North American Network Operators Group

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Re: Strange public traceroutes return private RFC1918 addresses

  • From: Stephen J. Wilcox
  • Date: Tue Feb 03 15:57:47 2004

On Tue, 3 Feb 2004, Petri Helenius wrote:

> Stephen J. Wilcox wrote:
> >>Why large MTU then? Most modern ethernet controllers don´t care if you´re
> >>sending 1500 or 9000 byte packets. (with proper drivers taking advantage of
> >>the features there) If you´re paying for 40 byte packets anyway, there is no
> >>incentive to ever go beyond 1500 byte MTU.
> >>    
> >>
> >
> >I think its partially due to removal of overhead and improvements you get out of 
> >TCP (bearing in mind it uses windowing and slow start)
> >
> Sure, if you control both endpoints. If you don´t and receivers have small
> (4k,8k or 16k) window sizes, your performance will suffer.
> Maybe we should define if we´re talking about record breaking attempts or real
> operationally useful things here.

By definition of this discussion about using large MTU we are assuming that 
packets are arriving >1500 bytes and therefore that we do have control of the 
endpoints and they are set to use jumbos