Re: transmech MTU comments

[Pekka Savola <pekkas@netcore.fi>]

Hi,

On Thu, 20 Nov 2003, Fred Templin wrote:
> Should we have as a goal the ability to support L2 bridges, switches,
> hubs, etc. that join media with dissimilar MTUs, but do not support
> IPv4 fragmentation and do not send "packet too big" ICMPs?
>  
> We answered "NO" to this 15 years ago when we allowed the
> approach now specified in RFC 1191 to go forward, and that
> decision took a viable design alternative off the table which had
> a profound effect on the shaping of the industry.
>  
> We're not going to fix this overnight by anything we do here, but
> allowing for generality (i.e., not expecting any IPv4 fragmentation
> support along the forwarding path) would be an important step
> toward restoring a level playing field. Let's not blow it again,
> given new opportunities to get things right.

Fred, I appreciate your concern about creating a robust and optimal
Path MTU Discovery mechanism, but IMHO this document -- which we're
moving towards DS -- just simply doesn't seem to be the right time and
place to do so.

There is little we can do to fix IPv4 at this point; IPv6 already
doesn't include fragmentation support along the path, and might be
enhanceable, in future, to support new methods.  We'll need to live
with what we have.


-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings