MTU path discovery and IPSec

Thu Dec 4 21:40:45 UTC 2003

Tony Rall wrote:

>On Wednesday, 2003-12-03 at 09:38 PST, David Sinn <dsinn at dsinn.com> wrote:
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>(And note that frag 1 often is not the first fragment to arrive at 
>downstream nodes.  In my example in (1), frequently frag 2 will reach 
>places before frag 1 does (if any router along the path reorders its 
>transmit queue based on packet size).)
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I agree with all I have snipped.
I was wondering would it not be wiser for fraggers to frag in half 
instead of just the overflow?

For instance, suppose router has to fragment 1500 byte packet to go over 
1476 GRE. Instead of having  a big packet/little fragment why not just 
divide in half?
This would give them more equal buffer treatment, but an even bigger 
potential win is to avoid perhaps a second (maybe ipsec?) fragmenting 
later on down the pipe.

Once you are going to do it, do it right. It is not as if your 
decreasing header overhead by producing small fragment packets. And I am 
assuming the whole packet is already in buffer when it comes time to 
fragment it.

>Tony Rall
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