Re: [tsv-area] Path MTU discovery when having varying MTU

On May 19, 2009, at 13:25, Carl Knutsson wrote:

> As Tero pointed out, there already is a way in ROHCoIPSec to send
> packets uncompressed.

True.  This would mean that the ROHCoIPsec path inherits the MTU of  
the tunnel minus IPsec overhead.
But one might want to do better than that, making use of the fact that  
for many packets IPsec tunneling overhead will be mostly cancelled out  
by the inner ROHC compression.

> The tunnel already keeps track of the MTU to
> compensate for the IP, ESP AH headers. So adding ROHC overhead should
> not a problem. Why not let the user decide whether or not to use ROHC
> segmentation, IP fragmentation or sending large packets through the
> uncompressed channel.

...where user is the person who configured the tunnel.
Sounds good to me.
As long as the signals that go to the end hosts allow them to do  
(PL)PMTUD predictably.

> We could list pros and cons and give some guidelines.

...which would pretty much elaborate on my previous sentence.

Gruesse, Carsten