-2007, at 16:04, Gian Constantine wrote:
>>
>>> I agree. The throughput gains are small. You're talking about a
>>> difference between a 4% header overhead versus a 1% header overhead
>>> (for TCP).
>>
>> 6% including ethernet overhead and assuming the very common TCP
>> timestamp option.
>
> Out of curiosity how is this calculated?
> [ytti at ytti.fi ~]% echo "1450/(1+7+6+6+2+1500+4+12)*100"|bc -l
> 94.27828348504551365400
> [ytti at ytti.fi ~]% echo "8950/(1+7+6+6+2+9000+4+12)*100"|bc -l
> 99.02633325957070148200
> [ytti at ytti.fi ~]%
>
> I calculated less than 5% from 1500 to 9000, with ethernet and
> adding TCP timestamp. What did I miss?
>
> Or compared without tcp timestamp and 1500 to 4470.
> [ytti at ytti.fi ~]% echo "1460/(1+7+6+6+2+1500+4+12)*100"|bc -l
> 94.92847854356306892000
> [ytti at ytti.fi ~]% echo "4410/(1+7+6+6+2+4470+4+12)*100"|bc -l
> 97.82608695652173913000
>
> Less than 3%.
>
> However, I don't think it's relevant if it's 1% or 10%, bigger
> benefit would be to give 1500 end-to-end, even with eg. ipsec
> to the office.
>
> -- 
>   ++ytti

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